Thermostat affecting boiler out

[Lab8888]

Hi I had a Vaillant ecotec 30kw boiler installed in 2020 and it heats the house up really nice. Then I had the same gas safe engineer install a smart salus thermostat.

Whenever I use the heating with the thermostat, the radiators get warm but do not warm the house up. If I switch back to manual on the salus receiver and use the boiler manually, it heats the house up really nice.

So in the summer, because assuming the salus is rubbish I had a different gas engineer fit the hive thermostat, so it can help me save money this winter. So tried the heating out and it warms the house up rubbish like the salus, upstairs radiators are warm but don’t warm the rooms up. I can’t switch to manual because the hive does not give me this option on their receiver.

Why do I have issues with my heating when controlled by thermostats? House is nice and toasty with the boiler operated manually if there is no thermostat controlling it.

Could the thermostats when in operation somehow be reducing the boiler output in comparison to using the boiler manually.

Any advice will be very much appreciated.

(I am currently waiting for the gas safe engineer to pay a visit to check the boiler output, and if that don’t work then disconnect the hive receiver so I can enjoy my heating).

 

[flameport]

Could the thermostats when in operation somehow be reducing the boiler output in comparison to using the boiler manually.

No. A thermostat is an on/off switch. That is all.
It will turn the boiler off once the set air temperature is reached.

If the house isn't warm enough, set the thermostat to a higher temperature.
If the thermostat is in a room which is generally warmer than other areas, the thermostat may need to be relocated.

Setting anything to manual will just mean the boiler is running all the time, the radiators will get blazing hot, the house will heat up to ridiculously high temperatures and you will waste vast amounts of fuel and money.

 

[Lab8888]

No. A thermostat is an on/off switch. That is all.
It will turn the boiler off once the set air temperature is reached.

If the house isn't warm enough, set the thermostat to a higher temperature.
If the thermostat is in a room which is generally warmer than other areas, the thermostat may need to be relocated.

Setting anything to manual will just mean the boiler is running all the time, the radiators will get blazing hot, the house will heat up to ridiculously high temperatures and you will waste vast amounts of fuel and money.

I have tried all this. It’s not effective in comparison to using the boiler without the thermostat.

Gas Safe man has tried to set the boiler output manually (saturday) and we ran the heating, but it was better on auto setting.

His going to come back on Monday so he can ring vaillant and troubleshoot.

 

[ericmark]

To types of wall thermostats, on/off and up/down, the up/down type are often fitted in main room, but on/off type are only there in the main to stop boiler cycling as weather warms up.

There are exceptions, but in the main rooms are controlled by the TRV's (thermostatic radiator valve) and these can often link to the main wall thermostat, this is the case with Hive, however Hive is an odd one out, at 22ºC it stops working, so room with wall thermostat must be under that limit.

In the main the wall thermostat acts as a hub, and if any TRV calls for heat it turns on boiler, however Drayton Wiser, Hive, Tado, all use their own electronic heads, they do not interchange.

 

[oldbutnotdead]

Did whoever fitted the new thermostats mention Opentherm? An Opentherm controller can control the boiler modulation level and may default to low flow temperatures for more efficient combustion. That's fine but if your rads are sized for 70° flow they may not heat the house adequately at 60°

 

[Mister Banks]

The Hive thermostat uses TPI to get to the selected room temperature, it’s not as simple as on/off. TPI is one method of saving energy. Look up online for detailed explanation on how TPI works.

 

[martygturner]

What is the temp ch flow set to....if its low when running the boiler permanently the house will heat up but if its low and you use a thermostat it may never get enough heat into the rads to warm the house up...basically the thermostat says heat and the boiler says I am at temp so go stuff yourself.

 

[RandomGrinch]

Why do I have issues with my heating when controlled by thermostats? House is nice and toasty with the boiler operated manually if there is no thermostat controlling it.

When the house is nice and toasty, may I ask what the measured temperature on the thermostat is reading?

 

[RandomGrinch]

What is the temp ch flow set to....if its low when running the boiler permanently the house will heat up but if its low and you use a thermostat it may never get enough heat into the rads to warm the house up...basically the thermostat says heat and the boiler says I am at temp so go stuff yourself.

Unless I'm missing something, wouldn't the thermostat just continue to call for heat in that circumstance - the boiler would be running permanently, as if it was in manual mode?

 

[ianmcd]

sounds like your Salus and your hive have been wired into the OT terminals on the boiler, they need to be wired to the on/off terminals

 

[martygturner]

Unless I'm missing something, wouldn't the thermostat just continue to call for heat in that circumstance - the boiler would be running permanently, as if it was in manual mode?

That would depend on the anti cycling delay that has been set and manual mode does not have anti cycling it just overrides everything and calls for heat and runs and runs...just try turning the flow temp up to 65 and see where you get.

 

[Lab8888]

sounds like your Salus and your hive have been wired into the OT terminals on the boiler, they need to be wired to the on/off terminals

I’ve attached pictures of the connections. Let me know if this is correct please.

 

[Lab8888]

That would depend on the anti cycling delay that has been set and manual mode does not have anti cycling it just overrides everything and calls for heat and runs and runs...just try turning the flow temp up to 65 and see where you get.

Flow temp is set at 75. Reaches 74/75

 

[Lab8888]

When the house is nice and toasty, may I ask what the measured temperature on the thermostat is reading?

When I use the electric heater instead of the boiler, the thermostat does show room temp above 19. It’s nice and warm but heating pre thermostat room temp was much warmer.

 

[ericmark]

I see the Bus terminals not used, so not using OpenTherm, so it uses the return water temperature to control boiler.

So the wall thermostat has just one job, turn off heating on a warm day.

So location is really important, it should be in a room normally kept cool, with no alternative heating, on a lower floor, with no outside doors, don't know your house, but my house not such room.

So we move to near enough engineering, which often means wall thermostat in the hall, and the TRV set so only on warm days will the central heating turn off.

This is nearly manual control, and selecting on/off depending on weather conditions will likely do the same.

Main thing to remember is the TRV is king, using as I do 9 programmable TRV heads no room will over heat, and as they close, the boiler auto turns off, or with a modulating boiler turns down. All the wall thermostat does is stop boiler cycling in warm weather.