Central Heating always on my Boilermate 3.

[scotty875]

Hi all.
This is my first post after several visits to DIYnot. I'm trying to diagnose the cause of my random CH and have searched through alot of similar posts so forgive me for posting something that seems quite commonplace at this time of year.
Over the years my CH issues have been dealt with by a large energy supplier and in the past repairs have included replacement 3 port valves, motor heads and circiut boards, but after last years 3 call outs only brief respite was obtained and I'm loathe to pay a monthly subscription for no real success.
The CH kicks in without the roomstat or programmer being on and I haven't noticed a connection between the CH coming on and the bm3 calling for DHW.
I've managed to check the programmer and roomstat are working properly so I moved on to checking the supply to the motor on the 3 port valve.
When the CH is on, irrespective of whether I want it on or not there is 240v between the neutral and the DHW, CH and boiler feed when checked at the circiut board.
I'm only a novice DIYer so I thought when the CH was properly off (ie no roomstat or programmer on, rads all cool) there would be just 240v to the DHW and boiler feed but found there was 390v (yes 390v) between neutral, DHW, CH and boiler feed. I rechecked this and tested my vault meter on another circuit to make sure it was working properly. To my mind this can't be right and would welcome any thoughts on this.
The diagnostic board at the top of the picture goes out when the CH comes which I haven't known it to do before, I haven't put my test meter on it so I don't what's going on there.
In the centre of this picture you can see the lower right portion of the pcb where I tested the outputs to the 3 port valve.
My next port of call was the valve and header but I couldn't get the cover off due to the pipe above it.
Any Ideas? I'll update next week, thanks in advance.

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• scotty875
• 5 Oct 2014
• 1

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• scotty875
• 5 Oct 2014
• 1

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• scotty875
• 5 Oct 2014
• 1

 

[flameport]

Over the years my CH issues have been dealt with by a large energy supplier and in the past repairs have included replacement 3 port valves, motor heads and circiut boards, but after last years 3 call outs only brief respite was obtained and I'm loathe to pay a monthly subscription for no real success.

That's fairly typical of those dreadful Gledhill contraptions.

Realistically, it is not worth spending any more time or money on the thing - the only certainty with those is that they will go wrong often and cost huge sums to repair, assuming you can even get parts for them now.

 

[picasso]

It could be the 3 port sticking, unlike a conventional system the 3 port does not do dhw, the 3 port can do heating and/or replenish the store, if it is sticking the central heating will come on every time the store is brought back up to temp you could try changing the 3 port head but thermal stores are notorius for sludge and could have damaged the valve body.

 

[scotty875]

I'm trying to nurse it through one more winter, I'm not flush with money currently. There can't be many left, truly awful as you say. I'm suspecting the control board at the moment until I can rule out the 3 port and motor. The fact that I can't clear the pipe above the motor casing makes me wonder if I need to drain the system and remove the pipe to access said case? The motor must have been replaced with a taller model last year as I remember having a look at the motor before. Worst case scenario is about £500 for boards and valves if I d.i.m., admittedly expensive for a sludged old system, any ball park figures for a suitable replacement? BG quoted £6k for a combi which I'm not keen on!
Thanks again for the replies.

 

[petit_pablo]

The diverter head is detachable, how much space is above it?

 

[scotty875]

About an inch, had a go at it yesterday,might clear with force,the cover is fairly flexible and judging from the calcium on the pipes it looks like that might have been persuaded like that before

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• scotty875
• 5 Oct 2014
• 1

 

[flameport]

BG quoted £6k for a combi which I'm not keen on!

BG prices are always vastly more than others.

You probably don't need another boiler - just to get rid of that Gledhill store, and put a normal unvented cylinder in the same place, plus a few modifications to connect the radiators to the boiler in the usual way.

 

[scotty875]

It could be the 3 port sticking, unlike a conventional system the 3 port does not do dhw, the 3 port can do heating and/or replenish the store, if it is sticking the central heating will come on every time the store is brought back up to temp you could try changing the 3 port head but thermal stores are notorius for sludge and could have damaged the valve body.

I have now noticed CH coming on every time the store is calling for heat, thanks for the direction picasso. Today I finally figured out how to take the head off, the valve spindle is fine as is the motor and the cam lobes are working the switches ok. When I switch the store off the valve is returning to its HW position ok so I have moved back to the SAC board. If I disconnect the white feed the motor won't go over to CH only or mid position which is what I'd expect with my limited knowledge. If I disconnect the programmer and roomstat from the board I'm still getting a feed at white wire. Would you suspect the SAC board?

 

[scotty875]

Ok, so today swspped the mid position Valve and head and same symptoms persist however the old one looked and felt on its last legs so not entirely awasted couple of hours.I'm now back to thinking the cause of the CH staying on its the main circuit board.these are going for about £160 and the diagnosticboard might need replacing to.I've come across central heating control packs at screw fix,I'm wondering if these would circumvent the control boards.Amy thoughts please, aside from complete system replacement which is probably acouple of years away.Thanks again.

 

[picasso]

Try this company for refurbished pcb,s

http://store.adlink.co.uk/

 

[repairwiz]

refurbished pcbs, fans and controls

http://igniteheatingspares.co.uk/

save ££££s compared to new parts

 

[scotty875]

Thanks again for the replies,it was indeed the main pcb board, paid about £140 for it.

 

[Agile]

Whilst not very reliable, I would still say that they are capable of useful operation.

The main problem is that so few engineers are very comfortable workin g on them!

I would not generally recommend Adlink but would suggest CET in Watford are more customer friendly.

Tony

 

[picasso]

I would not generally recommend Adlink but would suggest CET in Watford are more customer friendly.

Tony

You have changed your tune ! not long ago you would not touch repaired pcb,s now your recommending CET.