Potterton Profile Problem

The message from geoff contains these words:

Sorry, I should have made it clearer. I have the Installation and Servicing Instructions so I know which connections are which (if I think to look at the right diagram) but my problem is more basic than that - I am having trouble work out for sure what I should expect to see on a meter at each stage of the process. Which process is not being helped by the fact that I seem to have recorded volts on white the wrong way round when looking at the boiler last night.

T1 is white and goes to GV2. T2 is black and goes to GV1. T3 is blue and is common to GV1 and GV2.

When calling for heat volts present all the time across T2/T3 so is that the pilot light valve which remains lit during main firing?

When the main burner is firing there are volts on T1/T3 and loss of volts turns the main burner out so is the gas valve is OK and I need to look elsewhere for the fault?

But where and what do I look for?

Reply to
Roger
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Does the fan go out ?

it could be the overheat turning it off

Reply to
geoff

In message , Roger writes

While it's sparking, you expect to see volts across T2/T3, that's the pilot valve

Once the sparking stops, the pcb has sensed that the pilot is alight and opens the main valve which is across T1/T3

T2/T3 remains energised

Reply to
geoff

yebbut he said the pilot only goes out sometimes.

Reply to
John Stumbles

The message from geoff contains these words:

Not as far as I am aware but I have yet to establish a foolproof way of checking it is running.

Reply to
Roger

The message from John Stumbles contains these words:

Can't guarantee that it is always the case but sometimes the pilot flame has stayed lit and sometimes it has gone out between attempts to light the main burner and at least some of the times it has gone out the spark has been visible almost immediately.

I don't actually know what a Molex connector is but if it does come down to a bad solder joint then I don't think I could remake it sucessfully. (Now if only it was a matter of hitting it with a big hammer :-().

However the boiler is currently behaving itself so I will have to wait awhile before I can do any more checking.

Reply to
Roger

Furthermore the O/H cut out on this boiler is way upstream. IIRC it breaks all power to the boiler you get absolutely nothing at all until you have found the brown recessed button underneath and pressed it in.

Reply to
Ed Sirett

It also forces the pump on to keep the water flowing through the boiler.

/john

Reply to
John Kenyon

Re. your IIRC - that is exactly what the P.Profile here does. It happened about a month ago and, having pressed the recessed button (can't see what colour it is), the boiler has been running fine since. Is there anything I should be concerned about if this happens occasionally?

Reply to
Si

In message , John Kenyon writes

Not forever though. Until the boiler has cooled to an acceptable temperature?

Reply to
Si

I'm just checking, since, without flame sense problems, it's a rare (pcb) fault and I can't offhand think of an obvious reason for a reliable and regular main valve drop out

Reply to
geoff

If it happens often enough to motivate you to track down the problem you need to check how hot the flow pipe is getting when the cutout cuts out. An IR thermometer is useful for this (with a bit of plack insulating tape stuck on the pipe to give a good reading). If the temperature is OK but the cutout trips replace it. If the temperature really is getting sky high you probably need to check the boiler thermostat.

Reply to
John Stumbles

(I have both of these due to recent threads herein. :)

Thanks John. Tomorrow I'll take a reading of the pipe where it exits the boiler to get a baseline reading.

Reply to
Si

The message from geoff contains these words:

It has become an intermittent problem, and, thinking about it, it may have been around at a low level for some considerable time. What triggered my concern was getting up to a house that was 2 degrees short of being up to temperature, and that after a relatively warm night.

Is there any chance that the ignition lead (which is relatively new) is good enough to transmit the spark but not good enough to always pass the flame detection current (assuming that is the way it works)?

I happening to enter the kitchen (to prepare my tea) just before the room stat decided to call for heat. The on-off start-up procedure went through about 3 cycles before I abandoned food preparation and moved to the boiler. Having wasted a few cycles checking the obvious I set about watching both the volts on the main valve and the burner flame to see if the flicker in the flame that precedes cut-off was reflected in the voltage but the boiler had other ideas and I soon got fed up of waiting for a sign. After several minutes there was another hic-up, but just the one, so I had missed the chance to do some more checking.

Reply to
Roger

In message , Roger writes

IF the HT lead is faulty and doesn't flame sense, then you would hear it sparking again to try and ignite the pilot (which the pcb doesn't think is alight because ...)

Reply to
geoff

In message , Roger writes

You might be just as well having a pcb from me and then you know that you've eliminated the electronics ...

although I'm not convinced that the fault lies there

Reply to
geoff

The message from geoff contains these words:

You may be right. Expect a telephone call from me sometime this week.

Will I need a new ignition lead? It is relatively new but the original started shedding insulation when I disturbed it during a routine service. And if so where from? In the past I have gone to HRPC but they charge an arm and a leg.

Reply to
Roger

it sounds like there may be a reason why the pilot sometimes drops out (dirt around pilot burner or pilot injector). It might even be that the pilot flame needs adjusting (screw on gas valve for this, IIRC).

Should the flame die or move away from the spark electrode then the main GV will be killed in short order. The PCB is fairly basic and as soon as the the flame failure has occurred the spark generator will try to light the pilot again.

If the pilot flame/flame sensing was marginal then it's possible the boiler would effectively be operating on about a 50% duty cycle. Likely less than 50% of rated output aswell.

Reply to
Ed Sirett

In message , Roger writes

impossible to tell without seeing it

Local CH merchant ?

Reply to
geoff

What's a GV please?

Reply to
Si

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