Poor pressure on a megaflo??

[chrishutt]

For the benefit of anyone who finds the technical aspects of this rather confusing (which includes me), I offer this simplified explanation of how I think an accumulator might work. Corrections will be gratefully received - I'm on a learning curve too.

The function of an accumulator depends on the physical properties of the air sealed in it, particularly in relation to pressure and volume. These are determined by Boyle's Law, which states that for a gas such as air any increase in pressure results in a decrease in volume, and vice versa, so that pressure x volume is always the same (a constant), providing temperature remains the same. In this case pressure means absolute pressure which is gauge pressure (what we normally use) + atmospheric pressure.

For example if we start of with a bag of air at atmospheric pressure (1 bar absolute) with a volume of 10 litres, then we immerse it in water 10 metres deep (atmospheric pressure + 10 metres head of water (1 bar) = 2 bar) the volume will then be 5 litres. Doubling the pressure causes the volume to halve.

To take a more practical example with an accumulator of 200 litres volume and a precharge pressure of 0.5 bar gauge pressure (1.5 bar absolute pressure - gauge pressure + atmospheric pressure), a static mains pressure of 2 bar gauge (3 bar absolute) and a dynamic pressure at the outlet tap of only 0.5 bar gauge (1.5 bar absolute) with a flow of 10 litres/minute. (The low dynamic pressure and flow rate at the tap is of course the problem that the accumulator tries to solve.)

With no flow (tap turned off) the mains pressure (3 bar absolute) will apply throughout the system, so the air in the accumulator which occupied 200 litres at 1.5 bar (absolute) will now be compressed to 100 litres at 3 bar (absolute). Consequently the 200 litre vessel will now contain 100 litres of water at mains pressure.

When the tap is opened and assuming an initial flow of say 20 litres/minute, the dynamic pressure will start off at 3 bar (absolute) but gradually decrease (quickly at first) as the accumulator discharges its water store. As the pressure drops the flow rate from the tap will decrease, the proportion of flow from the accumulator will decrease and the proportion directly from the mains will increase until eventually the accumulator has fully discharged, the dynamic pressure is back to 1.5 bar (absolute) and the flow rate down to 10 litres/minute, all from the mains.

In the above example with 100 litres of stored water at 2 bar (gauge), the duration of the benefit of the accumulator might last (I would guess) about 10 to 20 minutes in total, although the benefit might only be substantial for about 5 to 10 minutes. I think the actual calculation would be quite complicated since the overall flow rate and the proportion of flow from accumulator and mains are constantly changing - I suspect calculus would be involved!

In practice a pressure boost from 0.5 bar (gauge) and 10 litres/minute to (again just guessing here) over 1 bar (gauge) and at least 15 litres/minute for up to 10 minutes might be very welcome indeed. Obviously higher or lower mains (static) pressures and larger or smaller accumulators would affect the results.

 

[doitall]

But I am annoyed at one individual who has made some rather personal comments. Morover, he says we have been conning the customers for whom we have fitted accumulators, the inference being that they are dissatisfied. Nothing could be further from the truth, like any good product, word travels and we are busier with this product than ever before.

And I'll say it again.

With an incoming mains pressure of 1.5bar and a minimum Megaflo requirement of 1.5bar with a recommended flow of 20 litres/m, the accumulator will not work, without a pressurizing device.

To test the net gain from an 85litre accumulator, installed at 1.5 bar as above to a megaflo, after heating the cylinder turn the mains off, and measure the total volume delivered at the outlet. the combination valve will allow NO water to enter the cylinder at 1.5bar. Deduct this from what the megaflo would deliver prior to the accumulator being fitted and the gain is zero.

Fit the accumulator on the cylinder side of the combination valve, possibly illegal, certainly not Wras approved and repeat the test. At a guess an additional 25% of the accumulator capacity and not enough for a decent shower.

An accumulator stores energy, and as such that energy must be greater than the system requirement. not rocket science even for a layman.

One more time, with an incoming mains pressure of 1.5bar, a stand alone accumulator will have NO gain when installed legally and as per Megaflo's minimum requirements, and anyone who says otherwise is conning the customer.

Now prove it or sue me, your talking trash buddy.

 

[simond]

We are not going to sue you, you buffoon. I suspect you are a man of straw anyway.

However, we can prove it to you down here in Surrey. We can take a pressure reducing valve to lower the standing pressure to 1.5bar on our demo site.

All I ask is that you pay our standard hourly time charges, since you aren't going to buy one. I might even make you a cup of tea - with a Cadburys chocolate biscuit

I won't charge you anything if it doesn't drastically improve the flow rate and performance. When (if) it does work you must agree to put a retraction on this forum, since you've been a bit off. remember, it takes a bigger man to admit you are wrong etc.

Alternatively, you could wait for the GAH demo van to come to your local merchant.

Or, and finally, you could read the excellent post from Mr Hutt above describing in detail the principle of an accumulator and stay quiet for a while.

 

[doitall]

You have to deduct the difference between the stored energy and the design pressure chrishutt.

If the available pressure (mains) is 1.5 bar the accumulator cannot store energy above 1.5bar, and the only gain will be from expansion as the water is heated. And could be contrary to Wras, Water, and Building regs when fitted after the combination valve

It should also be noted that the Megaflo already contains an air gap, and in that respect is no different to an accumulator.

