I've just had to replace the room thermostat on MIL's CH system, and
have installed a Honeywell CM927 programmable wireless stat.

The old stat had live, switched live, neutral and earth connections,
so I just linked the live to one side of the switch in the Relay Box,
with the switched live on the otherside of the switch. All works ok
except........

The live to the stat is actually switched by the old mechanical timer,
so the power to the relay box gets disconnected when the timer goes
off. The wireless stat seems to resync ok, but after a delay, and it
might lead to some unreliability later on.

As a temporary work around I've left the mechanical timer permanently
on, and relying on the HW cylinder stat to switch off the hot water
when it gets up to around 45C.

It's going to be quite a job getting a permanent live to the relay
box, even if I move it nearer to the airing cupboard where all the
rest of the gubbins is, and the distance (plus walls) from it to the
new room stat might affect the wireless ability.

An option I'd considered is to remove the live feed to the relay box
from the mechanical timer and connect it to the switched live from the
FCU for the system, thereby bypassing the timer. This would mean that
the hot water only is controlled by the timer, and the CH is only
controlled by the new stat (which of course has its own timer anyway).
I'd put a note somewhere prominent to warn of this.

Anyone see any problems with this?

On 07/04/2014 15:56, Davidm wrote:
I've just had to replace the room thermostat on MIL's CH system, and
have installed a Honeywell CM927 programmable wireless stat.

The old stat had live, switched live, neutral and earth connections,
so I just linked the live to one side of the switch in the Relay Box,
with the switched live on the otherside of the switch. All works ok
except........

The live to the stat is actually switched by the old mechanical timer,
so the power to the relay box gets disconnected when the timer goes
off. The wireless stat seems to resync ok, but after a delay, and it
might lead to some unreliability later on.

As a temporary work around I've left the mechanical timer permanently
on, and relying on the HW cylinder stat to switch off the hot water
when it gets up to around 45C.

It's going to be quite a job getting a permanent live to the relay
box, even if I move it nearer to the airing cupboard where all the
rest of the gubbins is, and the distance (plus walls) from it to the
new room stat might affect the wireless ability.

An option I'd considered is to remove the live feed to the relay box
from the mechanical timer and connect it to the switched live from the
FCU for the system, thereby bypassing the timer. This would mean that
the hot water only is controlled by the timer, and the CH is only
controlled by the new stat (which of course has its own timer anyway).
I'd put a note somewhere prominent to warn of this.

Anyone see any problems with this?


I have the same stat, connected the same way you have at the moment at
mu mum's house, and it isn't a problem at all - been like it for several
years.

I have set the timer to be on 24/7 for the heating (so its controlled by
the CM927), and timed for the DHW.


--
Toby...
Remove your pants to reply

On Mon, 07 Apr 2014 17:24:25 +0100, Toby wrote:

I have the same stat, connected the same way you have at the moment at
mu mum's house, and it isn't a problem at all - been like it for several
years.

Connect but not operated the same way.

I have set the timer to be on 24/7 for the heating (so its controlled by
the CM927), and timed for the DHW.

So the receiver has permenant mains. The OP has an old mechanical
timer it may not be possible to have the CH on "constant" and the HW
on "timed".

It should be OK to do what the OP suggests, connect the timed CH wire
dierct to the mains but it does depend a bit on how the rest of the
system is wired. It's quite possible that the timeswitch feeds both
the pump and room stat, the pump rund when ever the time switch says
CH on, the room stat then controls the boiler. Making the "CH timed"
wire permenantly live would mean the pump runs 24/7...

--
Cheers
Dave.

On 07/04/2014 15:56, Davidm wrote:

An option I'd considered is to remove the live feed to the relay box
from the mechanical timer and connect it to the switched live from the
FCU for the system, thereby bypassing the timer. This would mean that
the hot water only is controlled by the timer, and the CH is only
controlled by the new stat (which of course has its own timer anyway).
I'd put a note somewhere prominent to warn of this.

Anyone see any problems with this?


It would be normal practice to take the live feed for all stats and
timers from the FCU.
Then you have a single point at which you can isolate the system.

"dennis@home" wrote in message
eb.com...
On 07/04/2014 15:56, Davidm wrote:

An option I'd considered is to remove the live feed to the relay box
from the mechanical timer and connect it to the switched live from the
FCU for the system, thereby bypassing the timer. This would mean that
the hot water only is controlled by the timer, and the CH is only
controlled by the new stat (which of course has its own timer anyway).
I'd put a note somewhere prominent to warn of this.

