Hello All,

I have been following the recent excellent threads and am now coming
out of my confusion, I think.
Our existing solid fuel boiler is not going to cope with the
additional requirement of our extension and will be replaced by oil in
the nearish future. This will allow some degree of control (yippee).
My original plan was simple DHW stat and TRV's on all rads, but this ,
I now see, has difficulties in achieving 'boiler interlock'

From pointers given by various recent posters I believe I want:
1) two CH zones, since I have identified that all our rooms fall into
one of two distinct heating requirement patterns.
2) separate control of hot water.

Now... someone (BillR, I think) mentioned the Honeywell CM67's. Having
investigated, these look excellent, allowing each heating zone to be
controlled to different temperature levels throughout six different
periods of the day. I particularly like the look of the RF versions
and, AIUI, by linking to an additional HC60NG to be used as the
boiler/pump controller - as per honeywell installation guide - I
could then have TRV's on all the radiators except those in the 2 rooms
(1 room in each zone) where the CM67's are installed and this would
provide the required 'boiler interlock'. I think I'm OK with this so
far (?) Someone tell me if I'm not!

Then I come to the DHW....
I cannot see an equivalent beast to the CM67 for DHW purposes....
I guess I can use a simple cylinder thermostat - although I don't
necessarily want to have a tank full of hot water permanently. Even if
I did, how do I get this stat to talk to the HC60NG that is
controlling the boiler?? I am sure I am missing something very simple
here but cannot put my finger on it.
It may become clearer when I have the boiler installation information
to hand but in the meantime, I'd really appreciate if some kind soul
can enlighten me.

Perhaps there is something to be said for the old anthracite boiler...
a) light it once a year - DHW control is sorted
b) switch on the pump when you want the CH
c) twiddle with the TRV's
d) switch the pump off at bedtime
e) heat leak rad keeps the bathroom warm for the overnight tinkles and
f) the heatloss from the boiler keeps it warm for breakfast!
arhhh the simplicity!

TIA
Ian

My original plan was simple DHW stat and TRV's on all rads, but this ,
I now see, has difficulties in achieving 'boiler interlock'

Not really. Interlock is easily achieved. Any argument is about whether it
is worth achieving or not. The benefits of implementing the interlock depend
largely on the attitudes of the occupier. If the occupier doesn't mind turn
it off and on manually, then the interlock is not as effective in increasing
efficiency as when they are not. I prefer a system I can just leave well
alone, yet works efficiently.

It is possible to have an all-TRV system, even subzoned for timing. You
simply plumb as S-Plan, with a 3 channel programmer, or with separate
programmers conveniently located. But rather than using the 2 port valve
microswitches, you achieve interlock using a flow switch after the bypass,
but before the heating zone valves. The output from the flow switch can be
combined with the HWC zone valve microswitch to provide a boiler call for
heat.

Personally, I prefer to use a programmable room stat, as it allows different
temperatures at different times of day. Having implemented it, it very
effectively maintains temperature in all rooms, including those with TRVs,
provided the system is reasonably balanced. The rooms with the programmable
thermostats are those used most frequently (master bedroom and lounge). This
provides very accurate temperature in those rooms (measured away from the
radiator) and a handy nearby override mechanism.

The only problem is the kitchen, which doesn't get to temperature. However,
this isn't really a control issue, as the room is 5m x 2.5m, with 2 external
solid walls, 3 large windows, 1 door, french doors and a single tiny
radiator at one end suitable only for a little bathroom. I'm planning to put
a fan convector (i.e. Myson Kickspace 800) in to resolve this.
Unfortunately, there's no room for insulation, although the draught proofing
could be seriously improved.

I cannot see an equivalent beast to the CM67 for DHW purposes....

Do you mean an RF cylinder thermostat? I'm sure I've seen one somewhere.
However, I prefer to use proper cable when possible. My experience with
other RF stuff is that it isn't quite as reliable as a bit of twin and
earth. OTOH, if running cable is very difficult, then they are tempting.

When wiring this system up, you'll still need a normal programmer. The hot
water side handles HWC timing. The heating side acts as a master controller
for your heating zones. You normally set this side to either "OFF" or "24H"
and allow the programmable thermostats to handle any timing. There is good
reason for maintaining a separate programmer. Firstly, you can turn off the
entire system simply, without traipsing round the house to all the room
stats. Secondly, wayward teenagers wanting 30C in the middle of the night
(and having a programmable stat in their room) can be defeated. It is best
to leave on 24H, if possible, though, as the programmable thermostat can
keep a reasonable overnight temperature, such as 12C, rather than turning
off completely. However, if you go overboard in balancing up TRV radiators
so as to starve the master room, this may not be as effective. Doing so just
a little, though, helps maintain steady temperatures.

Christian.

