On 26/01/2014 17:41, Tom Pickles wrote:
My heating's been pumping over for a while now, spilling over the overflow from my header tank. I can't seem to get to the bottom of the problem.

I've extended the height of the open vent which is now two feed above the top of the header tank. I have also bent the arm of the float valve so that the water level in the header tank is about five inches high, but it still pumps over and out of the overflow.

I recently put fernox F3 through the system, flushed it all out and re-treated. I also descaled the boiler using fernox DS40 as part of the same job.

I have read that the aerjec air separator things can get blocked and cause pumping over, but I'm not sure how I would re-pipe it if I removed it, or perhaps it isn't a problem?!

Here's a photo I took of my pipe setup in the airing cupboard (ignore the leaky hot tank, that was quickly replaced):

http://i.imgur.com/iF75oHt.jpg

The pump flows from top to bottom.

Any ideas guys?

Thanks,

Tom

Have you actually watched water discharging from the vent pipe into the
F&E tank - or are you surmising that it does because it's going out of
the overflow?

What is the difference in level between the level controlled by the ball
valve and the level needed to overflow? If this difference is large (say
6") the static level is unlikely to increase by this amount just due
to expansion. Even if pumping over *is* occurring, that in itself won't
raise the level in the F&E tank - so if its rising above the overflow,
something else must be happening.

Is there a large cold tank in the attic, as the header for the DHW
system? If so, how does the water level in that compare with the level
in the F&E tank. If it's higher, have you considered the possibility
that the coil in your hot cylinder may be shot - resulting in water from
the DHW system leaking into to primary circuit?
--
Cheers,
Roger
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