On Sat, 13 Dec 2003 12:40:45 +0000, The Natural Philosopher
wrote:



Many people here have attempted to educate you on this point. You clearly
do not understand my old chum. So it is best you just take it as it is.

Best stop digging yourself into a deeper hole, my old chum.



No one has actually pointed out where it is said that this is not allowable.



While not wishing to get into a debate about what works and what
doesn't and what is and isn't good practice, I took a look through the
statutory instrument, the approved document to part L1 and some of the
good practice guides. I drew the following conclusions:

- The statutory instrument talks in very general terms about
requirements using words like "reasonable provision" and essentially
empowers the secretary of state to issue Approved Documents which are
not part of the legislation but guidelines..

- In the introduction to the Approved Documents it is stated that they
are guidance.

"Approved Documents are intended to provide
guidance for some of the more common
building situations. However, there may well be
alternative ways of achieving compliance with
the requirements. Thus there is no obligation
to adopt any particular solution contained in
an Approved Document if you prefer to meet
the relevant requirement in some other way."

The last sentence is in heavy type.


- In section 1.37 it states "requirements would be met". If this
document were prescriptive then it would say "requirements shall be
met". Likewise in section 1.38 it says "A way of demonstrating",
not "the way of demonstrating" and "temperature control could be" not
"temperature control must be".
In section 1.41, referring to interlocks the word "should" not "must"
is used.

- In section 1.46, an alternative way of showing compliance is to use
Good Practice Guide 302. This does indeed suggest that room
thermostats be used as part of a boiler interlock arrangement but also
comments on boiler energy management systems as being suitable as
well.


From all of this, I would conclude that room thermostats may be good
practice and used as part of demonstrating compliance with Part L1,
but I can see nothing in the Approved Document that mandates them and
it is certainly a long stretch to say that not having one in a new
installation is specifically illegal.





..andy

To email, substitute .nospam with .gl

On Sat, 13 Dec 2003 14:02:27 +0000, Andy Hall wrote:

From all of this, I would conclude that room thermostats may be good
practice and used as part of demonstrating compliance with Part L1,
but I can see nothing in the Approved Document that mandates them
and it is certainly a long stretch to say that not having one in a
new installation is specifically illegal.

What they want is the boiler to off, really off, when there is no
demand for heat. There are many ways to comply with this, hence the
"loose" wording of the documents.

Leaving power to the boiler and using the boilers output temperature
stat or return temp stat to switch the boiler off doesn't, IMHO,
comply with Part L1. Basically if the boiler can ever fire without
there being a demand for heat it does not comply.

--
Cheers
Dave. pam is missing e-mail

"Dave Liquorice" wrote in message
. 1...
On Sat, 13 Dec 2003 14:02:27 +0000, Andy Hall wrote:

From all of this, I would conclude that room thermostats may be good
practice and used as part of demonstrating compliance with Part L1,
but I can see nothing in the Approved Document that mandates them
and it is certainly a long stretch to say that not having one in a
new installation is specifically illegal.

What they want is the boiler to off, really off, when there is no
demand for heat. There are many ways to comply with this, hence the
"loose" wording of the documents.

Leaving power to the boiler and using the boilers output temperature
stat or return temp stat to switch the boiler off doesn't, IMHO,
comply with Part L1. Basically if the boiler can ever fire without
there being a demand for heat it does not comply.

A very good bottom line.


---
--

Checked by AVG anti-virus system (http://www.grisoft.com).
Version: 6.0.548 / Virus Database: 341 - Release Date: 05/12/2003

Andy Hall wrote in message ...
From all of this, I would conclude that room thermostats may be good
practice and used as part of demonstrating compliance with Part L1,
but I can see nothing in the Approved Document that mandates them and
it is certainly a long stretch to say that not having one in a new
installation is specifically illegal.
Thanks for the wider view, Andy. What concerns me is, I assume a room stat
can't do any harm, unless of course it fights with the TRVs in such a way
that the boiler doesn't know what the hell it's doing. Why the installers
should bother to disconnect the old stat is a mystery.
The other thing that would concern me is the reliability of the TRVs. I've
never had a stat fail but I've known plenty of TRVs seize up if they're not
adjusted from one year to the next.

In article , IMM abuse-
writes
It needs one by law.

Another drama queen . . . . .

Do you mean it doesn't?

I wasn't an arrestable offence the last time I checked. It is however required
by a legally enforceable statutory instrument, hardly meriting the dramatic
description along with rape, murder or even carrying out gas work when not
being a competent person.
--
fred

In message , The Natural Philosopher
writes
Christian McArdle wrote:

It's a bit of a fudge, but I can't find a better way of doing it!

Set the TRV to full (preferably replace, so the radiator is
lockshield both
ends). Then balance down the hall radiator using the lockshield so that it
warms up slowly and doesn't get very hot. Then, when the other radiators get
shut down via their TRVs, more water gets to the hall radiator. By the time
all TRVs have shut, the hall radiator gets the full force of the boiler,
heats the hall and the room stat shuts down.

I suppose you might argue that that we might as well set the stat to
45C in the evenings and let the TRVs do their job,

This would defeat the boiler interlock and make your system
inefficient, as
the boiler will continue to short cycle, heating your primary water which
may lose heat into areas not required to be heated.



(hint. I have done this for some considerable time. The boiler doesn't
short cycle at all. Only in the case of very poorly insulated CH pipes
and a fairly warm set of rooms, and very cold spaces through which the
pipes run [almost impossible to achieve together with fairly warm
rooms] do you get teh '5 minute burn, five minute idle' sort of cycle.
You MAY get this with a fully TRV'ed system with a bypass buit even
then its unlikley. The water has to cool down quiet a lot to overcome
boiler stat hysteresis, and in that time its almost certain that one or
more rads will have opened up the TRV's a tad and be calling for heat anyway. )


Have to agree with the NP.
Here its a fully TRV'd system, bypass loop and NO room stat.
Right now its about 10C outside, most of the radiators have gone off, a
couple (mostly lounge, its the warmest setting) are running at about
40C, just feeding enough heat into the room to balance losses. One or
two rads are barely warm, maybe 25C, (inlet pipe is hot), again just
trickling heat into the room. Overall very comfortable, very stable
temperatures. Boiler fires for about one minute in every ten.

TRV's are analogue controllers, in well designed system they can
throttle heat output to match room losses.
Rooms don't "reach temperature" and magically stay there, constant heat
loss needs to be balanced with heat input. You can control it digitally
with a stat turning the system on and off, or have a nice room by room
analogue control.

I do sometimes consider fitting a room stat, probably an RF one so it
can be moved around, just to experiment with the stability of the
system.

--
Steve

In message , Dave
Liquorice writes
On Sat, 13 Dec 2003 14:02:27 +0000, Andy Hall wrote:

From all of this, I would conclude that room thermostats may be good
practice and used as part of demonstrating compliance with Part L1,
but I can see nothing in the Approved Document that mandates them
and it is certainly a long stretch to say that not having one in a
new installation is specifically illegal.

