I'm after a little bit of impartial advice on my recent CH upgrade. It's a
bit of along tale, but quite simple in truth...

Our old CH system used a single room (house?) thermostat, located in the
hall. The radiators did not have thermostats fitted. Our house has a very
large conservatory, which was heated by a CH fed convector. Unfortunately,
because the room 'stat at the other end of the house would always turn off
before the conservatory was warm, we would be left with either a warm house
and cold conservatory or, after turning the 'stat up, a warm conservatory
and a _very_ warm house :-(

I've now had a Worscester Bosch 35CDi II combi fitted to replace my
(somewhat ageing) gravity fed boiler as part of some work we are having done
on the house.

Because of the conservatory problem, we have decided to remove the room
'stat and use radiator thermostats on all of the radiators, bar a single one
near the boiler. This should (apparently) allow each room to maintain its
own temperature and once the whole system reaches temperature, the system
will shut off because the returned water feed is at the same temperature as
the outgoing feed (apparently this is because it's heating only one
radiator).

I suppose my question is - is this a good plan, or am I going down the
totally wrong road? What considerations should I be making here? Can I run a
combi CH system without a house 'stat?

Thanks in advance for any help you can offer me - as you have probably
gathered, I know very little about plumbing ;-)

DIF

On Fri, 07 May 2004 18:50:55 +0100, Daern's Instant Fortress wrote:

I'm after a little bit of impartial advice on my recent CH upgrade. It's a
bit of along tale, but quite simple in truth...

Our old CH system used a single room (house?) thermostat, located in the
hall. The radiators did not have thermostats fitted. Our house has a very
large conservatory, which was heated by a CH fed convector. Unfortunately,
because the room 'stat at the other end of the house would always turn off
before the conservatory was warm, we would be left with either a warm house
and cold conservatory or, after turning the 'stat up, a warm conservatory
and a _very_ warm house :-(

I've now had a Worscester Bosch 35CDi II combi fitted to replace my
(somewhat ageing) gravity fed boiler as part of some work we are having done
on the house.

Because of the conservatory problem, we have decided to remove the room
'stat and use radiator thermostats on all of the radiators, bar a single one
near the boiler. This should (apparently) allow each room to maintain its
own temperature and once the whole system reaches temperature, the system
will shut off because the returned water feed is at the same temperature as
the outgoing feed (apparently this is because it's heating only one
radiator).

I suppose my question is - is this a good plan, or am I going down the
totally wrong road? What considerations should I be making here? Can I run a
combi CH system without a house 'stat?

Thanks in advance for any help you can offer me - as you have probably
gathered, I know very little about plumbing ;-)


The very best way would be to zone the conservatory independantly fromt the
rest of the house heating.

TRVs on cooler rooms is no bad thing.

However the arrangement you outline
assumes that you want to heat the conservatory whenever you heat the house
and to much the same sort of level.
If you can arrange for the conservatory to be independantly heated you can
opt for such things as having it mildly heated for plants even when you
are out or away. Alternatively you might want to avoid heating the
conservatory entirely in deep-winter? Again you will probably want your
heating system to stop heating the conservatory when the sun shines as
such locations are apt to have a large solar gain.

Depending on how the pipes are laid and the state of decor the ease of
doing what you want will vary. In essence you would block off the existing
feed to the conservatory then connect a new feed pipe from before the
first T to feed any house radiators. Both the existing pipework and the new
pipe would then have there own valves to control them independantly.
A programmable thermostat would be used to control the conservatory.

I guess others will want to give you their own 2ps.

--
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

"Daern's Instant Fortress" wrote
| Our house has a very large conservatory, which was heated
| by a CH fed convector. ...

Moving to TRVs is generally regarded as a Good Thing, and may actually be
required under Building Regulations (when you replace your boiler you may be
required to bring the whole system up to current standards).

However what you really should consider is putting your conservatory on a
separate 'zone' on the heating system, so you can programme it with its own
time and temp settings completely separately from the house. You will be
using a lot of heat to keep it warm in the depths of winter. Depending on
how the plumbing is arranged this may be a fairly simple job adding a zone
valve and an appropriate controller, or it may be a complete pain.

Owain

"Owain" wrote in message
...
"Daern's Instant Fortress" wrote
| Our house has a very large conservatory, which was heated
| by a CH fed convector. ...

Moving to TRVs is generally regarded as a Good Thing, and may actually be
required under Building Regulations (when you replace your boiler you may
be
required to bring the whole system up to current standards).

However what you really should consider is putting your conservatory on a
separate 'zone' on the heating system, so you can programme it with its
own
time and temp settings completely separately from the house. You will be
using a lot of heat to keep it warm in the depths of winter. Depending on
how the plumbing is arranged this may be a fairly simple job adding a zone
valve and an appropriate controller, or it may be a complete pain.

