Correct Central Heating setup - Thermostat + Radiator TRVs

[lmfy2k]

Hi all

im just reviewing out central heating system and was wondering if you can help with tell me which way i need to set it up to work efficiently

we have a Worcester 37cdi Bosch Gas Combi and a Honeywell CMT927 wireless thermostat, all the rads in the house have TRVs (minus the 2 bathroom rads which do not)

the way its currently setup is, the Boiler is set to number 5 (60 on the digital dial), The room thermostat set to 21C with timer and the Rad TRVs set to 4 or 5.

we have a very busy household and there is always someone at home during the day, ( elderly parents, wife+baby), so the thermostat is set to near enough 21C all day long and lower over night

the room thermostat is in the downstairs hall way, the hall way has a radiator ( i know it shouldn't have a TRV but it has and is set to max )

now the way i think it works is, the thermostat tells the boiler to fire up maintain 21C in the hall way. In turn all the rads will warm up and will switch off until it reaches whatever the temp number 4 is on the TRVs. or if the TRVs set to 5, it will only heat up to 21C because the room thermostat over rides this.

is this the correct way of having it? ive read that people set the room thermostat to 25C, then adjust the setting on the boiler so it controls the temp and ive also read the room thermostat should be in the room most used, ie the lounge.

so im a bit confused

any experts out there want to shed some light please?

 

[MichaelAwkward]

Are the TRVs the older ones or newer electronic ones that allow time settings individually? My understanding is that in most British home setups, they're basically useless.

EDIT: Only the radiator in the same room as the thermostat is directly related to it. The other radiators will simply stay on until their temperature settings on the TRVs are reached OR the room with the thermostat reaches the setting there. Hence why you should have the thermostat in the room likely to heat up the slowest/last. If you have the thermostat in the room most used (warmest besides the bathroom and kitchen), it will override all the other radiators and turn the boiler off when that room reaches the set temperature.

 

[Adam_151]

What you want to achieve in an ideal world is a return temperature of just under 55 Deg Centrigrade

Above this the boiler does not enter condensing mode and is less efficient
Too much below this and the rads do not have have an ideal temperature differental to transfer heat to the room efficiently (this can be compensated for by over sizing the rads to some extent)

Now the return temperature will depend on two things:

How hot it starts off at on the flow leaving the boiler (the temperature control on the boiler)

How much heat is taken out the system, which will depend on the temperature of the rooms being heated and the setting on the boiler

So the ideal setting on the boiler will vary throughout the year.

There are two things you could do.

Measure return temperature often and by trial and error work out what the boiler control should be set to at varius seasons through-out the winder (which will be a bit hit and miss)

Or see of there is a weather compenstion kit available for the particular boiler you have. This consists of an outside temperature sensor which is installed on a north facing wall and allows the boiler to manage itself more efficently