On Mon, 15 Dec 2003 16:23:12 +0000, Ian wrote:

Hello All,

I have been following the recent excellent threads and am now coming
out of my confusion, I think.
Our existing solid fuel boiler is not going to cope with the
additional requirement of our extension and will be replaced by oil in
the nearish future. This will allow some degree of control (yippee).
My original plan was simple DHW stat and TRV's on all rads, but this ,
I now see, has difficulties in achieving 'boiler interlock'

From pointers given by various recent posters I believe I want:
1) two CH zones, since I have identified that all our rooms fall into
one of two distinct heating requirement patterns.
2) separate control of hot water.

Now... someone (BillR, I think) mentioned the Honeywell CM67's. Having
investigated, these look excellent, allowing each heating zone to be
controlled to different temperature levels throughout six different
periods of the day. I particularly like the look of the RF versions
and, AIUI, by linking to an additional HC60NG to be used as the
boiler/pump controller - as per honeywell installation guide - I
could then have TRV's on all the radiators except those in the 2 rooms
(1 room in each zone) where the CM67's are installed and this would
provide the required 'boiler interlock'. I think I'm OK with this so
far (?) Someone tell me if I'm not!

Then I come to the DHW....
I cannot see an equivalent beast to the CM67 for DHW purposes....
I guess I can use a simple cylinder thermostat - although I don't
necessarily want to have a tank full of hot water permanently. Even if
I did, how do I get this stat to talk to the HC60NG that is
controlling the boiler?? I am sure I am missing something very simple
here but cannot put my finger on it.
It may become clearer when I have the boiler installation information
to hand but in the meantime, I'd really appreciate if some kind soul
can enlighten me.

I think that a better and more convenient solution to this would be
the Danfoss Randall TP75-RF (about to be replaced by TP7000-RF) for
the heating zones and a WP75-RF for the hot water. This would give
you completely independent time and temperature operation for each
zone and the hot water.

www.danfoss-randall.co.uk

These have a common receiver type and you can get up to 3 channel
receivers, although probably to order.

www.controlscenter.co.uk should be able to or any heating supplier.

You would sit the receiver at the boiler position and hook all the
demand outputs to the switched input of the boiler and possibly the
pump if the boiler doesn't have an overrun output for the pump.

If the motorised zone valves need to be in a position remote from the
boiler and you can get power there, then you could have additional
single channel receivers if you wanted. The receivers are trained to
the transmitted signal during installation and you can have multiple
receivers listening to one transmitting programmer.

Obviously this would cost a bit more to implement, but the trade off
is against wiring convenience and time .






Perhaps there is something to be said for the old anthracite boiler...
a) light it once a year - DHW control is sorted
b) switch on the pump when you want the CH
c) twiddle with the TRV's
d) switch the pump off at bedtime
e) heat leak rad keeps the bathroom warm for the overnight tinkles and
f) the heatloss from the boiler keeps it warm for breakfast!
arhhh the simplicity!

TIA
Ian


..andy

To email, substitute .nospam with .gl

In an earlier contribution to this discussion,
Ian wrote:


Then I come to the DHW....
I cannot see an equivalent beast to the CM67 for DHW purposes....
I guess I can use a simple cylinder thermostat - although I don't
necessarily want to have a tank full of hot water permanently. Even if
I did, how do I get this stat to talk to the HC60NG that is
controlling the boiler?? I am sure I am missing something very simple
here but cannot put my finger on it.
It may become clearer when I have the boiler installation information
to hand but in the meantime, I'd really appreciate if some kind soul
can enlighten me.


What you need is, in effect, an S-Plan-Plus [see
http://content.honeywell.com/uk/homes/systems.htm] with 3 zones, 2 for
heating and one for hot water.

Use a standard programmer and cyl stat to control the zone valve for the hot
water - with 2 or 3 on/off periods per 24 hours, as desired - but always the
same temperature unless you manually twiddle the cyl stat (which is probably
acceptable). On the same standard programmer, set CH to permanently on and
use its CH ON contact to feed the programmable room stats. The actual on/off
periods (and different temperatures if desired) are then controlled by the
room stats - which in turn control their respective zone valves.

The volt-free contacts on all 3 zone valves are connected in parallel - with
the output side controlling the boiler and pump. That way, the boiler and
pump will run whenever one or more zones requires heat and will shut down
when they are all satisfied - achieving the desired interlock.
--
Cheers,
Set Square
______
Please reply to newsgroup. Reply address is Black Hole!

In article ,
"Set Square" writes:

What you need is, in effect, an S-Plan-Plus [see
http://content.honeywell.com/uk/homes/systems.htm] with 3 zones, 2 for
heating and one for hot water.

Use a standard programmer and cyl stat to control the zone valve for the hot
water - with 2 or 3 on/off periods per 24 hours, as desired - but always the
same temperature unless you manually twiddle the cyl stat (which is probably
acceptable). On the same standard programmer, set CH to permanently on and
use its CH ON contact to feed the programmable room stats. The actual on/off
periods (and different temperatures if desired) are then controlled by the
room stats - which in turn control their respective zone valves.