What they want is the boiler to off, really off, when there is no
demand for heat. There are many ways to comply with this, hence the
"loose" wording of the documents.

Leaving power to the boiler and using the boilers output temperature
stat or return temp stat to switch the boiler off doesn't, IMHO,
comply with Part L1. Basically if the boiler can ever fire without
there being a demand for heat it does not comply.


Unless the outside temperature is maybe 15C +, there is continuous heat
loss from the house, therefore continuous heat demand. I glad Andy's
pointed out his interpretation of part L, as I did think I was
technically non-compliant having no room stat.

(I take 15C arbitrarily, the sort of the outside temp I would turn the
system off anyway. Other heat sources, people, TV's, cooking, solar gain
etc can be enough to keep the house comfortable)


--
Steve

On Sat, 13 Dec 2003 16:53:12 +0000 (GMT), "Dave Liquorice"
wrote:

On Sat, 13 Dec 2003 14:02:27 +0000, Andy Hall wrote:

From all of this, I would conclude that room thermostats may be good
practice and used as part of demonstrating compliance with Part L1,
but I can see nothing in the Approved Document that mandates them
and it is certainly a long stretch to say that not having one in a
new installation is specifically illegal.

What they want is the boiler to off, really off, when there is no
demand for heat. There are many ways to comply with this, hence the
"loose" wording of the documents.

The legislation does not support that level of detail. That is not to
say that implementing a room thermostat is not a good practice, but I
can find nothing more than a recommendation suggesting that one is a
good idea.

In my mind the question is, what constitutes a demand for heat?
TRVs typically reduce the flow to radiators rather than closing it off
completely unless the radiator is grossly over sized and the room
temperature overshoots from it or a heat gain from another room or
perhaps solar gain. Good temperature control in the rooms where TRVs
are fitted would be achieved by their reducing the water flow to the
radiators such that the heat output balances the heat loss at the
required room temperature.

The heat output of the radiator in the location containing the room
thermostat where one is used has to be reduced to ensure that the
rooms equipped with TRVs have reached their set point.

Once that has been achieved, the boiler is turned off if a room
thermostat is used with a simple boiler which delivers zero or full
output only.

There are, of course, room thermostats with proportional control which
turn the boiler on and off on a relatively short time constant to
control the average heat output so that it is reduced as the set point
is approached; and thus it is possible, even with a basic boiler to
limit temperature overshoot which is said to be a significant energy
waster.

As I understand it, though, there is an overhead in terms of
efficiency for each on/off cycle of a simple boiler which does full
power or off. Presumably, this is not substantial in comparison
with energy saved by the overshoot not happening otherwise there would
be no point.



Leaving power to the boiler and using the boilers output temperature
stat or return temp stat to switch the boiler off doesn't, IMHO,
comply with Part L1. Basically if the boiler can ever fire without
there being a demand for heat it does not comply.

I think that that may be taking too simplistic a view.

Given that the plumbing and heating industry is still very
conservative and persists in installing non condensing non-modulating
boilers, a room thermostat may well make an energy saving with it.
I rather suspect though, that this has more to do with limiting the
size of the temperature overshoot that can happen with oversized
radiators and TRVs, than of whether there are short burns of the
boiler.

One of the referenced good practice guides,

http://www.gas-news.co.uk/gpg302.pdf

discusses the fitting of room thermostats as part of an interlock
scheme, yet mentions boiler energy management, modulating and
condensing boilers only in passing, even though it is relatively
recent. It seems to me that this is really an attempt to put a
stick in the ground with the industry and to say that a room
thermostat is part of good practice with a simple boiler.

However, modulating boilers, condensing or not are rapidly appearing,
and even for the die-hard installer has some appeal because there is
less commissioning to do.

It's also worth pointing out that it is quite easy for fairly
sophisticated control capabilities to be built into the boiler as
well. Most of this can be implemented in the firmware of the
controller so from a manufacturing cost perspective is not a large
additional factor. I suspect that the reason that more isn't done
is because UK manufacturers have not had people with the skills to do
the work.

For example, my own boiler has a very comprehensive set of controls
and can have a number of additional sensors apart from those within
the case.

On the input side, as a minimum it measures flow and return
temperatures. On the output side, the microprocessor can control the
burn rate from 3 to 25kW or off and the pump from 20-100%.
Even with nothing else electrically connected, it will make a pretty
good attempt at maximising its efficiency. If the heat demand is
above the minimum 3kW then it will modulate the pump and burner
anyway, so the issue of turning off altogether doesn't arise. In the
range where some heat, but less than 3kW is required, it will come on
for a short period, initially once per hour, measure the water
temperatures and run until the heat demand reduces, then going off.
The on period is remembered and adjusted so that the boiler is not
coming on too much earlier or late than need be. I have seen the
time between burns go out to as much as three hours with this hookup.
During a normal day, it will have done a hot water cycle during this
period anyway.

This is a fairly reasonable control system as it stands, but the
manufacturer includes an outside temperature sensor anyway, which is
placed on a north wall. It is then factored in as an input term to
the controller, in effect providing a prediction based on the outside
temperature. With this connected and operational, the control
becomes rather better with an ability to adjust output before the
house temperature changes.

Note that this is achieved with no room thermostat. From logs of
burner operation, pump operation, water temperatures and internal
house temperatures, the set points are achieved rapidly and without
significant overshoot of inside temperature mainly through the
modulating behaviour of the pump and burner.

I have added a room controller which is made by Siemens specifically
for this boiler. Apart from time functions it has a temperature
sensor for inside the house so that the boiler is presented with this
information rather than just an on and off. The effect of adding
this is mainly the convenience of a remote temperature control and
even less temperature overshoot - now almost nothing.
There is an installer setting whereby one can alter the relative
sensitivity of this term and the outside temperature (loop gain
controls if you like). In fact the defaults seem to work the best
anyway.

So, I think that I could make a strong case to anybody who wanted to
enquire that even without a room thermostat, I can achieve better
energy use than a simple boiler with a simple thermostat because the
minimum power output is very low and the boiler's built in algorithms
do a pretty good job on their own.

The Approved Document and the referenced Good Practice Guide really
only present *a* simple solution using a room thermostat for basic
installations. Neither presents it as the *only* solution, and with
increasing capability of boilers' own algorithms becoming increasingly
part of mass market products, I suspect that these guidelines will
need to be updated.




..andy

To email, substitute .nospam with .gl

On Sat, 13 Dec 2003 18:20:50 -0000, "stuart noble"
wrote:


Andy Hall wrote in message ...
From all of this, I would conclude that room thermostats may be good
practice and used as part of demonstrating compliance with Part L1,
but I can see nothing in the Approved Document that mandates them and
it is certainly a long stretch to say that not having one in a new
installation is specifically illegal.


Thanks for the wider view, Andy. What concerns me is, I assume a room stat
can't do any harm, unless of course it fights with the TRVs in such a way
that the boiler doesn't know what the hell it's doing.

