Hi,

I'm trying to further my understanding of my central heating system. I
have read the various FAQ's in this forum but one question I have.

My system is the 'classic' fully pumped gas fired system with a hot
water tank. One radiator is in the HW circuit as a fail safe, along
with some towel rails, to warm them in summer even though the main CH
system may be off.

My Question is when the timer has both CH & HW on, how is this
conflict resolved. Does the controller prioritise HW, or is the switch
in a Tee position where it routes the water from the boiler to both HW
& CH ? IS HW only selected when the CH is OFF i.e in the summer ? I
tend to rely on a timer stat so my CH is always ON and I allow the
programmable stat to determine when the pump gets enabled

My tank has a moulded foam insulation plus an additional lagging
jacket. I'm finding in cold weather the house takes a long time to get
up to desired temperature, if at all. While this may be affected by
insulation etc, I wonder if the conflicting requirements of HW & CH
reduce the responsiveness. perhaps I should schedule HW much earlier
in the day and rely on good tank insulation to keep it hit until
evening ?

"jives11" wrote in message
...

Hi,

I'm trying to further my understanding of my central heating system. I
have read the various FAQ's in this forum but one question I have.

My system is the 'classic' fully pumped gas fired system with a hot
water tank. One radiator is in the HW circuit as a fail safe, along
with some towel rails, to warm them in summer even though the main CH
system may be off.

My Question is when the timer has both CH & HW on, how is this
conflict resolved. Does the controller prioritise HW, or is the switch
in a Tee position where it routes the water from the boiler to both HW
& CH ?

Yes

IS HW only selected when the CH is OFF i.e in the summer ? I

Yes

tend to rely on a timer stat so my CH is always ON and I allow the
programmable stat to determine when the pump gets enabled

My tank has a moulded foam insulation plus an additional lagging
jacket. I'm finding in cold weather the house takes a long time to get
up to desired temperature, if at all. While this may be affected by
insulation etc, I wonder if the conflicting requirements of HW & CH
reduce the responsiveness.

Yes

perhaps I should schedule HW much earlier
in the day and rely on good tank insulation to keep it hit until
evening ?

Yes or have HW on all the time (if tank well insulated)


--
Bob Mannix
(anti-spam is as easy as 1-2-3 - not)

In article ,
jives11 writes:

Hi,

I'm trying to further my understanding of my central heating system. I
have read the various FAQ's in this forum but one question I have.

My system is the 'classic' fully pumped gas fired system with a hot
water tank. One radiator is in the HW circuit as a fail safe, along
with some towel rails, to warm them in summer even though the main CH
system may be off.

My Question is when the timer has both CH & HW on, how is this
conflict resolved. Does the controller prioritise HW, or is the switch
in a Tee position where it routes the water from the boiler to both HW
& CH ? IS HW only selected when the CH is OFF i.e in the summer ? I
tend to rely on a timer stat so my CH is always ON and I allow the
programmable stat to determine when the pump gets enabled

It depends on how the system was designed and installed.
If you have a mid-position valve selecting heating and hot
water (which is probably most common), then the system can
do both together. If you have a prioritsed system, then hot
water gets priority as it takes a finite time to heat up,
which is usually less than it takes for you to notice the
house cooling down.

My tank has a moulded foam insulation plus an additional lagging
jacket. I'm finding in cold weather the house takes a long time to get
up to desired temperature, if at all. While this may be affected by
insulation etc, I wonder if the conflicting requirements of HW & CH
reduce the responsiveness. perhaps I should schedule HW much earlier
in the day and rely on good tank insulation to keep it hit until
evening ?

My H/W tank is heated from 05:00 to 05:30 each day. That
easily lasts a day unless I have several visitors. I have
a button to heat it for another half hour on demand in
such cases. If there's only me in the house, it lasts
the following day too.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

In an earlier contribution to this discussion,
jives11 wrote:

Hi,

I'm trying to further my understanding of my central heating system. I
have read the various FAQ's in this forum but one question I have.

