Baxi back boiler kettling and banging - best action?

[markdon]

Hi, we have a baxi back boiler, bermuda i think it is. Last year when we moved in it was a bit noisy but we had it drained, desludge treatment put in, the. Redrained and refilled with inhibitor.

Its not been too bad over winter, but its getting bad again. When the boiler ignites there is an audible woosh now, like on a stove top if you leave the gas for a few seconds before igniting? Its also bubbling and banging alot more.

We have 10 rads and over winter i stripped the front room down to redecorate and removed the rad, hosed it through and it was full of black gunk. Im now thinking the sludge treatment wasnt enough.

So. Number of options, as with most people we are on a budget, so cant upgrade to a combi, though i would love to!

Powerflush? Not looked into this only heard it mentioned, is it just like it sounds? Blast through the whole system to clean it out?

Remove each rad myself? Hose through each rad? Though this wouldnt do anything to pipes or boiler itself?

Other options?

Is it possible to clean the heat exchanger or is it a case of needing replaced?

Oh, one more strange one, the bathroom and spare room rads heat up when hot water is on? And the bathroom one (bar towel type) needs bleeding weekly, but ive looked under the flooring and there are no visible leaks there??

Many thanks for any help.

Mark.

 

[Agile]

You dont make it clear who did the desludging! How effective it is depends on the chemicals used and skill.

Nor do you mention having the boiler serviced. BBUs can be dangerous and an annual service is very important.

Taking each rad off is labour intensive but certainly shifts dirt. That leaves the boiler and pipework full of dirt.

Tony

 

[markdon]

Sorry for leaving out that info.

It was done by a plumber who has now moved out of the area, he also serviced the boiler and fitted a new gas valve. He used sentinel products though i cant remember which ones but he left the bottles in the loft with a date of when they were used. It was about 8mth ago i think.

Thanks.

 

[andytw]

Can you describe at what point in it's heating cycle does it bang ? e.g. As soon as it lights up, all the time, or just before it clicks off.

andytw

 

[markdon]

We have it set via room stat so when it comes on its on and off meeting room temp. It makes noises pretty much all the time its on, but definatley more when it is clicking off and cooling.

 

[andytw]

I had a long run in with mine which was banging loudly as it got to temperature and continued to bang for a while after the boiler had clicked off. This was a new problem as it had run for years without a problem.

Long story short...the spreader inside the heat exchanger had fallen apart. Once the spreader was replaced the boiler was again as quiet as it used to be.
The spreader distributes the water equally down all the channels of the heat exchanger rather than allowing a flow just down the middle two with the other channels not getting a good flow,... they boil.

I have heard and read on-line that the spreader is only required when the system is set up for gravity flow. This is not true and the Baxi manual says it must be fitted for all installations. (I think the myth that it is not required may come about because the spreader is supplied in a bag with the gravity flow injector tee.)

A clue as to whether this might be the cause of your banging problem would be to turn down the boiler stat which is accessed just below the fire.
Mine only banged when the boiler stat was set at the top of the dial.

andytw

 

[markdon]

I got all excited then i read the last sentance, mine is set to two on the boiler stat.

Thanks for the info though.

 

[mysteryman]

I found in my brother's house many years ago that the eejit who had installed it had fitted the injector tee so that it was injecting up the gravity return! Therefore, the gravity primaries ran backwards with the central heating on, the returns were cooling the boiler thermostat and so it boiled, bumped and banged.

 

[markdon]

Ah, thats something i had forgot to mention, the pipe that goes into the tank in the loft appears to have water coming out of it, but ive not witnessed it?

The pipe comes straight up, then 90 degree then 90 again so its pointing into the tank, looks like it runs straight up from boiler like an overflow perhaps? Not very good at describing things! But the inside of the tank the side where this pipe is its marked as if its scorched? And is wet.

Not sure if that helps with anything?

 

[markdon]

I will get in the loft at the weekend and get a pic of the pipe. Will also watch when boiler strts and ends to see if anything comes out of it.

 

[mysteryman]

If it is pumping over into the expansion tank, there is something wrong with the layout, probably since it was installed. The whole system will be sludged up and will need a thorough clean. All layout errors should be corrected.

 

[markdon]

I didnt know if it was pumping back due to the kettling, like it was creating pressure to boiled it back into the tank?

Whats my best course of action in your opinion? Obviously et a professional out, but i want to be sort of clued up on it so i dont get fleeced.

Thanks.

 

[mysteryman]

If it is pumping over, as distinct from boiling over, it is a layout error. If it is boiling over, it can be a failed boiler control thermostat, or as I described in my brother's house, a possibly different layout error.

 

[markdon]

How will i know the difference? If its pumping over it will be all the time the boiler is running? Boiling over would be just when its making noises?

The boiler stat, if that failed adjusting the control wouldnt make any difference? But i have ours set to two as any higher and it gets even noisier.

Thanks for the ideas so far.

 

[mysteryman]

If it's pumping over it will do it whenever the pump is running - if it's boiling over, it's probably a boiler thermostat fault, or could be a layout error. It's time to call in a pro.