We have gas central heating with a Potterton EP2001 controller.

Currently the controls are linked so that CH requires the HW to be on. I
would like to separate them as the hot water gets very hot since we had
a new insulated tank installed (approx 75 C) and I want to fit a
thermostat to the tank.

The controller can be set up so that the two are independent, but when I
have tried this the boiler pump doesn't come on.

I expect that I will need to change some of the plumbing too and fit
motorised valves.

How do I go about this?

thanks

dan

In an earlier contribution to this discussion,
Dan Smithers wrote:

We have gas central heating with a Potterton EP2001 controller.

Currently the controls are linked so that CH requires the HW to be
on. I would like to separate them as the hot water gets very hot
since we had a new insulated tank installed (approx 75 C) and I want
to fit a thermostat to the tank.

The controller can be set up so that the two are independent, but
when I have tried this the boiler pump doesn't come on.

I expect that I will need to change some of the plumbing too and fit
motorised valves.

How do I go about this?

thanks

dan

I suspect that you have a gravity HW and pumped CH system. If so, the room
stat will only control the pump, and the programmer has to force the boiler
to fire when CH is required - with the result that the HW gets hot whether
you want it or not.

There are *two* basic solutions - convert to a fully pumped system, or
convert to a C-Plan[1] system by fitting a cylinder stat and a motorised
valve in the HW circuit. The second is far simpler - but you have to be
careful where you fit the valve so that there is always an open connection
from boiler to vent pipe even when the valve is closed.

Going fully pumped is a better solution in many ways, but will require more
extensive changes to the pipework. You have the option of an S-Plan[1]
system with two 2-port valves or a Y-Plan[1] with one 3-port mid-position
valve.


[1] See http://content.honeywell.com/uk/homes/systems.htm for details of the
various control plans.
--
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,
Dan Smithers wrote:

We have gas central heating with a Potterton EP2001 controller.

Currently the controls are linked so that CH requires the HW to be
on. I would like to separate them as the hot water gets very hot
since we had a new insulated tank installed (approx 75 C) and I want
to fit a thermostat to the tank.

The controller can be set up so that the two are independent, but
when I have tried this the boiler pump doesn't come on.

I expect that I will need to change some of the plumbing too and fit
motorised valves.

How do I go about this?

thanks

dan

I suspect that you have a gravity HW and pumped CH system. If so, the room
stat will only control the pump, and the programmer has to force the boiler
to fire when CH is required - with the result that the HW gets hot whether
you want it or not.

The pump comes on for HW alone, and I think that it is unlikely to be a
gravity fed system as the tank is a long off being above the boiler.

None of this was clear from the original post, but I was thinking of a
tank stat - a room stat would probably be a good idea too.


There are *two* basic solutions - convert to a fully pumped system, or
convert to a C-Plan[1] system by fitting a cylinder stat and a motorised
valve in the HW circuit. The second is far simpler - but you have to be
careful where you fit the valve so that there is always an open connection
from boiler to vent pipe even when the valve is closed.

Going fully pumped is a better solution in many ways, but will require more
extensive changes to the pipework. You have the option of an S-Plan[1]
system with two 2-port valves or a Y-Plan[1] with one 3-port mid-position
valve.


[1] See http://content.honeywell.com/uk/homes/systems.htm for details of the
various control plans.

In an earlier contribution to this discussion,
Dan Smithers wrote:


The pump comes on for HW alone, and I think that it is unlikely to be
a gravity fed system as the tank is a long off being above the boiler.

None of this was clear from the original post, but I was thinking of a
tank stat - a room stat would probably be a good idea too.


So what controls *have* you got? What stops the radiators getting hot in
summer when you only want HW?
--
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,
Dan Smithers wrote:

The pump comes on for HW alone, and I think that it is unlikely to be
a gravity fed system as the tank is a long off being above the boiler.

None of this was clear from the original post, but I was thinking of a
tank stat - a room stat would probably be a good idea too.


So what controls *have* you got? What stops the radiators getting hot in
summer when you only want HW?

The controller has a timer in it and two sets of controls:
HW off- timed - once - continuous
CH off- timed - once - continuous

In the current mode the two are linked so the CH control must be no
higher than the HW. Currently CH is off and HW is timed. In the winter
both are set to timed.

In the winter I would like to be able to stop heating the HW when the
water in the tank is hot enough while still allowing the CH to be on.

There is an alternative mode that controls the two independently but
when I tried it the boiler fires but the pump doesn't run when CH only
is on.

I hope this explains a bit better.

thanks

dan

In an earlier contribution to this discussion,
Dan Smithers wrote:

Roger Mills wrote:
In an earlier contribution to this discussion,
Dan Smithers wrote:

The pump comes on for HW alone, and I think that it is unlikely to
be a gravity fed system as the tank is a long off being above the
boiler.

None of this was clear from the original post, but I was thinking
of a tank stat - a room stat would probably be a good idea too.


So what controls *have* you got? What stops the radiators getting
hot in summer when you only want HW?

The controller has a timer in it and two sets of controls:
HW off- timed - once - continuous
CH off- timed - once - continuous

In the current mode the two are linked so the CH control must be no
higher than the HW. Currently CH is off and HW is timed. In the winter
both are set to timed.

In the winter I would like to be able to stop heating the HW when the
water in the tank is hot enough while still allowing the CH to be on.

There is an alternative mode that controls the two independently but
when I tried it the boiler fires but the pump doesn't run when CH only
is on.