My system is the 'classic' fully pumped gas fired system with a hot
water tank. One radiator is in the HW circuit as a fail safe, along
with some towel rails, to warm them in summer even though the main CH
system may be off.

My Question is when the timer has both CH & HW on, how is this
conflict resolved. Does the controller prioritise HW, or is the switch
in a Tee position where it routes the water from the boiler to both HW
& CH ? IS HW only selected when the CH is OFF i.e in the summer ? I
tend to rely on a timer stat so my CH is always ON and I allow the
programmable stat to determine when the pump gets enabled


You haven't really told us enough to be able to answer that question. There
are several flavours of 'classic' systems, and they all behave slightly
differently. Have a look at
http://content.honeywell.com/uk/homes/systems.htm and try to work out which
'plan' you have. [It won't be C-Plan but it could be either S-Plan, W-Plan
or Y-Plan depending on the number and type of motorised valves present.]

A W-Plan system will heat *either* the HW *or* the CH, but not both at the
same time. If both are calling for heat, the CH demand gets suppressed until
the HW is hot. The other 2 plans can heat both the HW and the CH at the same
time, usually with equal priority.

My tank has a moulded foam insulation plus an additional lagging
jacket. I'm finding in cold weather the house takes a long time to get
up to desired temperature, if at all. While this may be affected by
insulation etc, I wonder if the conflicting requirements of HW & CH
reduce the responsiveness. perhaps I should schedule HW much earlier
in the day and rely on good tank insulation to keep it hit until
evening ?

A well insulated cylinder will keep the water hot for many hours, so you
don't have to heat it immediately before using it. If you have a
programmable stat on the CH, use that to time the CH (with CH on the main
programmer set to 'constant', and use the main programmer to time just the
HW - at a different time from when the CH is on.
--
Cheers,
Roger
______
Email address maintained for newsgroup use only, and not regularly
monitored.. Messages sent to it may not be read for several weeks.
PLEASE REPLY TO NEWSGROUP!

On Tue, 11 Mar 2008 06:12:34 -0700, jives11 wrote:

Hi,

I'm trying to further my understanding of my central heating system. I
have read the various FAQ's in this forum but one question I have.

My system is the 'classic' fully pumped gas fired system with a hot
water tank. One radiator is in the HW circuit as a fail safe, along with
some towel rails, to warm them in summer even though the main CH system
may be off.

My Question is when the timer has both CH & HW on, how is this conflict
resolved.

Good Q.

Does the controller prioritise HW, or is the switch in a Tee
position where it routes the water from the boiler to both HW & CH ? IS
HW only selected when the CH is OFF i.e in the summer ? I tend to rely
on a timer stat so my CH is always ON and I allow the programmable stat
to determine when the pump gets enabled

Systems can either the one-or-the other using a 3-way diverter valve or
both together if needed using a mid-way capable valve.

Older installations tend to have mid-way valves (Y-plan). More modern
ones ave diverter valves (W-plan) or more likely 2(or more) 2-port valves
(S-plan/extended S-plan).

What happens during both HW+CH demands depends on how the system was
installed. even with a mid-way valve the system may still effectively
prioritize the HW tank. The modern idea is that the HW cylinder can be
reheated very quickly typically (10-15 minutes for a bath full) and so
the house heating can be switched off while the HW cylinder is reheated.


My tank has a moulded foam insulation plus an additional lagging jacket.
Fine.
I'm finding in cold weather the house takes a long time to get up to
desired temperature, if at all. While this may be affected by insulation
etc, I wonder if the conflicting requirements of HW & CH reduce the
responsiveness.
Possibly.
Test 1. does the system heat the house when the HW is switched off?
perhaps I should schedule HW much earlier in the day and
rely on good tank insulation to keep it hit until evening ?

If the tank has a thermostat then it should only take a small proprtion
of the time to do HW.

There are dozens of reason why the heating is not adequate, HW coil short
circuiting the HC probably does not make the top 5.