Even then it won't do any harm as such. The fighting comes from a
few scenarios which can be avoided:

- Room stat is in a place where the radiator(s) have TRVs. As the
temperature rises, the room stat may switch off first. If this
happens then there is no more heat to there or the rest of the house.
Alternatively, the TRV may start to close down, effectively reducing
the heat contribution into the space and preventing the room stat from
operating unless the temperature goes much higher for other reasons
such as solar gain or heat gain from other rooms.

- Room stat in place where there is other heating - e.g. a living room
with gas fire or a kitchen. These contribute heat which is
effectively outside of the control loop and the room stat will react
by turning off the boiler early making the rest of the house cold.

By having the room stat where there is a non-TRV-controlled radiator
you create a control loop between temperature of that space and the
boiler firing. Ignoring the rest of the house for a moment, this
space will attain and be maintained at the room stat setting.

When you add in the TRVs for the other rooms, the trick is to ensure
that the radiator sizes and water flows are such that the TRVs are
starting to shut down before the room stat cuts off the boiler.

All of this is somewhat imprecise because the radiator water flows are
inter-related and of course heat passes from room to room.

You may want to think about using a radio linked room stat. These
have the advantage that apart from not needing to be wired all the
way, you can try different locations until happy with the results.
The sensor/control piece is battery powered and the receiver is fitted
near the boiler.



Why the installers
should bother to disconnect the old stat is a mystery.

It doesn't make a lot of sense, although if it was an old bimetal one,
using an electronic one would giver better control sensitivity.


The other thing that would concern me is the reliability of the TRVs. I've
never had a stat fail but I've known plenty of TRVs seize up if they're not
adjusted from one year to the next.

I've always used Invensys/Drayton ones and have never had the plunger
of one sieze up. I have had failures of the head part after 7-8
years but I have a couple that are still fine after 15.



..andy

To email, substitute .nospam with .gl

In message , Andy Hall
writes

[snip praise of technology way beyond the comprehension of most
Plumbers!]

Andy, I didn't realise your MAN Micromat boiler was so clever.
If only the UK industry would drag itself into the 21 century with some
decent control technology. The cost of implementation is next to FA, a
mid-range PIC or similar could do the job for a few quid. Even I could
knock something together in a week or so's work, and I only dabble with
PIC's and software occasionally.
Mind, can you imagine your average Corgi optimising the PID parameters
of the controller

No thought not.


--
Steve

On Sat, 13 Dec 2003 20:23:32 +0000, Steven Briggs wrote:

I glad Andy's pointed out his interpretation of part L, as I did
think I was technically non-compliant having no room stat.

Andy's setup if *very* sophisticated and in the 30th centuary compared
to most heating systems in the UK. I don't doubt that with such a
level of monitoring and control very good effciencies can be achieved
but those levels do not exist on the vast majority of installed
systems.

The test is can the boiler fire to keep itself and/or a small primary
loop warm/hot, if can then then, IMHO, it fails Part L1. There are
many ways, from a simple room stat or flow switch to systems like
Andy's, to achieve the desired result.

--
Cheers
Dave. pam is missing e-mail

On Sat, 13 Dec 2003 19:59:34 +0000, Steven Briggs wrote:

Right now its about 10C outside, ...
snip
... Boiler fires for about one minute in every ten.

And in the summer?

I know you (manually) turn the heating off, but if you don't?

--
Cheers
Dave. pam is missing e-mail

On Sat, 13 Dec 2003 22:24:27 +0000, Steven Briggs
wrote:

In message , Andy Hall
writes

[snip praise of technology way beyond the comprehension of most
Plumbers!]

Andy, I didn't realise your MAN Micromat boiler was so clever.

The controller is manufactured by a Dutch company called Encon who
appear to supply them to a number of German and Dutch condensing
boiler manufacturers. I am not sure whether they also write the
firmware but the copyright notices on the controller and the PC
software to link to it has MAN Heiztechnik and Encon listed. You can
monitor and log all of the inputs and outputs including the
temperatures, pump rate, fan speed (relates to burn rate), motorised
valve outputs and so on.

There are engineer's menus in the PC software for checking faults like
ignition failures, running times, etc. and you can make changes
within limits to some of the operating parameters than can't be
reached from the front panel, but nothing that would compromise
safety.




If only the UK industry would drag itself into the 21 century with some
decent control technology. The cost of implementation is next to FA,

Exactly. I haven't looked in detail at the electronics but it is
not sophisticated in terms of what's on the board.

The mechanical design is good in the sense that the major components
like the pump, condensate drain, heat exchanger and internal pressure
vessel plug onto the back panel and can easily be removed when
necessary. Likewise the materials and build quality are of a very high
standard and I suspect that that is where the main cost is.


a
mid-range PIC or similar could do the job for a few quid. Even I could
knock something together in a week or so's work, and I only dabble with
PIC's and software occasionally.
Mind, can you imagine your average Corgi optimising the PID parameters
of the controller

No thought not.

..andy

To email, substitute .nospam with .gl

Andy Hall wrote:

On Sat, 13 Dec 2003 12:40:45 +0000, The Natural Philosopher
wrote:



Many people here have attempted to educate you on this point. You clearly
do not understand my old chum. So it is best you just take it as it is.

Best stop digging yourself into a deeper hole, my old chum.



No one has actually pointed out where it is said that this is not allowable.




While not wishing to get into a debate about what works and what
doesn't and what is and isn't good practice, I took a look through the
statutory instrument, the approved document to part L1 and some of the
good practice guides. I drew the following conclusions:

- The statutory instrument talks in very general terms about
requirements using words like "reasonable provision" and essentially
empowers the secretary of state to issue Approved Documents which are
not part of the legislation but guidelines..

- In the introduction to the Approved Documents it is stated that they
are guidance.

"Approved Documents are intended to provide
guidance for some of the more common
building situations. However, there may well be
alternative ways of achieving compliance with
the requirements. Thus there is no obligation
to adopt any particular solution contained in
an Approved Document if you prefer to meet
the relevant requirement in some other way."

The last sentence is in heavy type.


- In section 1.37 it states "requirements would be met". If this
document were prescriptive then it would say "requirements shall be
met". Likewise in section 1.38 it says "A way of demonstrating",
not "the way of demonstrating" and "temperature control could be" not
"temperature control must be".
In section 1.41, referring to interlocks the word "should" not "must"
is used.

- In section 1.46, an alternative way of showing compliance is to use
Good Practice Guide 302. This does indeed suggest that room
thermostats be used as part of a boiler interlock arrangement but also
comments on boiler energy management systems as being suitable as
well.


From all of this, I would conclude that room thermostats may be good
practice and used as part of demonstrating compliance with Part L1,
but I can see nothing in the Approved Document that mandates them and
it is certainly a long stretch to say that not having one in a new
installation is specifically illegal.



Thank you Andy.






.andy

To email, substitute .nospam with .gl

Dave Liquorice wrote:

On Sat, 13 Dec 2003 14:02:27 +0000, Andy Hall wrote:


From all of this, I would conclude that room thermostats may be good
practice and used as part of demonstrating compliance with Part L1,
but I can see nothing in the Approved Document that mandates them
and it is certainly a long stretch to say that not having one in a
new installation is specifically illegal.


