boiler pressure rising constantly

[timcreggan]

having read the faq i believe my heat exchanger may be holed so i'm just looking for confirmation before ringing someone out.

its a worcester bosch 28cdi

i can use the pressure release to get it down to 1-1.5 bar but within an hour its at 3+ and activating the pressure release on its own.

if i turn off the water at the stop cock for the whole house it stops filling but i don't know if this proves anything

basically i'd like to know if theres a way of proving one way or the other if its the filling loop or the heat exchanger

also is there a good site out there for parts as i believe my boiler is obsolete now

ALSO i have not left the fill key in and no water drips when its removed, would this prove that the fill loop is ok?

 

[45yearsagasman]

If you have removed the plastic filling key and the boiler is not being used and the pressure still rises then the plate exchanger will be passing. Boiler is far from obsolete and the plate is readily available.
I reread and yes if the key is out and there is no drip then the problem is almost certainly the plate passing.
Quite an easily replaced part if you have a bit of diy skill.

 

[timcreggan]

have seen one for £74, is this cheap?

also i'm no plumber, much more of a lekkie, is there any chance of me flooding the house if i diy it?

 

[45yearsagasman]

Thats a reasonable price for that part.
You do need to turn of cold water and drain the boiler before starting. The PCB needs protecting from water damage and I usually disconnect the control panel and tie it up out of the way. For me about 45 mins work. If you are unsure get it done by a pro and save some heartache. Good luck.

 

[Agile]

Yes but if you turn off the supply to the house then probably not.

New plates are usually about £80.

Its odd that it rarely happens with any other boiler make. I have changed as many on Worcester as all other boilers together.

Even so its pretty rare, I have only seen one in the last couple of years.

Tony

 

[linkyplumb]

Yes but if you turn off the supply to the house then probably not.

New plates are usually about £80.

Its odd that it rarely happens with any other boiler make. I have changed as many on Worcester as all other boilers together.

Even so its pretty rare, I have only seen one in the last couple of years.

Tony

I have had two in the last fortnight, both worcester cdi, one a 28 and one a 35.

As already stated an easy job to do. Just watch that pcb. although it has(or should have the palstic shield on the back of the panel, water still might get in.

Graham

 

[timcreggan]

when you say drain the boiler, will that be a bucket under the boiler job?

how many litres of water will i be expecting to catch?

i have the manual so i'm sure i can find the proper drain if i look hard enough.

then once the water is off/boiler drained its just a quick swap and boiler/water back on?

no need to bleed anyhing etc?

 

[45yearsagasman]

There are 2 white hexagonal drain points LH and RHS underneath boiler to drain from. Don't touch the ch isolating valves and drain until its empty. Under normal conditions a bucket will do and have some rags to soak any stray water.
You will need to repressurise the system, bleed rads afterwards.

 

[timcreggan]

just done the job and its fixed the problem, but annoyingly one of the joins on the heat exchanger is leaking - the old one had loads of a putty like substance on it which i assume i need to seal the join correctly.

each of the joins has an 'o' ring and the two joins which can be tightened have been done up to within an inch of their lives but no luck.

i could live with the drip as it's nothing too amazing but i'd like te job done properly and if it's just a case of smearing the pipe with goo before fitting would be worth doing.

cheers

 

[45yearsagasman]

The only thing you should apply to a cleaned joint is silicone grease. Did you replace all washers and O rings that you disturbed? Its good practice to renew rather than reuse.

 

[timcreggan]

replaced 3 o rings and one flat washer - i guess the stuff on there was silicon grease as it was a nightmare to was off my hands

the pipe that is leaking seems an odd connection in that its just a small pipe that slides into a larger pipe with an o ring inbetween, no threads, just relies on the pressure of the threaded pipes either side to hold it in place.

if i whack a load of silicon grease on it before i fit it, will it seal up?