--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at http://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
Choosing a Boiler FAQ http://www.makewrite.demon.co.uk/BoilerChoice.html

On 11 Mar, 14:55, "Roger Mills" wrote:
In an earlier contribution to this discussion,



jives11 wrote:
Hi,

I'm trying to further my understanding of my central heating system. I
have read the various FAQ's in this forum but one question I have.

My system is the 'classic' fully pumped gas fired system with a hot
water tank. One radiator is in the HW circuit as a fail safe, along
with some towel rails, to warm them in summer even though the main CH
system may be off.

My Question is when the timer has both CH & HW on, how is this
conflict resolved. Does the controller prioritise HW, or is the switch
in a Tee position where it routes the water from the boiler to both HW
& CH ? IS HW only selected when the CH is OFF i.e in the summer ? I
tend to rely on a timer stat so my CH is always ON and I allow the
programmable stat to determine when the pump gets enabled

You haven't really told us enough to be able to answer that question. There
are several flavours of 'classic' systems, and they all behave slightly
differently. Have a look athttp://content.honeywell.com/uk/homes/systems.htmand try to work out which
'plan' you have. [It won't be C-Plan but it could be either S-Plan, W-Plan
or Y-Plan depending on the number and type of motorised valves present.]

A W-Plan system will heat *either* the HW *or* the CH, but not both at the
same time. If both are calling for heat, the CH demand gets suppressed until
the HW is hot. The other 2 plans can heat both the HW and the CH at the same
time, usually with equal priority.

My tank has a moulded foam insulation plus an additional lagging
jacket. I'm finding in cold weather the house takes a long time to get
up to desired temperature, if at all. While this may be affected by
insulation etc, I wonder if the conflicting requirements of HW & CH
reduce the responsiveness. perhaps I should schedule HW much earlier
in the day and rely on good tank insulation to keep it hit until
evening ?

A well insulated cylinder will keep the water hot for many hours, so you
don't have to heat it immediately before using it. If you have a
programmable stat on the CH, use that to time the CH (with CH on the main
programmer set to 'constant', and use the main programmer to time just the
HW - at a different time from when the CH is on.
--
Cheers,
Roger
______
Email address maintained for newsgroup use only, and not regularly
monitored.. Messages sent to it may not be read for several weeks.
PLEASE REPLY TO NEWSGROUP!


thanks.
Examining the inside of my airing cupboard with a torch I can see 2 2-
Port ACL lifestyle valves. One is definitely on the Tank coil pipe and
the other appears to be on the main CH circuit which the coil circuit
joins further up , if that makes sense. I'd guess that 2 * 2-way
switches can implement a 3 way mode where tank is open and HW is open
too.

This thread has been very useful. I have been tending to leave the CH
permanently on 365 days and regulate the house with the timer stat.
While this is fine in winter /cold weather , this may mean that during
Warm weather I'm probably briefly heating the house to create hot
water, as the CH will be still on as will the HW, for a couple of
hours a day at least.

Roger Mills wrote:

In an earlier contribution to this discussion,
jives11 wrote:


You haven't really told us enough to be able to answer that question. There
are several flavours of 'classic' systems, and they all behave slightly
differently. Have a look at
http://content.honeywell.com/uk/homes/systems.htm and try to work out which
'plan' you have. [It won't be C-Plan but it could be either S-Plan, W-Plan
or Y-Plan depending on the number and type of motorised valves present.]

Now I am confused :-(

It looks like my set-up is an S plan with a valve missing from the hot
water tank heating. All mine consists of is a valve that is controlled
by the room stat that open/closes the pumped supply to the central
heating. (Both hot water and rads are pumped with the same pump)
There are two separate circuits that are fed by one pipe from the pump,
then split for hot water and CH, with a valve in-between the rads and
the boiler and on their return to the boiler. Is this an S type?

I have a slightly different question to ask.
When the new boiler was installed, the plumber didn't wire it up as it
should have been and the pump runs all the time that the boiler is
powered up (not just when it is fired up). It it better to leave it like
that, or should I find the pump terminal, on the boiler, that shuts down
15 minutes after the boiler ceases firing each time/cycle?

