MegaFlo Pressure Issue - what should I expect?

[simond]

We've been fitting accumulators for nearly 7 years and in the right scenarios, they work very well.


If you have 2.8 static on the ground floor an accumulator will make a significant improvement to the Megaflo (not the best choice of unvented) performance, in terms of dynamic pressure.

Your installer should be recommending this if he was keen and au fait with his trade.

It is not worth specifying an accumulator smaller than the GC450 as this gives a useful boost for about 220 litres. The next size down only delivers just over half this, and as iterated earlier the bag boost lowers as the accumulator unloads the water, so the GC450 stays in the sweet spot longer, if you get my drift.

You would be best advised to increase your pipe size from the accumulator to the UV cylinder. No point in spending all the money and then not giving it the best chance.

 

[1456518Mike]

Thanks for the advice.

What size pipe would you recommend between the accumulator and the megaflow. It's currently 22mm run to the megaflow - would you suggest bigger? What size will the entry port to the megaflow be? I assume this is 22mm, so it will reduce at this last point (but appreciate that maintaining bigger pipe size up until this point could be beneficial).

What about the Grundfos HomeBooster. It would have to be in our garage (or maybe squeezed into the utility) and getting the 22mm pipe to it off the main is a bit of a pain with routing, but is doable. I think these deliver 3.7bar, so 3.2 after gravity to the loft, and being pumped, I assume that 3.2 is dynamic pressure rather than static?

So options would be:

1. Accumulator using the 2.5 bar static received in the loft to push out to the megaflo at 2.5 bar dynamic (= good shower for duration of pressure in accumulator). Assuming a 500ltr acc, this would give pressure for say the first 250, which at a shower rate of 15lpm, would give a strong shower for 17 minutes approx.

or

2. Grundfos HomeBooster, delivering 3.2 bar dynamic at the loft, reduced to 3bar by the PRV on the megaflow (= good shower for as long as you want it, provided there's enough coming back into the Grundfos tank to keep the pump supplied).

Assuming 15lpm drawn off for the shower, the Homebooster is fed by incoming mains at 22lpm, so would never run out of water. Even 2 showers running at 26lpm would only run it down at 4lpm (26 out, 22 in), and with 180 ltrs usable, would take 45 minutes of simultaneous showering (you'd need to be a dirty so an ss for that!)

So, to all the experts out there, WHICH ONE IS BEST!!??


.

 

[dcawkwell]

I think you have a lack of both pressure and flow.

My sister has an unvented tank and has 3.5 static and 25 litres per minute of flow and this is fine with the standard expansion tank.

I have an unvented cylinder and when it was first installed it was fine I had reasonable flow and pressure. I should explain I live in an old farm house just outsite town.
Due to leaks perhaps elsewhere I now seem to get no better than 2 bar
pressure that seems to drop similar to yourself.

Your pressure is a little on the low side similar to mine at 2 bar but this rapidly drops when running water. I think the first think to try is an accumulate I intend to get a 50-60 litre accumulate that should satisfy
most of the time. If the accumulator is supplying 5 litres and the other 5 litres is coming from the mains that would give and approximate 10 minute shower. It is possible to add an additional accumulate when I can judge the size needed.

I would prefer more pressure as well but the only way to achieve that would be a pump to increase the pressure up to about 3 bar.

 

[simond]

Internet forums are great for research, but sometimes the advice given on them is completely wrong.

You have to sort the wheat out from the chaff.

The post above is probably given with the best of intentions, but is just an assumption, written by someone who clearly does not understand how these things work and has never fitted one.

 

[1456518Mike]

Does anyone know how noisy a Grundfos Homebooster is? Would it be the same as a typical 2 bar shower pump?

Also, I'm thinking about how I could use it only when needed (shower time 7am-9am ish) and evening kids bath (7pm ish), as really all we are trying to do is make the showers more powerful, and as a bonus the bath fill quicker. Pressure at all taps is fine.

So, I'm thinking I could plug in the Homebooster into a timer switch, that gives it power at those times only. Therefore, it wouldn't kick in at all the rest of the time, even if a fair bit of water is drawn off (I think they have a small accumulatro built in to prevent the pump kicking in for every small draw, but the timer would ensure it is only on when really needed, even if the draw would normally be enough to trigger the pump).

It's either this of the accumulator, but I'm pretty sure we have to do one or other - I'll never be happy with the current showers. I'm based in Surrey, near Woking - is anyone interested in having a look and assessing the best approach, and giving me a quote?

 

[Agile]

The Grunfoss Home booster is your best solution if its fitted at ground level so its refilled with all the available open pipe flow rate.

An accumulator would also have to be at ground level to get the optimum results.

The Grunfoss is about as noisy as a more noisy washing machine.

It must be left connected at all times otherwise you will not get any hot water at all. When delivering a flow the pump must be running.

Tony