The volt-free contacts on all 3 zone valves are connected in parallel - with
the output side controlling the boiler and pump. That way, the boiler and
pump will run whenever one or more zones requires heat and will shut down
when they are all satisfied - achieving the desired interlock.

You will need to allow for pump overrun with most boilers.
The Honeywell schematic does not.

--
Andrew Gabriel

In an earlier contribution to this discussion,
Andrew Gabriel wrote:

You will need to allow for pump overrun with most boilers.
The Honeywell schematic does not.


This is true. In fact, it's only a small change from the Honeywell diagram.
The basic logic remains the same, but the output from the zone valves'
volt-free contacts drives just the boiler rather than the boiler and pump in
parallel. The pump is then connected to the boiler's pump control terminal -
which is live whenever the boiler is firing plus whenever the boiler's pump
over-run stat calls for circulation to continue.
--
Cheers,
Set Square
______
Please reply to newsgroup. Reply address is Black Hole!

On Mon, 15 Dec 2003 17:11:27 -0000, "Set Square"
wrote:

What you need is, in effect, an S-Plan-Plus [see
http://content.honeywell.com/uk/homes/systems.htm] with 3 zones, 2 for
heating and one for hot water.

Use a standard programmer and cyl stat to control the zone valve for the hot
water - with 2 or 3 on/off periods per 24 hours, as desired - but always the
same temperature unless you manually twiddle the cyl stat (which is probably
acceptable). On the same standard programmer, set CH to permanently on and
use its CH ON contact to feed the programmable room stats. The actual on/off
periods (and different temperatures if desired) are then controlled by the
room stats - which in turn control their respective zone valves.

The volt-free contacts on all 3 zone valves are connected in parallel - with
the output side controlling the boiler and pump. That way, the boiler and
pump will run whenever one or more zones requires heat and will shut down
when they are all satisfied - achieving the desired interlock.

Very many thanks to all who responded.
My missing link was the need to still have a normal programmer to
handle the DHW - not realising that the programmable room stats do not
replace the programmer. I now have a fairly large bulge appearing on
my forehead!

I don't really have a problem running cables everywhere since the
whole place will be redecorated following the extension. I
I've had a look at the Danfoss site and can see that that would meet
the bill but have noted the comment from Christian concerning the
potential reliability of the RF stats. Since one may be 20m from its
receiver , I think it makes more sense to go the wire route.

Is there anything to choose in reliability of the electronics or TRV's
between various manufacturers?

Thanks again all

Ian

Is there anything to choose in reliability of the electronics or
TRV's between various manufacturers?

Electronics are normally reliable. I'd buy a room stat mainly on the basis
of appearance, provided it had the required functionality. Brand in itself
wouldn't matter to me, except in that a good brand is more likely to
physically look better.

TRVs should be from a reputable manufacturer and expect to replace every 7
years or so when they start to get a little slow. Cheap ones may fail in a
couple of years.

Christian.

On Tue, 16 Dec 2003 14:54:43 +0000, Ian wrote:

On Mon, 15 Dec 2003 17:11:27 -0000, "Set Square"
wrote:

What you need is, in effect, an S-Plan-Plus [see
http://content.honeywell.com/uk/homes/systems.htm] with 3 zones, 2 for
heating and one for hot water.

Use a standard programmer and cyl stat to control the zone valve for the hot
water - with 2 or 3 on/off periods per 24 hours, as desired - but always the
same temperature unless you manually twiddle the cyl stat (which is probably
acceptable). On the same standard programmer, set CH to permanently on and
use its CH ON contact to feed the programmable room stats. The actual on/off
periods (and different temperatures if desired) are then controlled by the
room stats - which in turn control their respective zone valves.

The volt-free contacts on all 3 zone valves are connected in parallel - with
the output side controlling the boiler and pump. That way, the boiler and
pump will run whenever one or more zones requires heat and will shut down
when they are all satisfied - achieving the desired interlock.

Very many thanks to all who responded.
My missing link was the need to still have a normal programmer to
handle the DHW - not realising that the programmable room stats do not
replace the programmer. I now have a fairly large bulge appearing on
my forehead!

You don't.. You can have a programmable thermostat for the cylinder
as I mentioned - either wired or wireless.

If you do this plus programmable room controller(s), you don't need to
have an additional programmer at the boiler at all.

On the other hand if you are going for wired connection to the
cylinder, you could cover that using a simple cylinder stat and a
programmer at the boiler instead.



I don't really have a problem running cables everywhere since the
whole place will be redecorated following the extension. I
I've had a look at the Danfoss site and can see that that would meet
the bill but have noted the comment from Christian concerning the
potential reliability of the RF stats. Since one may be 20m from its
receiver , I think it makes more sense to go the wire route.