Dave

In an earlier contribution to this discussion,
Dave wrote:


It looks like my set-up is an S plan with a valve missing from the hot
water tank heating. All mine consists of is a valve that is controlled
by the room stat that open/closes the pumped supply to the central
heating. (Both hot water and rads are pumped with the same pump)
There are two separate circuits that are fed by one pipe from the
pump, then split for hot water and CH, with a valve in-between the
rads and the boiler and on their return to the boiler. Is this an S
type?
What you have described doesn't equate to *any* of the standard plans! It
sounds as if you have a system which, while being fully pumped, suffers from
many of the disavantages of a gravity HW and pumped CH system - in that
there is apparently no control of the HW temperature, and no boiler
interlock to turn the boiler off when HW and CH demands are both satisfied.
You would need another valve and a tank stat, and some adjustments to the
wiring to convert it to a pukka S-Plan system.

I have a slightly different question to ask.
When the new boiler was installed, the plumber didn't wire it up as it
should have been and the pump runs all the time that the boiler is
powered up (not just when it is fired up). It it better to leave it
like that, or should I find the pump terminal, on the boiler, that
shuts down 15 minutes after the boiler ceases firing each time/cycle?


The pump needs to run whenever there is a heat demand on the boiler -
including times when the boiler's internal thermostat has turned the burner
off. The pump shouldn't run when there's no demand on the boiler. If it
does, it's wired wrongly. If the boiler has dedicated pump connection
terminals to enable it to control the pump, that's where it should be
connected.
--
Cheers,
Roger
______
Email address maintained for newsgroup use only, and not regularly
monitored.. Messages sent to it may not be read for several weeks.
PLEASE REPLY TO NEWSGROUP!

In an earlier contribution to this discussion,
jives11 wrote:

Examining the inside of my airing cupboard with a torch I can see 2 2-
Port ACL lifestyle valves. One is definitely on the Tank coil pipe and
the other appears to be on the main CH circuit which the coil circuit
joins further up , if that makes sense. I'd guess that 2 * 2-way
switches can implement a 3 way mode where tank is open and HW is open
too.

Yes indeed. That is an S-Plan system which enables you to have just HW, just
CH or both at the same time.

This thread has been very useful. I have been tending to leave the CH
permanently on 365 days and regulate the house with the timer stat.
While this is fine in winter /cold weather , this may mean that during
Warm weather I'm probably briefly heating the house to create hot
water, as the CH will be still on as will the HW, for a couple of
hours a day at least.

If it's wired correctly, the radiators won't get hot when you're just
heating the HW (like in the summer) because the CH valve won't open unless
the programmer and room stat tell it to.

With an S-Plan system, the HW valve is controlled by the programmer and
cylinder stat, and the CH valve by the programmer and room stat. Secondary
contacts in the valve actuators close when a valve is fully open - switching
on the boiler and pump. So the boiler and pump only run when either or both
valves are open.
--
Cheers,
Roger
______
Email address maintained for newsgroup use only, and not regularly
monitored.. Messages sent to it may not be read for several weeks.
PLEASE REPLY TO NEWSGROUP!

Dave wrote:
differently. Have a look at
http://content.honeywell.com/uk/homes/systems.htmand try to work out which

Now I am confused :-(

My system at home looks nothing like any of those diagrams. For a
start,
those diagrams have three or four water pipes going to the boiler, my
boiler
only has two water pipes, see http://mdfs.net/Docs/Plumbing/Heating.gif

jives11, if your system is the same as mine, then:

If 'CH+HW' is selected, then at the programmed times the CH switch
activates. When the roomstat determines that the temperature is
below the set level it turns on, so turning on the value that lets
water to the radiators, and, via the unactivated HW switch, turns
on the boiler and the pump.

Looking at the plumbing diagram shows that this causes hot water
to be pumped through the whole system, hot water tank and
radiators.

If 'HW' is selected, then at the programmed times the HW switch
activates. This turns on the pump and the boiler, but, as the CH
switch is not activated, not the valve.

