Confused by Thermostat

[Groover75]

Hello, we recently purchased a house and we are struggling to maintain the temperature in it.

It has a Drayton digital thermostat in the hallway, gas central heating, a relatively new Worcester boiler and a Honeywell digital time control. All the radiators have controls and are set to the max setting. There is a radiator in the hallway but it doesn't have a temperature control.

I set the thermostat to a target of 20C. It never manages to get there. If the temperature climbs to 19C or 19.5C then the house feels warm, so that is fine. However the boiler seems to be on for 70% of the day.

The timer is set to enable the heating from 5am to 10pm (I work from home).

At 10pm the timer control shuts the central heating off. Within 20 minutes the house feels quite cold, however the thermostat is still showing 19C.

The next morning the heating comes on at 5am. We get up at 8am and the house feels warm, however the thermostat is showing 18C!

What is going on?

Thanks, Andy

 

[Diyisfun]

Have you tried moving the t/stat.
The temp indicated is the temp where the t/stat is, if you move it to another room, it may need to be set at say 24, to have the same house temp. Experiment, you wont break anything.

 

[D_Hailsham]

All the radiators have controls and are set to the max setting. There is a radiator in the hallway but it doesn't have a temperature control.

Setting the rad valves (TRV?) to max will not help. If you want the room at 20C set it to about 4. The valve will stay fully open until that temperature is reached and then close down slightly to maintain the temperature.

Is there a thermostat in the hall? If so, that's why there is no valve on the rad. Putting a TRV on that rad could prevent the thermostat controlling the boiler correctly.

Do all the rads feel equally hot?
Are there any cold spots on any of the rads?

 

[Groover75]

Thanks for the replies.

I will try moving the thermostat at the weekend.

All the radiators feel the same except the one in the hall, which is hotter. No cold spots that I could find.

When I got up at 8am the thermostat read 18C. It's now 1pm, the heating has been actively going all morning without stopping and the thermostat reads 18.5C. Not much of an increase for hours of gas usage.

Andy

 

[jackthom]

Is this a large older house and is it well insulated ?

 

[Diyisfun]

The current location, could be in a draught or just a cold spot, in my prev house the t/stat was set to 20 for a nice cosy home, this house its 14 its all about balancing & location.
With temperature you can feel hot at 18 & cold at 22, it really is trial & error, not really error its just try & try again, you will get what you want.
You hear people say my t/stat is set at 25, well if its in a warm place then that's what it is.

 

[D_Hailsham]

You hear people say my t/stat is set at 25, well if its in a warm place then that's what it is.

The place is warm because you have set the stat to 25, not the stat is showing 25 because the place is warm.

 

[Diyisfun]

If the stat is above a rad 25 will be warm there. but may not be warm elsewhere, the chances are elsewhere is cold

 

[Groover75]

When the thermostat read 18.5C the house felt cold. Now it reads 19C and the house feels warm. Seems the only conclusion is that the thermostat is faulty or in the wrong place. However it doesn't feel any colder stood next to it.

Andy

 

[D_Hailsham]

If the stat is above a rad 25 will be warm there. but may not be warm elsewhere, the chances are elsewhere is cold

Thanks for clarifying what you meant.

 

[nortonbob]

Could it be that the one really hot rad is taking most of the flow?, balance the system?,

 

[Groover75]

Bob, Thanks! I have noticed that two radiators are very hot, the two closest to the boiler.

I've never heard about balancing the system but I've now found this page that describes what to do:

http://www.devitto.com/Dom-De-Vitto...ake-your-central-heating-system-work-properly

I have an infrared thermometer so I will give this a try and see if I can balance it myself.

Andy

 

[footprints]

Have you tried simply wacking the stat up to 30 and seeing if the system is actually up to the job of heating the house?

 

[D_Hailsham]

I've never heard about balancing the system but I've now found this page ...

You may find How to balance a CH system more helpful.

 

[Groover75]

Have you tried simply wacking the stat up to 30 and seeing if the system is actually up to the job of heating the house?

Yes. Can't get above 19C, except in the room closest to the boiler. Boiler is on continuously.

Andy