Boilermate 2000 DHW - Fault Finding

[be11aml]

Another day, another problem with my Boilermate!

I have seen other similar issues to mine, but wanted to check with the forum before attempting the repair.

Issue: DHW goes cold after running tap/shower for 5-6 mins, this lasts 10-20s and then come back hot and around the cycle again.

There are no errors on the sensors and they seem to respond to what is happening at the taps. The store is at full temperature (77 degrees) and remain there during these issues.

This happens at all taps, DHW pump is set to 3 and seems to be spinning freely. System has been on and off many times and all sensor cable contacts have been reseated.

Measured voltage across pump, hit a max of 170V (should this be 240V?) . When the hot water fails, the pump stops, voltage = 0 V

The PHE temperature sensor reads 54-55 when the pump stops. DHW temperature senor only seems to get to about 48 max.

My guess is that the PHE is scaled up, as the PHE temperature should be less than 55 degrees. This is causing the pump to stop and only starts up when PHE temperature drops again.

I was wondering if any knows how the DHW temperature is actually controlled or what is really causing the pump to stop. Not sure if voltage at pump is linked to PHE temperature or DHW temperature or both.

Additionally, the PCB does buzz during the hot water demand, this might be part of the issue.

I have a British Gas homecare plan, but with £50 excess. The plan was to try and descale the PHE and see if there is any improvement. If so, replace at next convienient opportunity. If not, get BG in to start replacing PCBs and/or temperature sensors.

There are some very knowledgable people on here about these systems, so I was hoping for some input based on my findings.

I have read many posts on different forums and it seems that scale may be the issue

 

[ChrisR]

it seems that scale may be the issue

I suspect you're right.

G4Y may have other ideas

 

[be11aml]

Thanks for your response ChrisR.

Tonight, I wired the DHW pump to the 240V supply to prevent the cut out and see what would happen at full speed.

The PHE temp sensor was reading 65- 68 degrees, while the hot water started quite hot at 60 but seemed to get cooler during my shower, maybe as the store cooled a bit.

What still can't understand, is why does the PCB stop the pump, while the hot tap is still running?

If the control stops pump when PHE reaches 54/55 degrees, then poor heat transfer points to scale.

Still only getting 170V at the pump, when correctly attached and I was under the impression the PCB modulates this down and should not stop while the tap is running.

 

[Fellacim]

If its going cold after 5 or 6 mins then its probably not the plate. The sensors can be faulty even if they dont show an error message. Wiggling the sensors can bring up an error or if the temp changes massively as you do it also proves its faulty.


Terry

 

[45yearsagasman]

Sensors are common faults.........wish I had a fiver for every one.......

 

[misterdubya]

The boilermate DHW coil is notorious for scaling.

Clean or change it. Im so convinced its that, that if you but a new one and its not that Ill pay you for it.

Mr. W.

 

[dreadnoughtheating]

Ignoring the electrickery side of these sludge buckets, is the primary store of water full? not forgetting a possible blocked cold feed (use mains pressure and a short length of garden hose on the top tank outlet to blow some freshwater through the sludge) and secondly have you tried the blending valve - my local plumbase sells the Oventrop (absolutely identical to the gledhill one, except about 1/2 the price) valve, the originals do fail too.

DH

 

[be11aml]

thanks all for your input.

System is full and there are no blockages, I have recently put in some x800 via the F&E cistern, so no issues there.

I have fiddled with the sensors and now that you mention it, I have noticed some readings in the 80s at certain times. Although, I have never seen this while the taps are on.

Any thoughts on how the pump speed is actually controlled? As I said before, the pump stopping has got me confused. In another forum, someone had the same fault and it was scale.

Since I have to drain the system to change some radiator valves, I was going to take of the PHE and throw in some descaler to see if this improves the situation.

After that, the British Gas team can come out and start changing components not related to scale

 

[45yearsagasman]

The boilermate DHW coil is notorious for scaling.

Clean or change it. Im so convinced its that, that if you but a new one and its not that Ill pay you for it.

Mr. W.

The boilermate 2000 has a plate heat exch and not a coil.The older boilermate 11's had the coil.No blending valve either on the 2000!!!

 

[be11aml]

Here is a link to the forum I mentioned above.

http://forum.plumbingpages.com/viewtopic.php?f=9&t=2136&sid=30d02cdb7b2199e36b1a8897afd5ba1e

The only differences being that the running DHW temperature appears to be about 45 degrees, rather than the target 55 and I got a higher voltage at the pump before it stops.

Additonally, I have read through this forum for similar issues, but these seem to be sensor related.

http://gledhill-repairs.forumotion....ining-bm2000-to-replave-the-hw-sensor-t74.htm

Check the shower is still running cold. Feel a piep to see if you have hot water coming out of the boilermate feeding the hot water taps and shower. You probably don't you don't. Now see if the DHW pump is running. (It should be.) If it is, feel the pipe coming out of the store feeding stored water into the DHE. Is it scaldingly hot? (It should be.) Now feel the pipe with the DHW pump in it returning water back to the store for re-heating. Is it luke warm or cold? (it should be.)

The cool(ish) water being returned to the store from the HE suggests the HE is not suffering form water scale contamination. (Return water comes out HOT when this is the problem, the PHE sensor senses the rise, tells the board which then thinks you've turned the hot tap OFF even though you haven't, and stops the pump....)

 

[gas4you]

Boilermate store temp is not a given constant. I varies constantly, god knows why, but I don't!.

Does the HW demand bar go off when the HW at the tap goes cold?

 

[be11aml]

Thanks for your help Gas4You.

Just been to check what happens when water goes cold, here it is.

Everything is as expected initially, turn on tap, pump starts, DHW water temp about 47-49 degrees.

PCB buzzes the whole time the taps are on.

After 4-6 mins, buzzing stops, pump stops, DHW demand bar goes out. Water goes cold. PHE temp about 55 degress, DHW drops to about 35 degrees.

After about 5 s, PCB starts buzzing, pump starts, water temperature increases to normal again.

 

[be11aml]

Point I also noted, when taps are stopped, DHW bar stay on and buzzing continues for a while, before going out. PHE temp is quite high at this stage, a high PHE temp does not seem to explain the pump turning off.

Additionally, the DHW supply bar comes on 2-3 times for a few seconds after the demand has finished. Noticed this due to the PCB buzzing

 

[gas4you]

Hard to say anything really helpful from a distance, but it sounds more like an acb fault at the moment.

The very basic test of the acb is as follows.

TURN OFF mains supply to boilermate at wall.

Test that no power is present at the terminals in the boilermate.

LOOK FOR The 3 jumpers 2/3rds up on the left of the acb. They will be on 1, 3 & 4. Remove no 4 and put it on 5.

Turn power back on and board will go through self check and spin each pump in turn.

TURN OFF power at wall again, check terminals are dead, remove jumper from 5 and replace on 4.

This is such a basic check that as yet even with faulty boards, I've never had it come up with an error, but there is always a first time.

 

[be11aml]

Thanks once again gas4you

I've done the check with jumper 5 a few times and there is no error reported

As with the temp sensors, however, I understand that the buzzing is not a good sign.

What I really need is to find out what starts/stops the pump during DHW demand. If it is PHE temp, then it can only be scale.

Might have to sell a lung and call their helpline!