No Hot Water

HI, my boilermate 2000 is 8 years old and has been perfectly reliable until recently. I've been having problems with no hot water for a few weeks but I have found switching the Boilermate off at the mains and back on then leaving it for a while, the hot water would start working again and usually work for a few days or over a week before the problem returned.

Tonight it has happened again so I have decided to investigate and found this forum, which is fabulous as my usual plumber has never seen one of these before.

I have turned the mains power off and back on.
I have cycled through the LED displays and I am getting figures of 70, 25 and H85, which I think relate to store temp, heat exchanger and hot water.
Since I turned on the mains the middle figure is slowly rising, about 20 minutes now and it is up to 28.
When I turn on a hot water tap the "hot water" LED does NOT light up and I get cold water flowing.
The middle LED remains lit and the displays simply says "on".

After shutting the water valve on the feed pipe, I have removed the front cover of the hot water pump ( right most pump ) and it seems to spin freely and the small amount of water which came out was clean, not sludgy.

My boilermate has a cistern in the loft so fills itself automatically.

Does anyone have any ideas how to fix it and likely cost ?

Incidentally, I have never used the emergency mode in the 8 years I have had the system but I when I tried it there was a large electrical bang/flash from the heating element mounted externally on the right hand side of the unit and my house circuit breaker tripped !

Thanks in advance for any help.
Danny

Just to add, this morning I got up at 7am to let my girlfriend out and the heat exchanger temp was 68 - she didn't use any hot water.
I got up myself an hour later and the heat exchanger temp was 47 - got in the shower with fingers crossed and the hot water worked perfectly.
After my shower the heat exchanger temp was 59 !

I touched the heat exchanger and it was warm. In the past when my hot water has failed I have noticed the heat exchanger is cold to the touch, so the problem would appear to lie with the heat exchanger temperature control.

Any ideas ?

Check the ACB for fault codes ref the sensors.
Check the voltage at the DHW pump when running the hot tap.
Check unit is full and takes water from the header tank.
It means nothing that your header tank is full.
In an ideal world, yes it should fill automatic.
But the BM 200 could have a sludge problem.
And or the cold feed pipe from loft tank to unit could be blocked.
Read through all the posts on here ref BM 2000.
You will find lots has been covered.
Mike

Thanks for your help.
Do you know anyone competent with these systems in the Lancashire area as checking fault codes and voltages is beyond my scope of knowledge.
Thanks in advance.

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Mike

Brilliant, thank you.

What a saga this is turning into.
After several weeks of the appliance working for a few days after being switched off at the mains I finally tracked down a plumber who said he had worked on Boilermate 2000's before.
He came round and immediately diagnosed the heat exchanger pump, £120 for the part plus £60 to fit.
The system then no longer worked after a switch off and I had no hot water at all.
He came back the following week and replaced the sensor above this heat exchanger pump, £40 for the part and didn't charge labour.
This made no difference at all.
He then admitted he had never repaired one before and gave up, after relieving me of £220 !
I called another plumber who came today, spotted the old sensor which the other guy had replaced, checked that they were the same part number and swapped it for the heat exchanger sensor.
This has made no difference either so he is suggesting a faulty ACB which is a few hundred quid so I really want to be certain it is this before I spend any more money.
At the moment the hot water LED is permanently on but the heat exchanger pump is not running, and yet if I switch to "emergency hot water" the hot water works perfectly.
Store temperature is normal and heating works perfectly, DHW temp is 28, PHE temp is similar and drops rapidly as soon as you open a tap - the heat exchanger pump does not switch on.
Do I bite the bullet and buy an ACB or do I call another plumber ???