Central Heating Pumping Over

[JD Hogg]

Had a call today from a customer. The heating has been working fine all winter, they turned it off during the warm weather in March, turned it back on when it got cooler, since then, when the heating starts up in the morning there is lots of noise above their bedroom, where the F&E tank is and apparently the system gets a lot of air in it, rads go cold and he has to bleed the rads to let the air out.

The system has been in and working fine for 20 years. Ideal Mexico floor standing boiler, one zone valve for heating and a pump each for heating and HW both on the return and pointing down.

I popped in this afternoon for a quick look but all was working OK as he has bled the system today.

I tried to trace the pipes but couldn't find where the vent pipe is connected but the cold feed pipe is on the positive side of the pump.

I am thinking possible partial blockage or sludge in the CH flow somewhere?

Any other suggestions?
Cheers

 

[ecowarm]

Combined feed and expansion possible, on positive side of pump?

 

[DaveTidy]

Sounds like corrosion has settled through the off period. Hopefully it isn't a combined vent / feed as the boiler should have an overheat if it is (and these don't). Sounds like you'll have to check the vent and feed position (they may go back to the boiler if it's a mexico). What's the tank quality like, has it been pumping over and re-oxyginating the water? Might be pumping over if blocked with corrosion?

 

[diamondgas]

:iagree: check the water quality/colour! If the f&e water is hot then there's a problem regards pipework configuration. It takes some time before the issues associated with pumping over take effect, I've found systems will work and work then just give up without warning or not play up until work is carried out on the system! You go to replace the pump, turn the new one on and find nothing moving at all :32:

 

[Paulus]

Try a magnet on the pipes around the pump and zone valve. I wouldn't mind betting that it sticks like glue because sludge has settled in the pipes. I had exactly the same problem and one of the guys on here suggested this.

 

[hammers4spanner]

cut into rising main ,get a filling loop ,tee into below pump and blast mains water through primary circuit ,dont forget to shut pump off .
done this few times last few weeks as suddenly had batch of it

 

[Leo21]

If the system keeps needing venting it's sucking air down the expansion, wich would point to pipe work restriction. Usually it settles where the cold feed is connected. As said above a magnets a good idea.

 

[tamz]

Try turning the pump speed down

 

[Reltub]

Sounds like theres not enough head between pump and htg tank, which has caused pumping over which in turn has caused corrosion, talk them into an A rated sealed boiler