Lots of Air in 2 radiators

[futureechos]

History - New conventional boiler installed in March. Non Condensing, non combi. Worcester bosch.
Cold water tank in loft with expansion tank to fill central heating. hot water tank also in bedroom above boiler (which is in the kitched)

System only used lightly in summer for hot water, a little air.
Recently added a heated towel rail (complete system drain), and now using for Central heating and hot water a lot due to cold weather.

I am getting a lot of air in 2 radiators nearest the hot water tank, which I am bleeding every 2-3 days. (by a lot I mean top third / half of rad is air if you leave it for a week or so). Can occasionly hear air moving around downstairs rads but I assume it collects in the upstairs ones as no air found on weekly basis in downstairs rads.

The expansion tank ball cock is working OK, and as far as I can tell topping up the central heating. there is water in it etc.


Questions:
1) Is this normal and will it settle after more bleeding?
2) Can't tell if cause is new boiler install (done by corgi registered people) or the newer heated towell rail.
3) What can I do?

Thanks in advance. If I've missed some critical piece of info please advise.

ta
Mark

 

[jobloggs]

Did you add corrosion inhibitor when refilling? If not corrosion due to new oxygen rich water could be producing gas in system.

 

[futureechos]

Yes- originally when the boiler was replaced this was done by the installers, and I added some to the expansion tank on refilling the system.


I forgot to say the heated towel rail was added after the last radiator so the run to it is probably the longest. This gets no air in it, just wondering if this was relevant?

 

[Nige F]

"conventional" boiler.may be low water content, replacing old cast iron one with greater water content In my opinion, the old boilers used to act as a "settle" for air . Whereas the low water ones are basically just more pipework, like the rest of the system but convoluted inside the casing......I would assume CORGI`s would know if the pipe layouts are correct, so one other possibility is the pump drawing air IN through a micro-leak on the suction side . I`m not CORGI and won`t bother @ my age

 

[weareleeds]

As nige says you have air entrainment you need cold feed & expansion pipes on inlet side to pump with the cold feed nearest to it

 

[Soggy_weetabix]

Why do people asume a CORGI man has a more technical knowledge of a ch/system than any experienced plumber?

Pipe layout / knowledge of it requires an experienced plumber...CORGI registered or not

 

[futureechos]

As nige says you have air entrainment you need cold feed & expansion pipes on inlet side to pump with the cold feed nearest to it

OK so if I have a micro leak with getting sucked in, wouldn't water come out at some point? Is there a good way to find it, presume you wouldn't hear the air getting sucked in because of the noise of the pump?

Is the only way to replace the pipework from expansion tank?
Is the pipe likely to go direct to the pump, if not where else should i check for air intake?

Thanks very much guys. There's nothing like getting answer from the experts - its appreciated.

Mark