Radiators not getting hot

[Wallofthewolves]

Hi all i have a couple of problems with my heating system. Living in a reno and had some radiators moved/replaced. Last one fitted a couple of days ago in the hall after 2 months without one on When the heating is turned on it gets hot but then seems to cool down even though thermostat is right up, and the living room one seems cool too, i think these are the last radiators in the line if that makes sense so maybe need balancing? Also when Hot water is on, only a couple of rads upstairs are getting hot and the one in the kitchen directly below the boiler? Its a gravity fed system with HW tank. Appreciate any advice.

 

[motorbiking]

Close all the thermostats and 1, by 1 open them as each radiator gets hot. It could be some air in the flow/return. You could also turn the pump speed up to max for a few mins, to see if that can blow through.. Does the boiler have a pressure gauge or is there an expansion tank in the loft?

 

[Wallofthewolves]

Ive tried that and they all got hot but after a couple of hours one in hall is just lukewarm, theremostat turned right up definitely not at full temp. We have pressure guage on boiler and tank in loft. Thankyou

 

[JohnD]

Do you mean that some of the radiators are hot and some are cool? Turn off ALL the hot ones. What happens to the cool ones?

 

[Wallofthewolves]

Do you mean that some of the radiators are hot and some are cool? Turn off ALL the hot ones. What happens to the cool ones?

All are hot now other than the hall, which is furthest away from boiler, if i turn all off except that one it gets hot. Also when heating first comes on it gets hot, but after an hour or so it cools down, while others are still hot. Like i say thermostat turned right up.

 

[BlueLoo]

Stupid question:

Does the rad have a trv?

 

[JohnD]

if i turn all off except that one it gets hot.

then it may be a balancing problem.

feel the flow and the return pipes on each of your radiators. Assuming you do not have pipe thermometers, the flow (incoming) pipe should be "too hot to hold" and the return (outgoing) pipe should be "too hot to hold for long"

If any of the return pipes are surprisingly hot, turn down the lockshield on that radiator to fully closed, then open it half a turn only. Run it for half an hour before checking again. If you need to adjust a lockshield, turn it no more than a quarter turn at a time, and wait half an hour to see if that's right. The adjustment on a lockshield is almost all in a single turn from the closed position.

When radiators are fitted or replaced, it is quite common for the locksheld to be left wide open, which unbalances the system. So check the other rads as well. But you may as well start with the hottest one(s).

Balancing is not done by opening the cold rads wide, but by turning the hot ones towards closed.