e30cossie

Any help would be much appreciated.

My small water expansion tank in the loft is full of boiling water.I noticed this the other day as the ballcock imploded. The boiler runs for about ten minutes then the pipes start banging ,the 3 port valve starts clicking, The water pump sounds like glass flowing through it.The boiler trips off and a load of boiling water comes out the open vent pipe into the expansion tank.

You can then hear the boiler trying to start again with the fan clicking on and off for a few minutes. Then it all fires up again.


I don't think its ever worked well. I'v changed the pcb and the water pump.

I'v also drained the system before and there was no black sludge. I wonder could the system need flushing as there may be bad water flow?

rapidcossie

If it runs for tens mins with no probs then starts to make the noises it sounds like the thermostat on the boiler is faulty and its boiling the system.

There should be an over heat cut off on the boiler but that sounds like thats faulty too.

I take it your a a corgi reg gas engineer yeah?

Steve the Plumber

iTrader: (11)

Blocked cold feed!

TIFF

Its possible that the coil in the cylinder has a hole in it...........This is putting the heating system into the hot water and going up the expansion........

e30cossie

I'm looking at the wiring diagram

and found

Lo thermostat
Hi thermostat
overheat run off device
pump ???errun thermostat (cannot read what it says)

I'll get my friend from British gas to buy and fit the parts as he has diagnosed it wrong and already cost me.Thanks for the help.

I'v actually started a plumbing course at college this summer.
I have asked my lecturer and she told me that the water pump is in the wrong place and the pipe work needs reconfiguring.
As she just said this of the top of her head and the house was only built in 1994 I very much doubt this is the case.

e30cossie

Tiff that's a good idea. Is there a way to check ?

Steve the Plumber

iTrader: (11)

If the cylinder coil had split, it will cause the header tank to overflow!

Is the overflow dripping outside?

Where are you located

TIFF

I thought it could be that as he said the heating tank was full of boiling water.......

e30cossie

The overflow is not dripping. I found out the tank had boiling water in it as the week before the ballcock had imploded and I had been keeping an eye on it, and I have changed it. Just looked at the boiler and there are 2 water pipes on the top. One has a drain valve, Should I drain the system from here,Then connect a hose pipe here and flush it through? I'm in Luton.

Steve the Plumber

iTrader: (11)

If its a blocked system then normal draining and flushing wont do, IF its a blocked system a good power flush may cure your problem, failing that get somebody out you can trust not to rip you off and have a look for you, but chances are you've got a blockage somewhere in the airing cupboard.



Diagonosing is'nt always easy over the web, but we're all try to help!

e30cossie

Thanks for all your help (steve the plumber). I'll have a go at trying to fix it tomorrow and will let you know how it goes. Thanks again.

focusv8

Keeps the pump running after the burner has switched off, to cool the heat exchanger down.


Has it always banged or is it recent?

Is the boiler, Wall mounted, floor mounted, upstairs or downstairs.?

What make and is it the original boiler? (does the pipework near the boiler look like it's been altered to fit a new boiler)

.
.

e30cossie

My boiler is a myson apollo 50 and is feeding 6 small radiators.

The boiler has never seemed to be right as cuts in and out too often. The banging and boiling water going to the expansion tank has only just started to happen.

My boiler is wallmounted and my house is a 2 bedroomed coach house (all rooms are one level) house was built in 1994 and I'm pretty sure its the original boiler.



Today I changed the Lo stat,Hi stat and limit stat.

The Boiling water has stopped going in the expansion tank and no more banging,But the boiler now runs 30 seconds on 30 seconds off. It is heating the radiators and water but I know this is not right.

Is this right I'v brought a bottle of fernox heavy duty restorer and Im going to put it in my system for 7 days and then flush the system and see what happens.

I'v been told the myson appollo has a very small heat exchanger and might be blocked with lime scale.

PAUL S

iTrader: (8)

I had this exact same problem last year, I found that the thermostat probe that sits in the boiler had split so was not switching the boiler off once the water was up to temp, so the water was getting to hot after 10 mins or so and sending it up the expansion pipe and into the top up tank for the rads. Bought one for a couple of quid and fitted it and not had any problems since

e30cossie

I changed the Lo stat,Hi stat and limit stat today and the water is not boiling up any more,but it is working fine now no boiling water or noises but the boiler runs 30 seconds on 30 seconds off.

Fudgey

iTrader: (4)

i have had problems with mine too, you may have seen my thread.

anyway, it was cutting in and out very often, i now think due to a partially seized pump. i say partially as it would then run and pump water ok after a while

i have ust replaced the pump and so far, all seems to be ok

you say you have already changed the pump tho..

e30cossie

I changed the pump about 7 months ago. This was the first thing I did ,the arrow is pointing towards the 3 port valve.

I wonder if the water has been boiling over if the new pump may be damaged ?

You can feel the pump running and when you change the speeds feel the pump slow down or speed up.

Steve the Plumber

iTrader: (11)

Hot water wont damage the pump, they are designed to get hot,

Sorry mate, my monies on the cold feed!

e30cossie

At the weekend im going to drain the system. Try and blow some of the pipes through with nitrogen and put heavy duty restorer in the system for 7 days as the bottle says.

As said a few posts above. The thermostat must have been broken aswell as the water is not going into the expansion tank anymore.


Steve the plumber . I take it you mean the cold water feed to the boiler. All the help is much apreciated. thanks

Steve the Plumber

iTrader: (11)

Its the cold feed pipe from the little tank in the loft to the airing cupboard, normaly goes to a air separater (looks like a swirl pot) and has the pump normaly attached to the same pipe, that the cold feed and it normaly clogs up from the from the pipe that comes bottom of the air sep down to the pump region, but i do say NORMALY, because yours could be designed differently and it could be blocked elsewhere.

Turbosystems

iTrader: (5)

you sure you just haven't got an air lock in the cold feed

Steven_RW

On the subject of boilers.

Firstly I know FECK ALL about them so prepare for some really noob terms

I have a typical boiler and hot water tank system in a new house (built 4 years ago).

The boiler is in the utility room and whenever I go on holiday for a week or two (I live it heating the house, but obviously I don't use any of the hot water for the taps etc) I come back and the pressure has dropped and the boiler has turned itself off.

The only visible issue is a thin brown sticky residue sitting below the boiler. I have tried time and time to locate where the liquid is coming from and it "looks" like it is coming from the solid black (size of a decent apple) thing that MIGHT be the pump (as said, total noob).

It also now drops the pressure quite frequently - I would guess every week or two max, even with regular use.

Anyone got any ideas? Do I just need to get a pro out to have a look at the pump? It all operates fine but that leak is annoying

Cheers

RW

Steve the Plumber

iTrader: (11)

Is it a combi boiler?

If it is, it could be leaking out of the pressure relief valve outside, or even the auto air vent could be weaping?

Steven_RW

A combi boiler is one that heats the water as and when u turn the taps on yeah? If so, no, mine is a regular boiler that heats up water in a big secondary hot water tank beneath the stairs.

Thanks

RW

Cozzie Bhoy

I presume its an open vented system you have? Should look into making it a sealed pressure system. Works a lot better. Will need to fit a 10L pressure vessel and 3 bar blow off though aswell as a fill loop. If you leave it as it is with water 'pitching' into the header tank you'll get a continuous supply of fresh water into the system which will rot the rads from the inside out.

Cozzie Bhoy

If its not the auto vent or the safety valve like Steve suggested put a bottle of 'LeakSeal' in the system. Works very well for small leaks like yours seems to be if it takes a week to lose pressure.