Potterton Prima 40f - ignites, and then... goes out :(

[dangel]

I've just restarted the boiler (again) on just HW and this time.. it fired up. It kept going for 3.5mins exactly and then went back to pilot light only..

Exciting stuff!

 

[StevenJames125]

your boiler doesn;t have a perm pilot - an intermittent pilot, ie it comes on when a demand for heat/hot water - vent a radiator at the top of your house - does the water keep flowing.... if not: could be a blocked feed - any air in your system - what's the water quality like? is it very black and dirty or clear and clean?

aounds like it's overheating and locking out

have you had the pump vented (probably have)
and what's the resistance of the pump windings?

strange that the intermittent pilot stays on when the boiler locks out - very weird ......



new question: when you light the pilot, do you do it manually??? ie/ do you hold in a button and push another button to light it?

 

[dangel]

your boiler doesn;t have a perm pilot - an intermittent pilot, ie it comes on when a demand for heat/hot water - vent a radiator at the top of your house - does the water keep flowing.... if not: could be a blocked feed - any air in your system - what's the water quality like? is it very black and dirty or clear and clean?

aounds like it's overheating and locking out

have you had the pump vented (probably have)
and what's the resistance of the pump windings?

strange that the intermittent pilot stays on when the boiler locks out - very weird ......



new question: when you light the pilot, do you do it manually??? ie/ do you hold in a button and push another button to light it?

OK burner came back on for a bit in the interim just FYI - now back off again.

To answer your questions:

I did bleed two radiators - both upstairs - the bathroom one always has air in it when they need bleeding but I didn't find air in either. Water quality looks OK - not drinkable but certainly not what i'd describe as dirty.

I haven't vented the pump - worth doing?

Boiler is entirely controlled by the wall programmable panel - i'm just flipping the sliders for HW/CH to ON. Ignition is automatic entirely.

Next time it fires i need to check if the pilot goes off - thus far i haven't noticed.

Thanks!

 

[StevenJames125]

ok lwt;s start again from scratch

put h/w or htg on and does the boiler fire up? ..... if so, does it go off again shortly after? if so... does the pilot stay on or go out too?

 

[dangel]

ok lwt;s start again from scratch

put h/w or htg on and does the boiler fire up? ..... if so, does it go off again shortly after? if so... does the pilot stay on or go out too?

If I put just the HW on then one of these things will happen:

A) pilot ignition fires, pilot lights, remains on, clunk for main burner but nothing happens then after.

B) pilot ignition fires, pilot lights, remains on, clunk for main burner and main burner fires and stays on for x minutes and then goes off.

In both cases the pilot remains lit - the unanswered bit (because it's a bugger to reproduce every time because it doesn't always fully fire up) is whether the pilot then goes off. I am observing between running round the house for Mrs dangel (who seems to think other things are more important) checking the PC and the boiler

I hate intermittent faults lol

Incidentally, whilst the boiler was fired up the pipes at the top of the unit (feed and return for water) both got hot.

 

[StevenJames125]

could be a rectification fault ......


could be gas valve, pcb, pump..... sounds strange

if pilot goes out too - suspect recitification problem - i think your boiler uses same probe for ignition and rectification - may be dirty, out of position, bent under flame a bit, burner dirty prob etc

 

[Ihavenojob]

If the fan&pilot stay on its not overheating,if its not sparking when pilot is on then its rectifying ok,you need to check for 240v at white wire on gas valve,if present valve is faulty,if not its pcb.

 

[Rob]

Amazed this has gone to 2 pages and people are still suggesting circulation issue

Its not circulation as the main stat would interrupt the pilot.

Its not the pump

Its not a rectification fault as it ceases to spark

You need to check if your getting power to GV2 this is the main burner solenoid

Check for 230v between Blue (live) and White (neutral)

Dont test it with a neon

At a guess the solenoid is going OC

 

[StevenJames125]

I suggested gas valve fault hours ago - check resistance of gas valve

 

[Rob]

I suggested gas valve fault hours ago - check resistance of gas valve

You've suggested every part of the system from PCB to cold feed!

 

[dangel]

Thanks folks all good stuff - i've checked the voltage to GV2 and it's definitely OK which I guess means the valve is sticking rather than PCB fault as suggested. Sort of makes sense given the pilot stays on (and pump, and fan)

Time for an engineer and a new part! Will let you know how we get on!

 

[StevenJames125]

I suggested gas valve fault hours ago - check resistance of gas valve

You've suggested every part of the system from PCB to cold feed!

I didn't suggest cold feed

Without seeing it it's strange, you need to check/test parts
With power to gas valve and gas valve not opening test resistance of coil

 

[Rob]

I didn't suggest cold feed

if not: could be a blocked feed -

 

[StevenJames125]

that was because the engineer who looked at the system suggested no water in system - so I was going on that info - that's why I said let's start again

It's not easy going on what people say on here - you;r ebetter off starting from scratch and testing parts yourself - original posters suggested PCB so without testing I wasn't ruling it out

For free what do you expect?

 

[StevenJames125]

Rob - if the (main burner) solenoid in thr gas valve is OC as you suggested (and me too) - how do you explain that the burner comes on/boiler fires up for 3-4 minutes at a time before going out...... very strange! that's why pump etc were mentioned and need to be tested