Poor pressure on a megaflo??

[doitall]

We can fix your Megaflo if the standing pressure is over 1.5 bar.

Providing it has been installed for over a year and you are in our installation area. See our accumulator page on the web site.

Simon

For an accumulator to work satisfactorily it need to store water in excess of at least 50% of the delivery pressure. Ideal for high pressure low volume mains but a complete waste of money with low pressure mains.

The OP would need a standing pressure of at least 4-5bar to run a Megaflow in conjunction with an accumulator, in addition the accumulator would need to be a minimum of 60ltrs or half the volume of the Megaflow, whichever is the greater.

 

[Gasguru]

And the dualstream accumulator is only approved in conjunction with OSO unvented cylinders.

 

[simond]

The last two posts about how accumulators can be used and the patent restrictions regarding their application are erroneous.

We are fully conversant with their application and fitment, and while there are licencing conditions we are up to speed on these too, and make sure they are honoured.

Contrary to the nonsense written earlier, an accumulator will work excellently on 1.5bar, we are fitting a number of these a week. And we can help the Megaflo owner subject to certain conditions.

Conjecture is no substitute for experience, my intentions were to try to help the person with the poor flow rate. If you are not sure about a product, it's best to qualify your opinions, rather than write untruths as a statement of fact.

Just misleads everyone and gets the trade a bad name.

Best regards

A rather miffed Simon

 

[doitall]

A rather miffed Simon

Do tell I'm all ears.

An Accumulator stores water at a higher pressure and boosts the volume to maintain the flow rate.


If you have 1.5bar mains pressure suppling the accumulator and 1.5 bar operating pressure the store will be static, and loose its charge the minute an outlet is opened.

 

[davecon1]

Another joyous weekend! I've discovered that the water leaking through the tundish into the discharge pipe has caused a damp patch in the room downstairs (2 weeks after replastering and repainting the room). It turns out that the discharge pipe didn't exit the house enough and so leaked straight into the wall. I must remember to thank the plumber for that.

Anyway- back onto the topic. Every day the hot water comes on the megaflo discharges water continuously through the tun dish into. I've tried to regenerate the air gap but that does not seem to have any effect. The only thing that stops it immediately is turning on the hot tap- the leak stops immediately. Any ideas? The megaflow engineer and the original plumber are back this Friday.

Things seem to go from bad to worse and I don't know what to make of the doitall vs simond argument. Is an accumulator the thing to go for to sort out the pressure problem?

 

[ChrisR]

Wiv respek davecon sir are you sure you did the air gap regeneration properly?
It's very easy to misunderstand, and wind up not doing anything much.

Turn off the incoming mains (valve on the multifunction valve)
Open a hot water tap fully (lowest one)
Then you have to let air IN in order to let the water out. Hold open the temp and pressure relief valve whch sticks out of the side of the Megaflo. This means holding it for sometimes 15 minutes against a spring, which can be very boring. Sometimes they just about stay open without being held, (sometimes I've used the weight of a pair of mole grips to help)
When the guggling sucking noise stops there's no more water leaving the cylinder and you're done.

You MUST do this before you see the effect of the air gap in the Megaflo which I have referred to previously.
They usually take at least several months, if not years, to lose the air gap though...

Digressing a little, ordinary plain unvented cylinders do not have an air gap in them, so have a pressure vessel attached. The pressure vessel is precharged at say 3 bar - the air in it only squashes when the pressure goes over that due to the expansion of the heated water (ie by about 2%). As soon as you open a tap and lose that small volume, the pressure is back down to 3 bar. This is what leads to misconceptions about how Megaflo's and their like, work.
The air gap in a Megaflo starts off at 0 bar relative to atmosphere (not 3 bar), so when it's half squashed then its pressure is +1 bar, and so on. At 3 bar it's a third the volume it was. So the pressure drops a lot more slowly when the water leaves.

An accumulator works in much the same way as the air gap does in your Megaflo. As I tried to explain before, when you first open the tap you get hw at full pressure, which drops off as the air gap unsquashes (unless the incoming mains can keep up with it). The air works like a big spring.
The pressure does NOT collapse as soon as you open a tap.

An accumulator makes the effect last longer, and can be applied to the CW mains too. It will not make that initial pressure higher.
So if you find that your pressure is awful as soon as you open the tap (even at 2 outlets) then an accumulator won't help that.

Dave you really DO have to measure your mains static pressure (£12 gauge), or YES you can call Thames water and ask them.

You don't need anything like 5 bar for an accumulator to help, but if you have the 2.7 bar I think was mentioned and you don't get good flow even when the hw taps are first opened, then you have pipework limitations downstream of the Megaflo and an accumulator isn't the answer (unless you put one beside each tap!)

Simon I don't see an 'accumulator page' on your website.

 

[Gasguru]

A rather miffed Simon

I spoke at lenght with OSO last week on using their accumulator with other manufacturers unvented cylinders - they were adamant it could NOT be used as it would infringe the products approval.

