Boilermate BP (BMBP185) - what was in the standard electrical controls housing?

Hello, sorry, a little lengthy this, bear with me....

First - thanks to all who give freely of their time and advice - you guys help make the modern world a better place.

I have recently moved 2 months ago into a property off mains gas with a Danesmoor 28/32 oil fired boiler, open mains pressure DHW via Boilermate 185 and open CH system. It all works OK, but a recent issue when the boilermate and boiler circulating pump ran all night got me looking into the system. It seems to be somewhat lacking in control, and I wonder whether some of it is missing and has been 'bodged' to get it to work. I'm not familiar with stored DHW systems, all my previous houses have had mains gas combis.

OK, the issue of the boiler circulating pump running all night was easily solved - the stat on the boiler was set to a lower temp than the cylinder stat, set to 75dgeC, so the demand for hot water was never fulfilled by the boiler. Solved that by turning the boiler stat up a bit and the DHW stat down from 75 to 65degC - Still adequate for DHW and CH purposes but slightly more energy efficient than having a standing tank of water at 75degC radiating heat when the DHW is limited to 55degC by thermostatic mixer anyway.

A Gledhill manual was left with the Boilermate (but nothing else) and refers to a 'pump delay off timer' - I don't have one. Just a 2gang socket box with a row of 12 terminals. These are wired up with about half a dozen wires, none of which are identified as to what they are and what they feed! (Thanks whoever you were) The socket box was originally inside the BMBP185 per the factory supplied layout, but has been moved onto the floor adjacent.

Now, the control set up for DHW seems to be:

Fused spur mains 240V feed - cyclinder t/stat - boilermate pump - boiler. Yes, the boiler 240V live feed is fed direct through the Boilermate wiring, not through any auxiliary control contacts inside the boiler. So when DHW is not called for, the boiler is actually switched off and has no mains feed. When the boilermate stat closes, it fires up the pump and the boiler in parallel.

It gets better folks. the CH control is as follows:

Grasslin digital 7 day programmer - living room t/stat - boilermate pump - 2 way diverter valve. So, when heating is called by timer and room stat, a 240v feed energises the boilermate pump and opens the 2 way diverter valve to feed the CH rads. (The boiler will then fire up under the DHW control circuit above once the thermal store t/stat closes)

DHW and CH operate independent of each other, from two separate 240V feeds, with no interlocks but with a common control component - the circulating pump. There is only one circulating feed pump, it either feeds from boiler into the thermal store direct or via the diverting valve around the house rads and back to the store.

But there is no delay-off pump PCB or similar, so when the demand for boiler water heating is satisfied and the store t/stat opens, the pump and boiler shut off simultaneously. My concern is that leaves the boiler vulnerable to thermal overshoot and 'boiling off' if the boiler stat is set too high. That's why I turned the boilermate stat down to 65degC otherwise the boiler stat would need to be set to 82dgeC maximum, which risks it boiling off due to residual heat from the burner and heat exchanger.

Did someone at sometime remove some controls on this system, pump delay PCB or something and bodge it to work? Why they control the boiler by simple on/off switching is another mystery, rather than use the auxiliary contacts in the boiler intended for this purpose. Should I get it sorted out? It works fine, but it's not very clever how it is configured, not least a single pump being energised apparently from two separate mains feeds, one on the DHW side and one on the CH side. Is this normal practise guys?

Yours, a perplexed Boilermate owner!!

Boiler mate BP.
You will have 2 x 2 port zone valves ( S Plan)
Or 1 x 3 port valve. ( Y plan.
That is the 2 choices.
You should have a 2 channel programmer
1 for hot water
1 for heating.
I think the book you are looking at is for the Boiler mate II
Go to Gledhill website and download the Boiler mate BP manual.
And set the settings as per the book.
It is a thermal store, just like a battery as in charged!
So put the stat to 75c not 65c.
And the wiring centre whether Y or S plan is easy when you know how.
Read the correct book and all will be revealed.
Mike
MGC/H2O
Norfolk

Hello Mike, thank you for your reply. Further explanation:

Y-plan with 3 port valve I believe. I do have the correct manual, it's the Boilermate BP which is the simple cylinder only version, with only basic factory supplied accessories:

WWweb.gledhill.net/documents/BoilerMate_BP_Manual.pdf-

As stated above, the timer is Grasslin and single channel for heating ONLY, the hot water is not on any time-control, simply maintained at T/stat set point 24/7.

