Baxi Combi 80 HE high pitched noise

[MikeRosen]

Hi there - The pipes running to/from the Baxi 80 Instant HE boiler in my flat have started to make a loud, continuous, high pitched squealing noise when the central heating is firing. If I run the hot tap in the kitchen for a few seconds, the noise immediately stops, for a while at least. Bit of a problem as the noise is getting worse, wakes me up in the morning, and I'm worried what it might mean. The boiler is a little over two years old. It was last serviced just three months ago. The setup is that the boiler is in the loft. Noise is loudest where the copper pipes enter the flat from the loft.

Pressure is fine as far as I can tell - in the middle of the acceptable zone. Heat and hot water are working. No air in radiators. Boiler control panel shows nothing flashing.

I'm not a plumber or heating engineer but I'd like to have an idea about what might be going on before contacting anyone. Plus of course if there's anything I can do to fix it that would be great. Does anyone have any suggestions?

Thank you.

 

[tipintim]

Sounds like a pump problem. Could be a bit of dirt stuck in the pump, or a filter blocked maybe.
Does the system heat up as quickly as before?

 

[MikeRosen]

Hi, thanks for replying. It does still seem to heat up as quickly as before, yes.

 

[kay-jay]

try bleeding the pump

 

[tipintim]

Has it been fitted with the integral filling loop. Could be the double check valve singing to you.
Without being there Im scratching for ideas mate.
There is a filter on the return manifold that can be removed and cleaned.

 

[MikeRosen]

Hi, thanks for your answers. As a non-plumber I'm already out of my depth! There is a filling loop (metallic woven cable, correct?) attached (at both ends), and the pressure seems to be fine. I don't know what the double check valve is, so I guess I'm now looking at calling someone in. (Problem is the noise, though worsening, is intermittent, and by sod's law it won't be happening when I get a plumber in!)

 

[shorticus]

As your boiler is in the loft and is therefore at the highest point of your system my money is on air (or more specifically hydrogen) has collected at this point and needs venting, there's an aav (automatic air vent) just above the pump however there's a closure cap on it which may very well have been left shut. Whilst opening it (if this is the problem) is a straightforward job I'm afraid it's not a diy job unless you really know what your looking at

 

[Jonwells]

JThe problem is two fold.
You say noise happens when boiler is in heating mode and stops when you run hot tap. The baxi (has already mentioned by someone) has a gauze filter in the return is isolator to the boiler, when boiler is in heating mode it's trying to pump water round the heating circuit, but has the boiler has a built in bypass, it flowing through that as well.
The noise your hearing is the automatic bypass chattering or steam build up in the primary heat exchanger as water is not flowing through the boiler fast enough.
On a 80 (24 kw) I have found it to be both.
Cure; get an engineer to clear out gauze filter, simple about £60 in old money, but the trouble is the **** in the system, that needs to be addressed also, maybe when installed the heating wasn't power flushed correctly, who knows, so it will need either a proper power flush, £250 with chemicals and/or a filter installing on boiler return£120 get these done, no more problems, leave it and you risk needing a new plate heat exchanger, and other failure on boiler components. Jon