netaheat 80E on/off on/off

[sinden]

I have a Potterton Netaheat 80E. As far as I understand the beast it is a gravity system and has been serviced by a fully qualified Corgi gas engineer. I am happy with everything that he has done and that is not where the problem lies.

Everything was working fine until the pump failed and this was replaced. In order to do this he had to drain the system as the shut-off valves either side of the pump could not be undone – so he replaced the pump and 2 new shut-off valves.

Water turned back on and system re-filled – radiators got hot and plenty of hot water from taps.

That’s when the problem became apparent.

The boiler starts up and after the initial burn [15 mins] it shuts down and then starts again after a minute or so – then goes off – then starts again and burns for a minute or so then shuts down and then starts and then shuts down etc etc. It then just recycles like this.

We have now changed the room thermostat and the tank thermostat. I am told everything else is working just fine but neither he, nor I, can understand why it has started to do this.

He is suggesting that the PCB be changed but I don’t want to continue to change everything piece by piece if someone has either experienced this and knows what the problem is or actually knows how to cure the problem.

I hope I have given enough information – obviously the boiler is 15 years old but everything was fine until we changed the pump and drained the system – all suggestions gladly received to help excessive head-scratching currently going on.

Thanks everyone.

[sunbeam]

Re: netaheat 80E on/off on/off

does the boiler do this on water only?

[sinden]

Re: netaheat 80E on/off on/off

No. It does it with CH running as well as water.

[sunbeam]

Re: netaheat 80E on/off on/off

If it only does it on water and heating,I would say it's not the board,I would have another look at the room stat.did your old one have a neutral,or just live in live out,have you replaced it with one that needs a neutral?

[sinden]

Re: netaheat 80E on/off on/off

Replaced with up to date version of same stat with same wire connections

[sunbeam]

Re: netaheat 80E on/off on/off

are the pump valves fully open?
is the pump on the right way round?
what speed is the pump on?(put it on 2)

[sinden]

Re: netaheat 80E on/off on/off

Firstly, thanks for your help.
valves fully open and pump is right way around
was set on 3 - have now set it to 2 and will monitor - old pump was set on 3 so did same thing with new one.

[sinden]

Re: netaheat 80E on/off on/off

Problem still there. Boiler seems to be noisy - is this related to the draining of the system and trapped air. Could this be contributing to the problem?
The strange thing is that all radiators are getting hot and the hot water tank is providing plenty of hot tap water.
Adjusting the stats will also turn boiler on/off according to adjustment up or down.
I am confused!!! to say the least :cry:

[jase73]

Re: netaheat 80E on/off on/off

You say the bolier is a gravity system but if it uses a pump what pressure is the system running at. Do you have a pressure change over value between hot water and radiators or is in motorised? If its a pressure operated type it could be the valve is not getting fully opened due to low pressure. Try running your system at a slightly higher pressure.
It does sound like your circulation around the heat exchanger is being restricted and going out on over temperature.
I had the same problem with my Potterton boiler and the above seemed to cure it. Hope this is of some help.

[botmission]

Re: netaheat 80E on/off on/off

If the heating didn't work I'd have said it was an air lock or a blockage somewhere.

As it works I'd look at the burner pressure. If it's too high it would cause the boiler to cycle as you describe.

[sinden]

Re: netaheat 80E on/off on/off

Thanks for the thoughts and suggestions.
After visits from 4 professionals who each seemed to think it could be different things and having now changed the pump, the 2 stats and introduced a de-scaler into the system I have been quoted between £1100 and £1800 to fit the same replacement boiler (same make same model brand new Potterton). One suggested a new boiler and a power-flush for £2500.
However, not one of them was giving any assurance that it would cure the problem!
I am somewhat inclined to think (not knowing anything at all about heating and plumbing) that the most likely cause is indeed some form of blokage in the water feed to the boiler.
The rads and the water all get hot and since all rads are getting hot there isn't a circulation problem there.
I realise that this saga is going on a bit but I have a promise from another heating man that he will call within the next 7 to 10 days and have a look - meanwhile I am going to put some more de-scaler into the system since the plumber who put some in last week only put enough for a small system (10 rads) - whereas I have 17 rads.
Any further suggestions very welcome.

[botmission]

Re: netaheat 80E on/off on/off

Try some Sentinal Ferroquest as opposed to the descaler. Only leave it in, full on, for three hours, then drain and refill and then add inhibitor.

[NeilUK]

Re: netaheat 80E on/off on/off

Have you tried contacting Potterton directly? It may be worth getting one of their approved engineers to check out your boiler. I had an experience recently where a 3 year old boiler was doing strange things and none local heating companies could not fix it. A Potterton engineer was called in and he immediately diagnosed the fault which was due to a faulty PCB that had been recalled by Potterton and was therefore replaced free of charge.

[sinden]

Re: netaheat 80E on/off on/off

Thanks for that - tried calling Potterton and they will not send an engineer for any of their products over 10 years old. Seems silly to me but that is their position on older Potterton products!
If I need to replace the boiler it might not be with another Potterton although I don't know whether other manufacturers are the same about their longterm customers!?!?
You only learn these things when you need help.
Am going to follow suggestion from botmission next.