System venting Help and information on all topics relating to your central heating, air conditioning and ventilation issues.

[Gordon S]

I've recently had problems with my CH system where I needed to vent the pump (Grundfoss 15-50) everytime it was on otherwise I had no flow in the system.

Trying to be clever I decided to drain the system down and try and remove any air locks. In doing so I seem to have caused more problems!!

Now the boiler (Baxi WM 51/3RS) is making a "kettling" noise and cuts out after a few seconds. It appears that I now have air in the DHW system that is stopping the boiler from filling up.

I've tried venting the pump again but nothing appears to be coming out (did this with pump on, CH off and no demand for water, so as not to fire the boiler up)

As I'm now without CH or DHW any guidance would be greatly appreciated.

[ALDA]

CHECK THAT YOUR FEED AND EXPANSION TANK IS SUFFICIENTLY FILLED AND BALLCOCK IS WORKING OK TO SUSTAIN THE PRIMING AND VENTING OF THE SYSTEM.

[Gordon S]

Thanks Alda,

I've checked that and there is water in there and the ballcock appears to be operating OK.

However there was a lot of "gunk" in there, water full of brown, rust like stuff and a film around the ballcock.

I've now cleared most of this out and refilled with clean water. Anything else I can try?

Thanks,
Gordon

[ALDA]

G,

VENT PUMP FIRST.

THEN "FORCE AIR THROUGH SYSTEM TO EXPANSION TANK" BY CARRYING OUT THE FOLLOWING.

CLOSE DOWN EVERY RAD ON THE SYSTEM.

SELECT CH ONLY ON MAX DEMAND.

WAIT UNTIL BOTH THE FLOW AND RETURN FROM THE BOILER GET HOT.

WHEN FLOW IS GOOD THROUGH THE BOILER, FLOW AND RETURN, OPEN 1 RADIATOR.

WAIT UNTIL ITS HOT ALL OVER, BLEED IT, CLOSE IT AGAIN, THEN MOVE TO THE NEXT ONE.

REPEAT UNTIL ALL RADS ARE HOT.

BALANCE YOUR SYSTEM.

A.

[Gordon S]

Thanks A,

Unfortunately I'm falling at the first hurdle here, I've tried venting the pump but nothing is coming out of it.

Also the system I have doesn't allow just CH to be set. It's either just HW or HW and CH. The motorised valve just controls flow in to the CH system, there is nothing to prevent the flow through the water tank.

Cheers,
Gordon

[ALDA]

Forgot to mention in last post to prime and vent boiler, pump, flow and return primaries.

[Gordon S]

I've had another look at the setuo today. From the F&E tank in the loft a pipe comes down in the airing cupboard and through the pump.

On the other side of the pump is a "T" piece, one side to the motorised valve for controlling the CH and the other to the hot water tank

I'm assuming that the feed goes through the hot water tank heater then to the boiler downstairs. On the return side I can see the pipe coming back up with a connection across to the feed (above the pump) and then in to the loft as the expansion.

I've removed the pump to check it worked OK and it seems fine to me. With the pump removed I opened the valve above it, expecting to see water coming down from the feed tank. However there is nothing coming through. Does this suggest a blockage between the F&E tank and the pump or am I missing something?

[muttley]

check that the cold feed from your feed and expansion tank is not blocked,sounds very much this the case.Dosent matter how much you vent etc,if theirs no water going in, your going nowhere

[Gordon S]

The cold feed from the F&E tank WAS blocked.

I had a drain cleaning kit (basically some bendy wire) and managed to use that to free it up. Once this was done I followed your advice on how to force air through the system to the expansion tank.

All rads are now working and we have DHW again :D

I expect that my original problem with having to vent the pump all the time was caused by lack of water in the system, well, at least I hope it was.

Thanks for all your help,
Gordon

[ALDA]

THERE MUST BE A BLOCKAGE!
UNBLOCK.
START AGAIN.