gledhill boilermate 2000

[explumb]

Ive got one of these thermal stores in our rented house and 3 plumbers have been and failed through lack of experience to even diagnose my problem.

the hot water keeps running hot and cool, started about 3 months ago but admittedly its a intermittent problem. now from what knowledge i have, if this is an unvented storage system it shouldn't( and hasn't previously) run out of dhw untill say about 1/2-2/3 of the system has been used then it should have a pretty efficient recharge time.

I have typed in the search to some other forums and heat exchangers and other things have been mentioned but to my understanding it doesn't explain the swithing between hot to luke warm water every 10 litres or so, can anyone help plesae??

Many thanks for reading.

 

[fitz1]

did one , i think about 3 yr ago.there was a hot water thermistor on it that was dodgy.might not be the same but check for that.

 

[Woody76]

I had this exact same problem 18 months ago.

It was caused by scale build up in the plate heat exchanger. Had that replaced and the hot water was as good as new.

 

[BigBurner]

They are easily removed and descaled. B&Q sell Fernox plate descaler.

 

[Softus]

They are easily removed and descaled.

No they aren't.

B&Q sell Fernox plate descaler.

No they don't.

 

[Paul Barker]

In my experience it is more likely to be the temperature sensor which is an unusual electronic component having 0.1 degree accuracy (for unnecesarily fine gradations of performance) but poor longevity (the downfall of the bm2000 in many areas). There is one in the dhw side usually that one, the one in the primary side would be challenging to change.

Get one try it on the dhw side, see what happens.

 

[Softus]

I have typed in the search to some other forums and heat exchangers and other things have been mentioned but to my understanding it doesn't explain the swithing between hot to luke warm water every 10 litres or so, can anyone help plesae?

Paul Barker has a point, i.e. the DHW sensor has a very short life, presumably because of thermal cycling.

The other possible candidates, in order of decreasing likelihood, are:

1. Heat exchanger.
2. PCB;
3. Pump.

For your understanding, explumb, the reason that scaling can cause intermittent hot water is that the design (and calibration) of the system works correctly only when the heat transfer across the HEX is within a certain range. Once transfer drops below a certain point, the pump speed control circuit fails to cope with the information being provided to it by the sensors.

For the same reason, a misreading sensor will result the same symptoms, which is why people get confused. Diagnosis is fairly easy though, because the BM2000 displays to you what the sensors are reading.

If the store is up to temperature (circa 75°C) and the primary sensor (from memory, S3, but please check) is reading something close to that, then check what the DHW sensor (S4 ish) is reading.

If it's representative of what you get at the tap (probably 30-40°C), then I would suspect the heat exchanger. If in the range 50-65°C then I would suspect the sensor.

Changing the heat exchanger is mechanically easy, but risky if you don't drain the store. It can be done by using the isolating valves, but they're notoriously useless and often seize. If you remove the heat exchanger, then weigh it - I can tell you how much scale it has in it.

 

[BigBurner]

They are easily removed and descaled.

No they aren't.

4 unions. They are.

B&Q sell Fernox plate descaler.

No they don't.

They do.

 

[gas4you]

As a general rule hot/cold problems on these are 99% the temp sensors. There appeared to be a massive problem with the quality of the sensors around this time.

I always drain down and replace both sensors at the same time.

So far never had this fault that was anything else, but there is always the first time.

You should be able to tell if it is the sensors by the digital read out fluctuating extremely whilst hot tap is running.

Don't forget though, that once swapped and re-filled it will be about 30 mins before any good HW is available to test.

 

[Softus]

They are easily removed and descaled.

No they aren't.

4 unions.

They aren't unions, and even if they were, you can't just undo them.

They are.

You've never descaled one.

B&Q sell Fernox plate descaler.

No they don't.

They do.

You're wrong. Again.

 

[Softus]

IMHO, no.

But even if it did, what will you do for heating and hot water while you're doing it?

You're better off buying a new heat exchanger (IF scaling is the problem), then experimenting with a descaler on the old one.

If it works then you'll have a working spare for next time.

If you really want to fart ar*e around with descaling, I can send you an old heat exchanger for you to attempt it.

 

[BigBurner]

Toasty, you easily remove the heat exchanger by undoing unions. Yes, the Femox works. You may need two, or a large tub, as those tubs are for small combi plate heat exchangers. Run a hose through the plate, both sides before and after treatment. Try to screw the hose in to give full main pressure.

The plate heat exchangers are not cheap.

 

[gas4you]

Again, change the sensors first.

DS3 will descale the domestic side of the plate HE, but you should really use DS40 for the best job of cleaning the system side, which is more often than not the side that is blocked on most plate HE problems.

 

[gavinda]

Toasty, you easily remove the heat exchanger by undoing unions. Yes, the Femox works. You may need two, or a large tub, as those tubs are for small combi plate heat exchangers. Run a hose through the plate, both sides before and after treatment. Try to screw the hose in to give full main pressure.

The plate heat exchangers are not cheap.

well you may want to suggest also purchasing 2/3 cartridges of inhibitor as you'll be draining the whole thing down. and justbhow do you screw a hose onto a plate hex.

dumber by the day

 

[Softus]

Toasty, you easily remove the heat exchanger by undoing unions.

They aren't unions, and even if they were, you can't just undo them.

Yes, the Femox works.

You've never descaled one.

Gledhill regard the heat exchanger as a sacrificial part in hard water areas.

The plate heat exchangers are not cheap.

Nor are two tubs of Fernox, considering that they won't do the job.