please help me understand my new heating system?

merlin1

Hello all

It doesnt take much to confuse me at the best of times but my new heating system has me somewhat baffled so i wondered if someone could help me please. Apologies for such noob questions!

The background is that my 20 odd year old vaillant combi was replaced around 2 months ago. I now have a gloworm combi, honeywell timer/programmer by its side and a honeywell dial thermostat at the top of the stairs. (never had one these in my life).

(house is a 2 bed, 6 rads all with trvs apart from the top landing)

The fitters set the boiler heating temp at 75degs, the timer for 2 hours in the morning and 4 hours in the evening, its on 'auto'. all the new trv's are at maximum. they basically told me to now ignore all buttons on the boiler and the timer and to just use the thermostat dial to control things. or use 'extra hour' or 'override' if needed via the timer.

obviously since it was all fitted there has been no need for the boiler to fire for heating during its allocated times - until today. outside temp is only about 13degs and the house isnt much warmer but ive had no heating come on this morning during the allocated 2 hours.

if i go to the thermostat the dial clicks if i turn it up to around 21degs, the boiler fires and clicks again when i turn it down to 20degs, the boiler shuts off? no way is my house 20 degs today... brrrr.

sorry if that was longwinded but i wanted to give as much info as possible, so here are my questions...

am i right in thinking that if the house temp drops below 20degs at night then the heating should have kicked in this morning between
6 and 8am?

And if i wanted the heating to come on if the temp drops below 18degs at the thermostat instead of 21degs - how do i do that?

I am loathe to be talking about heating mid august, but i'd like to understand it before the winter comes

many thanks in advance
Merlin x

Cardew

The Honeywell dial thermostat at the top of the stairs operates, as you would expect, on the air temperature at the top of the stairs.


The rest of the house may not be at 21C - it can only sense the temperature in the area it is situated.


Your TRVs should not be set at maximum - what is the point of having them if they are always at maximum. Depending on the type of TRV their settings usually range from 16C to 24C. Most people would turn the bedroom TRVs down or off during the day and turn them up before going to bed.


You have the classical dilemma of where a wall thermostat should be situated. On the landing and that area in effect controls your heating, or in a living room and when that living room is at the required temperature there is no heating to the rest of the house.


The only thing you can do is experiment and find a solution that suits your requirements. It is no good me or anyone else on the forum telling you how to set the heating as there is no 'one size fits all' solution.

System

Your understanding of how the system works is correct. It is mid-day in the West Midlands and the OAT is 15C. My downstairs temperature is 16.5C and upstairs 18C. The reason for this is insulation. It is therefore possible that your upstairs thermostat was reading correctly - particularly, if it is located close to your HW cylinder. Most homes have the thermostat located downstairs in, say, the hallway. The reason for this is simple. Hot air rises so if the thermostat is placed upstairs then if you set 20C as a comfortable setting, then as soon as the temp upstairs reaches 20C the CH will cut off. There is no guarantee that your downstairs rooms will come anywhere close to this temperature.

So what are your options? Consider replacing the present room thermostat with a wireless device such as this:

http://www.plumbarena.co.uk/product/honeywell-dt92e-wireless-digital-room-thermostat/?

or Nest or Hive.

You can then place the thermostat in a downstairs room away from any heat sources that you would like to heat to a given temp - say 21C in the living room. You then control the temps in the other rooms by adjusting the TRV settings.

Or, alternatively, crank your existing room thermostat up to a temperature (by trial and error I'm afraid) when you know it will click on when the timer switches the heating on. You will need to use the TRVs to adjust the temps in each of the rooms. This may not be that energy efficient.

My guess is that your installer only fitted a room thermostat because it is now a legal requirement when new boilers are fitted. Putting it upstairs was probably the easiest thing for him to do as it wasn't necessary to run cables between the two floors.

Norman_Castle

all the new trv's are at maximum

TVR's prevent a room being overheated. They switch that radiator off when it reaches a set temperature. On mine, and I expect many others, the halfway setting is 70 degrees. Use the halfway setting as a starting point and adjust in small amounts over days until that room is becoming warm enough but not to hot.

merlin1

Cardew wrote: »

The Honeywell dial thermostat at the top of the stairs operates, as you would expect, on the air temperature at the top of the stairs.


The rest of the house may not be at 21C - it can only sense the temperature in the area it is situated.


Your TRVs should not be set at maximum - what is the point of having them if they are always at maximum. Depending on the type of TRV their settings usually range from 16C to 24C. Most people would turn the bedroom TRVs down or off during the day and turn them up before going to bed.


You have the classical dilemma of where a wall thermostat should be situated. On the landing and that area in effect controls your heating, or in a living room and when that living room is at the required temperature there is no heating to the rest of the house.


The only thing you can do is experiment and find a solution that suits your requirements. It is no good me or anyone else on the forum telling you how to set the heating as there is no 'one size fits all' solution.

Thanks Cardew I'll turn the TRVs down a bit. Is the wall thermostat alterable would you know? or is that click at 20degs kind of a preset?

