Boilermate 2000 / Suprima intermittent hot water

Having browsed all other topics on this forum, I can't find exactly the symptoms that my Boilermate 2000 is experiencing...
Hot water and heating is available first thing in the morning, and continues throughout the day until late afternoon. At this point, the Suprima stops firing although it's not in lockout (nothing special happens to cause this, i.e. no central heating necessarily or high hot water demand). The green and red light combined (looks amber) are on and flash every 3 seconds (waiting for a call for heat from the Boilermate I assume). The Boilermate heatstore (H46 for instance on display) temperature continues to fall gradually over the next few hours, down to 30-40 degrees. HL1 and HL2 are both on, HL3 is off. The left hand pump (boiler circuit) is running, lukewarm of course because the boiler's not firing. Central heating is off (presumably because heat store is below 60 degrees). Right hand pump is running constantly, even though taps are closed (is this normal operation?). F&E tank is full, but when screw on face of the heating pump is opened, no water trickles. Is there a huge airlock? I leave the screw out for a few minutes and the system gurgles, but still no water trickling from pump. I've tried to reset power - this switches the pump off, but still the boiler doesn't fire. Eventually, it's the kids' bathtime about 7pm (and they endure a shallow lukewarm bath, poor mites!). Still the boiler doesn't fire. The boiler suddenly springs into life about 9pm of its own accord i.e. no demand. It seems to be getting worse every day for the last 3 or 4 days. Any suggestions would be welcome. My plumber has suggested that the diaphragm might be leaking (to allow air into system). I'm wondering about the F&E supply pipe... could it be blocked? The tank is full, but maybe someone out there has experienced something like this before?

Hi Spencer,

Sounds like you may have multiple faults. Initially I would try draining the store to see if the f & e tank has a blocked cold feed, if the water in the f & e tank does not go down then you have a blocked cold feed.

If not then you have an air lock, have you tried venting your radiators?

The problems you described with the boiler firing could be either senor issues or a faulty pcb.

Hope this helps

Kind regards

Gary MK Group Limited

Thanks Gary, I'll try to drain down and check F&E level at the weekend. It seems to be an issue with DHW rather than heating. There's definitely air in the DHW circuit (due to gurgling in the Boilermate when I unscrew the DHW pump plug). Do you still think air in the heating circuit could be affecting it? Seems strange that the DHW pump runs constantly for a long time after taps are closed off. T1, T2 and T3 all read OK, and in theory are triggering a call to the boiler for heat (also LED1 and LED2 are on). Yet the boiler is flashing red and green together indicating that it's in standby waiting for a call. It could be multiple issues, or it could be that the boiler not firing is a consequence of an airlock or supply blockage. How hot should the heatstore get normally - I read 75 degrees in the manual, is this realistic? I just can't figure out why it's consistently working all day and night with the exception of about 4 hours (between about 5pm and 9.15pm, just when you really need hot water!)... you can almost set your clock by when the boiler will start firing again! Is there any master reset or diagnostics on the boilermate, or does it fully reset every time the power is off? In the manual, it refers to a diagnostic check by putting a jumper across jumper 5 - have you come across this, and if so will it tell me anything?

Try cracking the nut above the DHW pump be very careful though, does sound like you have an airlock. 75 degrees is realistic but you can check the set points on the pcb.

I would initially look to sort out the airock before tackling any other fault. Once you have water in the DHW pump then come back to me and I can talk you through a couple of tests.

Kind regards

Gary
MK Group Limited

Hi Gary,
Thanks for prompt response. I'll get back to you when I've tried relieving the airlock.

Problem resolved...
Having been given a bum-steer by a local plumber, I cut my losses and called in BG. They diagnosed and fixed the problem within the hour. The Boilermate was working correctly... it turns out that the whole 'airlock' thing was not related. The problem was with the Suprima PCB, nothing to do with the Boilermate. I had the Suprima PCB replaced in Dec 2009 by our local plumber when it 'failed' just before Christmas. This turned out to be unnecessary, as it was the gas valve that had failed. Having then replaced the valve, our 'trusty' plumber failed to finish the job properly. The BG engineer that fixed the Suprima on this occasion said that the boiler was over gassing. My local plumber has billed me £200 for the job, despite having misdiagnosed this problem and incorrectly calibrated the gas valve last time. I'm not impressed! BG, on the other hand, correctly diagnosed and fixed the problem (replaced PCB and thermistors), highlighted the gas valve issue, and all at a cost of £99.

Sorry for the rant, but thought I should close the loop in case anyone else experiences similar problems. Thanks to Gary for your help, and for responding so promptly.