Anyone see any problems with this?


It would be normal practice to take the live feed for all stats and timers
from the FCU.
Then you have a single point at which you can isolate the system.


You are correct, but I AIUI that is what the OP is intending to do.


--
Adam

On 07/04/2014 15:56, Davidm wrote:
I've just had to replace the room thermostat on MIL's CH system, and
have installed a Honeywell CM927 programmable wireless stat.

The old stat had live, switched live, neutral and earth connections,
so I just linked the live to one side of the switch in the Relay Box,
with the switched live on the otherside of the switch. All works ok
except........

The live to the stat is actually switched by the old mechanical timer,
so the power to the relay box gets disconnected when the timer goes
off. The wireless stat seems to resync ok, but after a delay, and it
might lead to some unreliability later on.

As a temporary work around I've left the mechanical timer permanently
on, and relying on the HW cylinder stat to switch off the hot water
when it gets up to around 45C.

It's going to be quite a job getting a permanent live to the relay
box, even if I move it nearer to the airing cupboard where all the
rest of the gubbins is, and the distance (plus walls) from it to the
new room stat might affect the wireless ability.

An option I'd considered is to remove the live feed to the relay box
from the mechanical timer and connect it to the switched live from the
FCU for the system, thereby bypassing the timer. This would mean that
the hot water only is controlled by the timer, and the CH is only
controlled by the new stat (which of course has its own timer anyway).
I'd put a note somewhere prominent to warn of this.

Anyone see any problems with this?

It sounds ok in principle, but doesn't the timer have separate channels
for HW and CH which would enable you to have CH on constant and HW on
timed? [The timer must have separate outputs for HW and CH - otherwise
you wouldn't be able to bypass it for CH but not HW]

What is the rest of the control system - I assume that it's fully pumped
rather than pumped CH and gravity HW? Is it a Y-Plan system with a
3-port mid-position valve or an S-Plan with two 2-port valves? What does
the wireless thermostat actually switch?
--
Cheers,
Roger
____________
Please reply to Newsgroup. Whilst email address is valid, it is seldom
checked.

On 07/04/2014 21:41, ARW wrote:
"dennis@home" wrote in message
eb.com...
On 07/04/2014 15:56, Davidm wrote:

An option I'd considered is to remove the live feed to the relay box
from the mechanical timer and connect it to the switched live from the
FCU for the system, thereby bypassing the timer. This would mean that
the hot water only is controlled by the timer, and the CH is only
controlled by the new stat (which of course has its own timer anyway).
I'd put a note somewhere prominent to warn of this.

Anyone see any problems with this?


It would be normal practice to take the live feed for all stats and
timers from the FCU.
Then you have a single point at which you can isolate the system.


You are correct, but I AIUI that is what the OP is intending to do.


Yes, I was confirming that its normal.

On Mon, 07 Apr 2014 22:47:49 +0100, Roger Mills wrote:

What is the rest of the control system - I assume that it's fully pumped
rather than pumped CH and gravity HW? Is it a Y-Plan system with a
3-port mid-position valve or an S-Plan with two 2-port valves? What does
the wireless thermostat actually switch?

As this is the MIL's place and has a mechanical timer I'd go for
gravity HW, pumped CH and no indenpendant time control for HW CH. CH
probably has off, on , timed. The HW will get heated whenever the CH
demands heat, something similar
to:

http://pcmpictures.danfoss.com/pcm/i...ageCache/29819
5_20_3.jpg


--
Cheers
Dave.

On 08/04/2014 09:09, Dave Liquorice wrote:
On Mon, 07 Apr 2014 22:47:49 +0100, Roger Mills wrote:

What is the rest of the control system - I assume that it's fully pumped
rather than pumped CH and gravity HW? Is it a Y-Plan system with a
3-port mid-position valve or an S-Plan with two 2-port valves? What does
the wireless thermostat actually switch?

As this is the MIL's place and has a mechanical timer I'd go for
gravity HW, pumped CH and no indenpendant time control for HW CH. CH
probably has off, on , timed. The HW will get heated whenever the CH
demands heat, something similar
to:

http://pcmpictures.danfoss.com/pcm/i...ageCache/29819
5_20_3.jpg

All the ones I have ever come across so far the CH output controls just
the pump and the HW output controls just the boiler. On a gravity feed
the boiler will satisfy hot water demand whenever it is needed.