Looking at the plumbing diagram, this shows that how water will
be pumped around just the hot water tank part of the system.

I don;t known what "plan" this is called, it doen't match any of
the refered diagrams, but is the system used in every house
I've ever lived in.

--
JGH

On 12 Mar, 15:33, "Roger Mills" wrote:
In an earlier contribution to this discussion,

jives11 wrote:
Examining the inside of my airing cupboard with a torch I can see 2 2-
Port ACL lifestyle valves. One is definitely on the Tank coil pipe and
the other appears to be on the main CH circuit which the coil circuit
joins further up , if that makes sense. I'd guess that 2 * 2-way
switches can implement a 3 way mode where tank is open and HW is open
too.

Yes indeed. That is an S-Plan system which enables you to have just HW, just
CH or both at the same time.

This thread has been very useful. I have been tending to leave the CH
permanently on 365 days and regulate the house with the timer stat.
While this is fine in winter /cold weather , this may mean that during
Warm weather I'm probably briefly heating the house to create hot
water, as the CH will be still on as will the HW, for a couple of
hours a day at least.

If it's wired correctly, the radiators won't get hot when you're just
heating the HW (like in the summer) because the CH valve won't open unless
the programmer and room stat tell it to.

With an S-Plan system, the HW valve is controlled by the programmer and
cylinder stat, and the CH valve by the programmer and room stat. Secondary
contacts in the valve actuators close when a valve is fully open - switching
on the boiler and pump. So the boiler and pump only run when either or both
valves are open.
--
Cheers,
Roger
______
Email address maintained for newsgroup use only, and not regularly
monitored.. Messages sent to it may not be read for several weeks.
PLEASE REPLY TO NEWSGROUP!

Thanks Roger, I hope it is wired as you describe as that would seem
the ultimate, and would suit my preferred current method of permanent
CH regulated by a CM67 programmable stat. HW is controlled in the
'normal' way i.e 2 shorts bursts - one before I get up and one in the
late afternoon.

The only unusual aspect is that I have 4 bathroom towel rails in line
with the HW , and a landing radiator which has no shut off valves so I
ssume is always in circuit in case of a "China Syndrome" type
malfunction. A couple of the rails are shut off

I can't say if the whole thing is balanced or not but I guess that is
a whole new area to discover

Roger Mills wrote:

In an earlier contribution to this discussion,
Dave wrote:


It looks like my set-up is an S plan with a valve missing from the hot
water tank heating. All mine consists of is a valve that is controlled
by the room stat that open/closes the pumped supply to the central
heating. (Both hot water and rads are pumped with the same pump)
There are two separate circuits that are fed by one pipe from the
pump, then split for hot water and CH, with a valve in-between the
rads and the boiler and on their return to the boiler. Is this an S
type?

What you have described doesn't equate to *any* of the standard plans! It
sounds as if you have a system which, while being fully pumped, suffers from
many of the disavantages of a gravity HW and pumped CH system - in that
there is apparently no control of the HW temperature, and no boiler
interlock to turn the boiler off when HW and CH demands are both satisfied.

I use the boiler stat to control the heat of the water, so that if the
power shower handle points vertically, you get water coming out that is
neither too hot, or too cold. The seams to work OK

You would need another valve and a tank stat, and some adjustments to the
wiring to convert it to a pukka S-Plan system.

I did have a tank stat on the old system, so I'll dig it out and wire it in.

I have a slightly different question to ask.
When the new boiler was installed, the plumber didn't wire it up as it
should have been and the pump runs all the time that the boiler is
powered up (not just when it is fired up). It it better to leave it
like that, or should I find the pump terminal, on the boiler, that
shuts down 15 minutes after the boiler ceases firing each time/cycle?



The pump needs to run whenever there is a heat demand on the boiler -
including times when the boiler's internal thermostat has turned the burner
off. The pump shouldn't run when there's no demand on the boiler. If it
does, it's wired wrongly. If the boiler has dedicated pump connection
terminals to enable it to control the pump, that's where it should be
connected.

That is what I thought.