I hope this explains a bit better.

thanks

dan


What I'm really trying to get at is what does the programmer actually
control? For example, are there any motorised valves? Is there more than one
pump? How many water pipes are connected to the boiler?

If both HW and CH are pumped, and if there is only one pump which runs
whenever either HW or CH is selected, and if there are no valves to allow
water to go to (say) the HW cylinder whilst preventing it going to the
radiators, you will get *both* HW *and* CH whatever the programmer is set
to.

If this is not the case, you must have some components that you haven't yet
told us about!

Starting at the boiler, can you draw a circuit diagram of the pipework - and
scan it and upload it somewhere with a link here - so that we can get a
better idea of the layout of your system.

[I still have a sneaking suspicion that you have a gravity HW system despite
your earlier comments. If this is the case, there will be 4 pipes (or maybe
only 3 if there's a common return) connected to the boiler - 2 big ones
going to the HW cylinder without a pump in them, and 2 smaller ones going to
the radiators - with a pump somewhere in the 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.
PLEASE REPLY TO NEWSGROUP!

Dan Smithers wrote:


The controller has a timer in it and two sets of controls:
HW off- timed - once - continuous
CH off- timed - once - continuous

In the current mode the two are linked so the CH control must be no
higher than the HW. Currently CH is off and HW is timed. In the winter
both are set to timed.

In the winter I would like to be able to stop heating the HW when the
water in the tank is hot enough while still allowing the CH to be on.

There is an alternative mode that controls the two independently but
when I tried it the boiler fires but the pump doesn't run when CH only
is on.

I hope this explains a bit better.

Although its hard to be sure, it sounds very much like you got a basic
gravity HW/pumped CH system. Does the pump run when the hot water is on
without the CH? If not, the HW system must be gravity.

As others have said, a bit of replumbing and conversion to fully pumped HW
and CH would be desirable, not just to stop your hot water getting too hot,
but because it also greatly reduces the time needed to reheat a cylinder of
HW.

Personally, I prefer systems with a separate motorised valve for each
circuit as fault diagnosis & repairs are a bit easier (IMO).

Tim

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

Roger Mills wrote:
In an earlier contribution to this discussion,
Dan Smithers wrote:

The pump comes on for HW alone, and I think that it is unlikely to
be a gravity fed system as the tank is a long off being above the
boiler.

None of this was clear from the original post, but I was thinking
of a tank stat - a room stat would probably be a good idea too.


So what controls *have* you got? What stops the radiators getting
hot in summer when you only want HW?

The controller has a timer in it and two sets of controls:
HW off- timed - once - continuous
CH off- timed - once - continuous

In the current mode the two are linked so the CH control must be no
higher than the HW. Currently CH is off and HW is timed. In the winter
both are set to timed.

In the winter I would like to be able to stop heating the HW when the
water in the tank is hot enough while still allowing the CH to be on.

There is an alternative mode that controls the two independently but
when I tried it the boiler fires but the pump doesn't run when CH only
is on.

I hope this explains a bit better.

thanks

dan


What I'm really trying to get at is what does the programmer actually
control? For example, are there any motorised valves? Is there more than
one pump? How many water pipes are connected to the boiler?

If both HW and CH are pumped, and if there is only one pump which runs
whenever either HW or CH is selected, and if there are no valves to allow
water to go to (say) the HW cylinder whilst preventing it going to the
radiators, you will get *both* HW *and* CH whatever the programmer is set
to.

If this is not the case, you must have some components that you haven't
yet told us about!

Like a hidden 2 port valve.

I have seen the following setup many times (a set up that could be like the
OPs system)

The HW and CH are fully pumped and where the pipework splits there is a 2
port valve on the CH side and no valves on the HW side.
The programmer is set for a gravity system with the HW output from the prog
calling for the pump and boiler and the CH output opening the 2 port valve
to allow the CH to get hot.

Adam

On Thu, 03 Jul 2008 09:43:39 +0100, Dan Smithers wrote:

We have gas central heating with a Potterton EP2001 controller.

Currently the controls are linked so that CH requires the HW to be on. I
would like to separate them as the hot water gets very hot since we had
a new insulated tank installed (approx 75 C) and I want to fit a
thermostat to the tank.

The controller can be set up so that the two are independent, but when I
have tried this the boiler pump doesn't come on.

I expect that I will need to change some of the plumbing too and fit
motorised valves.

How do I go about this?

thanks

dan

Read, faqs and wiki.


--
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,
ARWadworth wrote:

"Roger Mills" wrote in message
...

What I'm really trying to get at is what does the programmer actually
control? For example, are there any motorised valves? Is there more
than one pump? How many water pipes are connected to the boiler?

If both HW and CH are pumped, and if there is only one pump which
runs whenever either HW or CH is selected, and if there are no
valves to allow water to go to (say) the HW cylinder whilst
preventing it going to the radiators, you will get *both* HW *and*
CH whatever the programmer is set to.

If this is not the case, you must have some components that you
haven't yet told us about!

Like a hidden 2 port valve.

I have seen the following setup many times (a set up that could be
like the OPs system)

The HW and CH are fully pumped and where the pipework splits there is
a 2 port valve on the CH side and no valves on the HW side.
The programmer is set for a gravity system with the HW output from
the prog calling for the pump and boiler and the CH output opening
the 2 port valve to allow the CH to get hot.

Adam

That's certainly a possibility!
--
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!