What they want is the boiler to off, really off, when there is no
demand for heat. There are many ways to comply with this, hence the
"loose" wording of the documents.

Leaving power to the boiler and using the boilers output temperature
stat or return temp stat to switch the boiler off doesn't, IMHO,
comply with Part L1. Basically if the boiler can ever fire without
there being a demand for heat it does not comply.



The boler can never fire without demand for heat if its equipped with a
thermostat. I know of none that are not.

On Sun, 14 Dec 2003 00:47:43 +0000 (GMT), "Dave Liquorice"
wrote:

On Sat, 13 Dec 2003 20:23:32 +0000, Steven Briggs wrote:

I glad Andy's pointed out his interpretation of part L, as I did
think I was technically non-compliant having no room stat.

Andy's setup if *very* sophisticated and in the 30th centuary compared
to most heating systems in the UK. I don't doubt that with such a
level of monitoring and control very good effciencies can be achieved
but those levels do not exist on the vast majority of installed
systems.

Don't forget though that this part of the Building Regulations only
apply when a new boiler is fitted either into an existing property or
a new one.

My description of my own system was by way of illustration more than
anything else.

My conclusion from looking through the Approved Document and the Good
Practice Guide is that they are aimed at practitioners in the trade
who are still installing conventional simple boilers and simple room
stats because a) they understand them and b) they are cheap.

Therefore, given that that is the status quo, the point that struck me
was that the authors are suggesting the marriage of the two as good
practice because realistically that is what is often installed. They
even refer to this as a minimum set of controls. With a simple boiler
firing to full output or off and with simple bimetal thermostats,
short cycle firing as a result of TRVs being virtually closed down is
going to use some amount of energy which can easily be saved by
hooking up a simple room stat.

However, even with a relatively simple modern condensing boiler is
modulating to quite a low level and most that I have seen fire up at a
level according to the amount of heat demand as referenced by the
water temperatures. After all 3kW firing up for a minute once an
hour is actually less than the pump uses.



The test is can the boiler fire to keep itself and/or a small primary
loop warm/hot, if can then then, IMHO, it fails Part L1. There are
many ways, from a simple room stat or flow switch to systems like
Andy's, to achieve the desired result.

My point was really that it strikes me that the Approved Document and
Good Practice Guide make a point about the interlock thing because it
can be easily achieved with what is often still installed today not
that the authors are prescribing what *must* be done.

The legislation requires only that reasonable provision is made to
save energy.

Once modulating and condensing boilers become the norm as it is
suggested that will be the case within two years, the energy to be
saved by interlocking the controls with a room stat is likely to be a
lot less significant to the point where I suspect that using one will
not make a whole lot of difference.

I am assuming here that time controls will indeed remain as they are
which is to fully shut down the boiler and pump (notwithstanding
overrun) when the heating period has finished.

Remember that with burner modulation the heat output goes down to a
few kW to balance the heat loss so the residue of what we would be
talking about would be on days when for *part* of the heating period
boiler heat is required, but because of rising temperatures outside
not for all of it. The number of days a year when that scenario
happens in such a way that a very low burn rate of a few kW once or
twice an hour is too much is very small.
From an engineering standpoint at that stage it becomes very much a
corner case to worry about switching everything off.





..andy

To email, substitute .nospam with .gl

On Sun, 14 Dec 2003 02:03:09 +0000, The Natural Philosopher wrote:

The boler can never fire without demand for heat if its equipped
with a thermostat. I know of none that are not.

Feed a bog standard boiler with mains and tell it it can fire if it
wants to. As it is "cold" it will fire until it's stat says it's hot
then shut down. Yes? Now have you changed the laws of physics such
that this boiler will now *never* *ever* cool below the hysteris point
of it's stat and fire again?

"Demand for heat" does not include keeping itself/small primary loop
warm/hot.

--
Cheers
Dave. pam is missing e-mail

Andy Hall wrote:

On Sun, 14 Dec 2003 00:47:43 +0000 (GMT), "Dave Liquorice"
wrote:


On Sat, 13 Dec 2003 20:23:32 +0000, Steven Briggs wrote:


I glad Andy's pointed out his interpretation of part L, as I did
think I was technically non-compliant having no room stat.

Andy's setup if *very* sophisticated and in the 30th centuary compared
to most heating systems in the UK. I don't doubt that with such a
level of monitoring and control very good effciencies can be achieved
but those levels do not exist on the vast majority of installed
systems.


Don't forget though that this part of the Building Regulations only
apply when a new boiler is fitted either into an existing property or
a new one.

My description of my own system was by way of illustration more than
anything else.

My conclusion from looking through the Approved Document and the Good
Practice Guide is that they are aimed at practitioners in the trade
who are still installing conventional simple boilers and simple room
stats because a) they understand them and b) they are cheap.


I think that is precisely the case.



Therefore, given that that is the status quo, the point that struck me
was that the authors are suggesting the marriage of the two as good
practice because realistically that is what is often installed. They
even refer to this as a minimum set of controls. With a simple boiler
firing to full output or off and with simple bimetal thermostats,
short cycle firing as a result of TRVs being virtually closed down is
going to use some amount of energy which can easily be saved by
hooking up a simple room stat.

However, even with a relatively simple modern condensing boiler is
modulating to quite a low level and most that I have seen fire up at a
level according to the amount of heat demand as referenced by the
water temperatures. After all 3kW firing up for a minute once an
hour is actually less than the pump uses.



Precisely.

The issue is 'conservation of heat and power'.

The modve away from single stat installations to TRV'ed installations is
there to reduce unwanted heating of unused or little used rooms, and
allow better control of house temperature. The gains are potentially
considerable.

Keeping a single stat is a complete nonsense, excepat in the one case
mentioned - some idiot who runs his heating in the summer. In which case
one would likley set the stat above the level where it would ever come
on in winter, to make sure the TRV'sd actually do their work.

The short bypass loop TRV solution is IMHO arguably better than no
TRV's, and in practice no worse than a single stat would up - and indeed
may be better, because if the single stat is wound up with no bypass,
the bloody pump will stall.

I am not aware how the flow swiych thing actually works, because no one
has explanied how the flow switch senses deamand when the pump is
stopped. And if it simply cuts the boiler, not the pump as it were, then
its no different from using the boiler internal stat.




The test is can the boiler fire to keep itself and/or a small primary
loop warm/hot, if can then then, IMHO, it fails Part L1. There are
many ways, from a simple room stat or flow switch to systems like
Andy's, to achieve the desired result.


My point was really that it strikes me that the Approved Document and
Good Practice Guide make a point about the interlock thing because it
can be easily achieved with what is often still installed today not
that the authors are prescribing what *must* be done.

The legislation requires only that reasonable provision is made to
save energy.


Precsiely. In the same way that I was able to install single glazing in
a new build, by demonstrating overall energy efficiency.

