New Boiler & Vented Heat Bank Location

As always some flexibility needed when intrepteting regulations I think.

b) heating domestic hot water that passes through an integral pipe or coil.

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With this regulation in reference to a pressurised integrated (CH and HW) thermal store with expansion vessel and prv the system will NOT be pressurised from a cold mains supply at 3 bar but pressurised to 1 bar with relief at 3 bar as I think is how NU heats system is set up.

Bigburn said:

As always some flexibility needed when intrepteting regulations I think.

b) heating domestic hot water that passes through an integral pipe or coil.

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With this regulation in reference to a pressurised integrated (CH and HW) thermal store with expansion vessel and prv the system will NOT be pressurised from a cold mains supply at 3 bar but pressurised to 1 bar with relief at 3 bar as I think is how NU heats system is set up.

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A plate heat X is not an "integral pipe or coil", so no G3. It will be pressurised as it is above atmospheric pressure. Well it is atmospheric pressure inside the cylinder when charged to 1 bar, but the pressure will rise when hot, so pressurised. The pressure is certainly far less than unvented cylinders.


(b) a system providing space heating only;

(c) a system which heats or stores water for the purposes only of an industrial process

(b) is a CH buffer.
(c) means a vessel the size of a hosue with 300 bar does not need G3.

ChrisR wrote:

If you want to learn about an unusual appliance or system, install and maintain it, fine. Find out from installers and maintainers of them what the weak points are. Worry about any non-standard parts, worry about small companies. If one day you aren't around, or you're selling the property, you might have a problem. Be aware that about 99% of plumbers will take one look and suck in through their teeth and say "You want a Megaflo". Everything needs understanding and maintenance. Many heat-store systems need a lot more understanding than unvented cylinders, which although they need the "ticket", are pretty simple.

We get to see all sorts of systems, never with full documentation, often obsolete, where lack of understanding, poor design, poor installation or some combination leads to problems, and frustrated people who throw their hands up in despair. Often it doesn't take a lot to sort them out, but rather too often the people consulted aren't up to it!

If you want Alfa Romeo performance then don't buy a Ford, but ask yourself what really matters to you.

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Megawatt: Take ChrisR's advice and listen to me as I have installed many DPS system products including the Pandora

They are absolutely fantastic in terms of simplicity of design and ease of installation and maintenance, they use standard off the shelf components which are readily available (and always will be IMO) and DPS's support is excellent.

If you choose to install youself no problem so long as you are a capable plumber and get a Corgi in to fit and commission the boiler which will replace your Worcester once everything else is done. The Pandora you supplied the link to would do a fine job and, as already pointed out, you could use the Worcester 30cdi regular boiler and keep all of the system elements on the Pandora itself for future ease of maintenance (also you get a standard Grundfos rather than Bosch's system fitted circulator and a larger expansion vessel).

Whilst I cannot speak for other heat store systems, the Pandora in particular could not be simpler to understand, install or maintain and certainly requires no more understanding than unvented systems which have only become the "norm" due to the mass-market capabilities of their large manufacturers.

ChrisR's comment about the plumbers sucking air through their teeth is unfortunately true, is the customers perception of us as tradesmen and typifies everything that is wrong with our profession. My advice to you would be ... If you get one of the 99% who are incapable of looking at the Pandora and instantly knowing how it works and how to keep it working (with or without a manual) I'd send them packing and look for someone more capable.

To my professional colleagues, the Pandora design is the future IMO (from DPS or anyone else who picks up on their design), yes some competent DIY'ers can install and maintain them themselves and that is a good thing I think but by far the majority will still require installation and support - I'm living proof of that
They are completely prefabricated, simple to install and commission and great to work on further down the line. In other words, a heating engineers dream.

ChrisR: My guess is that you have never installed a DPS system (please correct me if I'm wrong) as

If you want Alfa Romeo performance then don't buy a Ford, but ask yourself what really matters to you

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isn't really appropriate as the Pandora or indeed the GXV systems will knock spots off the more well known competition in terms of performance.

