upstairs rad problem

plumber18

I installed new rads in my house and fitted trvs also. I have oil heating and also a back boiler. When i turn on the oil heating all the downstairs rads heat up 1 or 2 upstairs slightly heat. But when i turn on the pump on back boiler system all unstairs rads heat as good as the downstairs rads. there are no controls to zone any area or any room stats what could be the problem. this never happened with the old rads..

FoxT

But...
Have you checked the lockshield valves on the upstairs radiators? did you shut them off when you replaced the rads? You might want to open them all fully then back off a 1/4 turn. Then, close the lockshield valves on the downstairs rads a little.

For test purposes you should open the trvs fully.

Also, if the new rads are bigger than the old ones they may run cooler. You don't say why you replaced all the rads? If it is an old system then the pipework may need to be flushed. We had a problem where the kitchen was always cold so we decided to replace the old rad with a bigger one. The plumber doing the job found one of the pipes to the rad was blocked with debris, when he flushed it the problem was sorted.


AFAIK using the back boiler pump might pump hot water through the back boiler as well as through the rads, this would be a bad thing as you will be sending heat up the chimney. Does this happen?

- FoxT

plumber18

yeah all lock shield valves downstairs r nearly closed off still plenty of heat in these all lock shield valves upstairs r open full. system was flushed at time rads were replaced. when i turn off all rads bar 1 upstairs this heats up perfect with da down stairs ones.

reason rads were replaced was they were old and had no fins on back not great to heat the house

FoxT

...and, is it working? It can be hard to tell as they are so quiet. If not, you might consider fitting one. That's one for a plumber to advise on, though, I'd say.

You clearly are not getting enough HW to the upstairs rads. Enough to heat one or two but no more. It is only trickling up until you turn on the pump. This suggests that something happened around the same time as you replaced the rads.

- Possible blockage or obstruction to the main HW feed upstairs? I dont think so as that would be a 3/4 pipe so less likely to block.
- TRVs flow less water than your old valves did? Sounds dubious.
- New rads need more water pressure for a decent flow?
- or water pump for oil boiler conked?
- possible airlock in the HW delivery to upstairs that is impeding flow? When you bleed the upstairs rads is there decent pressure there?

Thats all I can think of, I'm afraid.

- FoxT

Sparkpea

how old is the pump on the oil fired system? what speed is it running at