They are pretty solid in fact. There are specific standards that they
are required to meet and incorporate error detection to avoid errors
due to interference problems.

I would regard them as a convenience if wiring is awkward, because
obviously they are more expensive as well. However, if you can wire
easily then that makes more sense.



Is there anything to choose in reliability of the electronics or TRV's
between various manufacturers?

I've used Danfoss and Honeywell controls and not had a problem with
either. Similarly their TRVs.

Since replacing a TRV typically involves a drain down if the problem
is in the base, then I would avoid the cheap products and again go for
Honeywell, Myson, Drayton, etc. Honeywell seem to be the most
commonly available at the merchants.




Thanks again all

Ian

..andy

To email, substitute .nospam with .gl

In an earlier contribution to this discussion,
Andy Hall wrote:

On Tue, 16 Dec 2003 14:54:43 +0000, Ian wrote:
My missing link was the need to still have a normal programmer to
handle the DHW - not realising that the programmable room stats do
not replace the programmer.

You don't.. You can have a programmable thermostat for the cylinder
as I mentioned - either wired or wireless.

If you do this plus programmable room controller(s), you don't need to
have an additional programmer at the boiler at all.



Whilst this is true, using a conventional programmer with its CH output
connected to the programmable room stats has the advantage that the heating
can be turned off from a single point (e.g. for the summer) without having
to re-programme the stats.
--
Cheers,
Set Square
______
Please reply to newsgroup. Reply address is Black Hole!

On Tue, 16 Dec 2003 16:40:30 -0000, "Set Square"
wrote:

In an earlier contribution to this discussion,
Andy Hall wrote:

On Tue, 16 Dec 2003 14:54:43 +0000, Ian wrote:
My missing link was the need to still have a normal programmer to
handle the DHW - not realising that the programmable room stats do
not replace the programmer.

You don't.. You can have a programmable thermostat for the cylinder
as I mentioned - either wired or wireless.

If you do this plus programmable room controller(s), you don't need to
have an additional programmer at the boiler at all.



Whilst this is true, using a conventional programmer with its CH output
connected to the programmable room stats has the advantage that the heating
can be turned off from a single point (e.g. for the summer) without having
to re-programme the stats.

True, although a simple switch near the boiler connecting the switched
outputs from the room programmers would achieve the same thing.

..andy

To email, substitute .nospam with .gl

True, although a simple switch near the boiler connecting the
switched outputs from the room programmers would achieve the
same thing.

Better to supply the feed to the programmable room stats, rather than the
switched returns. Then you only need a SP switch for the lot, instead of a
pole per zone.

Christian.

On Tue, 16 Dec 2003 17:32:02 -0000, "Christian McArdle"
wrote:

True, although a simple switch near the boiler connecting the
switched outputs from the room programmers would achieve the
same thing.

Better to supply the feed to the programmable room stats, rather than the
switched returns. Then you only need a SP switch for the lot, instead of a
pole per zone.

Christian.



No because they all come together at a common point at the boiler
anyway, to form the switched live to fire it up.

If you have two (or more) room programmers, you could bring their
demand signals and connect them together, then go through the switch,
bring in the HW demand and then into the boiler.

This is an "or" function of the room programmers followed by an "and"
created by the switch followed by an "or" with the HW.

Boiler = ((Prog1 OR Prog2 OR ...... ProgN) AND Switch) OR DHW



..andy

To email, substitute .nospam with .gl

In article ,
"Set Square" writes:
In an earlier contribution to this discussion,
Andrew Gabriel wrote:

You will need to allow for pump overrun with most boilers.
The Honeywell schematic does not.


This is true. In fact, it's only a small change from the Honeywell diagram.
The basic logic remains the same, but the output from the zone valves'
volt-free contacts drives just the boiler rather than the boiler and pump in
parallel. The pump is then connected to the boiler's pump control terminal -
which is live whenever the boiler is firing plus whenever the boiler's pump
over-run stat calls for circulation to continue.

That's not the problem. The problem is that when the last zone valve
closes, there's no water circuit for the pump overrun. You have to
make some provision for that.

--
Andrew Gabriel

"Set Square" wrote in message ...
In an earlier contribution to this discussion,
Andy Hall wrote:

On Tue, 16 Dec 2003 14:54:43 +0000, Ian wrote:
My missing link was the need to still have a normal programmer to
handle the DHW - not realising that the programmable room stats do
not replace the programmer.

You don't.. You can have a programmable thermostat for the cylinder
as I mentioned - either wired or wireless.

If you do this plus programmable room controller(s), you don't need to
have an additional programmer at the boiler at all.



Whilst this is true, using a conventional programmer with its CH output
connected to the programmable room stats has the advantage that the heating
can be turned off from a single point (e.g. for the summer) without having
to re-programme the stats.

I installed a Honeywell CM67NG RF recently. It has an 'off' setting on
the programmable thermostat part - which is not really off but a
user-selectable frost-free setting which is 5 deg C out of the box,
IIRC.