The spirit of the regulations is to avoid uncessary boiler firing, not
uneccessary pump action. Addong a single stat doesn't do anythung ecept
in the case where the whole house is already warmer than the heating
could actually make it, and the bozo has left the heating on..



Once modulating and condensing boilers become the norm as it is
suggested that will be the case within two years, the energy to be
saved by interlocking the controls with a room stat is likely to be a
lot less significant to the point where I suspect that using one will
not make a whole lot of difference.

I am assuming here that time controls will indeed remain as they are
which is to fully shut down the boiler and pump (notwithstanding
overrun) when the heating period has finished.

Remember that with burner modulation the heat output goes down to a
few kW to balance the heat loss so the residue of what we would be
talking about would be on days when for *part* of the heating period
boiler heat is required, but because of rising temperatures outside
not for all of it. The number of days a year when that scenario
happens in such a way that a very low burn rate of a few kW once or
twice an hour is too much is very small.
From an engineering standpoint at that stage it becomes very much a
corner case to worry about switching everything off.



Yup.
All I can say is that teh gains from 'single stat in the kitchen' to
'all TRV's and turn teh stat up to max' were significant for me. It
wasn;t ideal, but it worked pretty well for a few years.

I couldn't even use a single stat on my fan heaters now, because they
heating requirements for each room and the heat flow between then is far
too complex. AND they don't shut the flow down, because the stats
control the fans, not the flow, unlike TRV's.

One does the best one can with available technology.

Ideally one would have a stat in every room, and a zone valve, and some
temp sensors outside...and build a bigger version of what my car has -
they call it 'climate control - but as yet, no one makes such a control
box.

The cost to me to install, to save a piddly 50 quid of oil a year, would
be immense. Not least in terms of wioring, which would be equivalent to
a complete new lighting installation in complexity. Better savings are
assured by simply turning the whole heating system off when not
required. when I need heat, I simply slap the system on, overriding the
time clocks, and in summer its set to 'always off' and I simply punch it
on when the odd cold day turns up.








.andy

To email, substitute .nospam with .gl

Andy Hall wrote in message ...
You may want to think about using a radio linked room stat. These
have the advantage that apart from not needing to be wired all the
way, you can try different locations until happy with the results.
The sensor/control piece is battery powered and the receiver is fitted
near the boiler.
Interesting idea.Thanks.

Dave Liquorice wrote:

On Sun, 14 Dec 2003 02:03:09 +0000, The Natural Philosopher wrote:


The boler can never fire without demand for heat if its equipped
with a thermostat. I know of none that are not.


Feed a bog standard boiler with mains and tell it it can fire if it
wants to. As it is "cold" it will fire until it's stat says it's hot
then shut down. Yes? Now have you changed the laws of physics such
that this boiler will now *never* *ever* cool below the hysteris point
of it's stat and fire again?



A boiler that never ever fires again may meet your interpretation of the
regulations, but is likley to be of little use heating the house over
the winter..

A thermostat that is set high enough to allow all rooms to reach TRV
temperatures will almost certainly never cut the boiler pump off at all.

In short, its all ********. In practice, the house stat does nothing
anyway, except add further complexity and render th euse of the TRV's
relatively pointless.


"Demand for heat" does not include keeping itself/small primary loop
warm/hot.


Why not? a modulating boiler does that anyway in a sense.
Anyway, in all cases, I have suggested the optimium strategy is a
radiator in an airing cupboard or bathroom, un regulated.

You are so hung up on THEOY that teh practical issues appear to elude
you. No one runs CH when there is no need. Its on because the house is
cold. If its cold, it needs heating, and will CONTINUE TO NEED HEATING.

The odd theoretical case where the heating has been left on on a putrid
hot summers evening will be quickly corrected by the occupant.

A far more easily learnt activity than setting a house stat to
PRECISDE:Y the temperature required so that it cuts out once every room
has reached its desired temperature, as determined by a host of
independently adjustable TRV's, open windows, drughts, interconnecting
doors etc etc?

No. Its ********. There is no practical way to get a house stat set so
that it isn't either stopping heating before rooms are adeqauetely hot,
or never cuttting out at all.

"Steven Briggs" wrote in message
...
In message , Dave
Liquorice writes
On Sat, 13 Dec 2003 14:02:27 +0000, Andy Hall wrote:

From all of this, I would conclude that room thermostats may be good
practice and used as part of demonstrating compliance with Part L1,
but I can see nothing in the Approved Document that mandates them
and it is certainly a long stretch to say that not having one in a
new installation is specifically illegal.

What they want is the boiler to off, really off, when there is no
demand for heat. There are many ways to comply with this, hence the
"loose" wording of the documents.

Leaving power to the boiler and using the boilers output temperature
stat or return temp stat to switch the boiler off doesn't, IMHO,
comply with Part L1. Basically if the boiler can ever fire without
there being a demand for heat it does not comply.


Unless the outside temperature is maybe 15C +, there is continuous heat
loss from the house, therefore continuous heat demand. I glad Andy's
pointed out his interpretation of part L, as I did think I was
technically non-compliant having no room stat.

(I take 15C arbitrarily, the sort of the outside temp I would turn the
system off anyway. Other heat sources, people, TV's, cooking, solar gain
etc can be enough to keep the house comfortable)

That depends on how much the house is insulated and draught free. You could
fit an outside stat in a weatherproof box on the north wall. When above 15C
(in your case) the heating is off. Then you have an interlock.


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"The Natural Philosopher" wrote in message
...
Andy Hall wrote:

I am not aware how the flow swiych thing actually works, because no one
has explanied how the flow switch senses deamand when the pump is
stopped. And if it simply cuts the boiler, not the pump as it were, then
its no different from using the boiler internal stat.

It requires the pump to turn to see if a TRV has opened up giving flow. A
simplr timer can do this once every minute or so.



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"Steven Briggs" wrote in message
news
In message , Andy Hall
writes

[snip praise of technology way beyond the comprehension of most
Plumbers!]

Andy, I didn't realise your MAN Micromat boiler was so clever.
If only the UK industry would drag itself into the 21 century with some
decent control technology. The cost of implementation is next to FA, a
mid-range PIC or similar could do the job for a few quid. Even I could
knock something together in a week or so's work, and I only dabble with
PIC's and software occasionally.

Very few condensing boiler now do not have load compensation control, at
modulates the burner. The problems is that when you want full output at all
times, as when heating a thermals tore or quick recovery cylinder, most
can't do it. Some boilers do have terminals that when switched the
modulation is turned on or off. Some boilers, the Baxi is one and see
current thread on this, can either be full power or modulate, by only be
removing 3 jumpers from the control board.

Mind, can you imagine your average Corgi optimising the PID parameters
of the controller

Not in a million years. They need idiot proof controls. This is where well
specced combi's score well. They thinking is done for them and they just
connect up the pipes.

No thought not.



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"The Natural Philosopher" wrote in message
...
Dave Liquorice wrote:

On Sat, 13 Dec 2003 14:02:27 +0000, Andy Hall wrote:


From all of this, I would conclude that room thermostats may be good
practice and used as part of demonstrating compliance with Part L1,
but I can see nothing in the Approved Document that mandates them
and it is certainly a long stretch to say that not having one in a
new installation is specifically illegal.


