Boiler problem: flushing a dual tube heat exchanger

[praying4wind]

Hi,

Does anyone know of a proffessional service for cleaning heat exchangers?

I've got a Glowworm 18HXI condensing boiler. The system has only been in 18 months, but I think I've managed to block the heat exchanger with some debri whilst working on a radiator. It was fine before the radiator work but since flushing and filling, now makes a terrible howling/vibrating noise.

I've had the heat exchanger out and flushed it with i) mains pressure, ii) a Kamco power flusher (without acids).

There was some improvement, but the noise has come back. It's not scale as the heat exchanger appears shiny and clean + has only been in 18 months + suddenly the noise came on after radiator work.

The thing is the heat exchanger is micro bore and dual path? (two tubes in parallel between flow and return). I didn't bung each tube in turn so I reckon most of the flushing pressure would've bypassed any blockage in the other tube. Silly mistake I know.

I'm thinking of hiring the Kamco unit again, and bunging each tube in turn with a rubber stopper. However, this would be more money, and may not work, which is why I was wondering if there might be a professional service for this sort of thing! Hope someone can help.

Best Regards, Ryan.

[Lee]

Are you sure it's the heat exchanger? Sounds more like the pump...

Lee

[praying4wind]

Hi Lee,

Thanks for your reply. It's definitley not the pump as the noise dies as soon as the burner cuts and the system is in pump overrun.

It's also not the flue fan as I checked that closely and the bearings feel super smooth.

Cheers, Ryan.

[Lee]

We had very similar symptoms, after adding a rad and drain/refill. A *very* loud squeal and vibration that could be felt through all the rads - but only when the flow temp was higher than 76C, however, as soon as the burner cut out it went quiet.

Turned out to be a simple airlock in the pump, but shifting the air took ages. I think in our case because the axis of the pump was not perfectly horizontal.

It's worth investigating ;)

Lee

[praying4wind]

Thanks for the information Lee.

I'll certainly take another look at the pump. I did bleed it when re-filling, but as you say, it's worth checking out again. The pump axis is horizontal on our system so I hope any will escape easily. Cheers, Ryan.