Baxi Bermuda Inset BS/TS Back Boiler, again!

andrew1210 · 22 May 2010

Hi, some may remember in January that I had a problem with the above boiler due to it 'banging' loudly when the room thermostat was satisfied and the pump went off, but not the burner.

see //www.diynot.com/forums/viewtopic.php?t=211602 for more info.

Anyway, to cut a long story short, The engineer finally replaced the internal boiler stat. last week and the banging faded away but was still there, albeit quieter though. However on Thursday there on its initial fire up for heating I banged loudly once more, the engineer now suspects that it is sludge in the heat exchanger causing the thermal movment.

My question is, is there any chemical you can use (sentinel --??) to remove or even just break up this sludge? I also saw 'boiler silencer' in Screwfix, would this be any help?

Again thanks for any help you can offer and if you have any other suggestions, i'm all ears

petit_pablo · 22 May 2010

Im concered about this:

room thermostat was satisfied and the pump went off, but not the burner.

Is this still the case?

If so, get someone back who knows what they are doing. If the room stat goes off, then the boiler stat is irrelevant as there will be no demand on the boiler.

andrew1210 · 22 May 2010

Thanks for the reply, sorry, I should have elaborated, the burner does go off but after about a min.

IE. Boiler running -> Room Stat 'clicks' off -> 30 secs -> Boiler begins banging with increasing violence -> gas valve finally closes and banging fades away.

I could not see how it could have been the internal stat. as the boiler doesn't make a noise at all on 'hot water only' (gravity system)

petit_pablo · 22 May 2010

I will suggest again you get someone else in who knows what they are doing.

As soon as the room stat clicks off the boiler should be going off unless the HW circuit is cold.

Does the same thing happen if the boiler thermostat is turned right down as low as it will go?

andrew1210 · 22 May 2010

No, when the engineer was waiting on the part being ordered in he put the old thermostat down to 'low' and the banging almost dissappeared, only maybe a breief clunk or so when switching off after a cold start in the morning, he said the thermostat was out of calibration.

I could see the logic in that though as when the stat. was at 'LOW/MIN' the radiators were still getting rather warm.

Will phone for another engineer to come and have a fresh look at the boiler, just wondered if it was sludge in the HE as he described.

45yearsagasman · 22 May 2010

Iv'e just read the previous post and the present one and as far as I can see no one has asked you to describe fully the type of system you actually have,ie are there any motorised valves or is this as I suspect a gravity hot water and pumped heating setup.Just because its a Baxi inset don't assume that its fully pumped.

andrew1210 · 22 May 2010

Sorry again, I should have explained. I don't know too much about heating systems although the knowledge you gain on this site is unbelievable.

It is as far as i'm aware a gravity hot water system, no 2/3 port valves and you 'have to have HW to have CH', no independent control.

System installed 1999,

Old Sangamo 410 timeswitch, (from previous system)
Old Honeywell Room thermostat
Grundfoss pump

Hope this helps, if you need any more info. just ask,
Again, thanks for your assistance.

45yearsagasman · 22 May 2010

When the room stat shuts off the pump the boiler will shut down some time after on its control stat which is normal operation for a gravity system.Your problem is that these Baxi heat exchangers are not entirely suitable to be on gravity and do become noisy just prior to shutdown.The system would benefit from conversion to fully pumped controls and a good flush with correct inhibitor dosing.

andrew1210 · 23 May 2010

OK, yeah it is my grans system, and it has always clunked since installation in 1999 but only a minor click or two, never as bad as it has gotten recently. The engineer did suggest slude in the HE which could be causing 'thermal movement'

Would Sentinel X400 be any good in this case, then X100 afterwards?

Failing that, I'll consider getting the system converted as you mentioned, is this a lot of work?

Thanks Again

45yearsagasman · 24 May 2010

A fair price for flush and converting to fully pumped....not my area of expertise but I'm sure some of the install experts on here may be able to help.I think the x400 x100 route will not help a great deal. You are possibly looking at £900-1000 and 1.5 days?

diynot

If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.

Select the supplier or trade you require, enter your location to begin your search.

Are you a trade or supplier? You can create your listing free at DIYnot Local

Baxi Bermuda Inset BS/TS Back Boiler, again!

Similar threads