Powermax/Heatbank/UV?

[nickd]

I currently have a 4 bed house with a Potterton Profile 50 powering a Gledhill Boilermate which is about 15 year old. Having extended the house a couple of times, when the heat is on full blast on a cold morning, the first shower is fine but a consecutive shower runs cold.

Household is 2 adults and 2 kids, one being a pre-teenage daughter who loves long showers :-( . We have 2 bathrooms - one bath and two high flow showers.

I'm intending to replace the boiler with a condenser but the hot water issue is the difficult bit. I have read the various ramblings on unvented v heat stores and I'm still unsure as to which way to go.

The current thermal store has worked well so I'm not scared of the heatbank option, but DPS quoted me =A3945 for a 180L Pandora which wassignificantly more than the 210L Megaflo.

I like the Powermax for its compact design, but I'm concerned that I can't find any solid recommendations for it. Also I'm told the servicing is tricky. Does anyone have any experience of these?

Taking the separate boiler/cylinder route, I like the DIYability of the Heatbank and the associated safety. Is there any way I can go down this route for less money, or should I look at unvented?

[John Stumbles]

inc or ex VAT? 210L square Panny is about £800 (ex VAT) with standard

100kW heat exch, standard 22mm mixing valve, no CH pumps, controls etc. Letting them add CH or sealed system components seems to push the price way up. Even without that clobber it's still >£1K inc VAT which is probably a lot more than the buy price of a megaflo, but practically zero cost/hassle in the long term, unlike the unvented.

[Doctor Evil]

Gledhill have changed the specification over the years of th BoilerMate. Yours will have an internal DHW take-off coil. The ne models have plate heat exchangers. Is that so? It appears th thermal store is struggling to cope after house extensions. All is no lost.

Q1. Does the store gives adequate showers in summer when the heatin is not extracting heat from the store?

Q2. How did it perform, in heating and DHW, before the hosu extensions?

Q3. What percentage has the house increased in size?

Q4. Does the boiler heat the store via an internal coile, or does i heat the store direct (the same water in thye store and boiler)?

Q5. Is the CH taken off the store. Most Boilermates this is the case

Firstly:

a) I would replace the boiler with a larger boiler of approx 30k (twice the size of the extisting) with 28mm flow and return to th thermal store. This will give a far higher recovery rate and b heating up the store as water is being drawn-off.

b) Fit a blending valve on the boilers flow and return to ensure onl

75-80C water enters the store.

c) De-scale the DHW coil, as this may degrade performance if scale up. Ring Gledhill in Blackpool, they will recommend a solution t de-scale.

d) Fit a flow switch in the cold DHW feed to switch off the CH pum when DHW is called to prevent heat being extracted from the store t the rads when DHW is being called. The flow switch can energise relay to cut out the pump. Simple to do.

If still not up to scratch, then do:

e) Have the flow switch also override the thermal store cylinder sta and bring the boiler in immedately DHW is called. You could put thi on a 20.30,40 second time delay to prevent nuisance boiler cycling. This will pump heat into the store imediately, whereas if you rely o the cylinder stat you would have lost 1/4 to 1/3 of you hot wate before the boiler starts to pump heat into the store.

Installing the above two points is not difficult or expensive and save a wedge on a new store. This should cure the problem.

Further: If the store is being heated adequately and the problem is that th internal DHW coil is not man enough produce the hot water, which doubt from what you say, You can always retrofit a plate heat exchange and pump for DHW take-off and use the existing DHW as a pre-heat, i essence turning it into a hybrid heat bank/thermal store

-- Doctor Evil

[Christian McArdle]

Hmmm. I think I paid 750 inclusive for my 180L Pandora.

Christian.

[Doctor Evil]

Just to add. If the store is merely not large enough, a chea conventional cylinder can be installed (space permitting, could stacke over the existing store) to increase the thermal store size. If th BoilerMate has in internal DHW take-off coil then a pump is used t pump hot water from the extension cylinder to the main store

-- Doctor Evil

[Andy Hall]

Maybe they've seen sales improve........

[Gordon Henderson]

Double Hmm and a chin-scratch... They quoted me quoted nearly 1500 for what I wanted which is why I've embarked down the home-build route..

Gordon

[Andy Hall]

Perhaps the price depends on how grand the project sounds as a measure of your ability to pay....

[nickd]

standard

This price was ex-vat for the cylindrical version. I did specify a 3 way diverter with it, but still seems high.

[nickd]

Indeed it does have the internal coil. Also has header tank as part of the unit.

Absolutely. Not had any problems in the summer at all.

Thats a tricky one as the first extension was shortly after moving in. Heating has never been a problem, just that DHW runs out during cold weather. Noticed it mostly after second extension.

Approx 15%

Yes. Works well too.

exchanger

Thanks for the advice. The other problem I have is that I want to relocate the store downstairs. As it has a header tank attached, this is not possible without ripping the header tank off and running a pipe up to the loft, which i'm trying to avoid.