Neil

If you have two (or more) room programmers, you could bring
their demand signals and connect them together, then go through
the switch, bring in the HW demand and then into the boiler.

You couldn't put the switch on the output of the programmers, as that would
short the outputs of them together, causing the zone valves to open in
unison, rather than being individually controlled. You could put the switch
on the microswitch outputs of the 2 port zone valves. However, this would
not be ideal, as if the boiler fires due to the HWC zone valve demanding
heat, then the heating zone valves may already be open, causing unwanted
heat in the radiators.

You could always add relays. However, the standard (cheaper and simpler)
method is the sequence:

Programmer - Room Stat (programmable) - Zone Valve - Boiler (via
microswitches)
(or switch)

Christian.

In an earlier contribution to this discussion,
Andrew Gabriel wrote:

In article ,
"Set Square" writes:
In an earlier contribution to this discussion,
Andrew Gabriel wrote:

You will need to allow for pump overrun with most boilers.
The Honeywell schematic does not.


This is true. In fact, it's only a small change from the Honeywell
diagram. The basic logic remains the same, but the output from the
zone valves' volt-free contacts drives just the boiler rather than
the boiler and pump in parallel. The pump is then connected to the
boiler's pump control terminal - which is live whenever the boiler
is firing plus whenever the boiler's pump over-run stat calls for
circulation to continue.

That's not the problem. The problem is that when the last zone valve
closes, there's no water circuit for the pump overrun. You have to
make some provision for that.

Ah, I see! You're talking about the by-pass loop rather than the wiring. You
are perfectly correct - the Honeywell schematic doesn't show a by-pass loop
and ought to do so.

My point is also valid. The Honeywell electrical diagram shows the boiler
and pump feeds connected togther - so that the pump stops when the boiler
demand is turned off. For a by-pass to work, the pump needs to be controlled
by the boiler so that it can continue to run after the boiler has finished
firing.

--
Cheers,
Set Square
______
Please reply to newsgroup. Reply address is Black Hole!

In an earlier contribution to this discussion,
Neil Jones wrote:

"Set Square" wrote in message
...



Whilst this is true, using a conventional programmer with its CH
output connected to the programmable room stats has the advantage
that the heating can be turned off from a single point (e.g. for the
summer) without having to re-programme the stats.

I installed a Honeywell CM67NG RF recently. It has an 'off' setting on
the programmable thermostat part - which is not really off but a
user-selectable frost-free setting which is 5 deg C out of the box,
IIRC.

Neil

Sure - but the earlier discussion related to a system with 2 or more heating
zones, each controlled by a programmable stat. So you would have to turn
each of these off rather than doing it in just one place. Also, I'm not sure
that with some programmable stats you can effectively turn it permanently
off with disturbing the other settings. Maybe you can?
--
Cheers,
Set Square
______
Please reply to newsgroup. Reply address is Black Hole!

On Wed, 17 Dec 2003 09:56:38 -0000, "Christian McArdle"
wrote:

If you have two (or more) room programmers, you could bring
their demand signals and connect them together, then go through
the switch, bring in the HW demand and then into the boiler.

You couldn't put the switch on the output of the programmers, as that would
short the outputs of them together, causing the zone valves to open in
unison, rather than being individually controlled. You could put the switch
on the microswitch outputs of the 2 port zone valves. However, this would
not be ideal, as if the boiler fires due to the HWC zone valve demanding
heat, then the heating zone valves may already be open, causing unwanted
heat in the radiators.

Does your last sentence make sense ? If the heating zone valves are already
open, then this can only be because one or both of their timers are on and
one or both of their stats are demanding heat. In what way is heat in the
radiators then "unwanted" ? Apart from that, yes, the outputs can only be
commoned at the boiler after the zone valves, or independent zone control
will not be achieved.

--
I have a vitally important role serving as a bad example.

Mail john rather than nospam...

Does your last sentence make sense ? If the heating zone valves are
already open, then this can only be because one or both of their timers
are on and one or both of their stats are demanding heat. In what way
is heat in the radiators then "unwanted" ?

It is unwanted because it happens despite you switching the central heating
off. This switch should override the programmable thermostat.

So, the idea is to provide a master switch to turn off the heating. If that
master switch is after the zone valve microswitches, then the programmers
may call for heat and turn on the zone valves. The switch only prevents the
zone valves firing up the boiler. However, if the boiler fires up for DHW,
then the valves are already open and will pass water.

To work properly, you need to put the switch before the zone valves, so they
aren't open unnecessarily. This is easiest done by switching the feed to the
programmers, as doing so after the programmers requires relays, or a multi
pole switch.

Christian.

On Wed, 17 Dec 2003 09:56:38 -0000, "Christian McArdle"
wrote:

If you have two (or more) room programmers, you could bring
their demand signals and connect them together, then go through
the switch, bring in the HW demand and then into the boiler.

