Boiler and TRV controls

[Dezzer]

Hello,
I am raising this enquiry on behalf of my sister who seems to be having problems regulating and maintaining a decent temperature throughout her house.
The Boiler is a Worcester Bosch Greenstar 28i Junior, which is controled via a wireless Drayton Digistat +3RF thermostat.
Although the temperature is set at different levels throughout the day, they are roughly between 18 to 21 Degees C.

According to her Boiler manual the Temperature control, if used with TRV radiator valves, has to be set at level 6, which is 80 Degees C.

Although the Boiler and radiator valves etc and all controls are approx 1 year old, her Gas Bills are rather high compared with her previous, much older boiler.

The TRV valves are set to a comfortable level in each room, and the thermostat is situated in the passage, which is cooler than the downstairs rooms.

Can you please advise as to whether the Boiler Temp. control should be set at 6 (80 Degrees) when TRV's are fitted to radiators. If so, how many radiators throughout the house should have TRV's fitted.

I did think that if a by-pass system was fitted into the Central Heating system, then hot water would still be pumped around even if the trv's had closed.

Thank you,

 

[ianniann]

According to her Boiler manual the Temperature control, if used with TRV radiator valves, has to be set at level 6, which is 80 Degees C.

Huh?

her Gas Bills are rather high compared with her previous, much older boiler.

Are you comparing like with like? We just had the coldest December in I don't know how long, as part of an overall rather chilly year. Also, compare the actual cost of equivalent periods with meter readings, not estimated costs and definitely not the direct debit payment. Tariff rates may also have risen by 10% or more.

TRVs are recommended to be fitted to every radiator except the one in the room with the wall stat. Take that with a pinch of salt, but certainly it is a good thing for most people. When the TRVs start to shut down the boiler will modulate down and ultimately turn off. Running at 80C instead of 70C or 60C might delay this for a while but it won't stop it. One pokey radiator in the passage won't dissipate the 6kW or so that is the lowest output your boiler can manage. I suppose if all the TRVs had shut off and the passage was still getting heated at a very low level, the boiler would cycle on and off essentially wasting gas. You could check if a lot of the time most radiators are off but the passage is never reaching the stat temperature. The stat should only be set to a level that allows all the rooms to reach the right temperature and ideally go off shortly after that.

 

[Dezzer]

Hi,

Thank you for the reply.

When comparing the running costs we have been looking at the number of units used during a set period. My sister has used far more energy this year, compared to any other year.

Although she lives in a house, whereas I am in a detached Bungalow she has used approx 3 times the amount of energy compared to me. I do not have TRV's, and only an old Gloworm Boiler, but mine can be run with its control set at 1/4 and our rooms are really warm.

The question I was asking is basically, why does a boiler have to run at 80 degress when the room temperature required is under 25 degrees? I realise that the TRV's will shut down the radiators, but if one or more radiators does not have a TRV, then surely the boiler will keep firing up. I know that heat is lost whilst the water is being circulated but why is the boiler stat set so high.

I have probably missed the point somewhere along the line, but am curious on all your views.

Thank you,