What they want is the boiler to off, really off, when there is no
demand for heat. There are many ways to comply with this, hence the
"loose" wording of the documents.

Leaving power to the boiler and using the boilers output temperature
stat or return temp stat to switch the boiler off doesn't, IMHO,
comply with Part L1. Basically if the boiler can ever fire without
there being a demand for heat it does not comply.

The boler can never fire without demand for heat if its equipped with a
thermostat. I know of none that are not.

You are confused.


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"Dave Liquorice" wrote in message
. 1...
On Sun, 14 Dec 2003 02:03:09 +0000, The Natural Philosopher wrote:

The boler can never fire without demand for heat if its equipped
with a thermostat. I know of none that are not.

Feed a bog standard boiler with mains and tell it it can fire if it
wants to. As it is "cold" it will fire until it's stat says it's hot
then shut down. Yes? Now have you changed the laws of physics such
that this boiler will now *never* *ever* cool below the hysteris point
of it's stat and fire again?

"Demand for heat" does not include keeping itself/small primary loop
warm/hot.

Or heating the outside air when heat floats through the flue when off.


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"fred" wrote in message ...
In article , IMM abuse-
writes
It needs one by law.

Another drama queen . . . . .

Do you mean it doesn't?

I wasn't an arrestable offence the last time I checked. It is however
required
by a legally enforceable statutory instrument, hardly meriting the
dramatic
description along with rape, murder or even carrying out gas work when not
being a competent person.

Gosh!


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"The Natural Philosopher" wrote in message
...
Dave Liquorice wrote:

On Sun, 14 Dec 2003 02:03:09 +0000, The Natural Philosopher wrote:

The boler can never fire without demand for heat if its equipped
with a thermostat. I know of none that are not.

Feed a bog standard boiler with mains and tell it it can fire if it
wants to. As it is "cold" it will fire until it's stat says it's hot
then shut down. Yes? Now have you changed the laws of physics such
that this boiler will now *never* *ever* cool below the hysteris point
of it's stat and fire again?

A boiler that

.....he digeth much bigger hole for himselfeth...


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On Sun, 14 Dec 2003 16:15:04 -0000, "IMM" wrote:


"Steven Briggs" wrote in message
news
In message , Andy Hall
writes

[snip praise of technology way beyond the comprehension of most
Plumbers!]

Andy, I didn't realise your MAN Micromat boiler was so clever.
If only the UK industry would drag itself into the 21 century with some
decent control technology. The cost of implementation is next to FA, a
mid-range PIC or similar could do the job for a few quid. Even I could
knock something together in a week or so's work, and I only dabble with
PIC's and software occasionally.

Very few condensing boiler now do not have load compensation control, at
modulates the burner. The problems is that when you want full output at all
times, as when heating a thermals tore or quick recovery cylinder, most
can't do it. Some boilers do have terminals that when switched the
modulation is turned on or off. Some boilers, the Baxi is one and see
current thread on this, can either be full power or modulate, by only be
removing 3 jumpers from the control board.

All of which is very disappointing. If the boiler is going to have
a board of electronics with a microprocessor to read the temperatures
and control the modulation, then with virtually zero extra cost it
could directly monitor the cylinder temperature or cylinder stat and
operate the motorised valve. Given that, the boiler could be wound
up to full power for the hot water/thermal store cycle and back down
to modulating for the heating circuit when this is complete. All of
this can be accomplished with the controls available today, and simple
ones at that. In an existing property, there is almost certainly
wiring that will handle it all as well.





Mind, can you imagine your average Corgi optimising the PID parameters
of the controller

Not in a million years. They need idiot proof controls. This is where well
specced combi's score well. They thinking is done for them and they just
connect up the pipes.

No thought not.



---

..andy

To email, substitute .nospam with .gl

"Andy Hall" wrote in message
...
On Sun, 14 Dec 2003 16:15:04 -0000, "IMM" wrote:


"Steven Briggs" wrote in
message
news
In message , Andy Hall
writes

[snip praise of technology way beyond the comprehension of most
Plumbers!]

Andy, I didn't realise your MAN Micromat boiler was so clever.
If only the UK industry would drag itself into the 21 century with some
decent control technology. The cost of implementation is next to FA, a
mid-range PIC or similar could do the job for a few quid. Even I could
knock something together in a week or so's work, and I only dabble with
PIC's and software occasionally.

Very few condensing boiler now do not have load compensation control, at
modulates the burner. The problems is that when you want full output at
all
times, as when heating a thermals tore or quick recovery cylinder, most
can't do it. Some boilers do have terminals that when switched the
modulation is turned on or off. Some boilers, the Baxi is one and see
current thread on this, can either be full power or modulate, by only be
removing 3 jumpers from the control board.

All of which is very disappointing. If the boiler is going to have
a board of electronics with a microprocessor to read the temperatures
and control the modulation, then with virtually zero extra cost it
could directly monitor the cylinder temperature or cylinder stat and
operate the motorised valve. Given that, the boiler could be wound
up to full power for the hot water/thermal store cycle and back down
to modulating for the heating circuit when this is complete.

That is the idea. Some boilers have this function, but only a few.

All of this can be accomplished with
the controls available today, and simple
ones at that. In an existing property, there is almost certainly
wiring that will handle it all as well.

One way of fooling the boiler to ramp up to full power, is to parallel up
two wires from the return pipe thermostat temp sensor at the terminals at
the board. Find out what temps = what resistance. Then switch over to
either full resistance or none, whichever tells the board that the return
temp is cool when it isn't. Then the boiler us full on, and should not
interfere with the control logic of the safety circuitry. But the makers
would probably not like this.



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On Sat, 13 Dec 2003 22:24:27 +0000, Steven Briggs wrote:

In message , Andy Hall
writes

[snip praise of technology way beyond the comprehension of most
Plumbers!]

Andy, I didn't realise your MAN Micromat boiler was so clever.
If only the UK industry would drag itself into the 21 century with some
decent control technology. The cost of implementation is next to FA, a
mid-range PIC or similar could do the job for a few quid. Even I could
knock something together in a week or so's work, and I only dabble with
PIC's and software occasionally.
Mind, can you imagine your average Corgi optimising the PID parameters
of the controller


Right now most of the combi market have modulating burners and some sort
of anti-short cycling control as standard, so do all most condensing
models and many system boilers.
Installing middling and low tech boiler which only just scrape into Part L
compliance is not part of my game. (Eg. potterton Profile 'L'/Kingfisher
IIs etc)

In one or two installs for older people I have not tried to upgrade to a
programmable thermostat because user confusion would undoubtedly cost more
energy (mine and my van's fuel) that what it might save.
However these installs have most/all TRVs and a boiler with in built
anticycling controls.

