Thermostat in New Build House Not Doing Its Job... I think...

[Gigagator]

Hi all,

Please forgive any nonsense from me as I don't know much about heating systems.

Myself and my partner moved into a new build home back in Christmas 2016 and we've always had issues with getting the digital thermostat system to play ball and control our heating as we expect it to.

It's a two bedroom end-terrace with a Vaillant combi boiler and two Danfoss TP5000 Si (mains, not battery) thermostats, one upstairs in the master bedroom and the other downstairs in the small entrance hall.

My understanding is that if I set my downstairs stat to 23C, it should kick the boiler in to maintain that temperature. Once the stat sees the room at 23C it shuts the central heating off. Rinse, repeat.

Trouble is, the entrance hall gets hot very quickly, especially as it is joined to our kitchen so cooker, oven, tumble dryer frequently adding heat to the area.

We have always found that the thermostat knocks the heating off very prematurely while we are freezing our proverbials off in the living room, which is quite a large space and also includes the stairs.

The only way we have managed to overcome this is by setting the thermostat to something ridiculous like 29C just to keep the heating on so that the radiator in the living room has a chance to do its thing.

I have also always found the thermostats very inaccurate and read a few degrees above what the room temperature in the hall actually is.

Today, I placed a separate room thermometer in the hall and checked it a few hours later.

It read the temperature in the hall as just over 19C.
However, the room temperature displayed on the thermostat was 23C.

I have already set the temperature bias function to -1.5C so it used to be even worse than that!

Can anybody who knows their heating systems offer up any advice?

I am considering purchasing the optional TS2 temperature sensor and siting it in the living room so it more accurately controls the heating system based on the room we spend the most time in.

My next trick is to actually turn the radiator off in the hall, so that it doesn't heat up so quickly as to knock the heating off prematurely. Probably frowned upon but it's getting frustrating now.

 

[CBW]

Your from external sources will have an impact, however is the thermostat in the hall above the radiator?

 

[Nozzle]

You need to turn down the radiators in the rooms with thermostats.

Do you have TRVs or non-thermostatic adjustment on the rads?

They might also need balancing to force more water to the poorest performing rad.

Nozzle

 

[JohnD]

Trouble is, the entrance hall gets hot very quickly,

You need to balance the radiators so that the one in the hall gets less flow and so warms up slower than the other rooms.

This is not at all difficult though it takes a bit of time by trial and error. It is done by closing down the lockshield valve (not the normal one with a knob you might use to turn them on and off) so that it is only around half a turn open from the fully closed position. After adjusting it put the cap back on to prevent it being altered.

Do any of your radiators have thermostatic radiator valves?

It may also help to put a shelf over the hall radiator to break up the rising stream of hot air.

 

[ericmark]

I had exactly the same problem with mothers old house, I cured it by adding the thermostatic radiator valve (TRV) on the hall radiator, it does take some setting up, but it did work.

Idea is the TRV turns the radiator down before the target temperature is reached, so it would heat hall from 16°C to 18°C reasonably fast, but it slowed down getting it from 18°C to 20°C, giving time for rest of house to catch up.

The idea is some thing like EvoHome where the TRV heads send signals to the wall thermostat (really more like a control panel) and if any TRV wants heat the wall thermostat runs the boiler, there are other makes which do similar, Tado, Hive, Nest etc. However it gets expensive.

The eQ-3 and Terrier i30 TRV heads are much cheaper and have no link to the wall thermostat, they can be set up to do nearly the same, but it takes more work setting them up.

Years ago we had one wall thermostat and we balanced the system using the lock shield valve, but with the gas modulating boiler the return water temperature controls the boiler output, or a link to the ebus, however government rules have messed it all up, it seems to be considered that the house needs spiting into two zones and some weather link is required. But the ebus will not work with zone valves, so you have a really modern boiler but it has to be plumbed in using some antiquated system so all the cleaver stuff does not work. Likely the real law does not say you need zones, but people reading and interrupting the rules have likely got it wrong.

I would say yes you can fit cheap programmable TRV's and a wall mounted programmable thermostat and make it work, but if you want to be sure it will work without too much setting up, then look at EvoHome.

 

[dilalio]

Simplest solution is to have the roomstat moved to the room you are in the most.
This can be done wireless using RF.

 

[CBW]

Simplest solution is to have the roomstat moved to the room you are in the most.
This can be done wireless using RF.

Does this work? no longer the hallway?

 

[dilalio]

Does this work? no longer the hallway?

Its the simplest solution!
It works better than an unoccupied hallway with wide temp fluctuations... It depends on the "hallway" and it's usage.
If it's small and has no stairwell and/or infrequently used front door, it'll satisfy the demand whilst other rooms are still under temp.
If the opposite, it will keep calling for heat when other rooms are like saunas

 

[Notch7]

Its the simplest solution!
It works better than an unoccupied hallway with wide temp fluctuations... It depends on the "hallway" and it's usage.
If it's small and has no stairwell and/or infrequently used front door, it'll satisfy the demand whilst other rooms are still under temp.
If the opposite, it will keep calling for heat when other rooms are like saunas

My thermostat is in the lounge, I find it works well to keep an even temperature around the house, I keep it on 20C

 

[stem]

I had a similar problem to the OP in the house I live in now. So I replaced the radiator in the hallway (where the thermostat is) with a smaller one so that this room is now the last to heat up, and the rest of the house is toasty before the thermostat switches off the heating. (The living room wasn't an option for me as there's an open fire in there) However, in the case of the OP if the hall is open to other areas and heat sources, then that probably won't work.

Here's a guide to room thermostat location I wrote for someone a while back.

The positioning of the room thermostat is critical to the correct operation of the system. It should have overall control of the system, because it will save energy by shutting everything down when the ideal temperature is reached. (This boiler interlock facility is now, a requirement of the building regulations) If you rely solely on TRV's then the boiler will be cycling unnecessarily and wasting energy.

The room thermostat should be in a room that is not effected by other sources of heat such as an open fire, cooking equipment, or direct sunlight etc. It should not be somewhere drafty or too close to a window, especially if it's one that is opened in the winter.

It should be in a cool room, ideally the last to warm up. That way the other rooms will be warm enough, (but not overheated because of their TRV’s) before the room thermostat switches the entire heating system off.

At least one radiator in the room with the thermostat installed should not have a TRV fitted. Otherwise the TRV may interfere with the correct operation of the room thermostat.

The thermostat should be mounted about 1.5 metres from the floor, and not close to, or above a radiator.

Preferably it should not be on an outside wall, (although if you have well insulated walls, this is not quite so crucial.)

It should be in an area where air can circulate easily, not in a corner, or hidden behind curtains, or furniture.