Switching to TRV's

[Uno Hoo!]

I have a conventional 'wet' central heating system with radiators in each room fed from a wall mounted boiler in the garage. The boiler also heats the water via an indirect cylinder. There is a thermostat on the hot water tank which controls a motorised valve thus shutting off the supply to the tank when set temp is reached. There is a room thermostat in the hall that controls (I believe) the pump located near to the boiler. The room thermostat has a terrible lag on it and room temperature tends to get too hot and then too cold waiting for the stat to switch. I have put TRV's on the radiators in my lounge/dining room which have improved things somewhat - but in order to keep a hot supply feeding to these radiators I have to keep the room stat high which then overheats the rest of the house! I am now considering putting TRV's on all radiators apart from the bathroom (to allow for at least one 'by-pass'). One question: If after carrying out this work I then leave the room thermostat set high, will this result in the pump running virtually permanently, and if so is this likely to cause any problems?

Kev

[Christian McArdle]

Yes it will cause problems and you will technically break the building regulations for energy effiency. It isn't the pump running that is the problem. It is the boiler running continuously, short cycling trying to keep the central heating water hot when no radiators are on.

The correct solution is to replace the room thermostat with a modern electronic, preferably programable type. If the poor performance is because it has been placed in an unheated space, then move it. Although many people favour the hallway, I prefer to place the thermostat in the most occupied room. The room with the thermostat should have lockshield valves both ends of any radiators to prevent users turning them off.

An alternative solution is to install a flow switch, which can turn the boiler off when the flow through the radiators falls below a certain amount. This will also comply with regulations. If you do so, it is best to replace the pump with something like a Grundfos Alpha, which won't mind operating in these conditions.

Christian.

[John Stumbles]

But don't do that if you use a gas fire or have open fires etc in that room, as the effect of the extra fire will be to turn down the CH and make the rest of the house colder!

[Uno Hoo!]

Thanks both for that!

Kev

[Paul Barker]

Clearly, renew your roomstat, and get your trv's barr the one where th

rstat is

-- Paul Barker