Potterton Netaheat Electronic works, except when it doesn't

[Morkin]

Hi, I have seen quite a few threads about problems with Netaheats, but I haven't seen this exact problem addressed. Apologies if it has and I've missed it.

It's a Netaheat Electronic 6-10. I am going to get it replaced when I have some alterations done in summer, but I was hoping to keep it going until then, to avoid having to pay twice for installation of the new boiler, because it would need to be moved to a newly-built wall.

Problem: when the boiler has been off for a while, that is for an hour or more, it ignites successfully and works normally. But if it has been running within the last hour or so, the main burner often fails to reignite next time it is required. Once it does fail to ignite, I have to turn the boiler off, or turn the programmer or room thermostat off, to prevent it from attempting to ignite, for about an hour. After that, it comes back to life.

The failure sequence is: fan comes on, pilot ignites successfully, main burner never ignites, pilot and fan stay on.

So, I guess it could be the gas valve, which I understand is basically uneconomic to fix, or it could be something else like a PCB component, which might be worth a try. Any opinions?

 

[Agile]

I would not expect the gas valve to be at fault, although it could be.

However, as its gas/combustion related, we dont advise on such matters.

It could be the PCB but probably a much simpler cause.

The obvious advice is to get a competent gas reg engineer !

Tony

 

[Morkin]

I got an RGI in the other day, but unfortunately, at that time I did not realise that the boiler was semi-working - I only discovered later that it would start OK if I left it for an hour or so.
Anyway, he had a look and said he was confident it was the gas valve. But of course, he didn't know that the boiler sometimes does run OK. I'm not casting aspersions on his opinion. For all I know he's correct. Just seeking second opinions on the cheap, I guess

 

[Agile]

Its only possible to diagnose faults in front of boilers!

I have this suspicion that he came, glanced at it, said it was the gas valve which are no longer available and he will fit a new boiler for you for £1600.

But its essential for an engineer to be given all the information about the recent history of faulty boilers as these clues sometimes are helpful to the diagnosis.

Wondering how much he charged for that!

Tony

 

[Morkin]

I may have used the wrong terminology when I said "RGI". The company seems to be more in the repairs business rather than installs. He was there for about 25 minutes while I looked on. Charge was their half-hourly rate of £51 inc. VAT. He did not say anything about installing a new boiler. He observed that the valves are very difficult to get except on eBay etc., but if I could get one he would be willing to fit it.

 

[Agile]

Have you noticed if the boiler carries on sparking when the pilot light ignights but the main burner does not?

Thats often difficult to see because the spark is inside the flame!

Did he use an electronic test meter?

Did he say which make of gas valve your boiler has ( or see the colour of bits of it? ).

Tony

 

[Morkin]

I don't think it continues to spark, but I will look more closely when I get back.
Don't know if he used a meter. I was in the room and saw him poking around in the electronics but I didn't watch everything closely.
I don't think he identified the valve make, but I looked up some valves online while he was leaving and he ran through them saying which ones were suitable for this particular model of Netaheat or not.

 

[Morkin]

Well, it doesn't seem to spark continuously.

I tested the voltage across PCB terminals T1 and T3 (gas valve). When it's working the voltage is 237. When not working it seems to vary between about 218 and 200. I'm not sure if that is enough to explain the apparent failure of the gas valve to operate. The troubleshooting section of the manual says that it needs "240V across T1 and T3".

 

[Agile]

We are not permitted to discuss gas/combustion issues on this forum.

But if the voltage is low and thats why its not working then it could well be another cause!

Tony

 

[Morkin]

OK, I guess I should have read the forum guidelines properly. I'll keep any further musings on this problem to myself. Thanks for your comments and rest assured I'm certainly not going to be opening up the case or going anywhere near the gas parts.

 

[RF Lighting]

Are the terminals you were testing at the incomming connection to the boiler from the mains?

 

[Morkin]

Are the terminals you were testing at the incomming connection to the boiler from the mains?

Well, I'm not sure that I'm allowed to talk about it, but if I were I'd say no, they are from the control PCB to the gas valve.

 

[RF Lighting]

Probably not. There's a lot of trade protection goes on in here

Ah right. Have you checked that the incomming voltage remains steady when the other voltage is dropping off?

 

[Morkin]

Probably not. There's a lot of trade protection goes on in here

Ah right. Have you checked that the incomming voltage remains steady when the other voltage is dropping off?

Yes , that stays at 240vac or thereabouts.

 

[RF Lighting]

Oh that's a shame. It definatley sounds like the fault is within your boiler. I was hoping it might have been a supply fault which you could have fixed.

All I can suggest is check that all the connections in the boiler are sound and that any plugs are pushed fully home. Other than that then I think you'll need a plumber to repair it for you