I'll reply once for Ed and Owain's replys, as you both say more or less the
same thing:

I see where you are coming from with the seperate zones, but surely turning
the TRVs down in the winter (or if we are not using the room) amounts to the
same thing. The conservatory will be out of circuit and not using any
energy. Likewise, when the sun shines, the room is warm, the TRVs are off
and I'm not spending money. Am I missing some subtlety here?

As a general system question, when using TRVs, is it normal to *not* have
any room thermostats at all and what is the best practice for managing this?
Should I have all of my rads with TRVs or just leave one without?

Thanks for your replies on this subject. They're much appreciated!

DIF

"Daern's Instant Fortress" wrote in message
news:jdVmc.411$yp3.400@newsfe1-win...

"Owain" wrote in message
...
"Daern's Instant Fortress" wrote
| Our house has a very large conservatory, which was heated
| by a CH fed convector. ...

Moving to TRVs is generally regarded as a Good Thing, and may actually
be
required under Building Regulations (when you replace your boiler you
may
be
required to bring the whole system up to current standards).

However what you really should consider is putting your conservatory on
a
separate 'zone' on the heating system, so you can programme it with its
own
time and temp settings completely separately from the house. You will be
using a lot of heat to keep it warm in the depths of winter. Depending
on
how the plumbing is arranged this may be a fairly simple job adding a
zone
valve and an appropriate controller, or it may be a complete pain.

I'll reply once for Ed and Owain's replys, as you both say more or less
the
same thing:

I see where you are coming from with the seperate zones, but surely
turning
the TRVs down in the winter (or if we are not using the room) amounts to
the
same thing. The conservatory will be out of circuit and not using any
energy. Likewise, when the sun shines, the room is warm, the TRVs are off
and I'm not spending money. Am I missing some subtlety here?

Yes: the boiler is still on demand, and producing hot water (even though
it's not doing a lot since it'd only trying to heat the one un-TRVed rad.


As a general system question, when using TRVs, is it normal to *not* have
any room thermostats at all and what is the best practice for managing
this?
Should I have all of my rads with TRVs or just leave one without?

Leave one without and have a room thermostat sensing the temperature in the
('master') space that it heats. Then that 'stat can turn off the entire
system when that space is warm enough. It means you have to adjust the
valves on that rad so that it puts out little enough heat that the rest of
the house gets enough heat to satisfy their TRVs before the master space
gets too hot and the stat turns off, but hey! this is plumbing & heating,
not rocket science :-)

For a better system you'd have each space monitored and heating controlled
by its own thermostat, with the boiler told to provide heat when any of the
room 'stats demanded. Having 2 or more zones rather than treating the whole
house as one space is a step towards this ideal (and therefore A Good Thing
(tm) :-).

As a general system question, when using TRVs, is it normal to *not*
have any room thermostats at all and what is the best practice for
managing this?

It is permitted to use TRVs on all radiators and with no room thermostat.
However, you must still achieve boiler interlock if you wish to comply with
the Part L1 approved document.

One way of doing this is the following:

1. Install automatic bypass valve.

2. Install flow switch in heating circuit (*AFTER* ABV, *BEFORE* radiators)

3. Use flow switch output as a call for heat (simple on S-Plan, more complex
wiring for Y-Plan)

4. Wire pump permanently (or for a more sophisticated system, run the pump
on an 'OR'ed combination of the boiler pump output and a timer which
produces 5 second pulses every 10-15 minutes when the programmer CH On is
active).

Should I have all of my rads with TRVs or just leave one without?

Either. TRVs on all radiators is preferred. You can use a permanently open
radiator (lockshield both ends) instead of an automatic bypass valve, but it
must still be the only radiator BEFORE the flow switch. Putting it after the
flow switch will result in the interlock being ineffective. Putting any
other radiator before the flow switch will result in that radiator's call
for heat being ignored (although it will still heat up if other radiators do
call for heat).

Christian.

P.S.

You should still subzone the conservatory if at all possible, as this would
allow different timings to the rest of the house. It is possible, if you
want reduced timing periods for the conservatory but don't want the
disruption of running new zoned pipework, to do a "subzone lite". To do
this:

1. Implement the flow switch interlock above.
2. Do not install TRV in conservatory.
3. Install 2 port 22mm zone valve on conservatory radiator/convector.
4. Install programmable room stat in conservatory.
5. Wire zone valve to run when room stat activates.
6. Ignore zone valve switch outputs.

This will result in the conservatory system operating as a separate zone,
provided that the house programmer is set to heating on. This is a very good
idea, as it allows the conservatory to be heated only when required. If you
use it as a dining room, for example, you can set it to come on from 7pm to
9pm, for example, whilst being cold the rest of the day.