Ace High boiler - no CH

[Neil67]

Hi all - newbie here with a problem...

Today I replaced the diaphragm on my Halstead Ace High combi boiler. All went well, I now have hot water again. It's the second time in 10 years I've done this, so not a virgin to the (non gas) side of the boiler.

HOWEVER - I now have no CH.

The CH was on for about half an hour after I powered up the boiler again this lunchtime - then went off, and hasn't been on since.

Going through some fault finding - I'm getting 230V across terminals 1&2, as expected and the CH thermistor is giving a reading of around 12K. This is as expected too? Odly though, if I disconnect the CH thermistor and power up the boiler, it ignites for about 10 seconds before shutting off again.

Does anyone have any other suggestions? I'd rather not shell out £200+ for a new pcb is there's another component I should be looking at first - or indeed have misunderstood the thermistor resistance, and it indeed is dead.

I should add that the DHW is working perfectly. The boiler fires up when hot water is drawn and it's piping hot. Just no CH.

I do have an external thermostat which controls the CH - that's clicking at around 14 degrees at the moment. It's been on the boiler for at least 5-6 years, and have no reason to suspect that's faulty.

Any other diagnostics would be greatly appreciated.

Many thanks

 

[MANDATE]

Don't know if this will help, it does have fault finding

http://www.ultimatehandyman.org/PDF/Halstead/Halstead-Ace-AceHigh-Installation-Manual-41-333-77-

 

[Neil67]

Thanks mandate - sadly that's a dead link & I can't seem to find that pdf on their site. Maybe its been taken down?

 

[Slugbabydotcom]

http://www.ultimatehandyman.org/PDF...-AceHigh-Installation-Manual-41-333-77-78.pdf

 

[MeldrewsMate]

The diaphragm PUSHES the diverter shuttle to the CH position, it returns to DHW duty under spring force. Perhaps the diverter shuttle is stuck in the DHW position (and it being sticky could be why the diaphragm failed?).
FROM MEMORY...
I think you can easily remove the complete diaphragm head from the DV, then check the shuttle actuating pin moves freely back after it's pushed in. If not it's a full drain of the boiler and thorough clean of the DV shuttle and housing.

 

[Neil67]

Slugbaby - thanks - that's actually the manual I have here and have been working to.

Meldrewsmate - that's really interesting... would that be the the bolt that the diaphragm pin does through? I have to hold my hand up and say I only replaced the plastic and rubber parts. <slaps head>

Perhaps I should have done the lot... there's a little job for tomorrow then

If not that - forgive me I'm having a glass half empty moment... would the diverter switch be a likely culprit?

 

[MANDATE]

Hi Melrews Mate. Are you sure the diaphragm pushes the diverter to the CH position?.
My understanding is that the diverter is pushed to the HW water position when a hot tap is opened. Opening a hot tap removes the pressure on one side of the diaphragm, allowing the diverter to move left across to HW position.
At the end of its travel it triggers a micro switch which lights the boiler.
Closing the hot tap allows pressure to build up again and allows diverter to move right back to CH.
The second micro switch to the rear of the diverter is related to the CH.

 

[Neil67]

I must admit that was what I thought happened - re the diaphragm.

Update - I have sourced a reconditioned PCB for £50, so picking that up tomorrow. I'm convinced it's control related.

The diverter valve keeps being mentioned.. what other names would that be known as? I can't see diverter valve in the parts list

 

[Agile]

Hi Melrews Mate. Are you sure the diaphragm pushes the diverter to the CH position?.
My understanding is that the diverter is pushed to the HW water position when a hot tap is opened. Opening a hot tap removes the pressure on one side of the diaphragm, allowing the diverter to move left across to HW position.
At the end of its travel it triggers a micro switch which lights the boiler.
Closing the hot tap allows pressure to build up again and allows diverter to move right back to CH.
The second micro switch to the rear of the diverter is related to the CH.

When the DHW demand ceases the diaphragm pin retracts and the diverter hopefully follows it under its spring pressure!

The gland by the switch often sticks!

Tony

 

[MANDATE]

Agree! I couldn't see 'diverter valve' mentioned. It shows the flow switch body in the parts list but does not mention or show the housing to which it is secured.
However it is a sliding valve that diverts the system water to the radiators or through the shorter circuit of the HW heat exchanger.
It would appear the valve may not be returning to CH position so worth checking the gland mentioned by agile.
Also micro switches do seem to cause problems and it would be worth testing the one to the rear of the housing

 

[Neil67]

When the DHW demand ceases the diaphragm pin retracts and the diverter hopefully follows it under its spring pressure!

The gland by the switch often sticks!

Tony

Doesn't the fact that the burner shuts down after the DHW demand is withdrawn signify that the diaphragm pin is doing it's job?

 

[Agile]

Its the diverter valve pin which is relevant.

Can you watch it operating the V3 microswitch as water is turned on and off.

Tony

 

[Neil67]

THANK YOU everyone.

I've just picked up & installed a reconditioned PCB and the boiler fired into life. I now have hot radiators again.

Looking forward to the thermometer in the hall getting back into double figures!

Great to know this forum exists and that there are people on it who are prepared to offer their experiences and advice.

Thanks again