 

[ChrisR]

Dia -
If there's no restriction in the supply pipe you're right, an accumulator makes no difference. If there is a restriction, an accumulator does make a difference; it helps, with the extent depending on many factors including but not limited to those which I and others have outlined.
The Unvented Cylinder is a bit of a red herring, it doesn't alter the principle. Essentially we are talking about a non return valve and a pressure vessel.

Simon
Yes I daresay we all knew enough of what patents are.
We also know that companies play games with them. GAH's name is on a naïvely futile attempt, now predictably abandoned, to patent the concentric balanced flue of all things; and it isn't their only activity of this type.
As I said before, many patents are sought for marketing reasons rather than a desire to protect an invention. Building of mystique is part of the bull which follows. Hickman's Workmate patent had people worrying that they couldn't produce a folding table, and B&D were happy to let the myth persist.

You said the patent was online and it isn't,
you said you had an accumulator web page which you've been told isn't apparently there.
Many times we have sought to clarify the "unique" features of the device and and its patent, but each time all we get is another plug for your company and GAH and a repeat that you are happy selling a product. Fine for you, but not useful here.

We aren't simpletons. To actually say that "copyright permission would be requred to reproduce the patent", is rather odd and makes me look for ulterior motives. Why not tell us what it covers in a sentence or two?
Mystique?

 

[doitall]

We are not going to sue you, you buffoon. I suspect you are a man of straw anyway.

However, we can prove it to you down here in Surrey. We can take a pressure reducing valve to lower the standing pressure to 1.5bar on our demo site.

All I ask is that you pay our standard hourly time charges, since you aren't going to buy one. I might even make you a cup of tea - with a Cadburys chocolate biscuit

I won't charge you anything if it doesn't drastically improve the flow rate and performance. When (if) it does work you must agree to put a retraction on this forum, since you've been a bit off. remember, it takes a bigger man to admit you are wrong etc.

Alternatively, you could wait for the GAH demo van to come to your local merchant.

Or, and finally, you could read the excellent post from Mr Hutt above describing in detail the principle of an accumulator and stay quiet for a while.

We have several large projects in your area and it would be my pleasure to proove you wrong.

However since you insist, you can pay my standard rate when it fails miserably.

Next time I'm in town, maybe later in the year. expect a call.

emails in my profile if you want to send contact details.

 

[doitall]

http://www.accumulators.co.uk/accumulators/Accumulators.htm

 

[simond]

It is online, all valid patents are accessible online at the Patent Office. It is not my role to debate patents with you - we fit Kidd boilers but I'm not authorised to discuss their patents in public.

Surely you are not expecting me to debate the merits and scope of the patent in a public discussion forum?

NB: The patent is not GAH's. They are the licensee.

I have been accused of promoting our small installation company so was loath to publish our water boosting web page; I will list it here but if it comes out blank it will have been removed by the moderator;

http://www.hwch.co.uk/boosting.html

Mystique? Non!

 

[simond]

Just as I thought.

It has been truncated - does anyone know how to publish a URL here?

Try going to our www page (hwch.co.uk) and pressing the water boosting button.

 

[chrishutt]

You have to deduct the difference between the stored energy and the design pressure chrishutt. If the available pressure (mains) is 1.5 bar the accumulator cannot store energy above 1.5bar, and the only gain will be from expansion as the water is heated. And could be contrary to Wras, Water, and Building regs when fitted after the combination valve.

Firstly, I'm not sure what your first sentence means. My example was based on a mains pressure of 2.0 bar (for the sake of simplifying the subsequent arithmetic). I understand that the stored energy cannot be greater that that provided by the static mains pressure (excepting the extra margin due to expansion). But are you perhaps not taking account of the low dynamic pressure that would result from an inadequate supply pipe from the main, which would be the reason for considering an accumulator in the first place?

Secondly, expansion vessels are fitted after the combination valve (PRV, etc.) and an accumulator is just an oversized expansion vessel, so I don't see why it should be in breach of regs.

 

[ChrisR]

It is online, all valid patents are accessible online at the Patent Office.

I don't see that on the Patent Office website.

does anyone know how to publish a URL here?

Well the buffoon seems to have managed it.

Surely you are not expecting me to debate the merits and scope of the patent in a public discussion forum?

What's your problem?
"The Workmate is a folding work bench with a vice on top". "You can make and sell a folding picnic table". And you can quote me on that.

Mystique? Non!

Bull*hit, then?

 

[simond]

Chris R

I used the Patent Office's esp@cenet on line service. It was there two years ago and I've just checked the site and esp@cenet is still offered.

I don't care if you see my URL or not, but it was you that suggested we didn't have one.

If somebody would be kind enough to tell me how to do it, I'll put it up there.

Otherwise, I'll mow the grass.

 

[chrishutt]

Simon's site name seems to have an automatic block on this forum! If I write it as www dot hwch dot co dot uk it might work. The pressure boosting / accumulator link is via one of the icons.

 

[simond]

Thanks Chris H

But I think it's knobbled you too!

 

[Softus]

However, we can prove it to you down here in Surrey. We can take a pressure reducing valve to lower the standing pressure to 1.5bar on our demo site.

Excellent - I'm in the market for your product.

I have a customer whose supply is always 1.5 bar - never more and never less - and it just isn't high enough. It sounds like your accumulator willl increase the dynamic pressure!

Please let me know when you the positive results of your demo and I'll call you with my credit card details.