biasi 24s overheating

[karry]

Which valve?

I assume you mean isolater valve but which one / where?

 

[Homesafe]

Under boiler on flow and return pipes.

 

[Homesafe]

How did you check the diaphragms if you didnt isolate or drain system??
Funny!!

 

[karry]

I never touched those until this problem
I have drained it several times and have been careful to turn off / on iso valves

The rads heat up (partially) anyway so not that

Could it be PCB?

 

[onecog]

Your symptoms of boiler firing up then cooling and firing up again point to main temp probe,diverter valve or jammed by pass valve and these i would check first providing as said above that all iso valves are open.

 

[karry]

checked DV - pin coming out a long way

Checked DV temp probe - removed connector and burner carried on past 80 degrees - replaced connector burner switched off at 75

PRV not checked yet - what am i looking out for?

Want to check DV again,Agile says can be checked from actuator side - can someone please explain how bearing in mind I do have wall unit next to boiler on that side

Is PRV repairable?

Which is main temp probe - one attached to diverter valve or the one clipped the flow pipe in sealed compartment?

Regards

 

[Agile]

Loosen two locking screws and the diaphragm unit can be moved to the left and then pushed back to expose the left hand gland.

With a solid cylinder about 12 mm diameter the pin can be felt and pushed.

It needs to return fully to divert to heating.

Although it does need to be checked it seems unlikely to be the problem. The movement is about 9 mm.

I also wonder about iso valves.

Tony

 

[karry]

I know DV pin moves out but was wondering whether it returned fully.
When is Diaphragm unit is removed, I did not think I would be able to see the pin as I have very limited access to that side due to wall unit.

Onecog suggests faulty by-pass valve and Temp probe

Wouldnt the fact that CH seems to work albeit short cycles the BPV is OK?

Also removed TP connector forces burner to stay on longer and reconnected TP turns of burner at just below MAX - wouldnt this suggest TP OK?

Can DHW & CH temp probes swapped around to test?

Regardsi

 

[onecog]

A jammed by-pass could cause the boiler to overheat.
Do you have a manual for this boiler ?

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• onecog
• 3 Feb 2013
• 1

Untitled

• onecog
• 3 Feb 2013
• 1

Untitled

• onecog
• 3 Feb 2013
• 1

 

[karry]

Hello Onecog,
Yes I have both Installer and service manuals.

Can I clean / service the BPV?

I have checked the manual and will swap the Temp Probes as they are identical.

Diverter Valve - Could I pull the pin back towards rest position to make sure it has fully come back

Regards

 

[karry]

I checked pin on DV and it is 9mm on Diaphragm side when at rest As Agile advised.

I could not take the pipe off to remove BPV i.e I took the spring clips of and expected the pipe to pull off but it wont budge. I cant get much leverage on it due to it being so close to the wall and I dare not use any tools as crowbar it off.

According to the manual, its simple - remove the clip and pull the pipe off

I drained the whole system and noticed that the boiler stayed on longer but the length it stayed got shorter with time that within half hour it was back to 30 second cycles - the temp it went up to is even less, it heats upto 70 before flames switching off - it will do thos for a few hours and lock out

 

[Agile]

You have been following your own ideas rather then a logical process!

Have you removed the pump head and inspected the impellor for dirt?

Tony

 

[karry]

First thing I suspected was the pump
Checked and was working fine but changed it anyway in case it had lost oomph

 

[Homesafe]

Its definatley a circulation issue but your the one at the boiler.
It would have been more cost effective to get a good engineer to sort it from the off, but hey its your wonga.

 

[karry]

Tried 3 gas safe engineers - They are contractors to a major social Housing Association I work for so are recognized professionals.

They said it could be anything because many causes can display same symptoms - Since its an old boiler it would be beyond economical repair. They quoted £1000 to £1200 Supplied and Fitted depending on make of boiler.

I have had occasional issues with it in the past but have always got them resolved. So i thought I might gamble small amount before I part with £1000 for a new one.

You suggested blocked By-pass valve - does that not come in play if the circulation is completely blocked - But I have 5 out of 8 rads warming up so there must be some circulation - However it does lock out after several hours of heating and cooling in quick succession

The By-pass pipe is that a push-fit secured with wire clip or is there anything more securing it?

What is the cure for overheating main HE if that is the issue?

Thanks in advance