Boilermate 2000 ignores store satisfied temp.. T1_OFF

scenario..

-store temp drops to or below the 'Store Calling Temp' T1_ON
-boiler to store pump starts, boiler fires.
-continues to fire and pump until store reachs and exceeds 'Store satisfied temp' T1_OFF.
-boiler has now reached it max temp so shuts down.
-boilerenemy2000 continues to call for heat, and run the pump despite the fact the store has reached or exceeded(1-2 degrees) the T1_OFF temp.
-pump will run and run, thus moving nice hot water from store round to the boiler, so losing heat faster than it needs to and wasting elec...this will run for hours and hours, slowly depleting the store of its heat
- this only thing that will snap it out of this state is to turn on the central heating or call for DHW. As soon as you do this (exactly as you do this, its like a switch) the call for heat stops. Then the boiler to store pump will go into its overrun stage and turn of a couple of minutes later. Finally peace!

Looks like a bug in the coding to me? Any ideas how to fix?

Any help would be much appreciated.

my two cents.....complicated electronics are needed for travel to the moon...not my central heating! A couple of manually set thermostats for T1_ON and T1_OFF is what this system needs...And a timer for heatstore operation times...boilermate2000, most wasteful system ive ever seen.

Hi Jonny

From what you have described, it sounds like the main control board has a fault in the processor and requires replacing.

Thats what i suspected. Complicated electronics and central heating don't and have no need to mix, pointless use of processors!

Do you think that removable chip in the middle is where the coding is, i think that may be an eprom chip, which can and do fail, perhaps i can just replace this one chip, or does the whole board come as one?

Any idea on prices for board or chip?

Thanks

Hi,

I have never heard of replacing the chip on the pcb board, so would be interested in hearing about that?

New PCB would cost around £230.00 plus carriage.

Kind regards

Gary

MK Group Limited

that chip on the front, the one with the version number on, is just a push fit, its not soldered to the board like the other chips are..im assuming so they could release updates of the coding...i'll see if i can source one. I suspect not. Gledhill not exactly a customer focused(Post sale that is!).

Doesnt seem to be hurting there business to much though, but if i replace this sucker it wont be with another gledhill!! I may keep the tank, it is bloody well insulated, but that board is going!!

J0nny2000, if you are good in electronics you can fix your PCB yourself. Or at least try with no harm. Yuo need to replace 5 electrolitic capacitors on the board 2x(10uFx50V), 2x(47uFx50V) and 1x(220uFx25V) but make sure you buy with at least 105C to survive in hot condition.
And FYI, that big chip in a socket is microcontroller with code programmed inside it. You are right about EPROM failure but it most of the time happens when data written often in it but it is not the case for this controller although it is possible to have corrupted code. The main problem is power on the board filtered by cap and if it is noisy then controller won't start or do weird things

i might give that a whirl..!

At the moment ive turned down the pump speed to min, and im just letting it run. Sometimes a satisfied store temp will coincide with someone asking for hot water or a central heating call, in which case that will 'jog' the board into realising its satisfied. Sometimes it wont and it will run and run, but on min pump speed i dont notice it.

I will check my bills in three months see how they are looking. If there are bad i will try replace the parts you mentioned. Hopefully wont cause the problem to get worse.

Thanks for the info.

Cross reference to this post for capacitor part numbers:
https://gledhill-repairs.forumotion.net/t1219-continuous-heating-dead-acb#7762

Hi J0nny2000,

I've got exactly the same problem as you - boiler demand stays set even after the upper temperature is reached.  And it will "realise its mistake" if either the heating or HW demand switches on while it should be in its boiler-satisfied state. It'll then switch off the boiler and continue to run the pump-overrun for a bit as it's supposed to.

I've replaced my ACB with a brand new unit, expecting that it would fix the problem.  It hasn't :-(

Not sure where to go with this next.  I belive that the solid-state relays used on the board can get stuck if the load becomes too inductive, and from examining the PCB routing, it looks to me like the LEDs are showing the output state of the SSR, rather than the input control (coming from the micro-controller).  If I'm right, then the problem might be on the boiler side. Other demands coming on-line are perhaps injecting enough spikes into the circuit to allow the SSR to switch.

At the moment I'm flicking the heating or HW to get the thing to switch off before I go to bed.  If I do get to the bottom of it, I'll let you know.

Out of interest what temperatures are the three sensors showing when you use SW2 to step through them? The boiler should go off once the store temp (first push of SW2) has gone above 78 and comes back on once it drops below 75 or 74 I believe. If the boiler cannot get the store above 78 the boiler will keep running. When you say you replaced the ACB was it a brand new board or a used unit? Regards.

The three readings when cycling SW2 are:
upper-circle: 72 (current store temp)
lower-circle: 52 (PHE)
H: 61 (hot-water)

The two thresholds for the store are:
upper: 75
lower: 68

New board is a genuinely new board from keeptheheaton

According to the manual the board is meant to adapt to the performance of the boiler, so the thresholds aren't fixed. I can stand and watch the heat store get up to and beyond 75 degrees and the boiler demand light stays on. If I turn on a tap, so that the HW pump starts, then the demand light goes off.

By the way, my rambling about the LEDs indicating the relay output-state is nonsense. The LEDs are on the input side of the relays, so the processor is doing that.

My last roll of the dice is to get a new store sensor. The displayed temperature may be a filtered version of what the sensor is telling the board, if the sensor is noisy I'm speculating that it prevents the processor switching off the boiler.

More results next week....

I'd swap the ACB out if you have seen the temp go above the set level the boiler should switch off as soon as it goes over, the boiler pump will then run for 3 mins to remove residual heat. I made a video (before I made myself a fancy test bed) that shows what happens or what should happen with the various inputs/outputs. Might just check the jumpers are set right I don't think it would give the problem you are seeing but never say never! Hope you crack it. Murray Video is here - https://www.youtube.com/watch?v=OP5-i_vi1Pw&t=306s

Do you have more than 1 temperature sensor

May not be the same unit as mine, but it had a temperature sensor at the bottom and top of the thermal store

It may have even had a mid one

They look identical on my unit and so could be swapped to see if the symptoms change

1 will control the minimum temperature and 1 the top

Hi J0nny2000,

I saw your post from a while back about you boiler pump running on on your Boilermate 2000. I have a similar problem and was wondering if you were ever able to resolve the issue and what the cause was?

Thanks for any info you might have!