Old ones tend to be Off, Once daily, Twice Daily, On.
(or dial settable by the quarter hour with pins)

To make mine control the CH so that either CH or Woodburner or Manual
could run the CH pump I had to add one mains relay to make the CH live
output available to a pair of NO contacts for pump and boiler.

This highlighted a switched live vs permanent live issue with the
original boiler wiring leading to inelegant thermostat shutdowns.

Seems odd now that the devices all contain a micro that they don't offer
a facility to gate the requests together inside the controllers.

(and have driven outputs called "boiler" and "pump")

That would do fine for most simple domestic setups.

--
Regards,
Martin Brown

On 08/04/2014 09:09, Dave Liquorice wrote:
On Mon, 07 Apr 2014 22:47:49 +0100, Roger Mills wrote:

What is the rest of the control system - I assume that it's fully pumped
rather than pumped CH and gravity HW? Is it a Y-Plan system with a
3-port mid-position valve or an S-Plan with two 2-port valves? What does
the wireless thermostat actually switch?

As this is the MIL's place and has a mechanical timer I'd go for
gravity HW, pumped CH and no indenpendant time control for HW CH. CH
probably has off, on , timed. The HW will get heated whenever the CH
demands heat, something similar
to:

http://pcmpictures.danfoss.com/pcm/i...ageCache/29819
5_20_3.jpg



Except that the OP mentions a cylinder stat, which you wouldn't normally
have in a gravity HW system (Unless it's a C-Plan).
--
Cheers,
Roger
____________
Please reply to Newsgroup. Whilst email address is valid, it is seldom
checked.

On Mon, 07 Apr 2014 22:47:49 +0100, Roger Mills
wrote:

On 07/04/2014 15:56, Davidm wrote:
I've just had to replace the room thermostat on MIL's CH system, and
have installed a Honeywell CM927 programmable wireless stat.

The old stat had live, switched live, neutral and earth connections,
so I just linked the live to one side of the switch in the Relay Box,
with the switched live on the otherside of the switch. All works ok
except........

The live to the stat is actually switched by the old mechanical timer,
so the power to the relay box gets disconnected when the timer goes
off. The wireless stat seems to resync ok, but after a delay, and it
might lead to some unreliability later on.

As a temporary work around I've left the mechanical timer permanently
on, and relying on the HW cylinder stat to switch off the hot water
when it gets up to around 45C.

It's going to be quite a job getting a permanent live to the relay
box, even if I move it nearer to the airing cupboard where all the
rest of the gubbins is, and the distance (plus walls) from it to the
new room stat might affect the wireless ability.

An option I'd considered is to remove the live feed to the relay box
from the mechanical timer and connect it to the switched live from the
FCU for the system, thereby bypassing the timer. This would mean that
the hot water only is controlled by the timer, and the CH is only
controlled by the new stat (which of course has its own timer anyway).
I'd put a note somewhere prominent to warn of this.

Anyone see any problems with this?

It sounds ok in principle, but doesn't the timer have separate channels
for HW and CH which would enable you to have CH on constant and HW on
timed? [The timer must have separate outputs for HW and CH - otherwise
you wouldn't be able to bypass it for CH but not HW]

What is the rest of the control system - I assume that it's fully pumped
rather than pumped CH and gravity HW? Is it a Y-Plan system with a
3-port mid-position valve or an S-Plan with two 2-port valves? What does
the wireless thermostat actually switch?
It's a Y-Plan, with 3 port mid position valve. The wiring is a bit of
a challenge as all the connections have been crammed into a single
width surface box (what you'd normally use for a 13a socket) with choc
blocks, rather than use a proper wiring centre box.

The mechanical timer has on/of switches for CH and HW, and then a
single switch of timed/continuous, so the option of HW timed + CH
continuous isn't provided for.

I'll have to check how the pump is fed, I'd don't know if it comes via
the boiler (Netaheat Electronic) on an over-run circuit.

On 08/04/2014 13:10, Davidm wrote:
On Mon, 07 Apr 2014 22:47:49 +0100, Roger
wrote:

On 07/04/2014 15:56, Davidm wrote:
I've just had to replace the room thermostat on MIL's CH system, and
have installed a Honeywell CM927 programmable wireless stat.