A better quote would be

Why pay BMW prices for a car with no extras when you can pay less for a top of the range Honda which will last as long and perform as well

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Having the name and greater market share doesn't necessarily make it the best.

esra_ptrap said:

They are absolutely fantastic in terms of simplicity of design and ease of installation and maintenance, they use standard off the shelf components which are readily available (and always will be IMO) and DPS's support is excellent.

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The expansion vessel on the top appear to be a standard off the shelf item too. They deflate it and allow hot water to expand into it. Water expands a certain volume so it juts enters the vessel and stays there. If it overboils it just stays there.

ChrisR's comment about the plumbers sucking air through their teeth is unfortunately true, is the customers perception of us as tradesmen and typifies everything that is wrong with our profession.

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How many on this forum do you read who say, if it is this or that walk away. Not dedicate to providing a service and assisting the customer.

Many will not do simple research, only supplying appliance they are familiar with and available, with a big discount to him, at the local trade counter.

One person approached me and said a plumber said that a new boiler has to go on an outside wall. and that the new kitchen needed partially ripping out. If the idiot did some simple research he would have found that the Keston could have fitted in the internal cupboard replacing the old cast conventional flued boiler and had plastic drain pipe fed up the chimney for the flue.

My advice to you would be ... If you get one of the 99% who are incapable of looking at the Pandora and instantly knowing how it works and how to keep it working (with or without a manual) I'd send them packing and look for someone more capable.

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Yep. Send the jug out.

To my professional colleagues, the Pandora design is the future IMO (from DPS or anyone else who picks up on their design),

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I think DPS patented the design, so anyone else selling it would need to pay royalties to DPS.

A better quote would be

Why pay BMW prices for a car with no extras when you can pay less for a top of the range Honda which will last as long and perform as well

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Having the name and greater market share doesn't necessarily make it the best.

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The new builds went for unvented cylinders, so they took off. Councils did too. One council in London took out all the unvented cylinders as they dripped on the people in the pavements below via the discharges. They put in thermal stores.

I see Gledhill and Range sell thermals stores in volume to developers, so the unvented cylinder may wane.

As to the Pandora replacing unvented cylinders, they are a dream as you say. They have no mains supply or overflow pipes. They can be fitted anywhere in the house giving great flexibility to house designers with no need to have the cylinder cupboard on an outside wall. A few developers have caught onto this and are using the Pandora.

Eco house builders have caught on, and not having a copper discharge pipe through the wall extracting heat from the house 24/7 is a great advantage. One 28mm copper pipe through the building fabric can really screw up the U values of the house. They install HepVo traps to prevent heat being extracted via the soil pipe and fit Pandora heat banks.

Thanks all for your help, much appreciated.

Pandora it is subject to final costs and I'll let you know how I get on.

Andy

Nobody (ESPECIALLY WS) has actually answered (or even recognised) the mis-match between a heatstore (ANY operating above 65 degrees) and a condensing boiler - which EVERY installer is obliged to fit under the current Building Regulations.

Sorry - they CANNOT work efficiently when combined. Either the heatstore won't be hot enough to provide hot water effectively, or the boiler will condense for only a fraction of total burn time.

If any of the heatstore manufacturers can persuade Government to change the Regs and allow conventional / system non-condensing boilers to be installed, specifically for use with heatstores, all well and good. Then it would be worth considering how well they REALLY stack up against well-designed alternative systems, in terms of initial and through-life costs. Hint: given the effort put into the current Building Regs, this won't happen any time soon, so any further debate is a waste of time.

And I HAVE visited the DPS site and tried various configurations through the design wizard provided. Only ONE model (GXV) claims to be compatible with condensing boilers: this is apparently achieved by somehow blending the return water to keep it below 55 degrees for as long as possible (I assume by stratifying the store). The range of design operating temperatures for the various models is stated to be 70 to 85 degrees but I could find no data about (eg) hot water performance at the low end of this range or what percentage of the 'typical' recovery period the Return water can be kept below 55.

croydoncorgi said:

Nobody (ESPECIALLY WS) has actually answered (or even recognised) the mis-match between a heatstore (ANY operating above 65 degrees) and a condensing boiler - which EVERY installer is obliged to fit under the current Building Regulations.

