Baxi Bermuda 552 gurgling and bubbling. Gravity fed.

[corkgasket]

Hello, Just joined. I value any ones advice here please.

I have a Baxi back boiler in the living room inside the fireplace. The primary circuit (from the heat exchangers to the cylinder) seems to bubble like mad and occasionally clatters waking me up at night and irritating me during the day. This I want to cure because there must be air in the system and I do not know how to 'bleed' it.

The HW must be on to work the CH. Both produce piping hot water happily but the problem noise (and I guess poorer energy efficiency) does not go away.

I can not seem to find a bleed valve anywhere on the primary circuit to or on the pipes leading to or from the cylinder. The header tank was cleaned and the CH system was thoroughly drained and flushed and topped up with Fernox during the summer. The radiators were (eventually) bled fully by late October, I have not needed to do these since and the rads appear fine now. Recently I have noticed that the header tank now has a black scum on the surface of the water.

Much appreciated. James

 

[kirkgas]

is the temp of the water excessive? if so please take care as there may be a problem with the thermostat which if left unchecked could lead to the heat exchanger bursting

 

[corkgasket]

Thank you kirkgas, I am worried now. Yes the water is very hot from the taps from the cylinder. I have also turned the black dial from 3 to HIGH on the boiler this evening because I read somewhere that I could dislodge sludge in the heat exchangers if I did this. The bubbles are still there, knocking gone (although it is intermittent sometimes) and I can hear water pouring back down the pipes once the gas has stopped.

Please can you just make sure that I know which thermostat needs replacing, the one that is attached to the CYLINDER or the one in the hallway which i set at about 60 degrees celcius.

I also read somewhere that I should drain the system with fernox -again. I am happy to do this in March time, but not now if it helps. I have already done this though.

Thanks again.

 

[kirkgas]

it is the boiler stat which requires to be checked, sorry to be victor meldrew, but i would turn it off till it is checked, i have seen a few of these split, and black sooty water pouring all over the floors aint pretty

 

[doitall]

I would check you have water in the header tank if you have one.

A lot of these were connected to primatic cylinders, is the tap water dirty

Should read the post properly so ignore.

 

[expertgasman]

is the temp of the water excessive? if so please take care as there may be a problem with the thermostat which if left unchecked could lead to the heat exchanger bursting

Thats a tad dramatic, I fear. If there is a vent, then theres no way a faulty stat will split a casting.

 

[kirkgas]

is the temp of the water excessive? if so please take care as there may be a problem with the thermostat which if left unchecked could lead to the heat exchanger bursting

Thats a tad dramatic, I fear. If there is a vent, then theres no way a faulty stat will split a casting.

sorry, i beg to differ, i can remember 2 properties from years ago where the boiler stat was left out of the pocket after a service, done by 2 different guys months apart, where the exchanger burst and flooded the flat and 2 below what a mess it was, unless you could offer another explanation as to why the exchanger burst and flooded the house, about 6 hrs after the guy left the stat out, the boiler was about 15yrs old so it could have been one of theose things, but to happen twice would lead me to suppose it was because of the stat being out,

 

[expertgasman]

Ok, if we assume that there was a direct link betweeen the boiling and the cast leaking then there had to be a pre existing problem. If the boiler was vented, and normally you have a vent AND a cold feed through which pressure is releived, in fact not allowed to build up in the 1st place, I would speculate that there was already either a crack or leaking gasket. The only thing preventing a noticeable leak may have been sludge and corrosion. The turbulence created by the boiling may have been sufficient for this to have been disturbed.

 

[kirkgas]

Ok, if we assume that there was a direct link betweeen the boiling and the cast leaking then there had to be a pre existing problem. If the boiler was vented, and normally you have a vent AND a cold feed through which pressure is releived, in fact not allowed to build up in the 1st place, I would speculate that there was already either a crack or leaking gasket. The only thing preventing a noticeable leak may have been sludge and corrosion. The turbulence created by the boiling may have been sufficient for this to have been disturbed.

a perfectly acceptable explanation, but as i advised the OP, best to get it checked in case his is the same, im not saying it will def blow up but i have seen 2 burst and they do cause some mess

 

[namsag]

Not getting involved in debate about casting but its a failed boiler stat and i have seen header tank get that hot its distorted and floodeed the house and took out both upstairs and downstairs completely in the matter of hours.
Get it fixed ASAP 20 quid part half hour repair

 

[corkgasket]

Thank you all for your comments folks, I think its great to have the opportunity of speaking to so many knowledgeable and experienced experts, I am so grateful.

Just to put you in the picture. There is a vent going up to the loft to overflow into the cold water tank and it is a spur attached to the primary circuit pipe that comes from the top of the coil inside the HW tank (hope that makes sense, i wonder whether I can draw a circuit diagram for anyone). The primary circuit pipe at the bottom of the HW cylinder from the heat exchangers has a white 'SUNVIC' box attached to it. Is this a pump or a tap/switch? It whirs whenever the heat goes on. I think that the system is 'kettling'.

I need to know what to do next, please feel free to agree/disagree and suggest:

1) Replace the thermostat that slips into the heat exchanger.

2) Replace the thermostat on the water cylinder.

3) I have a feeling that the heat exchangers may be sludged up, as so many of you guys suggest that it may be. Can anyone suggest the right fernox product? Any hints about how to de-sludge it properly please?

4) Have a fourth (detailed on-going) search for some sort of air bleeder valve for the primary circuit, will their definately be one?

Waiting in real anticipation here, thanks.

 

[Axel]

What to do next:

0) Turn off the boiler.

1) ......

 

[corkgasket]

Thank you, then what?

1)....

 

[corkgasket]

Just been doing some research, I can get a new thermostat 042818 for about £17.98. That appears a good investment and prevenatative cure even if it is not the problem.

By draining the sytem (the radiators) will the primary circuit (I keep calling it this I hope that this is the name for it) be drained too? What happens with all the sludge? Is there some sort of de-sludging formula that sits in their and boils away for a couple of hours before draining?

Thanks.