How to bleed un-coprative central heating pump

[Timgear]

Hi all,

I have a gravity fed system, I have removed a few radiators in the house to flush the sludge out as there were cold spots on them. I also did a full system flush with cleaner and with a preventer from Screwfix.

The only thing now is trying to bleed the central heating pump. It is a grundfos installed in a downward flow.

I have tried to bleed it with the large silver screw but it doesn't seem to get all the air out. The pump is working and getting the water to the radiators but it's not at full efficiency.

I had an idea of jeryrigging a hose to the bleed hole to attempt to force water in while the pump is off to push the air back up the pipe or to attempt to suck the air out.

Is there anything I'm missing or that would be easier to bleed the pump?

TIA, Tim.

 

[cross thread]

Try bleeding with everything off

 

[ianmcd]

Are you bleeding it with the zone valves set to manually open ?

 

[Timgear]

Try bleeding with everything off

Thanks for the response!

I have tried on and off, I did find turning the pump on to agitate the air and then off and bleed, on, off bleed etc help remove most of the air but I'm concerned the little air left could arise internal damage, plus it's a really annoying sound!

 

[Timgear]

Are you bleeding it with the zone valves set to manually open ?

They are all set open yes.

 

[ianmcd]

They are all set open yes.

How many are there ?

 

[Timgear]

How many are there ?

Total system is 9, 4 downstairs, 5 upstairs.

 

[ianmcd]

Total system is 9, 4 downstairs, 5 upstairs.

Those are thermostatic radiator valves, you have zone valves and they need to be set to manual when bleeding the system,do you have a HW tank if you do post some pics of the cupboard they are usually in there

 

[Timgear]

Those are thermostatic radiator valves, you have zone valves and they need to be set to manual when bleeding the system,do you have a HW tank if you do post some pics of the cupboard they are usually in there

Sorry, yeah I have 1 zone valve fitted.

Would it not bleed due to the valve holding a small vaccume on the pump?

Edit: the lever on the valve is very floppy and doesn't appear to be doing anything.

 

[HERTS P&D]

Have you bleed the valve at the rear of the cupboard?

Andy

 

[ianmcd]

OK that is a 3 port mid position valve , for future referance you have an open vent Y plan system, turn the heating and HW both off then move the lever on that valve across to manual and latch it then try bleeding again

 

[Timgear]

Have you bleed the valve at the rear of the cupboard?

Andy

Cheers Andy, yep both valves were bled and a little air from the one attached in line with the pump.

 

[Timgear]

OK that is a 3 port mid position valve , for future referance you have an open vent Y plan system, turn the heating and HW both off then move the lever on that valve across to manual and latch it then try bleeding again

Will try now, thanks for the heads up on the type of system!

 

[ianmcd]

Have you bleed the valve at the rear of the cupboard?

Andy

As Andy says these are both manual bleed valves you need to manually open them to release any trapped air

 

[Timgear]

As Andy says these are both manual bleed valves you need to manually open them to release any trapped air

View attachment 217673

The one in the rear is attached to the hot water shower pump, the one closest gave off a little gas when I bled it just now.