Room thermostat. Why?

[dcbwhaley]

I am having my old boiler (hearing only not dhw) replaced with a supposedly more efficient modern one. The engineer insists that, according to regs, he cannot turn it on unless there is a room 'stat. Since each radiator has its own 'stat this seems superfluous. He has suggested that I mount it in the front hall which is not heated. In that position it will not be in the thermal loop and will simply act as a very expensive on/off switch.

What is the point of the that reg and is my engineering giving me good advice?

 

[Octopus]

Having a room stat is very sensible advice, and placing it in the hall away from radiators and drafts is the thing to do.

This will be a wireless device and thus the very occasional change of batteries may be required.

 

[Leesparkykent]

The minimum requirements to meet part L of the building regs when replacing a boiler are a room thermostat, TRVs are required on at least the bedroom radiators and preferably on all ( with the exception of the room with the thermostat) and a Timer/programmer.

below is the link for the part L documents.

http://www.planningportal.gov.uk/buildingregulations/approveddocuments/partl/approved#Download2


Edit: you don't want to place the thermostat in the hallway if it doesn't have a radiator.

 

[Leesparkykent]

You can get a plumbcenter branded wireless thermostat/programmer for £51 which is made by Honeywell and is the same as the Honeywell branded one but has a slightly different front cover. The Honeywell branded one is more than double the cost of the plumcenter branded one.

Center radio frequency programmable room thermostat

 

[dcbwhaley]

Thanks for your interest but it doesn't really answer my question. What is the purpose of the overall 'stat? It will always be set to a temperature higher than that of the hottest rad' 'stat so will never operate. But if I do have to have one where should it go - given that the hall is unheated?

 

[Octopus]

You can lead a horse to water .....

Get the chap who has quoted to talk you through the options and if you don't like the input, get a 2nd or 3rd opinion.

 

[ImpededLoop]

You need the thermostat in the room with the least heating in it. If it was in the room with the most heating, it would switch off the heating circuit before the other rooms were warm enough.

Also, you say that all the rads have trv's. You need at least one without, or a bypass loop so that the boiler and pump don't end up working against a dead head (no circulation).

 

[dcbwhaley]

You need the thermostat in the room with the least heating in it

Thay rather contradicts the Kent sparky who said I shouldn't put it in a hallway without a rad.

Also, you say that all the rads have trv's. You need at least one without, or a bypass loop so that the boiler and pump don't end up working against a dead head (no circulation).

Yes I have a bypass loop. Can noone really tell me what the 'stat does apart from satisfying the regs? I will probably fit one to satisfy the installer then rewmove it and sell it on eBay

 

[davesparks]

You need the thermostat in the room with the least heating in it. If it was in the room with the most heating, it would switch off the heating circuit before the other rooms were warm enough.

Also, you say that all the rads have trv's. You need at least one without, or a bypass loop so that the boiler and pump don't end up working against a dead head (no circulation).

The heating system should be balanced such that all rooms heat up equally, with the thermostat being in the room with the rad which has no TRV.

The rad without the TRV will be on the wrong side of a motorised valve to act as the bypass for the pump overrun. A seperate bypass is required unless it's a Y plan system where the valve remains open to the cylinder

 

[Leesparkykent]

The TRV's on the radiators are good for individual room temperature control. The only thing is the TRV's don't stop the boiler from firing up so the boiler is either on or off. A wall thermostat will tell the boiler to stop firing when it reaches a desired temperature.


By adding a thermostat you will save money on your heating costs and have good temperature control through out the property. The savings you will make will more than pay for the cost of a thermostat.

 

[davesparks]

Thay rather contradicts the Kent sparky who said I shouldn't put it in a hallway without a rad.





Yes I have a bypass loop. Can noone really tell me what the 'stat does apart from satisfying the regs? I will probably fit one to satisfy the installer then rewmove it and sell it on eBay

Your radiators should be balanced so that all rooms heat up evenly.
One rad should have no TRV, this room should have the thermostat in it.
With the system balanced all rooms should achieve the same temperature as set on the stat at the same rate.
Fine balancing of each room can be achieved with the TRVs in the other rooms.

The stat effectively switches the boiler off when the heating is up to temperature. In your current setup all of the TRVs will shut when the rooms are up to temperature but the boiler will continue to fire wasting fuel as heat is dumped through whatever bypasses etc are in the system.

 

[Leesparkykent]

Or an automatic bypass valve fitted between the flow and return pipework, before the valve and after the pump.

 

[ImpededLoop]

The heating system should be balanced such that all rooms heat up equally, with the thermostat being in the room with the rad which has no TRV.

In an ideal world, yes I agree, but there are many situations where that's not case as the hallway doesn't always have room for a large enough radiator. In practice this doesn't usually matter as it's not a room that you sit around in.

The rad without the TRV will be on the wrong side of a motorised valve to act as the bypass for the pump overrun. A seperate bypass is required unless it's a Y plan system where the valve remains open to the cylinder

I also agree, but the OP indicated that this boiler was for heating only so there's unlikely to be a valve.

 

[pjeffrey]

OP's question was quite simple to answer. The TRVs only control the heat of the rads but not the boiler. The room stat is there to turn the boiler off and on. Without it you'd have to manually turn it on and off or it'd be on all the time (until overheat).

 

[Leesparkykent]

OP's question was quite simple to answer. The TRVs only control the heat of the rads but not the boiler. The room stat is there to turn the boiler off and on. Without it you'd have to manually turn it on and off or it'd be on all the time (until overheat).

Already been stated....#10 and #11

 

[pjeffrey]

Already been stated....#10 and #11

True, things just seemed to be going off at bit of a tangent

 

[dcbwhaley]

OP's question was quite simple to answer. The TRVs only control the heat of the rads but not the boiler. The room stat is there to turn the boiler off and on. Without it you'd have to manually turn it on and off or it'd be on all the time (until overheat).

Doesn't the boiler have its own 'stat on the return water? Placing a thermostat in an unheated room will not control the boiler since it will be on all the time. And since I only turn the rads on (with the TVR) in the room I am occupying I would need to carry the 'stat around with me for it to be effective

 

[davesparks]

Doesn't the boiler have its own 'stat on the return water? Placing a thermostat in an unheated room will not control the boiler since it will be on all the time. And since I only turn the rads on (with the TVR) in the room I am occupying I would need to carry the 'stat around with me for it to be effective

The stat should not be fitted in an unheated room

 

[pjeffrey]

Doesn't the boiler have its own 'stat on the return water? Placing a thermostat in an unheated room will not control the boiler since it will be on all the time. And since I only turn the rads on (with the TVR) in the room I am occupying I would need to carry the 'stat around with me for it to be effective

The stat should not be fitted in an unheated room

Absolutely, otherwise it would be a waste of time.

The BS says:

The heating system shall be provided with means to limit the temperature of the spaces it is heating.

The return temp does not effectively tell the boiler what the room temperatures are.

Also:

Where individual thermostatic radiator valves (TRVs) are used they shall not be the sole means of control for the heating circuit but shall be used in conjunction with other controls which ensure that the boiler is shut off, or reduced to minimum burning rate for solid fuel, when not required.

 

[dcbwhaley]

Absolutely, otherwise it would be a waste of time.

The BS says:The BS says:


The heating system shall be provided with means to limit the temperature of the spaces it is heating.

Fair enough if that is the regs. But which room should |I put the 'stat in bearing in mind that any room in the house can be unheated at some time or other.