Many thanks for your info. I'll get round to correcting all this when
the weather warms up a bit and we can live on one tank of hot water for
a while.

Regards

Dave

In an earlier contribution to this discussion,
Dave wrote:

Roger Mills wrote:

What you have described doesn't equate to *any* of the standard
plans! It sounds as if you have a system which, while being fully
pumped, suffers from many of the disavantages of a gravity HW and
pumped CH system - in that there is apparently no control of the HW
temperature, and no boiler interlock to turn the boiler off when HW
and CH demands are both satisfied.

I use the boiler stat to control the heat of the water, so that if the
power shower handle points vertically, you get water coming out that
is neither too hot, or too cold. The seams to work OK

It will work after a fashion, with two major drawbacks:
1. You have to run the boiler at a suitable temperature for the DHW (about
60degC) so the radiators can't get any hotter than this, whereas they need
to be at 80+degrees to generate their full heat output
2. The boiler will waste energy by cycling on its own stat even when the DHW
is hot enough and the CH valve is closed.

You would need another valve and a tank stat, and some adjustments
to the wiring to convert it to a pukka S-Plan system.

I did have a tank stat on the old system, so I'll dig it out and wire
it in.
Wire it in to what? Unless it has a valve to control, you *still* won't have
a proper S-Plan system.
--
Cheers,
Roger
______
Email address maintained for newsgroup use only, and not regularly
monitored.. Messages sent to it may not be read for several weeks.
PLEASE REPLY TO NEWSGROUP!

In an earlier contribution to this discussion,
jgharston wrote:


My system at home looks nothing like any of those diagrams. For a
start, those diagrams have three or four water pipes going to the boiler,
my
boiler only has two water pipes

The diagrams are *schematics* - showing how they *function* rather than
exact representations of the pipework. With the exception of W-Plan they all
show 3 connections to the boiler. But it doesn't take a lot of imagination
to visualise what they would be like if you combined the HW and CH returns
before taking then back to the boiler. There would then only be 2 boiler
connections, and they would look more like your diagram.

see http://mdfs.net/Docs/Plumbing/Heating.gif


That's useful - I can see what you've got, and it almost certainly pre-dates
any of the standard Honeywell 'plans'. In the 60's and 70's, the 'norm' was
to have a gravity HW circuit and pumped CH circuit. What you have is one
step up from that in that it's fully pumped. But it still doesn't provide
independent control of HW and CH (you can't have CH without HW) nor boiler
interlock - as provided by most of the 'plans' - and the thing is that it
would be so easy to update it to take advantage of a much better control
system.

jives11, if your system is the same as mine, then:


No it isn't - he's got a proper S-Plan system.
--
Cheers,
Roger
______
Email address maintained for newsgroup use only, and not regularly
monitored.. Messages sent to it may not be read for several weeks.
PLEASE REPLY TO NEWSGROUP!

Roger Mills wrote:

In an earlier contribution to this discussion,
Dave wrote:


Roger Mills wrote:


What you have described doesn't equate to *any* of the standard
plans! It sounds as if you have a system which, while being fully
pumped, suffers from many of the disavantages of a gravity HW and
pumped CH system - in that there is apparently no control of the HW
temperature, and no boiler interlock to turn the boiler off when HW
and CH demands are both satisfied.

I use the boiler stat to control the heat of the water, so that if the
power shower handle points vertically, you get water coming out that
is neither too hot, or too cold. The seams to work OK


It will work after a fashion, with two major drawbacks:
1. You have to run the boiler at a suitable temperature for the DHW (about
60degC) so the radiators can't get any hotter than this, whereas they need
to be at 80+degrees to generate their full heat output
2. The boiler will waste energy by cycling on its own stat even when the DHW
is hot enough and the CH valve is closed.

Yes, I understand that. I have always been worried about the constant
pump running and didn't consider this.

You would need another valve and a tank stat, and some adjustments
to the wiring to convert it to a pukka S-Plan system.

I did have a tank stat on the old system, so I'll dig it out and wire
it in.

