I think a couple of people installed Heat Banks last year - what are your views having run them for a while?
Can anyone explain the relative merits of heating the heatbank directly or indirectly? Why would I choose to make the primary circuit pressurised or vented? Are there any other heatbank suppliers than DPS or Gledhill?
A while ago someone recommended the Worcester Greenstar(?) boiler, any more good/bad reports?
DaveS
I'm still not 100% clear on the diffence between a heatbank and a thermal store. We have a Range thermal store, and it's very good. Boiler (oil) fires for long, efficient runs, and radiators heat up very quickly compared to conventional system.
Ours is heated directly (the water in the cylinder is circulated to the boiler and back).
Thermal store = immersed coil for DHW take off Heat bank = an external high efficient plate heat exchanger. for DHW take off.
Heat banks are more efficient and produce higher DHW flow rates. Heat banks can be de-scaled very easily and resist scale more effectively.
Not much diff then, really. Ours has an immersed coil, but whether you use it is optional. I didn't, preferring to use an external heat exchanger.
When direct "all" the boilers heat goes into the store. When indirect you are relying on the efficiency of the coil.
In theory pressurised has little advantages over vented when using a heat bank, as long as the system is fitted correctly and inhibitor is used and replaced every 3-4 years. Pressurised does away with the F&E tank, in a heat bank this can be integrated with the store.
Range cylinders:
Many of the underfloor companies provide their own heat banks (usually made to order from other companies)
So, far so good with these. Just make sure the system is cleaned before installation and correct inhibitor used and replaced every 3 - 4 years.
Use an integrated heat bank, where the CH and DHW are off the store.
Quiate a bigb difference.
You should have used the coil as a pre-heat. Also this can be used for low flowrates and the pump and plate come to supply the higher flowrates. This prevents the pump cutting in when the tap is on for a second or two, which is quite common.
Then you actually have a heat bank!
Christian.
Another way is split the DHW and have the coil supply all outlets, except the showers and baths where high flows are required, then the plate heayt exchanger does that.
The coil has a pressure limit, so the coil supply would need a pressure reducer before it and the cold supplies that are used for mixers also taken after this reducer too.
The plates can go up to 10 barish, so no need for pressure reducers on this leg for hot or cold and full power showers can be used, if the mains are man enough.
Direct enables the full boiler output to be used. Also, you can have as many direct heat sources and sinks (i.e. radiators) running off the heat bank, like a huge Dunsley Neutraliser.
Indirect has the advantage that the controls are exactly the same as a conventional system. It also allows sealed pressurised primary circuits. This is good as it allows you a full choice of modern condensing boilers (some of which can't run vented) and has all the benefits that go with sealed operation (see the FAQ).
You can mix and match if desired. This would involve having a modern condensing boiler on the indirect coil, whilst having your Aga, solar heating and/or solid fuel boiler off the heat bank.
Radiators can be run off the heat bank (essential if you have even a partially direct system) or off the boiler primary circuit, leaving the heat bank solely for hot water heating.
I've had it almost a year now. Runs like a dream.
Christian.
WooHooo!!
All the top condensing boilers have vented versions: Worcester-Bosch, Keston, Glow Worm, Ideal, etc. Combi boilers by nature are all pressurised, but you would not use one of these with heat bank anyway.
Also making the primary pressurised with a direct heatbank (i.e. the bulk contents of the cylinder are pressurised) means that for Building Regulations section G purposes it counts as a sealed storage system and must therefore be installed by a certified installer.
Having the primary vented, whether with an integral F&E tank or not means that this can be a DIY job, although is still subject to a Building Notice because of part L1.
However, some boilers will not accept having an open vented primary, so the choice then becomes making the heatbank a pressurised one (professional installation) or having one with a coil on the input side from the boiler (primary is pressurised) and the bulk water in the heatbank being tertiary and open vented and separate from the primary. This can be a DIY installation with Building Notice for part L1.
.andy
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These are available, but rare and termed directly pressurised.
Few and far between. There are plenty of state-of-the-art condensing boilers that are vented.
Oh another advantage of having the boiler direct is that boiler cycling can be eliminated by using two cylinder stats. And there is no limit on the size of the boiler. The larger the better. So, if a good deal is around on a large boiler you can get it. Sometimes the difference between a large output boiler and allow model is only a £100 or so. Well worth spending the extra on a direct heat bank. Oversized boilers on an indirect coil will cycle, as when on a normal rad circuit too.
I wanted to make the point because there are direct heatbanks on the market and it is not always immediately obvious that they are not suitable for pressurised primary operation.
I've got one.
Of course, and there are quite a few around that won't accept open venting. I simply raised the point so that it is not overlooked.
Another point here is that if a heatbank is direct and is using an internal tank for the F&E, it muct be installed so that the tank is above the highest radiator. .andy
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They are suitable.
You have not got a heat bank.
About the only constraint.
This can be quite a significant constraint, especially if a loft conversion is envisaged at some point. However, it can be overcome by having a sealed pressurised circuit for problem radiators (or even all of them) running off a pumped plate heat exchanger off a direct heat bank loop.
Christian.
From the DPS site:
"GX units are only suitable for a vented boiler / heating systems with a Feed & Expansion Tank."
That's not the point. There are boilers around that are designed for sealed system use. Vaillant ecoMAX is one example in addition to the Micromat that I have,Viessmann is another.
True, but worth mentioning as people do sometimes install cylinders on the ground floor.
.andy
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.. or even from the primary circuit via a zone valve and heat exchanger as I did for my workshop....
Needs another pump though.....
.andy
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I've never seen a presurised heat bank advertised. You lose many of their advantages by doing so. They would require much more expensive type approval, too. Unpressurised heat banks can be used with pressurised central heating systems with the use of additional heat exchangers and pumps (or indirect coils). This is usually safer and more convenient.
Christian.
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