Back to the cold radiator

[polly filler]

Put the pump on the return pipe before the boiler

[thirty-six]

Header tank needs to be above the highest system point. If it's a sealed system, just raise the system pressure. Pump needs to be capable, check that it's full speed if a variable pump and that it can cope with the height.

[puffernutter]

Having either been away or been very busy for the last few weeks I've had no time to play, but over the weekend I though I'd try something.

I have had a spare central heating pump for a while, so I thought as the problem appears to be a lack of flow in this copper "extension" let's give it a helping hand! The pipe run was easily accessible and I made up two 22mm to 15mm adaptors and a I had a couple of 15mm to

15mm push fit flexi pipes and inserted the pump in the 15mm radiator feed pipe (making sure I had the flow the correct direction!)

I had a power socket nearby and for this experiment I decided to turn it on and off manually, looking to parallel it up with the "main" pump if it worked. I initially set the speed on "1".

As we have a wood burner, I had to wait until the evening when we lit the fire to see what effect it would have.

Once the main central heating pump had enabled, I left it for a while to get the main system hot and then I turned on the secondary pump. After an hour it had no effect, so I upped the speed to "2". After a short time there was definite heat in the pipes and soon the radiators in the cloakroom and utility room were geting warm. There didn't appear to be any detrimental effects on the rest of the system, so result! My only concern was that the pump motor in the new pump was warmer than I would expect (based on the water temperature) and I wondered if it was working harder than expected. I considered getting a mechanical immersion heater time switch set to switch on and off every 30 minutes to cycle the load.

However. last night (Sunday) the fire was lit and again, I left the main system to get warm before turning on the secondary pump. Prior to turning the pump on I felt the radiators in the cloakroom and utility room and both were warm. I double checked the secondary pump and it wasn't turned on. A fluke? Had it been turned on and I'd just subconciously turned it off? Its an age thing - you begin to doubt yourself at times!

This morning, I lit the fire again, this time making sure that the secondary pump was off and again the radiators in the cloakroom and utility room were warm! So it looks like, even with all my best attempts and bleed valves etc., there must have been air in that branch and the initial pump running has cleared the air lock. The bad news is that I'll probably have to leave the pump in situ, so that if I ever drain the system, I can bleed it again!

Thanks for all the help and here's to a warm Christmas on the downstairs libray/loo!

Cheers

Peter

[hugh]

In message , puffernutter writes

Glad to hear it's sorted. I would guess that when you initially bled the cold radiators you probably didn't leave the bleed valve with water coming out long enough for the air to travel from where it was at the top of your pipe run right through to the radiator in order to escape. But the simplest solution as has been suggested before would be to put in a bled valve at the top point of your pipe run or as close to the top as you can but just after it.