Poor pressure on a megaflo??

[ChrisR]

So £1810 for parts, plus fitting, for 50 gallons storage.
Except you can't use the tanks cos you got a UV cylinder already and it breaches a phantom patent.

Or, let me think now, you could have big rectangular thingies with water in , I've sure I've seen them somewhere, about a hundred and fifty quid all in?
You still need a pump - but no water supplier approval, and you can buy one today.
And if you put a big mains pipe in it runs for ever, and ever, and ever, without losing pressure.

Tough call.

 

[doitall]

Call it £3k for an additional 23litres over 10 minutes 40 - 17lts

Size which could be a slight problem 668mm x 1575mm x 2 x the cylinder.

Net weight is 69.5Kg x 2 x cylinder.

 

[doitall]

Chris, Can we assume from your calculations that, a combi/shower would have a far greater benifit than an un-vented/bath set-up then, and what would be the time saved to fill say a 50litre bath ?, ( would it be less than 30seconds )

 

[chrishutt]

Not sure which Chris that question is addressed to, but I'll have a go at answering. Any boost provided by an accumulator will start to decay immediately that a tap (or shower) is opened. The rate of decay will be greater if the flow from the tap is greater. In the example you give above, a combi supplying a shower is likely to have a much lower flow rate than an unvented cylinder filling a bath.

However when filling a bath the rate of decay of the boost isn't really the issue. It's a question of how long it takes to fill the bath, so any size of accumulator will speed this up. If the bath required 50 litres and the accumulator stored 50 litres, the filling time would only be limited by the pressure drop of the pipework and fittings between accumulator and bath tap, so might be as little as a minute, even if mains flow was negligible.

I would say that the more testing scenario for an accumulator is supplying a shower, since the demand can outlast the boost. However this might be viewed as a useful deterrent against people spending too long in the shower! Or an encouragement to turn the shower on and off as required during the shower rather than leaving it running.

I think accumulators can offer the best solution to poor mains flow in certain circumstances (where upgrading the mains supply isn't a viable option), but I would be looking at much cheaper generic products rather than the Coldstream accumulator. As I posted earlier a 200 litre surge tank is available for £200.

 

[ChrisR]

I would certainly go along with that. There are plenty of situations where we all see them helping, say where a Megaflo has been installed on a poor mains supply. The flow when you turn the hot tap on is great, for a while. Quite a while longer than I would have expected, in fact.
When a Megaflo internal air gap is depleted, I get more moans because the "pressure has gone", than I do because of a dribbly "overflow".

All an accumulator is doing (unless there's a pump involved) is temporarily overcoming pipe resistances. If you put the accumulator right by the tap, then you get huge (initial) flow rates, same as you do if you open a tap which is right on a street main.
Bath (say60 litres?) in 30 seconds?, sure it's possible.

An infinitely big accumulator on the end of a 2m length of 28mm pipe,
with 1.5 - 2 bar, would deliver 10 litres per second. (I'm hedging a bit, the pipe itself would have 1 bar across it, but you have to allow for the resistance of the apertures at each end) That’s a bath in 6 seconds.

Plumbing fittings are very resistive though. A well installed Megaflo, on 3 bar mains, with a few metres of pipe to a typical (grohe, say) shower mixer/hose will only give 16-18 litres/minute.
Traditional bath taps are much better. Though 40-60 litre/minute isn't rare from high pressure low resistance supplies (such as in hotels), 25-30l/min is much more common from that megaflo (or accumulator) at 3 bar.

 

[simond]

Doitall

Are you going to offer me an apology now?

It would be quicker and more honourable than editing all your previous posts........

NB: Thanks to everyone, it's been fun. I've especially appreciated Chris H's submissions, whose technical work has always been painstakingly complete and thorough. A man whom we would welcome on our team any day.

 

[ChrisR]

A man whom we would welcome on our team any day.

I'm sure we would all have him on "our team".

But who would have you on theirs ?

 

[chrishutt]

I've especially appreciated Chris H's submissions, whose technical work has always been painstakingly complete and thorough. A man whom we would welcome on our team any day.