--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at www.diyfaq.org.uk
Gas fitting FAQ http://www.makewrite.demon.co.uk/GasFitting.html
Sealed CH FAQ http://www.makewrite.demon.co.uk/SealedCH.html

On Sun, 14 Dec 2003 16:57:44 +0000, Andy Hall wrote:

On Sun, 14 Dec 2003 16:15:04 -0000, "IMM" wrote:


"Steven Briggs" wrote in message
news
In message , Andy Hall
writes

[snip praise of technology way beyond the comprehension of most
Plumbers!]

Andy, I didn't realise your MAN Micromat boiler was so clever.
If only the UK industry would drag itself into the 21 century with some
decent control technology. The cost of implementation is next to FA, a
mid-range PIC or similar could do the job for a few quid. Even I could
knock something together in a week or so's work, and I only dabble with
PIC's and software occasionally.

Very few condensing boiler now do not have load compensation control, at
modulates the burner. The problems is that when you want full output at all
times, as when heating a thermals tore or quick recovery cylinder, most
can't do it. Some boilers do have terminals that when switched the
modulation is turned on or off. Some boilers, the Baxi is one and see
current thread on this, can either be full power or modulate, by only be
removing 3 jumpers from the control board.

All of which is very disappointing. If the boiler is going to have
a board of electronics with a microprocessor to read the temperatures
and control the modulation, then with virtually zero extra cost it
could directly monitor the cylinder temperature or cylinder stat and
operate the motorised valve. Given that, the boiler could be wound
up to full power for the hot water/thermal store cycle and back down
to modulating for the heating circuit when this is complete. All of
this can be accomplished with the controls available today, and simple
ones at that. In an existing property, there is almost certainly
wiring that will handle it all as well.


Andy, the Baxi Barcelona is _such_ a poor design no ammount of tinkering
with the electronics could redeem it.

I went to one the other week:
The customer was reporting smell of un/burnt gas/gas fumes in their
utility room. Turned out the the drain plug on the condensate trap had
split in half and was hanging off. Damp flue gasses were filling the room.
[How the f**k did they manage to get CE or GC type approval?]
There was no water on the floor because these boilers don't actually
produce condensate, which is just aswell since when they do (at start up)
it finds it way out by every route _except_ the trap.

Such boilers (chosen by a large installation company) have held/put back
the industry many years.



--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at www.diyfaq.org.uk
Gas fitting FAQ http://www.makewrite.demon.co.uk/GasFitting.html
Sealed CH FAQ http://www.makewrite.demon.co.uk/SealedCH.html

On Sun, 14 Dec 2003 11:14:42 +0000, Dave Liquorice wrote:

On Sun, 14 Dec 2003 02:03:09 +0000, The Natural Philosopher wrote:

The boler can never fire without demand for heat if its equipped
with a thermostat. I know of none that are not.

Feed a bog standard boiler with mains and tell it it can fire if it
wants to. As it is "cold" it will fire until it's stat says it's hot
then shut down. Yes? Now have you changed the laws of physics such
that this boiler will now *never* *ever* cool below the hysteris point
of it's stat and fire again?

"Demand for heat" does not include keeping itself/small primary loop
warm/hot.


One of the things that so far as I known nobody has yet mentioned is the
nature of the boiler that is being controlled.

With a fanned flued boiler when the burner cuts the heat exchanger is in a
box which is fairly well insulated.

With a conventional or balanced flue boiler the heat exchanger then
becomes a radiator fitted on the outside of the house through which
the pump is pushing hot water!

--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at www.diyfaq.org.uk
Gas fitting FAQ http://www.makewrite.demon.co.uk/GasFitting.html
Sealed CH FAQ http://www.makewrite.demon.co.uk/SealedCH.html

On Sun, 14 Dec 2003 18:52:12 +0000, "Ed Sirett"
wrote:



Andy, the Baxi Barcelona is _such_ a poor design no ammount of tinkering
with the electronics could redeem it.

I went to one the other week:
The customer was reporting smell of un/burnt gas/gas fumes in their
utility room. Turned out the the drain plug on the condensate trap had
split in half and was hanging off. Damp flue gasses were filling the room.
[How the f**k did they manage to get CE or GC type approval?]
There was no water on the floor because these boilers don't actually
produce condensate, which is just aswell since when they do (at start up)
it finds it way out by every route _except_ the trap.

Such boilers (chosen by a large installation company) have held/put back
the industry many years.

I'm amazed by this.

Clearly whoever designed this or more realistically selected the off
the shelf components for it just didn't pay attention to detail.

I would have thought that since the prime requirement is safety, any
component that is, in effect in the flue pathway or can become so,
should be thoroughly checked for suitability. Probably this
component has a cost of a penny or two.

In looking through manufacturer installation guides when boiler
selecting I found one (can't remember who now) who has the electronics
board near the top of the appliance close to the heat exchanger.
Great idea for reliability.

I was distinctly underwhelmed by the build quality of the Glow Worm
Fuelsaver that I had before the present boiler. After removing the
inside cover around the burner to replace the thermocouple, the
remaining metalwork has razor sharp edges and corners.
That's just sloppiness and there is no excuse for it.

Clearly the manufacturers are not employing the best from the
engineering profession......




..andy

To email, substitute .nospam with .gl

In message , Dave
Liquorice writes
On Sat, 13 Dec 2003 19:59:34 +0000, Steven Briggs wrote:

Right now its about 10C outside, ...
snip
... Boiler fires for about one minute in every ten.

And in the summer?

I know you (manually) turn the heating off, but if you don't?

Er yeah. Run times are gradually reduced as the weather warms up, then
its off ~May to ~October. But being a tight Yorkshireman I wouldn't be
leaving the heating running unnecessarily anyway
The 1 hour boost button does the job on the old cold day.

--
Steve

On Sun, 14 Dec 2003 14:13:12 +0000, The Natural Philosopher wrote:

The boler can never fire without demand for heat if its equipped
with a thermostat. I know of none that are not.

Feed a bog standard boiler with mains and tell it it can fire if it
wants to. As it is "cold" it will fire until it's stat says it's
hot then shut down. Yes? Now have you changed the laws of physics
such that this boiler will now *never* *ever* cool below the
hysteris point of it's stat and fire again?

A boiler that never ever fires again may meet your interpretation of
the regulations, but is likley to be of little use heating the house
over the winter..

Read what I wrote "...tell it it can fire if it wants to." As an
example only, the control line from the external systems is
permanently in "heat demand". In a real installation that control line
would reflect the demand for heat and thus when the boiler cooled it
would not fire "just because it can" provided there was no demand for
heat.

A thermostat that is set high enough to allow all rooms to reach TRV
temperatures will almost certainly never cut the boiler pump off at
all.

Who said anything about TRVs the crux of the matter is not letting the
boiler fire unless there is a demand for heat. How that "demand for
heat" is determined is very much open to design and interpretation.

"Demand for heat" does not include keeping itself/small primary
loop warm/hot.

Why not?

Because you are keeping something hot that doesn't need to be hot.
Thus burning fuel you don't need to burn and therfore reducing overall
effciency.

No one runs CH when there is no need.

I wouldn't like to put any money on that.