Please supply a contact at OSO, if what your saying proves to be correct it would help one of my customers as they would prefer an accumulator option rather than the inconvenience of replacing their incoming main.

 

[simond]

It is a shame that I can post what is a 100% relevant, and technically proven reply to a respondent, and then an ignoramus puts in print that I have coned (sic) my customers.

I suggest 'Doitall' checks the patent describing how this product works. A very clever chap called Steve (a proper heating engineer with an understanding of the difference between flow and pressure) designed it about 8 years ago. It should make him a very wealthy man, and deservedly so.

My company has never coned (or conned) anyone, the comment is slanderous and without foundation.

On a more positive note, regarding using the accumulator with other cylinders, Mr Gasguru, things are not as straightforward as OSO make out. They themselves do not touch the accumulators, the system integration of their cylinder with the accumulator is carried out by a third party. We have fitted OSO/accumulator units (even on 1.5b mains!) and they are a good piece of kit.

Whilst there are restrictions on accumulator usage and application, the information you have gleaned from OSO is not the whole story. Commercial confidentialities prevent me from elaborating in this forum.

I am sorry I cannot go into more detail, Mr Gasguru.

As for Doitall, Plumbing NVQ1+2 would be a wise investment, and perhaps a good lawyer. I suggest his advice is treated with a good degree of scepticism by members of the public seeking learned trade guidance. Mr Chris R's helpful and informed reply was what I think he should aspire to.

Over and out

Simon

 

[wilhelm]

simond , have you looked up the word..sanctimonious

thought not.

 

[Gasguru]

So OSO aren't telling me the whole truth and I shall need to do further investigation then?

 

[doitall]

Simple, Simond go fit one for the Dave No win No fee contract.

Dave can time how long to fill a bath before and after.

Still getting my head around the megaflow engineer, the first thing he should have done was check the pressure/volume.

That should be the first thing when he next calls.

For the record, ask the megaflow for his opinion about an accumulator as well.

 

[doitall]

On a more positive note, regarding using the accumulator with other cylinders, Mr Gasguru, things are not as straightforward as OSO make out. They themselves do not touch the accumulators, the system integration of their cylinder with the accumulator is carried out by a third party. We have fitted OSO/accumulator units (even on 1.5b mains!) and they are a good piece of kit.

I am sorry I cannot go into more detail, Mr Gasguru.

=OSO. Oso Dualstream can be used where there is a poor mains flow rate. It combines an Oso cylinder with a cold water reservoir/ accumulator that supplements the incoming main.

Whilst there are restrictions on accumulator usage and application, the information you have gleaned from OSO is not the whole story. Commercial confidentialities prevent me from elaborating in this forum.

What restriction woulds that be then SimonD ? Wouldn't be they don't work if the standing pressure is equal to the operating pressure by any chance.

Assuming the OP has room in the cupboard for another tank nearly the size of the cylinder, and of course the extra £1000.00 needed for you to fit it, what would you say the time saving would be in filling a standard Bath ? 5-10 % perhaps or shall we go for the 50% minimum speel

 

[DP]

Was in a similar situation where a Megaflow had been fitted onto a 15mm copper water mains many bends and elbows down the pipe from where it entered the property.

Tee'd the 15 mains at entry point, 22mm branch directly to Megaflow and pressure is a lot better than before.

This thread seems to suggests the enduser has an installation where the installer (while competent) does not either care about his work or does not understand system operations.

Am at present rectifying bad instal problems on another UV cylinder. Does not even have a motorised valve fitted. MV was lying on the deck.

 

[simond]

Gasguru,

If you are not directly competing with us (see www.hwch.co.uk) I would be pleased to have a brief chat during working hours and we can compare notes.

Doitall,

My company has offered a no win no fee solution to accumulator customers, as it goes. Some non-technical customers don't understand the physics and it makes them happy to have this peace of mind.

If DaveCon1 is in our service area and is interested I see no reason why I shouldn't offer it to him, too.

Best regards

Simon
HWCH Ltd

 

[davecon1]

Wiv respek davecon sir are you sure you did the air gap regeneration properly?
It's very easy to misunderstand, and wind up not doing anything much.

Turn off the incoming mains (valve on the multifunction valve)
Open a hot water tap fully (lowest one)
Then you have to let air IN in order to let the water out. Hold open the temp and pressure relief valve whch sticks out of the side of the Megaflo. This means holding it for sometimes 15 minutes against a spring, which can be very boring. Sometimes they just about stay open without being held, (sometimes I've used the weight of a pair of mole grips to help)
When the guggling sucking noise stops there's no more water leaving the cylinder and you're done..

Hey Chris

I followed the instructions to the word on the side of the megaflow- the only difference in them vs what you'vw written is that I turned the cold off at the mains. I then opened the kitchen tap (lowest) and the water drained out pretty quickly (first a flow then a dribble). After that I held the valve and it stopped gurgling/sucking within about 30 seconds. After that I turned the tap back on and opened up the cold supply.

Does that sound right? It's really odd that the problem has never happened until a few weeks ago!