Wire it in to what? Unless it has a valve to control, you *still* won't have
a proper S-Plan system.

We have a tame plumber that will do the pipe work, so that is not a problem.
Thanks for that.

Can anyone advise just how far up the tank should I fit a thermostat. I
used to have it about 1/3 above the bottom of the tank.
We are having a new hot water tank some time this year and it will be
pre insulated with foam. I can cut a hole for it and insulate it again
after I fit the thermostat.

Many thanks to all who have posted

Dave

Roger Mills wrote:
my boiler only has two water pipes

The diagrams are *schematics* - showing how they *function* rather than
exact representations of the pipework. With the exception of W-Plan they all
show 3 connections to the boiler. But it doesn't take a lot of imagination
to visualise what they would be like if you combined the HW and CH returns
before taking then back to the boiler. There would then only be 2 boiler
connections, and they would look more like your diagram.

I know they're functional schematics, but, probably because I'm an
electrician, I tend to expect functional schematics to have some
relationship to the equtipment they represent. A central heating
pluming circuit is essentially a parallel lighting circuit - live feed
out, tee off to emitters in parallel, return back to source.

see http://mdfs.net/Docs/Plumbing/Heating.gif
That's useful - I can see what you've got, and it almost certainly pre-dates
any of the standard Honeywell 'plans'. In the 60's and 70's, the 'norm' was
to have a gravity HW circuit and pumped CH circuit. What you have is one

Everywhere I've lived since 1969 has been like that (except the one
place I lived which had no heating at all. Get up, fill coal bucket,
get fire started...)

interlock - as provided by most of the 'plans' - and the thing is that it
would be so easy to update it to take advantage of a much better control
system.

My boiler's been wearing out and I plan to get it replaced, and moved
to a more useful location. The plumber can put in whatever system
is appropriate - as long as it still give me a tank full of hot
water

--
JGH

In an earlier contribution to this discussion,
jgharston wrote:


I know they're functional schematics, but, probably because I'm an
electrician, I tend to expect functional schematics to have some
relationship to the equtipment they represent. A central heating
pluming circuit is essentially a parallel lighting circuit - live feed
out, tee off to emitters in parallel, return back to source.

Indeed - and it matters not one iota whether the returns join before going
back to source, or whether they go separately - this does not affect the
*function* of either an electrical or a water circuit.
--
Cheers,
Roger
______
Email address maintained for newsgroup use only, and not regularly
monitored.. Messages sent to it may not be read for several weeks.
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"Roger Mills" wrote in message
...
In an earlier contribution to this discussion,
jgharston wrote:


I know they're functional schematics, but, probably because I'm an
electrician, I tend to expect functional schematics to have some
relationship to the equtipment they represent. A central heating
pluming circuit is essentially a parallel lighting circuit - live feed
out, tee off to emitters in parallel, return back to source.

Indeed - and it matters not one iota whether the returns join before going
back to source, or whether they go separately - this does not affect the
*function* of either an electrical or a water circuit.

But may make a difference to the pipe sizes needed.

In an earlier contribution to this discussion,
dennis@home wrote:

"Roger Mills" wrote in message
...
In an earlier contribution to this discussion,
jgharston wrote:


I know they're functional schematics, but, probably because I'm an
electrician, I tend to expect functional schematics to have some
relationship to the equtipment they represent. A central heating
pluming circuit is essentially a parallel lighting circuit - live
feed out, tee off to emitters in parallel, return back to source.

Indeed - and it matters not one iota whether the returns join before
going back to source, or whether they go separately - this does not
affect the *function* of either an electrical or a water circuit.

But may make a difference to the pipe sizes needed.

Yes, of course - and to cable sizes in the electrical analogy. But my
previous post was in the context of a discussion as to the *functional*
equivalence or otherwise of heating schematics which show either separate or
combined HW and CH returns - so I didn't feel it necessary to mention pipe
sizes.
--
Cheers,
Roger
______
Email address maintained for newsgroup use only, and not regularly
monitored.. Messages sent to it may not be read for several weeks.
PLEASE REPLY TO NEWSGROUP!

