Halstead Finest Problem - Here we go again

[stellaman]

Hi There,
I've read previous posts on this "wonderful" boiler and just want to ask a few questions about my specific problem.
I've had a couple of installer friends (they dont really do repairs!!) take a look at my Halstead Finest which keeps going to safety lockout. They've cleaned the fan housing out. Diaphram is good. Changed the Air Pressure switch and i had a new board in February, changed the thermistor and checked the other main parts.
Boiler gets to temp and locks out, with the cover off it doesnt lock out and water comes out of the overflow.
Does this sound like the overheat thermostat is at fault or could this be something else?
any suggestions would be appreciated.
Many thanks, Nick

 

[kevplumb]

check the hoses to the aps and check the fan venturi

 

[stellaman]

Thanks for the quick reply.
One of the pipes had a split in and was replaced. They cleaned out the fan venturi too

 

[bengasman]

...Boiler gets to temp and locks out...

At what temperature does it lock out? Ch or dhw? All the time or sometimes?

 

[stellaman]

started out with just the CH and now does is sometimes on the DHW but not always. It always goes to lockout on the CH when the presure reaches around 1.7 bar

 

[bengasman]

... It always goes to lockout on the CH when the presure reaches around 1.7 bar

At what temperature does it reach 1.7 bar?
And what is the pressure cold?

 

[stellaman]

i dont have a display for the temperature sorry.
the cold pressure is just under 0.75

 

[bengasman]

Initial thoughts went to dying pump, do all the rads get hot? Odd that it works fine with cover off.

 

[stellaman]

yep all the rads heat up as normal. with the cover off it stays on but then water comes out of the overflow which lead me to thinking it was the overheat stat or possibly the circuit board has gone (it is under warranty).

 

[kevplumb]

check the expansion vessel pre charge

 

[ollski]

try linking all three terminals on the aps together to rule out the fan and venturii for the cutting out problem...its almost always this, the venturii has to be absolutely spotless.

 

[stellaman]

thank you for the tips. i will get these completed to rule them out.
cheers

 

[Rob]

try linking all three terminals on the aps together to rule out the fan and venturii for the cutting out problem...its almost always this, the venturii has to be absolutely spotless.

This. Blowing down the venturi doesn't count as cleaning it.

Also if it's ok with the cover off (apart from the pressure increase) then its almost certainly an air flow fault.

 

[stellaman]

sorry got caught up answering queries in the building regs section.
so this may not be an overheating problem then? will have the venturi cleaned properly and check then. Strange how sometimes it runs longer than other times though

 

[Agile]

The fan impeller and venturi have to be cleaned with water to get them clean.

However, I dont advise DIYers to do anything to the fan or even open the combustion chamber when they are not gas registered.

Tony