Thorn Apollo 30/50 overheating

[bigal50]

A pensioner I know had only 2 radiators working out of 6 so I drained the system down,removed the radiators and gave them a good blast through then cleaned all the pipework and manifolds.On re-instating the sytem it was all going well and the 6 radiators were now very hot.Thats when we realised that the boiler was not shutting down.The Hi-off-lo switch works to power the main burner.Thinking the hi or lo stats were faulty they were both changed to no avail.
Could anyone tell me at what temperature the hi and lo stats should operate at ? It seems to be a very course method of control although the manual does mention an optional programmer.
At the moment I am guessing that the wires from the hi-lo stats have a short somewhere which is preventing the stats from doing their job.As the boiler is probably around 30 years old I expect the internal wiring may have degraded a bit.I'm a bit puzzled by all this as I never touched the boiler so not sure if it's pure coincidence/bad luck.
Before I dig the AVO out and go faultfinding can anyone think of anything obvious I should check or are there any known faults in this area ?
thanks for reading
big al

 

[45yearsagasman]

Big Al, If you never touched the boiler then who the feck changed the Hi Lo stats? Just a thought.

 

[bigal50]

Big Al, If you never touched the boiler then who the f**k changed the Hi Lo stats? Just a thought.

Hi 45yearsagasman ,my pensioner friend bought and fitted them,I was hoping not to get involved with the gas or electrics as I was the one who done all the radiator and pipework flushing.

 

[45yearsagasman]

I can't find any details of the stats but would assume Hi would achieve approx 75-80C and LO 60C. I have never found the wiring to deteriorate. Have the stats been fitted correctly? Hi-Brown, Lo White. Have you taken flow temps and checked temp rise across heat exch? Bypass (if applicable) set correctly?

 

[bigal50]

I can't find any details of the stats but would assume Hi would achieve approx 75-80C and LO 60C. I have never found the wiring to deteriorate. Have the stats been fitted correctly? Hi-Brown, Lo White. Have you taken flow temps and checked temp rise across heat exch? Bypass (if applicable) set correctly?

Hi again 45yearsagasman,thanks for your comments about the stats.I assume they were correctly fitted before the work started but I haven't been back and wont see it again until saturday.I'll let you know what I discover.
thanks again
big al

 

[twgas]

with all due respect, you are obviously not competent to repair a boiler, it's bad enough people playing with their own boiler when they don't know what they're doing but to do so with someone else's, I would say is somewhat foolish.

 

[joe-90]

It's not a gas part. People fix their own cars and light switches - so why not?

 

[twgas]

are the stats not within the sealed case?

 

[45yearsagasman]

Welcome back Joe. The parts are inside a sealed combustion chamber and as such the work is deemed to be gas related.
Do everyone a favour and try not to spoil the forum with your uneducated inane wind up postings.

 

[Agile]

Its worse because these boilers are about 20 years old now and the seals generally in poor condition!

Tony

 

[bigal50]

I can't find any details of the stats but would assume Hi would achieve approx 75-80C and LO 60C. I have never found the wiring to deteriorate. Have the stats been fitted correctly? Hi-Brown, Lo White. Have you taken flow temps and checked temp rise across heat exch? Bypass (if applicable) set correctly?

Hi again 45yearsagasman,thanks for your comments about the stats.I assume they were correctly fitted before the work started but I haven't been back and wont see it again until saturday.I'll let you know what I discover.
thanks again
big al

Hi again 45yearsagasman,when I returned I removed the brown lead from the high stat and the main burner could still light.Looking at the circuit drawing shows that the suppressor is the only other route for power and when I dis-connected it the boiler operates correctly.As the suppressor contains capacitors an AVO can only show if the suppressor has an internal short.Other than substitution,do you know of any way to test the suppressor.
thanks
big al

 

[45yearsagasman]

I know of no other way to test supressors other than what you have done.
Remove it as a temp fix and fit replacement when you can obtain one.
It is not a safety critical part.

 

[Agile]

I dont follow what you have done.

The supressors are usually two wire with a 100 ohm resistor in series with about 0.1 μ F capacitor.

Others can be three or four wire and contain inductors and capacitors. These can be tested but that needs extra equipment or experience.

The supressors were probably fitted specifically to prevent arcing on the thermostat contacts and prolong their life!

They also reduced TV interference in old 405 line days but that became irrelevant when they ceased in the 1960s.

Tony

 

[Ian Francis]

Hi

I've got a blown suppressor, did you manage to source a new one?
I can't seem to find one and could use a little help.

 

[ianmcd]

you should start your own post, Hi_jacking an old post is against site rules, the suppressor will have a value stamped on it , you will et one the same value at any electronics place or online, will be less than £1 usually