You couldn't put the switch on the output of the programmers, as that would
short the outputs of them together, causing the zone valves to open in
unison, rather than being individually controlled. You could put the switch
on the microswitch outputs of the 2 port zone valves. However, this would
not be ideal, as if the boiler fires due to the HWC zone valve demanding
heat, then the heating zone valves may already be open, causing unwanted
heat in the radiators.

You could always add relays. However, the standard (cheaper and simpler)
method is the sequence:

Programmer - Room Stat (programmable) - Zone Valve - Boiler (via
microswitches)
(or switch)

Christian.


I see what you're saying....



..andy

To email, substitute .nospam with .gl

On Wed, 17 Dec 2003 10:54:24 -0000, "Christian McArdle"
wrote:

Does your last sentence make sense ? If the heating zone valves are
already open, then this can only be because one or both of their timers
are on and one or both of their stats are demanding heat. In what way
is heat in the radiators then "unwanted" ?

It is unwanted because it happens despite you switching the central heating
off. This switch should override the programmable thermostat.

So, the idea is to provide a master switch to turn off the heating. If that
master switch is after the zone valve microswitches, then the programmers
may call for heat and turn on the zone valves. The switch only prevents the
zone valves firing up the boiler. However, if the boiler fires up for DHW,
then the valves are already open and will pass water.

To work properly, you need to put the switch before the zone valves, so they
aren't open unnecessarily. This is easiest done by switching the feed to the
programmers, as doing so after the programmers requires relays, or a multi
pole switch.

I think I missed the point about the master switch ;-) Sounds a bit like
overkill as the two zone programmers can be co-located anyway.

--
Do the impossible and your boss will add it to your duties.

Mail john rather than nospam...

I think I missed the point about the master switch ;-) Sounds a bit like
overkill as the two zone programmers can be co-located anyway.

Co-location is impossible. They are programmable room thermostats. They
won't sense the right temperature if they are in the wrong room. I suppose
you could use a multi-channel programmer and straight room stats. However,
this would cause many disadvantages. Firstly, this system doesn't allow
different temperatures at different times of day. Secondly, manual override
(i.e. boost/advance) buttons will be in a dark cupboard under the sink with
bottles of bleach in the way, rather than on a convenient well lit nearby
wall.

Christian.

On Wed, 17 Dec 2003 13:00:05 -0000, "Christian McArdle"
wrote:

I think I missed the point about the master switch ;-) Sounds a bit like
overkill as the two zone programmers can be co-located anyway.

Co-location is impossible. They are programmable room thermostats. They
won't sense the right temperature if they are in the wrong room.

Oh do shut up ;-) I thought the OP had mentioned RF devices, so was
presuming he was putting the sensors in suitable rooms, with the actual
programmers nearer the (um, let's see) zone valves, I guess. They don't
*have* to be next to one another, but it would be simpler if they were.

--
A seminar on Time Travel will be held 2 weeks ago.

Mail john rather than nospam...

Christian McArdle wrote:

Does your last sentence make sense ? If the heating zone valves are
already open, then this can only be because one or both of their timers
are on and one or both of their stats are demanding heat. In what way
is heat in the radiators then "unwanted" ?


It is unwanted because it happens despite you switching the central heating
off. This switch should override the programmable thermostat.

So, the idea is to provide a master switch to turn off the heating. If that
master switch is after the zone valve microswitches, then the programmers
may call for heat and turn on the zone valves. The switch only prevents the
zone valves firing up the boiler. However, if the boiler fires up for DHW,
then the valves are already open and will pass water.

To work properly, you need to put the switch before the zone valves, so they
aren't open unnecessarily. This is easiest done by switching the feed to the
programmers, as doing so after the programmers requires relays, or a multi
pole switch.


Have I missed somethinhg here?

My three way time controller has buttons that switch off any of its
three zones?

Completely. No thermostats or valves are energized.

So no pump and no boiler.



Christian.

Have I missed somethinhg here?
My three way time controller has buttons that switch off any of its
three zones?

The proposal is for programmable room thermostats and no overall programmer,
just a switch to turn off the entire heating system (except HWC).

Obviously, a 3 channel programmer with non-programmable stats is a different
system, also with an easy way to totally turn off the heating. However, it
doesn't allow a local button for override/boost and doesn't allow different
temperatures at different times of day.

Christian.

The proposal is for programmable room thermostats and no overall
programmer, just a switch to turn off the entire heating system
(except HWC).

P.S. I don't see the point of not having a programmer instead of a switch.
You probably need one anyway for the hot water side, and a twin channel
isn't much more than a single channel. I suppose some people would find it
simpler to operate a switch, given that the timing function is unlikely to
prove useful.

Christian.

Christian McArdle wrote:

Have I missed somethinhg here?
My three way time controller has buttons that switch off any of its
three zones?