It's this one: WWweb.oilstoves.co.uk/webdocs/technical/bubble/Bubble_Grasslin_Time_Clock_Operating_Instructions.pdf SINGLE channel only.

On P.16 of the Boilermate BP brochure is shown an installation wiring diagram, figure 12, with the 'wring centre' being a 12 terminal rail. That I have, but the wiring is not configured in accordance. The boiler does not have a continuous 240V lived feed and is not regulated by a switched live signal, it is controlled as I described above. Similarly the pump is not fed via the boiler as it is in Fig 12, it is fed direct through the cyliner t/stat.

It all works, rather crudely. But my concern is that if I set the cylinder stat to 75degC 'per the Gledhill book' I will need to set the boiler stat to max 82degC (on a Danesmoor 28/32) to satisfy demand. Now WITHOUT a pump over-run to remove residual boiler heat (standard practise for boiler and pump control) when the boiler switches off it's got water in it at 82degC and the residual heat may boil this water off resulting in venting off into the F&E tank.

So, erring on the side of caution I have set the cylinder stat down 10degC to 65degC and pro-rata the boiler stat to about 75degC. That's got the boiler under much better control, it fires up once or twice a day for 5-10 minutes to charge the thermal store, whereas before when the boiler stat was set way too low, so it never satisfied demand, it was firing up a dozen+ times a day for very short bursts, (very inefficient) and I was losing heat from the thermal store in the piping between the store and the boiler, as the circulating pump was running continuously and the circulation piping is not insulated.

It does seem a very crude and Heath Robinson set up. Would it be advisable to get it 'sorted out', by that I mean?:
1. the boiler controlled using the switched live not simply via crude on/off mains feed electrical disconnection
2. a pump over-run, either by feeding the pump through the boiler control (per Gledhill scheme) or installing a delay-off relay on the pump fi teh boiler control does not faciliate this.
3. maybe HW programmble control, but I don't see much benefit to this provided the thermal store is not wasting/losing energy, which provided the pump is off when the boiler is off, it won't be.

Al

Hello Mike the boilerman,

Long time ago I posted a query on a CHW and CH installation to a Gledhill BMBP215 (not 185 as it turns out) unit that seemed to defy all logical explanation.

Next week the system will be corrected by a competent tradesperson to a standad 'Y' plan using a Honeywell V4073A 3-way diverter valve and a DU144 auto bypass valve, to be on the safe side. (There are two dump rads without TRVs, but if these are closed I want to ensure adequate min flow through the boiler so it doesn't trip out on overheat protection.)

Well, the system as it is now is neither 'S' or 'Y' plan, for reasons only known to the installer. I suspect incompetence on their part since there is no other logical explanation. The DHW heat exchanger to the thermal store charges all the time whenever the pump is energised. Yup, even when CH is called for. Water, being water, is lazy and likes to take the path of least resistance, so most of my boiler flow goes through the thermal store and not into the CH system. Now with 20 rads incl. 6 doubles on the system over 3 levels the CH is, unsurprisingly, glacially slow to warm up. The furthest rads can take 1/2 hour to get even luke warm. I spotted that problem over the winter (first winter in the house) and realised something was not right - the rads were cold but the return to the boiler was hot such that the boiler was modulating down and then switching off, even with cold rads in a cold house. The boiler is adequately sized, the pump is adequately sized, there was no air in the system, so something was wrong on the control.

The only control for CH is a 2-way Honeywell valve powered from the heating timer + room stat circuit. Now the thermal store stat was set to 70degC (plenty adequate for mains pressure DHW limited to 55degC) but would over-charge up to 80+ degC with the CH on, wasteful of energy when the DHW is not needed.

So, the wiring is now re-configured to standard Y-plan and plumbing fix due next week when the system will be drained off anyway due to bathroom renovation works. Ever heard of the like? To whomever installed the Gledhill I salute you. You, Sir, are an incompetent plonker.