Accumulator and PRV question

[Biggles..]

Swings and roundabouts, a good proportion of ours is installing break tanks and boosters, where accumulators just won't do the job.

 

[Agile]

When using the mains water as the direct input then to use showers a residual dynamic pressure needs to be maintained to operate showers. Ideally about 1.0 bar to ensure a nice tingly feeling from the shower jets. This results in a lower useable flow rate!

When a break tank and booster pump is used, then the full open pipe flow rate of the incoming supply is available and this is often about twice the dynamic flow rate.

So the dynamic flow rate can often be doubled using the booster pump and supplied at about 3.0 bar which gives a very good shower indeed!

If the flow rate taken does not exceed the open pipe flow rate, then that is a continuous flow rate and does not run out like an accumulator.

Tony

 

[simond]

So what is wrong with booster pumps in a domestic environment?

- the water stored in the tank is not potable, because it is not atmospherically sealed
- they use electricity to run
- in the case of a mains failure most of the water stops working
- there is no redundancy unless you buy two or more and a pump controller
- they are noisy, and the pump noise can be transmitted with the water
- the pumps suffer air based cavitation on the impellers which makes them vibrate, which shortens the life

In commercial situations, there are many applications for break tanks, but of course in the commercial world, noise, chlorination and maintenance are rarely a problem.

Regarding the flow rate, talking domestically, accumulators can meet a similar performance to a pump and in many cases exceed it; the decay in the boost of the accumulator would of course usually be matched to the hot water storage in a domestic scenario - in other words, by the time the dynamic flow had dropped significantly, you'd be having a cold shower anyway.

 

[Agile]

In the London area the incoming water pressure is often very poor and often does not exceed 1.5 bar in the areas I visit.

At that pressure an accumulator performs very badly and needs to be very large.

But a break tank and pump will restore the pressure and flow to a good performance.

But all that is irrelevant as a loft tank and shower pump will do all that in the traditional UK way. But not in a flat of course if no roof access.

Tony

 

[simond]

In such situations we'd advise a pumped accumulator. The pump only runs slowly and lobs no more than 12 litres a min into the accumulator, so is quiet compared to a break tank. System still works for the duration of most power cuts, it's potable water etc etc.

 

[Dan Robinson]

In the London area the incoming water pressure is often very poor and often does not exceed 1.5 bar in the areas I visit.

Try visiting some nicer areas

At that pressure an accumulator performs very badly and needs to be very large.

Not necessarily. I have a 300 litre set in the loft of a house on top Highgate Hill (the irony of my last comment is not lost here) running beautifully.

In such situations we'd advise a pumped accumulator

What pump do you use? Is it the horrendously expensive TWS one? I'm, thinking of making my own. Although the place where I buy my vessels are looking at their own version too.


Fired this bad boy up last week:

Pushing 3 bar through this pipe work from Italy:

With Hansgrohe brassware.

Customer reports an improvement over their 3 Bar Lowera and 450 break tank set up it replaced.

Nice little earner if not a little worrying when it didn't perform at the first attempt of setting the pre charge.

Left it at 2Bar and all was gravy

 

[St0rmer66]

How many litres is that Dan?

 

[simond]

Perfect! We've used some Italian large vessels and one of them looked like a space rocket on legs. However, I stick with TWS now because the founder of the accumulator in the UK, Steve Elsey, looked after us in the early days and his estate get a licence for each one sold.

 

[Dan Robinson]

That's a 750 litre vessel stormer. Heavy barsteward even before being filled. Guess it weighsweighs you 600kgs now


Cheers Simon. Will get a current price for a loading pump from tws. But I recall them being crazy.

 

[simond]

They are around the same price as a GC450 accumulator if you get it open frame mounted.

The same gear, once in the TWS sound reducing metal box, as you say, gets ridiculously priced IMHO. But the combination is WRAS approved.