The old stat had live, switched live, neutral and earth connections,
so I just linked the live to one side of the switch in the Relay Box,
with the switched live on the otherside of the switch. All works ok
except........

The live to the stat is actually switched by the old mechanical timer,
so the power to the relay box gets disconnected when the timer goes
off. The wireless stat seems to resync ok, but after a delay, and it
might lead to some unreliability later on.

As a temporary work around I've left the mechanical timer permanently
on, and relying on the HW cylinder stat to switch off the hot water
when it gets up to around 45C.

It's going to be quite a job getting a permanent live to the relay
box, even if I move it nearer to the airing cupboard where all the
rest of the gubbins is, and the distance (plus walls) from it to the
new room stat might affect the wireless ability.

An option I'd considered is to remove the live feed to the relay box
from the mechanical timer and connect it to the switched live from the
FCU for the system, thereby bypassing the timer. This would mean that
the hot water only is controlled by the timer, and the CH is only
controlled by the new stat (which of course has its own timer anyway).
I'd put a note somewhere prominent to warn of this.

Anyone see any problems with this?

It sounds ok in principle, but doesn't the timer have separate channels
for HW and CH which would enable you to have CH on constant and HW on
timed? [The timer must have separate outputs for HW and CH - otherwise
you wouldn't be able to bypass it for CH but not HW]

What is the rest of the control system - I assume that it's fully pumped
rather than pumped CH and gravity HW? Is it a Y-Plan system with a
3-port mid-position valve or an S-Plan with two 2-port valves? What does
the wireless thermostat actually switch?
It's a Y-Plan, with 3 port mid position valve. The wiring is a bit of
a challenge as all the connections have been crammed into a single
width surface box (what you'd normally use for a 13a socket) with choc
blocks, rather than use a proper wiring centre box.

The mechanical timer has on/of switches for CH and HW, and then a
single switch of timed/continuous, so the option of HW timed + CH
continuous isn't provided for.

I'll have to check how the pump is fed, I'd don't know if it comes via
the boiler (Netaheat Electronic) on an over-run circuit.

That tells me all I need to know - don't worry about exactly how the
pump is controlled - it will either be in parallel with the boiler, or
controlled by it if it needs to over-run.

What you are proposing will be fine. Disconnect the programmer's CH ON
wire and feed it (the wire) from a permanent live. Then use the
programmer just for the HW. As long as the permanent live comes from the
same FCU as the rest of the system, you will still be able isolate the
lot when necessary. The only thing to be aware of when using the CM927
as the only timer for the CH, you will no longer have an absolute OFF
because - even in the Off position - it will still act as a frost stat.
That's not normally a problem.
--
Cheers,
Roger
____________
Please reply to Newsgroup. Whilst email address is valid, it is seldom
checked.

On Tue, 08 Apr 2014 19:00:29 +0100, Roger Mills
wrote:

On 08/04/2014 13:10, Davidm wrote:
On Mon, 07 Apr 2014 22:47:49 +0100, Roger
wrote:

On 07/04/2014 15:56, Davidm wrote:
I've just had to replace the room thermostat on MIL's CH system, and
have installed a Honeywell CM927 programmable wireless stat.

The old stat had live, switched live, neutral and earth connections,
so I just linked the live to one side of the switch in the Relay Box,
with the switched live on the otherside of the switch. All works ok
except........

The live to the stat is actually switched by the old mechanical timer,
so the power to the relay box gets disconnected when the timer goes
off. The wireless stat seems to resync ok, but after a delay, and it
might lead to some unreliability later on.

As a temporary work around I've left the mechanical timer permanently
on, and relying on the HW cylinder stat to switch off the hot water
when it gets up to around 45C.

It's going to be quite a job getting a permanent live to the relay
box, even if I move it nearer to the airing cupboard where all the
rest of the gubbins is, and the distance (plus walls) from it to the
new room stat might affect the wireless ability.

An option I'd considered is to remove the live feed to the relay box
from the mechanical timer and connect it to the switched live from the
FCU for the system, thereby bypassing the timer. This would mean that
the hot water only is controlled by the timer, and the CH is only
controlled by the new stat (which of course has its own timer anyway).
I'd put a note somewhere prominent to warn of this.

Anyone see any problems with this?

