Potable Water Accumulator/ Expansion Vessel Questions.

[doitall]

The GAH unit is well made and designed for your purpose.

The 500 litre size is the optimum in terms of price and performance. If you fit a smaller unit you may exhaust it on occasional heavy use and believe me, the difference between what you have now and after fitment will be very noticeable indeed.

The siting of the unit near to the boiler will depend on the heat loss from the boiler, newer units are much better in this respect. Bear in mind that in the summer most people's cold water storage tanks are in very hot locations.

Good practice says that wherever possible take the kitchen tap feed off prior to the NRV fitted to the accumulator circuits.

There are cases where the use of an electric pump set are the only viable option, but if you have 2bar static then you don't need it. Bear in mind 2bar is 29PSI!

We fit an awful lot of these and have been doing so for some years, in contrast to many others on this forum. We have not had a single accumulator failure. Those thinking of standard expansion vessel reliability may be forgetting the temperatures exposed to a cold water system are very different.

The GAH system uses components in production for many years in borehole applications in the USA; their cold water is very similar to ours

Unfortunately Simond has a vested interest in GAH, and as he says he has fitted loads and therefore no-one else is an authority on them.

We don't fit loads Simon, we fit hundreds, and know a little bit, see pics

 

[Agile]

I dont understand why you are so fixated on having a flow rate of 20-30 li/min!

Half of those in London only have a flow rate like yours.

Few people seem to understand accumulators. They work best with a high static pressure.

Your 2 bar and a 500 li accumulator will only give about 160 litres down to a dynamic pressure of 1 Bar or a little more down to 0.5 Bar.

They do not give 500 litres!!!

As suggested a cistern/pumpset will give the whole 200 li of storage volume at about 3 bar output pressure and is vastly more suitable as well as giving a constant output pressure.

The pressure available from an accumulator reduces as its capacity empties. They only give good performance to about 25% of their volume.

Tony

 

[robsant]

Doitall..

thanks for for the information... that was why i didnt want to go with the pump route. I wanted potable hot and cold water throughout the house. (its not easy trying to guarantee a 4 year old wont drink from the wrong tap).

Agile..

i didnt realise that about the accumulator, i guessed i would get maybe 250litres useable out of a 500 litre vessel.

I dont suppose anyone can recommend someone in the Merseyside area who is corgi registered, qualified for unvented, and knows about increasing flow / pressure ?

I may be best getting someone to have a look at the whole problem.

 

[doitall]

250Ltr would depend on the draw-off rate, for example if you were drawing 4 time what the mains could supply the accumulator would deplete rapidly.

An accumulator works by stabilizing the flow rate, say 12 Ltr/m from the mains and 12 Ltr/m from the vessel, giving you something like 500Ltrs.

Now for the tricky part, if you draw-off say 48 Ltr/m you only get 1/4 mains and 3/4 accumulator, so you would be down to nearer 200 Ltrs before the pressure dropped. them's only estimate figures and not actual.

The dewey waters sectional tanks are double skinned insulated and suitable for potable water, and fit for drinking unless they are connected to a water softener, where it is not advised. But in any case the same would apply to an accumulator

You could if you wanted the extra work, supply the basins from the mains anyway.

I think SimonD covers your area.

Hope all that made sense

 

[Agile]

I think SimonD covers your area.

A round trip of almost 400 miles ???

Today with the M40 closed and the M1 at double capacity that would have been a five hour journey!

By the way the Grunfoss storage pump is potable water!

Tony

 

[kevplumb]

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[simond]

A 500 litre accumulator will typically contain around 260 litres of water that is usable.

The mix of water from the mains and from the accumulator varies according to the depletion of the charge. Since the accumulator stabilises at full charge, the mix when draw offs are taken is very low from the mains, because of the higher dynamic pressure from the air bag.

In practice you draw very little from the mains until the accumulator is nearly discharged, and therefore you must size the accumulator for the peak load, not 50/50. Many accumulator installs are delivering 50l/m off a main delivering 10l/m.

This principle can be evidenced by those without an accumulator, who notice an initial surge when taking water from an unvented HW cylinder - from the air charge in the expansion zone.

The best way to convince people is to show them. On an internet forum we can all talk the talk; some customers are justifiably sceptical after reading this forum and others.

I suggest the OP finds an accumulator installer in his area and asks to see one in operation; we always offer this in Surrey and Kent because there is no better way to blow away the misconceptions and hearsay from some respondents on this forum.

PS: We have just sold a number of accumulators to an Australian gold mine, but unfortunately I didn't have the time to make a photographic record of them leaving our warehouse Usually take pictures of the wife and kids, dog etc.

 

[simond]

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Is there an interpreter in the house? Can Tony Glazier elaborate? And what is a Marra? Is it a whippet?