Sorry - they CANNOT work efficiently when combined. Either the heatstore won't be hot enough to provide hot water effectively, or the boiler will condense for only a fraction of total burn time.

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This has been explained to you in the past. It is clear you are slow. I will try again.

Plate Heat Xs, are highly efficient pumping water backinto the bottom of the cylinder at 20C and below. The water remains stratified through the cyldiner because of speaders. This mean that the water at the bottom is returning to the boiler at very low temperatures.

The stores give buffering to the boiler and the CH. You need to understand buffering.

If any of the heatstore manufacturers can persuade Government to change the Regs and allow conventional / system non-condensing boilers to be installed, specifically for use with heatstores, all well and good.

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I fail to see what the hell that would achieve.

And I HAVE visited the DPS site and tried various configurations through the design wizard provided. Only ONE model (GXV) claims to be compatible with condensing boilers:

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All of them are.

this is apparently achieved by somehow blending the return water to keep it below 55 degrees for as long as possible (I assume by stratifying the store).

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Again you fail to understand. The GX has a blending valve on the flow/return. This is to ensure that the water entering the store at the top is full boiler temp. The GX's prime aim is to combine the stores output with a boiler, and keep the store size small. Aimed at the council market in flats.

A cylinder with the bottom at 20C will condense like crazy.

The range of design operating temperatures for the various models is stated to be 70 to 85 degrees but I could find no data about (eg) hot water performance at the low end of this range or what percentage of the 'typical' recovery period the Return water can be kept below 55.

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With the bottom ~20C it will be very efficient with efficiency dropping off towards the end of the burn.

In summer when only the top half of some heat banks are heated for DHW, the cool return water from the plate is returned at the bottom unheated CH section. As the top half is being cooled as DHW is being drawn off the warmer water in CH section rises and the cooler returned water stays at the bottom way below dew-point.

Have an outside weather compensator on the bottom CH section, use larger rads for a 60-40 temp diff as in Scandinavia, and this ensures most of the time the bottom section, is very cool an the CH has buffering and water at the ideal temperature via the compensator.

The Germans are way into thermals storage and especially buffers.

A thermal store is a great neutral point and buffer for CH and
the boiler. Worth having for that alone. Also TRVs on all rads with all zones going back to the store (the neutral point) is an advantage. All using the same water, no heat exchangers to reduce efficiency. A DHW only unvented cylinder does not give you what a pressurised thermal store/heat bank does in any way.

In Germany a heat buffer is becoming pretty standard on many installations, just a small cylinder in the CH line, the thermal store/heat bank does this for free, it also does boiler buffering for free too...and it gives high flow instant DHW.

Here is one German system. They use a pressurised cylinder with fresh water in the boiler and through the heating circuit. Look at the system as primary water and add an external plate heat exchanger for DHW take off and it is all there for the UK market.

http://www.solarserver.de/solarmagazin/anlagejanuar2002-e.html

I had a brainwave in the night on the two combi system.

Combine them for heating in tandem, but use integral mechanical clock so that both come on for initial warm up period, then one for half the on period other one for other half. That way they each do nearly half the work of a 40kw combi.

As for the Buffer of Water systems, I am scared to ask because he will just send me to loads of reading material I don't have time to read. BUT here goes, what in presis is the benefit of a buffer?

WS has a different understanding of 'weather compensation' than I do.

The KEY POINT is that the CH system is designed for a 'warm-up time'. This should remain the SAME, WHATEVER the outside temperature. So a weather comp automatically adjusts the temperature of the RADIATORS downwards as the outside temperature increases. This has the following useful effects:

- the WHOLE SYSTEM, including the boiler, only gets as hot as necessary, so no input energy (ie. gas) is wasted.

- the boiler Return temperature is minimised, so the boiler can condense as much as possible.

- the room temperature stays much closer to the setpoint, with fewer over- and undershoots.

You may well ask 'What about heating the hot water when the boiler is only running at (say) 50 degrees because it's a warm day?'. Good point: a weather-comped system MUST have some means to 'pop up' the boiler temperature to satisfy a hot water heating demand, then pop it back down to the compensated temperature as soon as it's satisfied.