It sounds ok in principle, but doesn't the timer have separate channels
for HW and CH which would enable you to have CH on constant and HW on
timed? [The timer must have separate outputs for HW and CH - otherwise
you wouldn't be able to bypass it for CH but not HW]

What is the rest of the control system - I assume that it's fully pumped
rather than pumped CH and gravity HW? Is it a Y-Plan system with a
3-port mid-position valve or an S-Plan with two 2-port valves? What does
the wireless thermostat actually switch?
It's a Y-Plan, with 3 port mid position valve. The wiring is a bit of
a challenge as all the connections have been crammed into a single
width surface box (what you'd normally use for a 13a socket) with choc
blocks, rather than use a proper wiring centre box.

The mechanical timer has on/of switches for CH and HW, and then a
single switch of timed/continuous, so the option of HW timed + CH
continuous isn't provided for.

I'll have to check how the pump is fed, I'd don't know if it comes via
the boiler (Netaheat Electronic) on an over-run circuit.

That tells me all I need to know - don't worry about exactly how the
pump is controlled - it will either be in parallel with the boiler, or
controlled by it if it needs to over-run.

What you are proposing will be fine. Disconnect the programmer's CH ON
wire and feed it (the wire) from a permanent live. Then use the
programmer just for the HW. As long as the permanent live comes from the
same FCU as the rest of the system, you will still be able isolate the
lot when necessary. The only thing to be aware of when using the CM927
as the only timer for the CH, you will no longer have an absolute OFF
because - even in the Off position - it will still act as a frost stat.
That's not normally a problem.
Excellent, thanks Roger. Now I just need to get the test meter out and
locate the correct wires in the "rats nest" connection box!

"Davidm" wrote in message
...
On Mon, 07 Apr 2014 22:47:49 +0100, Roger Mills
wrote:

On 07/04/2014 15:56, Davidm wrote:
I've just had to replace the room thermostat on MIL's CH system, and
have installed a Honeywell CM927 programmable wireless stat.

The old stat had live, switched live, neutral and earth connections,
so I just linked the live to one side of the switch in the Relay Box,
with the switched live on the otherside of the switch. All works ok
except........

The live to the stat is actually switched by the old mechanical timer,
so the power to the relay box gets disconnected when the timer goes
off. The wireless stat seems to resync ok, but after a delay, and it
might lead to some unreliability later on.

As a temporary work around I've left the mechanical timer permanently
on, and relying on the HW cylinder stat to switch off the hot water
when it gets up to around 45C.

It's going to be quite a job getting a permanent live to the relay
box, even if I move it nearer to the airing cupboard where all the
rest of the gubbins is, and the distance (plus walls) from it to the
new room stat might affect the wireless ability.

An option I'd considered is to remove the live feed to the relay box
from the mechanical timer and connect it to the switched live from the
FCU for the system, thereby bypassing the timer. This would mean that
the hot water only is controlled by the timer, and the CH is only
controlled by the new stat (which of course has its own timer anyway).
I'd put a note somewhere prominent to warn of this.

Anyone see any problems with this?

It sounds ok in principle, but doesn't the timer have separate channels
for HW and CH which would enable you to have CH on constant and HW on
timed? [The timer must have separate outputs for HW and CH - otherwise
you wouldn't be able to bypass it for CH but not HW]

What is the rest of the control system - I assume that it's fully pumped
rather than pumped CH and gravity HW? Is it a Y-Plan system with a
3-port mid-position valve or an S-Plan with two 2-port valves? What does
the wireless thermostat actually switch?
It's a Y-Plan, with 3 port mid position valve. The wiring is a bit of
a challenge as all the connections have been crammed into a single
width surface box (what you'd normally use for a 13a socket) with choc
blocks, rather than use a proper wiring centre box.

The mechanical timer has on/of switches for CH and HW, and then a
single switch of timed/continuous, so the option of HW timed + CH
continuous isn't provided for.


Are you sure it is a Y plan and not a W plan? They LOOK very similar but the
W plan must always heat the HW. Double check the number on the "3 port
valve" it may well turn out to be a 3 way diverter port.

--
Adam

On 09/04/2014 18:40, ARW wrote:
"Davidm" wrote in message
...
On Mon, 07 Apr 2014 22:47:49 +0100, Roger Mills
wrote:

On 07/04/2014 15:56, Davidm wrote:
I've just had to replace the room thermostat on MIL's CH system, and
have installed a Honeywell CM927 programmable wireless stat.