Hengus wrote: »

Your understanding of how the system works is correct. It is mid-day in the West Midlands and the OAT is 15C. My downstairs temperature is 16.5C and upstairs 18C. The reason for this is insulation. It is therefore possible that your upstairs thermostat was reading correctly - particularly, if it is located close to your HW cylinder.

Thanks Hengus that makes sense, the house is pretty well insulated. we dont have a cylinder though what with it being a combi system.

Most homes have the thermostat located downstairs in, say, the hallway. The reason for this is simple. Hot air rises so if the thermostat is placed upstairs then if you set 20C as a comfortable setting, then as soon as the temp upstairs reaches 20C the CH will cut off. There is no guarantee that your downstairs rooms will come anywhere close to this temperature.

So what are your options? Consider replacing the present room thermostat with a wireless device such as this:

http://www.plumbarena.co.uk/product/honeywell-dt92e-wireless-digital-room-thermostat/?

or Nest or Hive.

You can then place the thermostat in a downstairs room away from any heat sources that you would like to heat to a given temp - say 21C in the living room. You then control the temps in the other rooms by adjusting the TRV settings.

Or, alternatively, crank your existing room thermostat up to a temperature (by trial and error I'm afraid) when you know it will click on when the timer switches the heating on. You will need to use the TRVs to adjust the temps in each of the rooms. This may not be that energy efficient.

maybe increasing the thermostat by a degree a day or something until it eventually clicks on?

My guess is that your installer only fitted a room thermostat because it is now a legal requirement when new boilers are fitted. Putting it upstairs was probably the easiest thing for him to do as it wasn't necessary to run cables between the two floors.

you may well be right there! i never had one before and i certainly didnt expect one this time. the cabling runs up into the loft space then back down via the bathroom into the kitchen to the boiler!

Norman_Castle wrote: »

TVR's prevent a room being overheated. They switch that radiator off when it reaches a set temperature. On mine, and I expect many others, the halfway setting is 70 degrees. Use the halfway setting as a starting point and adjust in small amounts over days until that room is becoming warm enough but not to hot.

I'll set them all to half way now Norman thank you

i do feel daft! I never thought i'd get baffled by heating system! :rotfl:

Cardew

merlin1 wrote: »

Thanks Cardew I'll turn the TRVs down a bit. Is the wall thermostat alterable would you know? or is that click at 20degs kind of a preset?

20C(68F) is considered an 'average' temperature in a house.


The wall thermostat is most certainly alterable, but, as pointed out above, you may have to have it above 20C to get heating in the remaining rooms.


Again as stated above, the siting of that thermostat is always a compromise and to get the system to work to your satisfaction is a matter of trial and error.


It may be an idea to turn off the TRVs in the bedrooms during the day and leave the doors open. That way with warm air rising the landing will be kept slightly cooler and the CH operate at a lower temperature.

merlin1

Cardew wrote: »

20C(68F) is considered an 'average' temperature in a house.


The wall thermostat is most certainly alterable, but, as pointed out above, you may have to have it above 20C to get heating in the remaining rooms.


Again as stated above, the siting of that thermostat is always a compromise and to get the system to work to your satisfaction is a matter of trial and error.


It may be an idea to turn off the TRVs in the bedrooms during the day and leave the doors open. That way with warm air rising the landing will be kept slightly cooler and the CH operate at a lower temperature.

In that case i'll leave it at 20C - i have never known what the house temp was before having never had a thermostat, so i'm probably over thinking things and getting a bit panicky over what it should be

Thinking about it i will turn off the bedroom TRVs full stop. neither of us like hot bedrooms at night and we've always managed with thicker bedding. in fact my heating has never been on over night anyway - so what you suggest may well work as far as the system kicking in at the allocated time in the morning

Thanks again Cardew

ETA - the heating has just come on (timer set for 4pm), i had moved the thermostat wheel past the click to about 21degs earlier this afternoon. this should carry on now until the timer ends at 8pm yes? boiler on and off to maintain 21degrees for that period?

Cardew

merlin1 wrote: »

Thanks again Cardew

ETA - the heating has just come on (timer set for 4pm), i had moved the thermostat wheel past the click to about 21degs earlier this afternoon. this should carry on now until the timer ends at 8pm yes? boiler on and off to maintain 21degrees for that period?

Yes the boiler should go on and off to maintain the landing temperature at 21C.


The living room temperature will be determined by your TRV setting.

merlin1

yes, its all becoming clearer now Cardew! the boiler is currently off and the temp in the living room has dropped very quickly so i've turned the TRV up a notch so that the room gets a bit warmer before the boiler turns off next time - hot air rising i think made it turn off a little premature for downstairs...

sheesh, get me an open fire and a lump of coal or two... :rotfl:

retired2011

I have a digital thermometer with a remote sensor that sits on the top of the thermostat as my thermostat just has numbers from 0 to 9.

I have the thermometer in my lounge.

That way I know my thermostat is working.