The proposal is for programmable room thermostats and no overall programmer,
just a switch to turn off the entire heating system (except HWC).

Obviously, a 3 channel programmer with non-programmable stats is a different
system, also with an easy way to totally turn off the heating. However, it
doesn't allow a local button for override/boost and doesn't allow different
temperatures at different times of day.



Fairy nuff. Sounds amusing enough.

I am going to radically side with a single IMM comment, that circulation
hot water through fan convectors does a fair job of heating without the
fans on.

If you are really picky, fit a motorized valve.

I can;t answer for teh Kickspace, but my 'vectors had no balancing
valves. These are manadatory to stop them hogging CH flow. If you have a
motorsized valve per convector that may not be such a problem - since
hey will hog till the romm warms up only.




Christian.

If you are really picky, fit a motorized valve.

Well I was always going to install at least one valve, shared between the
two. However, I'm leaning towards installing two now. The main objection to
having two was aesthetic anyway.

I can;t answer for teh Kickspace, but my 'vectors had no balancing
valves. These are manadatory to stop them hogging CH flow.

Well, I'd prefer a proper balanced system anyway even if fully valved. I was
intending to install balancing valves if none were fitted. The technical
specs don't mention it, but do say what flow rate you need through them to
get full power, with the obvious implication that you should throttle them
down to that if you want anything else on the system to work.

Christian.

On Wed, 17 Dec 2003 10:05:48 +0000, Set Square wrote:

In an earlier contribution to this discussion,
Andrew Gabriel wrote:

In article ,
"Set Square" writes:
In an earlier contribution to this discussion,
Andrew Gabriel wrote:

You will need to allow for pump overrun with most boilers.
The Honeywell schematic does not.


This is true. In fact, it's only a small change from the Honeywell
diagram. The basic logic remains the same, but the output from the
zone valves' volt-free contacts drives just the boiler rather than
the boiler and pump in parallel. The pump is then connected to the
boiler's pump control terminal - which is live whenever the boiler
is firing plus whenever the boiler's pump over-run stat calls for
circulation to continue.

That's not the problem. The problem is that when the last zone valve
closes, there's no water circuit for the pump overrun. You have to
make some provision for that.

Ah, I see! You're talking about the by-pass loop rather than the wiring. You
are perfectly correct - the Honeywell schematic doesn't show a by-pass loop
and ought to do so.

My point is also valid. The Honeywell electrical diagram shows the boiler
and pump feeds connected togther - so that the pump stops when the boiler
demand is turned off. For a by-pass to work, the pump needs to be controlled
by the boiler so that it can continue to run after the boiler has finished
firing.

It all depends on the boiler.
In my own home the bathroom towel warmer is the bypass.
On other systems I have doen with S plan I have used a boiler that does
not require (an external) bypass.


--
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 Wed, 17 Dec 2003 12:36:21 +0000, John Laird wrote:

On Wed, 17 Dec 2003 10:54:24 -0000, "Christian McArdle"
wrote:

Does your last sentence make sense ? If the heating zone valves are
already open, then this can only be because one or both of their timers
are on and one or both of their stats are demanding heat. In what way
is heat in the radiators then "unwanted" ?

It is unwanted because it happens despite you switching the central heating
off. This switch should override the programmable thermostat.

So, the idea is to provide a master switch to turn off the heating. If that
master switch is after the zone valve microswitches, then the programmers
may call for heat and turn on the zone valves. The switch only prevents the
zone valves firing up the boiler. However, if the boiler fires up for DHW,
then the valves are already open and will pass water.

To work properly, you need to put the switch before the zone valves, so they
aren't open unnecessarily. This is easiest done by switching the feed to the
programmers, as doing so after the programmers requires relays, or a multi
pole switch.

I think I missed the point about the master switch ;-) Sounds a bit like
overkill as the two zone programmers can be co-located anyway.

I over-hauled a large heating system last year.
4 Heating Zones and DHW. All this used a Keston C40 which has seperate
temperature control for heating and HW. It is true that for a short while
the boiler output is at a higher temperature whilst the tank is being
reheated.

However the extra heat in the radiators is not a particularly big problem
and is further minimized by the fact that the water circuit for the DHW
coil is very much lower than for the radiator zones. (Short run of 22mm
pipe right off the 28mm main manifold). This means that very little water
is inclined to go through the radiator for the 10 minutes (typically)
whilst the tank is reheating.

Another way would have been to use a large 28mm 3 port diverter valve with
DHW priority which would kill the heating during DHW reheat.
However experience shows that some people like to turn the heating & HW
off if the go on away in winter and resent waiting the _entire_ cylinder
reheat time say 25mins (170 litre, nominal 14kW coil) before the radiators
_start_ to heat up.


--
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 Wed, 17 Dec 2003 13:00:05 +0000, Christian McArdle wrote:

I think I missed the point about the master switch ;-) Sounds a bit like
overkill as the two zone programmers can be co-located anyway.