The old stat had live, switched live, neutral and earth connections,
so I just linked the live to one side of the switch in the Relay Box,
with the switched live on the otherside of the switch. All works ok
except........

The live to the stat is actually switched by the old mechanical timer,
so the power to the relay box gets disconnected when the timer goes
off. The wireless stat seems to resync ok, but after a delay, and it
might lead to some unreliability later on.

As a temporary work around I've left the mechanical timer permanently
on, and relying on the HW cylinder stat to switch off the hot water
when it gets up to around 45C.

It's going to be quite a job getting a permanent live to the relay
box, even if I move it nearer to the airing cupboard where all the
rest of the gubbins is, and the distance (plus walls) from it to the
new room stat might affect the wireless ability.

An option I'd considered is to remove the live feed to the relay box
from the mechanical timer and connect it to the switched live from the
FCU for the system, thereby bypassing the timer. This would mean that
the hot water only is controlled by the timer, and the CH is only
controlled by the new stat (which of course has its own timer anyway).
I'd put a note somewhere prominent to warn of this.

Anyone see any problems with this?

It sounds ok in principle, but doesn't the timer have separate channels
for HW and CH which would enable you to have CH on constant and HW on
timed? [The timer must have separate outputs for HW and CH - otherwise
you wouldn't be able to bypass it for CH but not HW]

What is the rest of the control system - I assume that it's fully pumped
rather than pumped CH and gravity HW? Is it a Y-Plan system with a
3-port mid-position valve or an S-Plan with two 2-port valves? What does
the wireless thermostat actually switch?
It's a Y-Plan, with 3 port mid position valve. The wiring is a bit of
a challenge as all the connections have been crammed into a single
width surface box (what you'd normally use for a 13a socket) with choc
blocks, rather than use a proper wiring centre box.

The mechanical timer has on/of switches for CH and HW, and then a
single switch of timed/continuous, so the option of HW timed + CH
continuous isn't provided for.


Are you sure it is a Y plan and not a W plan? They LOOK very similar but
the W plan must always heat the HW. Double check the number on the "3
port valve" it may well turn out to be a 3 way diverter port.


Good point. And the wiring is different, so the OP needs to know which
it is when trying to decipher the rat's nest wiring.

The proposed solution - of using the original timer to time the HW and
the new programmable stat to time the CH - would sort of work, except
that you wouldn't get any CH until the HW demand was satisfied (even if
HW is OFF at the programmer!) The only way to have CH without HW is to
turn the cylinder stat right down so that it is satisfied even when the
tank is cold.
--
Cheers,
Roger
____________
Please reply to Newsgroup. Whilst email address is valid, it is seldom
checked.

"Roger Mills" wrote in message
...

The proposed solution - of using the original timer to time the HW and the
new programmable stat to time the CH - would sort of work, except that you
wouldn't get any CH until the HW demand was satisfied (even if HW is OFF
at the programmer!) The only way to have CH without HW is to turn the
cylinder stat right down so that it is satisfied even when the tank is
cold.

We never did come up with a solution using the HW off connection on the
programmer to overcome this. What would happen if the HW OFF was connected
to the brown on the divertor valve - I know it would not work:-)

Feel free to email me if you want to chat off group with suggestions and you
are interested - I no longer have your email address

Cheers
--
Adam

On 10/04/2014 17:55, ARW wrote:
"Roger Mills" wrote in message
...

The proposed solution - of using the original timer to time the HW and
the new programmable stat to time the CH - would sort of work, except
that you wouldn't get any CH until the HW demand was satisfied (even
if HW is OFF at the programmer!) The only way to have CH without HW is
to turn the cylinder stat right down so that it is satisfied even when
the tank is cold.

We never did come up with a solution using the HW off connection on the
programmer to overcome this. What would happen if the HW OFF was
connected to the brown on the divertor valve - I know it would not work:-)

Feel free to email me if you want to chat off group with suggestions and
you are interested - I no longer have your email address

Cheers

The email address in my SIG works, even though it's not my regular one.

I've just had a look at a W-Plan diagram, and I reckon that connecting
HW-OFF to the diverter valve *would* work. That would force the valve to
the CH position and the room stat would control the boiler and pump. The
state of the tank stat would be immaterial.
--
Cheers,
Roger
____________
Please reply to Newsgroup. Whilst email address is valid, it is seldom
checked.