If you have a heat store operating at (say) 80 degrees, you will need blender valves to adjust the hot water temperature to a safe level AND to set the radiators to a 'compensated' temperature.

And, as I said several times already, if it maintains the heatstore at 70 or 80 degrees, the opportunities for the boiler to condense and therefore operate at max efficiency WILL be reduced. Having spoken to DPS and (only now) fully understanding how layering in the store is preserved, I AGREE that GXV versions of the heatstore DO maintain layering and minimise Return temperature BUT the Pandora product is NOT GXV-type.

I have lived with a Range Flowmax fully vented thermal store in a 4 bedroomed house with 3 children for the last 10 years. A thermal store is great!

And now I am going to instal a tandem system of 2 thermal stores, this time from Neward Copper Cylinder Company that will do the same thing for a large 5 bedroomed house.

Why?

Well, if you get past the bit in the argument that you need to have a pressurised thermal store in order to have mains pressure hot water (which is just not true ... and why would you want so much hot water under pressure anyway in your home?) and let me explain that irrespective of boiler or heatsource type, a vented heatstore is simple and effective to use.

Mosty people have 1 source of heat - a boiler. Forget about condensing or not, a boiler is a unit that uses energy or fuel and creates hot water. If water is to be used in the home, then it is primarily for 2 reasons; Heating or Domestic Hot Water (DHW) and dependant on your space heating type, you may only need 35°C or as much as 65°C (underfloor versus radiators) and DHW at the point of use should be between 35°C and 42°C where it is used.

Now, you do not have to store lots of DHW in order to have mains pressure hot water. What you need is a heatstore that is capable of acting as a buffer between your boiler and your supply that feeds your hot taps. In the middle is an exchanger - either a plate heat exchanger or a coil in you thermal store. Any good system will supply 30 to 35 litres of DHW at 40°C per minute - dependant of course on the temperature of the heatstore.

So why have a heatstore at all? Well initially I bought one as a replacement to an indirect cylinder that had a seam fail on it after possibly 40 years. I liked the idea of an integral header tank (i.e. get rid of the system and DHW header tanks) and the notion with the Range product that through a PHE, the water would be at mains pressure. As I was not replacing the boiler, this was literally a 1 day DIY task and involved connecting 6 pipes to the existing circuit. Simple.

What I also noticed was that as I now had a buffer between my space heating radiators / DHW heat exchanger and my boiler, my boiler cycled less - i.e. when the heatstore called for heat and started the boiler circuit pump (the boiler is subservant to the heatstore) it came on for longer and had less startup/shutdown cycles. This gave me about a 7% improvement on fuel consumption.

Now, if you are considering multiple heat sources, the a heatstore is great at linking everything together - especially as a vented system just needs the odd thermostat and pump adding so that when the flue on a log burner reaches a high temperature (over 150°C), water can be passed to and from the heatstore, reducing your bills on the main fuel/energy type.

The arguements about condensing boilers and return temperatures are largely irelevant when (as other have noted) the tank is large enough and design well enough to stratify the layers or zones of heat within the heatstore. For me condensing boilers that are working optimally are fine, but this means that they should be sized a higher than required as it is the cycling of the boiler that often consumes more energy than the heating requirments. Every heating specialist knows that the bigger the mass or water (volume) within a system, the less the boiler will cycle.

A heatstore, unvented, with an integral header tank (sometimes referred to as a combination unit) does not require building regulations notification as there is no risk of overpressurising a large amount of water and they do really work.

Plumbers who insist that the boiler has to be replaced and a pressurised 'unvented' system is the only way to go are doing so purely because they want to make lots of money from you.... and make the installation simple from their part.

Save energy by servicing your boiler annually and keeping it going until it springs a leak or needs the burner replacing (in which case it may be chaper to fit a new boiler). The heatstore is purely a useful way of interfacing your space heating and DHW needs with a boiler - a boiler is simply that, it boils water.... kepp it that way and don't waste money on lots of technology that may give you 1 or 3 percent more efficiency - by the time they (may) have paid for themselves, they will be broken and due for replacement.

Keep it simple.