Potterton Netaheat MkIIF 16-22

[Mutley1955]

WITH ROOM STAT SET FOR DEMAND AND BOILER STAT MID RANGE WHEN THE BOILER SWITCHES ON THE PILOT LIGHTS, TWENTY OR SO SECONDS LATER THE MAIN BURNER IGNITES. RUNS FOR THREE OR FOR MINUTES THEN MAIN BURNER SHUTS DOWN. IT THEN SITS WITH FLUE FAN RUNNING AND PILOT LIGHT ALIGHT WITH NO MAIN BURNER WHILE HOUSE GOES COLD. ANY IDEAS ANYONE?

 

[ChrisR]

Pump bust.

 

[Mutley1955]

Pump bust.

Sorry, pumps running with no probs, checked spindle rotation but thanks for reply

 

[Mutley1955]

Sorry but checked pump via spindle, going like a good en, Thanks for reply though

 

[JohnD]

edited: incorrect suggestion.

 

[cross thread]

mercury vapour gas valve if its getting 240 volts and not opening then maybe pilot to small of poss just knackerd,positive pressure boiler with a few saftey issues reaiiy best left to the EXPERTS

 

[Mutley1955]

The boiler is a Potterton Netaheat MkIIF 16-22 with working Grunfos circulating pump. Boiler about twenty years old and working well til Thursday.
open vented system with expansion tank in loft (full) Venting highest rad produces greyish water at pressure. It does send hot water through all the rads in the house but does not run full cycle (until room stat is satisfied)

 

[pannierstan]

Pump bust.

Come on Chris! whats this are you having an off day? The pilot light is on and the fans running meaning that the boiler is still in demand. Plus its an F model which means its got the same sort of running sequence as the Profile.
I would look at PCB or check for power to main gas solenoid first. If there is no power to the main solenoid then its the PCB.
If you are really good you might want to check if you can hear the ignition sparking when the pilot and fan are on which would indicate that the pilot is not being proved again pointing to poss PCB knacked.

Stan

 

[ChrisR]

OOps, a momentary lapse, Stan.
Seems I'm not the only one though.
Though the IIF's have a crude pcb, it's the Electronic models which have the Profile type pcb
The F's gas valves get their power from a Relay!

Perhaps we's both better check with Matron before we answer anyone else?

 

[Agile]

Either the mercury switch or an intermittent circuit in the gas valve second stage. ( I think that the pilot does not light until the APS is made ! )

It needs careful testing electrically to determine when the fault lies.

Again as stated this is a job for a CORGi as these are potentially dangerous boilers.

Tony

 

[Mutley1955]

Thanks for your time and trouble gents, been out the trade twenty four years now and obviously out of my depth. Corgi on way tomorrow.
Should the need arise. any ideas for a reasonably priced direct replacement I don't want to dismantle the house to change pipework, flues etc.

 

[ChrisR]

The circuit diag is on the Partsarena/baxi site and not hard to follow on this model. Once the boiler has actually stopped, fault finding takes a couple of minutes. The parts are all available too.

If the width of the space the boiler's in is tight, your options may be limited, and I bet your gas pipe is undersized. Don't think I've seen one on a Netaheat that wasn't!

 

[Agile]

The Worcester 12Ri or 18Ri make good replacements for a Netaheat as long as the gas pipe is upgraded.

However, they are still repairable by a competent engineer who understands them.

Tony

 

[pannierstan]

OOps, a momentary lapse, Stan.
Seems I'm not the only one though.
Though the IIF's have a crude pcb, it's the Electronic models which have the Profile type pcb
The F's gas valves get their power from a Relay!

Perhaps we's both better check with Matron before we answer anyone else?

My apologies too Chris. Again the mind is cloudy these days and the Netaheat badging never stuck that well. I seem to remember the MK1 and the electronic the most. So the MK11F had the white rodgers gas valve is that right? but still had the same ign box.

Stan