Boilermate 2000 dhw pump running continuously

Hi I have a boilermate 2000 m210 with switch manufactured 21/9/2001. Chip version 29/01i.

Recently started to find hw ran cold, but after a minute or 2 heated up again. Not sure if this is a symptom of an underlying problem but has been tolerated.

Yesterday we had the boiler replaced. Was a potterton suprima 100 29kw, now Worcester greenstar ri 30kw.

After install, heating working fine but no hw. Bar 3 on led display was showing. After checking circuit board connections, power supply to dhw Pump and turning spindle (not ceased) today it started to work. Nothing was changed.

However now dwh pump runs continously. led display shows st on. When hot water drawn dhw bar lights but led 3 heating pump on does not come on. And stays off even though pump is still running.

Led temperature settings:
T1 at 74
T2 at 7
Dhw at 63

Using infrared thermometer temperatures are:
dhw pipe at sensor 51.4
Phe 49.5
Supply at tap 51
Manual p5 suggests water outlet temperature regulated to 52 by ecs.

Any idea why dhw pump runs even when no hot water is being drawn?

Do I have a faulty sensor or ecs perhaps, or is this normal operation?

Thanks for your help.

Sorry T2 at 70

Hi, I guess there could be several causes but I suspect that you are seeing the early stages of the GT155 (or GD131) going wrong.  The DHW pump running constantly is often a first indicator, often followed by random heating on and offs, then no display and all green LEDs on.  That can take a while to happen of course.  My Youtube video shows how the PCBs should work https://www.youtube.com/watch?v=OP5-i_vi1Pw&t=194s and this one shows typical indication of failure; https://www.youtube.com/watch?v=W3wmeMnvgns&t=143s

Easiest way of checking is by swapping the pcb for a reconditioned one, I can supply one check my website for details.  https://murraymartin.yolasite.com/purchase-page.php

Regards Murray

Thanks Murray, the videos were very informative, thankyou :slight_smile:.

I ran the test, version was u21. It ran through the test sequence as described in video showing the test number on screen, the appropriate leds lit (including dwh) and pumps ran, except dhw pump which remained on for whole test cycle.

Not sure what that means?

I checked for error codes using buttons, none displayed.

My neighbour replaced his boilermate with a standard hw cylinder a while back when they had boiler replaced (his bm was working ok) and I kept the circuit board from it.

It is the older version, is that compatible with mine, can I do a straight swap and are there any disadvantages?

Regards Paul

Hi yes you can do the swap it should work just fine. From your test it is likely that the solid state relay for the dhw has gone short circuit, or the driver circuit for it has gone faulty. The 4th green if fitted is not for the dhw pump, as it is a variable output it does not have an indicator led. Happy to recondition your old pcb for you as a spare. Regards Murray

Thanks I'll try to swap over at weekend, I like the idea of having a backup, I'll contact you once I've got the other one in. Thanks for your help very much appreciated:slight_smile:

Hi Murray I swapped the boards over, the "new" one seems to be working and hot water pump only comes on when tap on.
I tried the test mode by holding down sw2 at power on but board display hung on 888. The chip label says cb v 25 9-01ws and has the larger chip between display and main philips chip.
Just wondering if that version number requires the jumper change to run test mode? Don't want to short the board without checking with you first?
Thanks again Paul

Hi, yes test mode is triggered by jumper on position 5, that said if it is working OK I would not bother, it does not really tell you much that is not already apparent from the fact that it is working (-:

Regards Murray