Radiators - some hot, some warm

[Oldskoolskater]

Hi all

Having looked at the FAQ for answers I have become confused and would like clarification on the above matter. Some rads are hot - Do I close up the lockshield valve more on these rads? Some rads are warm - Do I open up the lockshield valve more on these rads?

I noticed some talk of pump speeds also. I have a sealed system with a combi - (Vokera 80 Excel SP) can I regulate pump speeds with this?

Cheers

Oldskool

[Set Square]

Yes, but see below.

When the system is properly balanced, you should have more or less the same temperature drop across each rad. Ideally, you need to measure the temperature of the flow and return pipe on each rad - for which an IR non-contact thermometer makes life a lot easier - and progressively close the lockshields on the rads with the lowest differential (i.e. the hottest rads) until they are all the same. The *actual* differential isn't critical, but 11 degC (20 degF) is the norm unless you have a condensing boiler - so a flow temp of 82 degC and a return temp of 71 degC would be good. If, when you've got all the rads with the same drop, this drop is significantly more than 11 degC (except in the case of a condensing boiler) you need to increase the overall flow rate by turning the pump up a notch or two, if it's adjustable.

The flow (inlet) temperatures should all be very close to boiler outlet temperature. If any are significantly less than this, you need to investigate the pipework.