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Rayburn Driven Central Heating Problem - Upstairs Cold?

I have a Rayburn Gas CH system with a seperate pump.
The cooker / boiler is in the basement kitchen with 3 rads.
The ground floor has 4 rads.
Upstairs we have 4 rads.
All rads have TRVs fully working. System about 10yrs old in good condition.
All rads are clear of air / sludge etc.
We also have a loop in the loft tank to heat the domestic water.
The problem is that the 4 upstairs(bedroom) rads only work when the downstairs 7 rads are turned off at the TRVs either manually or when the temperature switches the TRVs off.
Could it be that the pump is not strong enough to lift the water up to the upstairs?
Last 2 winters the pump sounded awful frequently. Also when we turned the boiler temp up above 70deg it sounded like a poltergeist was thrashing all over the pipework with a hammer. It was pretty loud the higher the temp.
This autumn it's all been quiet but only partially working.
Any ideas please greatly appreciated.
PS I'm not sure how effective the system is on the domestic hot water as we do use an immersion heater also.

JC
November 2009

Rayburn Heating, Home Heating Systems Central Heating Upstairs

Thanks John. I've tried adjusting the lockshields downstairs down to 1/2 turn from closed but it still doesnt move any water through to the top 4 rads.
It's strange. I would have expected a slight flow even a trickle but it takes about half an hour till the bottom 7 radiators have got thoughroughly heated enough to shut the TRVs off then all of a sudden the top 4 get hot really quickly.

JC
November 2009

Many thanks for the above. I need to get a panel off to see what pump is fitted. I've seen it but can't remember off hand.
I've noticed that there are at least 2 sets of instructions for different makes of pumps so it looks like the system has been eating them for fun before we moved in here ( 3 years ago).
Any ideas of a decent pump make? Dont say dunlop greenflash :)
Cheers

JC
November 2009

pump has to work very hard to feed that system u dont say what pump, try reducing the flow to rads as u get closer to where the pump is sighted this is done by closing the lockshield side of the rads and then cranking them open about 2 rotations this constricts the amount that the rad will let through so that the water that cant get through will travel to next rad etc etc this should produce an even heat throughout u really need a good pump though this will stop any banging

sean
November 2009

Your heating system needs balancing...that is, some of the lockshield valves on the radiators need to be closed down a bit, so that the hot water is forced to go around the radiators that usually remain cool. Try turning the lockshield valves fully off, and then open again 3/4 of a turn, and see what happens. Keep all TRV's open full and set the circulating pump to position 3 if its adjustable.

John
November 2009