Thanks for that generous comment Simon, but are you sure didn't mean Chris R? He came up with the rather neat formula and is generally way ahead of the rest of us on these more arcane technical issues.

Anyway I'm not sure that I'd be a good team player. While the team was trying to make a profit I'd be fiddling around for hours trying to achieve optimal flows or whatever. Such obsession with detail doesn't sit well with hard-nosed business objectives, as I know to my cost.

It would be helpful Simon if you were to supply some actual measurements from one of your installations so we could compare our theoretical figures with practical results. You've been rather reticent up to now. It can't all be subject to commercial confidentiality, surely?

 

[simond]

Hello Chris

OK, I can take some measurements at home. I have a 450litre (nominal, actual capacity 200-250 litres) accumulator and a 310 litre unvented.

Without accumulator, the water main delivers 18 l/m and a standing pressure of 3 bar.

My flow meter only goes up to 22 litres and frankly the pressure and flow would make holding it under the bath tap very difficult (and wet).

I could measure the time taken to fill n litres in the bath, if you like. What do you suggest?

 

[oilman]

Hello Chris

OK, I can take some measurements at home. I have a 450litre (nominal, actual capacity 200-250 litres) accumulator and a 310 litre unvented.

Without accumulator, the water main delivers 18 l/m and a standing pressure of 3 bar.

My flow meter only goes up to 22 litres and frankly the pressure and flow would make holding it under the bath tap very difficult (and wet).

I could measure the time taken to fill n litres in the bath, if you like. What do you suggest?

Yeeeeeeaaaaaaaaawwwwwwwnnnnnnnnnnnnnnnnnn!!!!!!!


Just provide some figures and say how you got them, stop prevaricating, who cares how you do it, just do SOMETHING

 

[Softus]

...just do SOMETHING

Hear hear. With bells on.

 

[gastight]

This has been one the most illuminating discussions on this forum. Excellent contributions from all the regulars backed up with sound arguments.

 

[gastight]

This has been one the most illuminating discussions on this forum. Excellent contributions from all the regulars backed up with sound arguments.

 

[chrishutt]

I didn't think anyone else would be following it! The OP seems to have lost interest way back. But gratifying to know it was appreciated more widely.

OK, I can take some measurements at home. I have a 450litre (nominal, actual capacity 200-250 litres) accumulator and a 310 litre unvented.

Without accumulator, the water main delivers 18 l/m and a standing pressure of 3 bar.

My flow meter only goes up to 22 litres and frankly the pressure and flow would make holding it under the bath tap very difficult (and wet).

I could measure the time taken to fill n litres in the bath, if you like. What do you suggest?

With an accumulator that size, and 3.0 bar static pressure, I don't think anyone (even doitall) would doubt for a moment that you enjoy copious flows .

It would be more interesting to look at the actual performance of a more marginal situation, say a static pressure of just 1.5 bar and a modestly sized accumulator (say 100 litres). Not everyone has the space or the spondulics for a 450 litre one.

 

[doitall]

Doitall

Are you going to offer me an apology now?

It would be quicker and more honourable than editing all your previous posts........

NB: Thanks to everyone, it's been fun. I've especially appreciated Chris H's submissions, whose technical work has always been painstakingly complete and thorough. A man whom we would welcome on our team any day.

Why would I want to do that, you haven't proved didly squat yet.

Ok so you 18 litres a minute at 3bar standing pressure, you could easily have 18litres a minute flow rate at the outlet without the accumulator at that pressure.

Impressed Chrishutt ? No.

I have 3.2bar at home and a dam sight more than 18 litres a minute with very little pressure drop except weekends, when the pressure drops to 2.8 ish bar.

The OP has 18 litres a minute flow rate at an unknown pressure, in the example the 2 Chris's work out, the accumulator would best deliver 12litres a minute. I shall assume for a balanced flow, thats 6 litres hot and 6 lires cold.

And after laying out £3k ++++ Wow some improvement.

And I haven't included the structural strengthening required to take the weight of 2 x 69gk net, accumulators, plus a 200 litre Megaflow at 258 Kg, or the 2m square room to fit them in. Perhaps I should allow another £12k to build a plant room for them as well.