Co-location is impossible. They are programmable room thermostats. They
won't sense the right temperature if they are in the wrong room. I suppose
you could use a multi-channel programmer and straight room stats. However,
this would cause many disadvantages. Firstly, this system doesn't allow
different temperatures at different times of day. Secondly, manual override
(i.e. boost/advance) buttons will be in a dark cupboard under the sink with
bottles of bleach in the way, rather than on a convenient well lit nearby
wall.

I agree the idea of a master switch is well useful for maintenance if
nothing else.


--
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

Ed Sirett wrote:

On Wed, 17 Dec 2003 13:00:05 +0000, Christian McArdle wrote:


I think I missed the point about the master switch ;-) Sounds a bit like
overkill as the two zone programmers can be co-located anyway.

Co-location is impossible. They are programmable room thermostats. They
won't sense the right temperature if they are in the wrong room. I suppose
you could use a multi-channel programmer and straight room stats. However,
this would cause many disadvantages. Firstly, this system doesn't allow
different temperatures at different times of day. Secondly, manual override
(i.e. boost/advance) buttons will be in a dark cupboard under the sink with
bottles of bleach in the way, rather than on a convenient well lit nearby
wall.


I agree the idea of a master switch is well useful for maintenance if
nothing else.




I am pretty sure its mandatory - my whole heatng system is run off a big
switched fused spur with its own neon and switch bang next door to the
controller and very near the boiler. I thought you had to do this with
all boilers extractor fans etc etc.

"Set Square" wrote in message ...
In an earlier contribution to this discussion,
Neil Jones wrote:

"Set Square" wrote in message
...



Whilst this is true, using a conventional programmer with its CH
output connected to the programmable room stats has the advantage
that the heating can be turned off from a single point (e.g. for the
summer) without having to re-programme the stats.

I installed a Honeywell CM67NG RF recently. It has an 'off' setting on
the programmable thermostat part - which is not really off but a
user-selectable frost-free setting which is 5 deg C out of the box,
IIRC.

Neil

Sure - but the earlier discussion related to a system with 2 or more heating
zones, each controlled by a programmable stat. So you would have to turn
each of these off rather than doing it in just one place. Also, I'm not sure
that with some programmable stats you can effectively turn it permanently
off with disturbing the other settings. Maybe you can?


You can, because the programmable stat part is battery powered,
whereas the receiver/controller part is wired into the boiler control
system. If you power of the boiler it removes power from the
receiver/controller (which actually decides to turn the boiler on/off)
but the thermostat itself is still on.

I agree the idea of a master switch is well useful for maintenance
if nothing else.

But then, that would be entirely different. The propsed switch only turns
off the central heating side and certainly doesn't isolate anything. The
boiler should remain powered.

Obviously, some sort of DP isolation should be provided to the entire
system, too. I've ended up with two DP isolators on mine. The boiler and
cylinder are in the loft. The heating zone valves and programmer are in the
understairs cupboard. I have a DP isolator in both locations, both of which
isolate the entire system.

Christian.

In an earlier contribution to this discussion,
The Natural Philosopher wrote:



I am pretty sure its mandatory - my whole heatng system is run off a
big switched fused spur with its own neon and switch bang next door
to the controller and very near the boiler. I thought you had to do
this with all boilers extractor fans etc etc.

Yes, you need an isolating switch for the *whole* system - but that's not
the point! This discussion is about turning off a multi-zoned heating system
*without* also turning off the hot water.
--
Cheers,
Set Square
______
Please reply to newsgroup. Reply address is Black Hole!

On Thu, 18 Dec 2003 01:12:12 +0000, The Natural Philosopher wrote:

Ed Sirett wrote:

On Wed, 17 Dec 2003 13:00:05 +0000, Christian McArdle wrote:


I think I missed the point about the master switch ;-) Sounds a bit like
overkill as the two zone programmers can be co-located anyway.

Co-location is impossible. They are programmable room thermostats. They
won't sense the right temperature if they are in the wrong room. I suppose
you could use a multi-channel programmer and straight room stats. However,
this would cause many disadvantages. Firstly, this system doesn't allow
different temperatures at different times of day. Secondly, manual override
(i.e. boost/advance) buttons will be in a dark cupboard under the sink with
bottles of bleach in the way, rather than on a convenient well lit nearby
wall.


I agree the idea of a master switch is well useful for maintenance if
nothing else.




I am pretty sure its mandatory - my whole heatng system is run off a big
switched fused spur with its own neon and switch bang next door to the
controller and very near the boiler. I thought you had to do this with
all boilers extractor fans etc etc.

I am not suggesting that the programmer replaces proper DP isolation.
I'm talking about, say, you want to diagnose the boiler, you are testing it
out live but want to be sure you don't have a CH demand only a HW one.



--
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