Thermal Store Replacement Advice

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Hi,

I currently have a Boilermate 2000 (BM185) Thermal store attached to a Potterton Suprima 60L in my town house. I've noticed recently that the boiler goes through phases of continually being called for heat even though the store temperature is above the satisfied temperature.

As the store only ever achieves 69C, Gledhill and two other independent plumbers have said they believe the internal pipework within the tanks of the BM2000 are blocked/restricted and it cannot be serviced. They believe the boiler is delivering a higher temperature than 70C back to the store, but it's not able to transfer the heat inside it. All have commented the store temperature should be in the high 70's. So I'm now looking at replacement options.

The BM2000 is located in an airing cupboard on the top floor of the house, and the boiler is located in the kitchen. It's connected to 13 radiators of various sizes. We have a family bathroom and two en-suite shower rooms which both contain thermostatic mixer showers. We both appreciate the mains pressure hot water the BM2000 delivers. At the moment there is only me and my wife in the house, but we are thinking staying here long term and numbers could increase. We've got a Nest thermostat which we'd like to keep.

I've had two plumbers offer advice on possible solutions, and both are different.

One plumber recommended we go for a Vaillant Unistore 260L connected to a Vaillant ecoTEC plus 428 boiler. He said while the Suprima is ok, it would struggle connected to the Unistore. I've read that the Unistore and boiler should be connected to a Vaillant controller using eBus, however my plumber said that wouldn't make sense with the Nest thermostat.

The other plumber suggested we consider the Vaillant ecoTEC plus 937. He felt this would be a good solution to our needs. He also suggested the Viessmann range of boilers as well, but I can't remember the details. He commented there would no need for motorised valves if we used them. He said Viessmann were a very good brand and he'd had no callouts on any of the many he had installed.

We're currently in the process of renovating our kitchen, so now it's tempting to consider getting the boiler moved to our garage which is only a few feet away, but I think it would be expensive to get that done.

Would appreciate some help/advice on the above as I wasn't expecting to get two completely differing views on the approach.

Many thanks in advance.
 
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If there is nothing wrong with the boiler, then keep it and connect it to any decent quality stainless steel unvented cylinder...Job done... 937s are great in theory but not so great in reality..
 
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Your current problem may just simply be that the boiler is set to a too low flow temperature that it will never satisfy the store.

Those stores expect a high temperature to store much heat at all.

A non con boiler like a Suprima is designed for a max flow temp of 82 C.

For heating an indirect store you need a differential of about 10 C between boiler output and store satisfied temperature.

A Viessmann 222 would be a very good solution to your needs!

Tony
 
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A Nest is only an on/off control which is very basic and not as good an modern weather compensation.

Tony
 
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Your current problem may just simply be that the boiler is set to a too low flow temperature that it will never satisfy the store.

Those stores expect a high temperature to store much heat at all.

A non con boiler like a Suprima is designed for a max flow temp of 82 C.

For heating an indirect store you need a differential of about 10 C between boiler output and store satisfied temperature.

A Viessmann 222 would be a very good solution to your needs!

Tony

The issues with the BM2000 and Suprima have been on-going since we moved in nearly 3 years ago. I've got British Gas homecare, and numerous engineers have commented on the low store temperature and said the boiler couldn't supply the temperature demanded by the store. I don't think the system was ever serviced in the 9 years previous. There was certainly no inhibitor in it which I've been told is very important with the BM2000. The Suprima has always been set on Max as recommended.

It's resulted in quite a few parts being replaced over the years. The DHW and PHE sensors were replaced on the BM2000. The Suprima's had thermistors/thermostats changed and 2 new PCBs in the last 2 years as it kept locking out. The Suprima now seems fine.

BG want to replace the boiler and heating pumps as apparently their 'resistance readings' are out of tollerance. I've no idea what that means, and Gledhill think they're wrong. Failing that they're going to replace the BM's ACB, again Gledhill think there's nothing wrong with it.

The store seems to get to 68/69C relatively quickly when you do something to cause the temp to drop quickly - putting the heating on normally does this. However, when it gets to 69C it stops. After a power reset of the BM2000 the satisfied and call for heat temps are reset to the factory default of 77/74C, but after a while it gives up an adjusts down to 69/62C.

The BM2000 having phases of continually demanding heat from the boiler is a new issue. The boiler fires for about 10/15 seconds then goes off with the green LED flashing, then about a minute later fires again. It tries to go into standby but the BM2000 continues to call for heat, so the process continues for several hours.

My neighbour has exactly the same set-up with the difference being his is not a town house, so the BM is one floor closer to the Suprima. His store temp is around 75/76C.

As we're going to be replacing the kitchen soon, I feel now is the time to try and do something about the situation properly. I don't want to have a new kitchen put in to then find I need to replace the boiler or do major pipe work changes!
 
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It definitely sounds like a circulation problem but I'd be looking at restricted flow through the boilers main heat exchanger rather than blockages in the boilermate.
 
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As it happens I have just removed a perfectly operating 300 Excel Thermal Store (due to space reasons) if the OP is interested.

A few cosmetic blemishes from where assorted data loggers have been attached, but only a couple of years old.

100kW plate heat exchanger on the side for hot water generation.
 
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As it happens I have just removed a perfectly operating 300 Excel Thermal Store (due to space reasons) if the OP is interested.

Thanks for the offer. At the moment British Gas seem to think they can resolve the issues I'm having.

As a result they're going to fit a new boiler pump, heating pump and ACB on the BM2000. This was against the advice of Gledhill who said none of the above would work. It is based on a consensus from several other BG engineers he spoke to.
 
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So BG have been out and replaced the 2 pumps and ACB on the BM2000. So far, the boiler isn't continually being asked for heat as much as it was before. However, there's no improvement in store temperature.

The engineer suggested I might like to get a quote for replacing the system as they had lots of good offers at the moment. The salesman has just left. Here's what's being quoted:

Worcester Greenstar 40CDi Regular £1600
Boiler electrics £200
internal condense pipe £120
horizontal flue £210
gledhill unvented 210l cylinder £1350
25l expansion vessel - £170
powerflush £475
spirotrap mb3 - £240
installation £1900

After 'discounts' have been applied it works out at £5,500.

I had a look at the boiler and it seems like a massive boiler to be putting in place of the existing Suprima, both in terms of output and physical size. I told the engineer I didn't want another Gledhill unit. He said they don't install Megaflo anymore as they've had too many problems with them and he couldn't go into details. He made no mention of the Vaillant Unistore.

He came up with a revised quote to include a baxi megatech twincoil solar ready 190l unvented cylinder at £2175 which in turn pushed up the total to £6300! I'm struggling to find any information on the baxi unvented cylinder online.

Any thoughts on what's being quoted above?
 
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Boiler is average at best, and mentally over sized if you 18kW boiler managed in the past.

Typical case of a brain dead salesman doing the job of a decent installer trying to achieve targets.

I would use a Megaflow due to stupid price for average quality from a Parent company (Baxi) whom I don't trust.

Not going to comment on price as I haven't seen the situation.

But those line prices look like a collection of random numbers designed to lower the appearance of the install costs.
 
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His initial suggestion was to have a standard cylinder and use electric pumps to bring up the pressure of the hot water. I said to him I wasn't remotely interested in getting into that sort of installation which he seemed surprised at.

I won't be using them at all, but I thought I'd post here what they'd quoted.
 

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