Its on because the house is cold. If its cold, it needs heating, and
will CONTINUE TO NEED HEATING.

Yes and the control system will signal the boiler when heat is
required.

The odd theoretical case where the heating has been left on on a
putrid hot summers evening will be quickly corrected by the
occupant.

Maybe, maybe not. I can't be arsed to dig out the documentation to see
if the interlock has to be automatic or if manual will suffice and
certainly not to maintain an argument with someone who is not prepared
to read properly or think beyond their own little world.

Suffice to say that if a manual interlock satisfies Part L1 then it's
not worth the paper it's written on.

No. Its ********. There is no practical way to get a house stat set
so that it isn't either stopping heating before rooms are
adeqauetely hot, or never cuttting out at all.

Works pretty well here considering the draftiness of the window
frames, the gales outside, lack of insulation and the variable sizing
of rads (some huge for the room some tiny). I'm sure it will improve
as those "features" are corrected.

--
Cheers
Dave. pam is missing e-mail

In article , The Natural Philosopher
writes
BillP wrote:

"stuart noble" wrote in message
...

snip


If the room stat has been removed, the installation does not meet the
minimum requirements of Part L building regs.





Can you show me exactly where this is stated?

My Part L building regulations have no mention of use of thermostats
beyond stating thet either TRV's or other thermostats should be used.

Ther is no issue with teh boiler running continuously. Boilers stop when
their own internal stats detect the return flow is up to temperature.


I seen no reaosn to install flow switches unless too simply protect the
pump...but a bypass loop does that anyway. Also how does the system
detect the condition when a TRV has opened up? It can't unless teh pump
is switched on to check flow rate...

There seems to be an urban myth here.


With a TRV system, the idea is to pump more or less continuously, and
let the TRV's decide on demand. The boiler merely cuts in when the
return flow has dropped to the boiler stat level.

Use of TRV's with an overall zone stat makes them essentially useless.
Either they are still demanding heat when the main stat cuts out, or
they have shutdown before it itself does, in which case it never
does.... you cannot have a romm or area controlled by two stats on
essentally the same zone.

With all due respect, you and Christian are talking what appears to be
twaddle.





Try www.gasman.fsbusiness.co.uk/controls - seems to have a lot a
diagrams courtesy of JAG++

--
Andrew

On Sun, 14 Dec 2003 23:31:24 +0000, Andrew
wrote:




Try www.gasman.fsbusiness.co.uk/controls - seems to have a lot a
diagrams courtesy of JAG++

I think that the link should be

http://www.gasman.fsbusiness.co.uk/controls.htm

I like the JAG++ label by the way. Very subtle, unlike its object.

This is not high quality information.

There are some notable errors in the text:

"Since April 2002 it is mandatory as part of the Building regulations
that all new and updated systems have a room thermostat fitted
preferably in the main living area and in a room with a radiator and
no other source of heat"

It is not mandatory, it is only recommended as good practice.

The text in this also takes a very simplistic view of boiler operation
and assumes one with a simple on/off input control that is
non-modulating.

"This is because once all the rooms are up to temperature all the
TRV's will be closed, but your boiler will still be producing heat at
about 78 deg °C."

This would only be true for a non modulating boiler.

"If you have a condensing boiler then do not fit too many TRV's,
usually no more than a third of all radiators, as they will reduce the
high efficiency of the boiler"

This is utter garbage.

"This also shows the actual size difference between 15mm and 8 mm
which is why Small Bore (15mm) systems will always be better than
Micro-Bore (8mm) as far grater volumes of water can pass through 15mm
making the boiler work more efficantly making it more reliable"

This is also utter garbage.

The pasted in documents towards the bottom of the page are not from
JAG++ at all, they are from TACMA, the Association of Controls
Manufacturers. Unsurprisingly, they propose a long list of controls
but at least mention in passing that there are other ways.

If the shoddy plumbing job with the motorised valves half way down the
page is an indication of their best practice, I am not impressed.




..andy

To email, substitute .nospam with .gl

No one runs CH when there is no need.

Basically, you are proposing to use yourself as the room thermostat, by
manually turning off the heating when it isn't needed. However, systems
should be installed to be operated by less diligent people. The room
thermostat turns off the system for other people.

Its on because the house is cold. If its cold, it needs
heating, and will CONTINUE TO NEED HEATING.

No it won't. It might come on at 7am, with the timer and stay on until 11am,
when the outside temperature has risen on this fine winter's day and there
is plenty of solar gain. Then, around 5pm, it starts getting nippy again, so
the boiler fires up again. Of course, you may propose your manual controls
such that you have to notice every day and turn the thing on and off.
Myself, I prefer to get electronic equipment to do this for me.

Christian.

The legislation does not support that level of detail. That is
not to say that implementing a room thermostat is not a good
practice, but I can find nothing more than a recommendation
suggesting that one is a good idea.

Although the approved documents propose methods that are not totally set in
stone, you still have to implement a suitable level of compliance to the
original intent. If the approved document says that you need a boiler
interlock, then you can implement a system without one provided you can
prove with calculation or measurement that your alternative system has the
equivalent level of safety/energy efficiency or whatever. I don't see anyone
proposing to install joists with less that those specified in the approved
documents without further calculation. There are plenty more approved
documents with suggestions that no-one would contemplate breaking, so why
are people thinking that Part L1 is optional. No-one states that the SEDBUK
'D' boiler restriction in Part L is optional, so why the interlock? Yes, the
approved documents are optional. No, you can't just ignore their contents
without implementing their intent in another way.

In order to get the building regulations approval, you need to get your
alternative system examined and passed by the building control department.

In my mind the question is, what constitutes a demand for
heat? TRVs typically reduce the flow to radiators rather
than closing it off completely (...)

I would suggest that mostly closed off TRVs are still counted as a demand
for heat. However, there are situations when there is absolutely no demand
for heat. This can occur during the middle of the day in marginal
conditions, or in the summer. The control systems should be sufficient to
prevent boiler firing during these times. You can't rely on some spod to do
it for you (who may have limited mobility or understanding of the system),
when it can be done so easily by electronics.

Christian.

From an engineering standpoint at that stage it becomes very much
a corner case to worry about switching everything off.

Yes, but this requires the occupant to turn the heating off depending on the
weather/time of year (and many people won't). Why bother requiring the user
to do this, when a simple electronic device can do it for them. with proper
controls, you can leave your heating on 365 days a year without energy
wastage. Many people do.

In any case, I really don't see the problem with adding an interlock to a
TRV based system. Just put a flow switch after the bypass/always on radiator
and have it cut the boiler demand power. Set the pump to run for programmer
CH on. Job done.

The legislation requires only that reasonable provision is made to
save energy.

I would be surprised if the court (or building control department) decided
that a reasonable provision is a system described in the approved document
with an important feature missing. OK, a totally different system not
directly comparable, but not a suggested system made less efficient. The
approved document describes a suitable simple modification to an all TRV
system that seems perfectly reasonable, reliable and easy to implement and
prevents the wastage of energy.

Christian.