"Roger Mills" wrote in message
...
In an earlier contribution to this discussion,
dennis@home wrote:

"Roger Mills" wrote in message
...
In an earlier contribution to this discussion,
jgharston wrote:


I know they're functional schematics, but, probably because I'm an
electrician, I tend to expect functional schematics to have some
relationship to the equtipment they represent. A central heating
pluming circuit is essentially a parallel lighting circuit - live
feed out, tee off to emitters in parallel, return back to source.

Indeed - and it matters not one iota whether the returns join before
going back to source, or whether they go separately - this does not
affect the *function* of either an electrical or a water circuit.

But may make a difference to the pipe sizes needed.

Yes, of course - and to cable sizes in the electrical analogy. But my
previous post was in the context of a discussion as to the *functional*
equivalence or otherwise of heating schematics which show either separate
or combined HW and CH returns - so I didn't feel it necessary to mention
pipe sizes.

The big difference is that you really need to run the maximum size cable
everywhere but that isn't so with water.
You could get away with running smaller cables, like water, but you would
need a lot of fuses in odd places.

On Sat, 22 Mar 2008 00:19:44 +0000, Roger Mills wrote:

In an earlier contribution to this discussion, jgharston
wrote:


I know they're functional schematics, but, probably because I'm an
electrician, I tend to expect functional schematics to have some
relationship to the equtipment they represent. A central heating
pluming circuit is essentially a parallel lighting circuit - live feed
out, tee off to emitters in parallel, return back to source.

Indeed - and it matters not one iota whether the returns join before
going back to source, or whether they go separately - this does not
affect the *function* of either an electrical or a water circuit.

Have to disagree, but I might have mis-understood you. It is improtant
that the return from the HW coil comes before or after /all/ the
radiators returns join together.

In an electrical circuit the voltage drop (equivalent to pressure
diffence) along conductors is typically two magnitudes less than across
the 'loads' (equivalent to radiators).
In plumbing this is not true, if the return from the coil divides the
return from upstairs and downstairs (say) then this happens:
A small proportion of the return water from the coil will travel against
the usual direction of flow into the returns from one lot of radiators
and then via the point where the radiators flows are joined into the
other radiators and then via their return pipework to the main return.
It's only a small pressure difference but it can and does drive enough
primary water into radiators to cause a problem in summer.

An indication that this is happening is that the warmest of the radiators
warm up from the return end, whereas when this happens due to the zone
valve letting by or thermosyphoning the radiators heat up from the flow
side.

--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at http://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
Choosing a Boiler FAQ http://www.makewrite.demon.co.uk/BoilerChoice.html

In an earlier contribution to this discussion,
Ed Sirett wrote:

On Sat, 22 Mar 2008 00:19:44 +0000, Roger Mills wrote:

In an earlier contribution to this discussion, jgharston
wrote:


I know they're functional schematics, but, probably because I'm an
electrician, I tend to expect functional schematics to have some
relationship to the equtipment they represent. A central heating
pluming circuit is essentially a parallel lighting circuit - live
feed out, tee off to emitters in parallel, return back to source.

Indeed - and it matters not one iota whether the returns join before
going back to source, or whether they go separately - this does not
affect the *function* of either an electrical or a water circuit.

Have to disagree, but I might have mis-understood you.

Yes, you have!

It is important
that the return from the HW coil comes before or after /all/ the
radiators returns join together.


Yes, I quite agree, but this discussion wasn't about that - but was about
one of the schematics on the Honeywell page which shows separate HW and CH
returns. Someone was maintaining that it was nothing like his system because
his returns were combined before going back to the boiler - and I was
pointing out that it made no functional difference (obviously subject to
your point about combining the rad returns before teeing in the HW return,
but that wasn't an issue in this particular case).
--
Cheers,
Roger
______
Email address maintained for newsgroup use only, and not regularly
monitored.. Messages sent to it may not be read for several weeks.
PLEASE REPLY TO NEWSGROUP!