I have read various solutions to the above problem and (I think) I have
exhausted them all. Any advice would be appreciated.
Baxi Barcelona open vented, with two 2 port valve circuits. The pump
is situated between the air separator and the two valves in the flow of
the boiler. The Boiler is situated in the garage with 28mm pipework up
to the valves, air separator and pump (all in an airing cupboard on the
landing. The air vent goes vertically to the small header tank in the
System plumbed in about 7 years ago and originally had this problem but
though I cured it by lowering the header tank water level to 2 inches
and extending the vent height. Recently replaced a large hall radiator
with one about 3/4 its size. During balancing the system I found it had
been pumping over again (dirty water in header tank).
As the pump was getting noisy I replaced it with a Grundfoss "smart"
pump. When I removed the old one I foung it had quite a lot of hard
black sludge on its ports. I then realized this was probably due to the
oxygen from pumping over.
Had the boiler serviced and is OK! I asked the engineer for advice,
and was told to clean the system as there was probably some restriction
in the flow.
Cleaned it with Sentinel X300 and ran boiler on high temperature with
all valves open, but still the problem exists. It did clean the system
slightly but I have alway had X100 in it and I did take all the old
radiators off the walls and cleaned them when I plumbed in the system.
When the boiler starts and the pump switches off at the end of priming
and when the boiler stops I get about a tumbler measure pumped over. I
think there is also some fluid coming into the tank from the C/H circuit
feed. I tried closing a gate valve (in the feed) so it was only just
open, but it obviously did not improve the pumping over.
Even with the pump on its lowest speed (both auto and fixed) I still
have the problem.
The Baxi installation manual did not specify a need for a bypass and as
I have 2 towel warmers without TRV's I assumes it would make no difference!!
Well that's the sorry saga so far, I would appreciate any comments on my
system and any possible ways I can cure the problem as its now exhausted
I am tending to think it is my design that may be the problem as I have
always had problems with air in the system!!
Thanks & sorry for the length of this message.
- posted 12 years ago