Hot and cold Radiator output...

[aircom8]

I have a central heating problem that needs solving and would be grateful for any suggestions please.

SYSTEM SPEC:
New boiler, electronic LCD radio thermostat/receiver, heating/hot water programmer, pump [all fitted two days ago].

Original C/H cylinder, radiators - 15yr old pipe work and Thermostatic radiator valves (TRV) to all radiators.

PROBLEM:
Even though the boiler seems to run okay [hot water not a problem] I am unable to maintain a constant heat output from any of the fitted new/old style radiators. A normal case scenario would be the heat output running too hot at say (TRV) setting 3, then goes cold a short time after turning down the (TRV) a small amount. The bottom of the radiator in most cases is not as warm hot as the top of the radiator. I have bled air from all radiators.

 

[footprints]

The TRV's do not control the temperature of the radiator they just turn it on or off. The TRV's are sensing the room temp and controlling it by cycling the rads on and off as required.

Regarding the temp difference on the rads the top will heat up first so if it quickly gets shut off by the TRV the whole rad may not heat fully, if there was air in the system you would have cold tops and hot bottoms on the rad.

You can get hot tops and cold bottoms on old systems with sludge, but with a new boiler fitted that is most unlikely as the installer would normally flush the system and you would have had the problem before the boiler exchange.

 

[aircom8]

The TRV's do not control the temperature of the radiator they just turn it on or off. The TRV's are sensing the room temp and controlling it by cycling the rads on and off as required.

Regarding the temp difference on the rads the top will heat up first so if it quickly gets shut off by the TRV the whole rad may not heat fully, if there was air in the system you would have cold tops and hot bottoms on the rad.

You can get hot tops and cold bottoms on old systems with sludge, but with a new boiler fitted that is most unlikely as the installer would normally flush the system and you would have had the problem before the boiler exchange.

Thank you for the information "footprints". What is the explanation for all the radiators acting the same i.e, super hot then cold with a minor regulation of the TVR?

The new boiler and other parts were supplied and fitted by a gas safe plumber working directly for a main C/H company. To my knowledge he drained down the system as per usual but didn't flush it through as such. And yes, the problem did exist before the exchange - that was part of the reason to replace the boiler.

 

[footprints]

Because as said TRV's turn on or off, if the TRV is at the point of closing off just moving it even half a number will put the valve on the seating and the rad will cool.

Like having a room thermostat controlling a one bar electric fire, room cold bar on, room hot bar off.

The only thing that will alter the temperature of the rads is the thermostat on the boiler controlling the temp of the circulating water.

To test the rads for sludge bang all thermostats including the wireless room one to maximum and leave for an hour or so, if the rads heat fully all is ok.