Potterton NetaHeat problem

[Bob Eager]

We have a Potterton NetaHeat (soon to be replaced, but not until after this winter).

When I got up this morning, it had failed to start. Symptoms are that on energising the circuit, the fan runs. There is then a loudish clicking noise, repeated a couple of times; this sequence is then repeated after a few seconds, indefinitely (well, until I turned it off). The noise

*sounds* louder than the usual click to fire the boiler, but I can't be certain.

The pilot never lights, so it never gets to teh stage of firing the whole thing.

I'm not a boiler person, so unless this is trivial (which I very much doubt) I'm getting someone in. However, I'd like to know what it's likely to be....all help much appreciated!

[Brian Sharrock]

OK; that tells you that there's power to the unit and that the fan is working ... it pressurise the casing causing presure senssor to energise which ;- a .. applies electrical power to a chargiing circuit which causes a spark to jump across a rather primitive gap. AND b .. applies power to a solenoid - on the gas manifold- admitting a little flow of gas to the pilot light tube in the path of the spark.

You seem to hear the first but not the second, Can you easliy get to the boilers exhaust pipes? If so, cup your hand near the exhaust and sniff. Is it 'gassy' or just fresh air? If 'gassy, then the pilot light 'gas' is being admitted - so the solenoid/ manifold is OK. But the spark-gap arrangement is kaput. If the smell is of fresh air then the manifold is kaput ( or not receiving the signal ...)

The pilot light _mut_ be aflame; it cause a signal to admit gas through the manifold to the main burners. No pilot, no main burner.

it _could_ be ; new manifold valve; or a new control board; or ... anything.

[Andy Hall]

I had one of those many semesters ago which exhibited the same problem.

It was the spark generator which lights the pilot that had become aufgeficht.

[Dave Plowman (News)]

First thing I'd do is to remove the pilot jet and clean it carefully. Use carburettor cleaner which you'll get from Halfords, etc. If it's not allowing enough gas through the spark ignition won't light it, and they do get gunged up over the years.

[CJK]

Other thing that happens with these is the earth electrode of the spark gap gets eroded and the gap eventually becomes too big for the spark. You could have a look and perhaps bend it so it is a bit nearer - or preferably replace it.

If so, be very careful replacing the case. These boilers have positive pressure and any seal failures can have serious consequences (or trapping the wiring in the seal). There are a number of H&S incidents recorded about these boilers (google will find them), & some fatalities. Quite safe if properly looked after but be careful.

Alternately, it is the igniter circuit - in my case resoldering a dry joint was all that was required.

Do not try if you are not confident you know what you are doing, & buy a good CO alarm.

Chris K