[Doctor Evil]

You can have the store downstairs. Have it as high as possible so th header is near the ceiling and above the boiler. I hope that sort that.

Now the heating system. Make the CH circuit a pressurised circui isolated from the store. Take the CH flow and return off the store ( assume the pump is on the store) and run the two pipes into a plat heat exchanger (the size of a book). Take the rads flow and retur into the other two ports of the plate. Install a new pump for th rads. This isolates the CH from the store. Install a pressurisatio kit on the rads side of the plate, so you can have all the rad anywhere, with: vessel, blow-off, guage, filling loop. You will hav two pumps running the CH. Just have the two pumps off the same wire so both are either off or on. The whole lot should cost you abou £150, inc pump.

- Install a large boiler with 28mm flow and return

- Clean out the scale in DHW coil

- install a flow switch on the cold DHW mains to cut out the CH pump when the DHW is being called, making it a priority system. A smal relay from maplin in a plastic housing will do to switch the pumps i and out.

The larger boiler will reheat very fast.

That will solve all probs

-- Doctor Evil

[nickd]

That's certainly a solution I hadn't considered. What size heat exchanger would you recommend for this?

Overall though, I still have a problem in that I don't think I have the room to get the boiler sufficiently lower than the cylinder in the area where I need to install it. If I could find a way to raise the header tank I'd be in business. How much above the boiler could I get away with?

[Doctor Evil]

A normal 14 plate job will do the heating side. Do a Google on thi group for GEA, Ecobraze. You need a heating boiler. Try the Glow Wor condenser. They do one around 27-30kW. A basic open vented boiler Worcester Bosch Greenstar do a similar. You will have to check th makers specs for the head, which is usually a matter of inches. Yo can detach the header tank from the Boilermate, so this can easily g up near the ceiling.

If you need a new thermal store try the Gledhill Systemate, using modulating heating boiler; it comes with the pressure vessel. This wil do the job with the heating being run directly. Gledhill thermal stores and many cylidners, are all now in nice square neat cases that don' have exposed pipes and look like a boiler house, and are heavil insulated. They have the optional electric backup which will als provide heating as well as DHW if the boiler is down. Not cheap but class quality act. I have one

-- Doctor Evil

[nickd]

Hard to see how I can do this. As the store is in service I can'tsee clearly how the tank is attached to the cylinder. Seems to have welded ties, but the main connection between the two is not obvious. Any experience of this?

I looked at the Systemate and was impressed, but can't seem to find a price guide anywhere on here.

Incidentally, in my original post I asked if the Powermax was an option. I have since received a tip from Baxi Potterton employee who advised me against it. Apparently after the warranty has run out, nobody wants to insure them, not even Baxi Potterton. Also the parts are expensive and hard to get hold of.

[Doctor Evil]

The header tanks were detachable. Depending on model and year then. Get your model number and rung Gledhill, they will put you right. If it cannot be detached theb install a small F&E tank on brackets at high levels on the wall and cut into the existing pipes serving the extising header tank. Check pipes sizes

The new Boilermate is as impressive. Travis Perkins can supply one, so give them a ring. They use thick grade copper sheet for all their products. The thermal store alone, which runs on atmospheric pressure, can take up to 1 bar.

The Powermax was originally made by IMI using a thermal store. Potterton bought them out and make it into an unvented cylidner. Feedback has been sketchy.

Try the Gledhill Gulfstream 2000. A combined boiler thermal store all in one package. Once again, not cheap, but a class act.

Or look at the Ideal Istor:

experinece of the Istor as few are around.

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[nickd]

cannot be

Excellent. I've found the feed pipe round the back of the store now so I think I'll be able to re-use it. Would it be worth using the store just for hot water and having the CH straight off the boiler?

[Doctor Evil]

If the header tank is on the ground floor then no, as the F&E tank has to be higher than the rads. If the header tank can be higher than the boiler, get an open vented "heating boiler", and use a plate heat exchanger off the BoilerMate for the CH, which will get the rads over the header tank. Only the CH circuit on one side of the plate will be pressurised.

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[nickd]

Sorry, I didn't make it very clear. I think I can get the F&E tank higher than all the rads now, so I could easily have the whole system OV.

In this case, I don't need the heat exchanger and can connect it exactly as it is at the moment (with a larger boiler) or I could take the CH off the Boilermate and feed it seperately (which would give me the whole store for DHW).

Which do you think would be best?

[Doctor Evil]

The larger boiler should be adequate to re-heat fast enough and solve any problems. Take the CH off the Boilermate as that is how it is currently and this eliminates inefficient boiler cycling. If there are problems even with a larger boiler, you can make the system a DHW priority system by inserting a flow switch on the cold main just before it enters the store, and have this, via a cheap relay from Maplins (about £5) cut out the CH pump. So when DHW is called the CH is not extracting heat. Of course, get the DHW take off coil cleaned out. This will entail pouring chemicals into the coile. Best done when you have the thermal store out.

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