Heat bank or conventional system?

[Emma]

Hi - can anyone help?

We've just had our water supply pipes (from mains to meter and fro meter to stop-c*ck) changed from lead to 32mm blue poly pipe, i anticipation of fitting a heat bank/ thermal store. For most of the day the flow has improved dramatically - although m plumber's flow-cup only goes up to 17 litres a minute, the flow is wel over that and my rough tests of timing the filling of a 12 litre bucke make me think we now have around 30 litres a minute. However, at peak times (particularly between 7 and 8 am - when we nee it most) the flow dies down to around 15 to 16 litres a minute Pressure also falls, from 4.75 bar for most of the day, to 3 bar a peak times. What I need to know, is whether 15 litres a minute will be enough if w go for a mains pressure system like a heat bank. We have a big house and once all our work is finished it will be three-storey with bedrooms and three bathrooms (One shower room, one with shower ove bath, and one with separate shower and bath). The likely peak needs ar a shower, bath, washing machine and dishwasher all going at the sam time. We were thinking of going for a Gledhill Boilermate (probabl Boilermate BMA225), with the heat bank positioned on the ground floor in the utility room next to the boiler. However, if the flow is not going to be good enough, I think we'r going to have to put in a conventional system. We have a crappy comb boiler (Saunier Duval!) at the moment, which is on it's last legs There is room for a couple of cold water end-to-end coffin tanks in th lower part of the attic (higher front part of the attic is bein converted and will have a shower room, so we would need a negative hea pump), and the hot water tank could go where the heat bank would have but all the pipework will be an extra hassle. Any thoughts, recommendations, preferences

-- Emma

[Emma]

Hi - can anyone help?

We've just had our water supply pipes (from mains to meter and fro meter to stop-c*ck) changed from lead to 32mm blue poly pipe, i anticipation of fitting a heat bank/ thermal store. For most of the day the flow has improved dramatically - although m plumber's flow-cup only goes up to 17 litres a minute, the flow is wel over that and my rough tests of timing the filling of a 12 litre bucke make me think we now have around 30 litres a minute. However, at peak times (particularly between 7 and 8 am - when we nee it most) the flow dies down to around 15 to 16 litres a minute Pressure also falls, from 4.75 bar for most of the day, to 3 bar a peak times. What I need to know, is whether 15 litres a minute will be enough if w go for a mains pressure system like a heat bank. We have a big house and once all our work is finished it will be three-storey with bedrooms and three bathrooms (One shower room, one with shower ove bath, and one with separate shower and bath). The likely peak needs ar a shower, bath, washing machine and dishwasher all going at the sam time. We were thinking of going for a Gledhill Boilermate (probabl Boilermate BMA225), with the heat bank positioned on the ground floor in the utility room next to the boiler. However, if the flow is not going to be good enough, I think we'r going to have to put in a conventional system. We have a crappy comb boiler (Saunier Duval!) at the moment, which is on it's last legs There is room for a couple of cold water end-to-end coffin tanks in th lower part of the attic (higher front part of the attic is bein converted and will have a shower room, so we would need a negative hea pump), and the hot water tank could go where the heat bank would have but all the pipework will be an extra hassle. Any thoughts, recommendations, preferences

-- Emma

[Christian McArdle]

I'm intrigued that you can have 3 bar static, but only manage 15lpm through

32mm MDPE. Perhaps you are measuring at a particularly narrow bodied kitchen mixer tap? Otherwise, the only explanation is that you've still got some sort of restriction in the pipework, probably on the supplier's side.

Christian.

[John Stumbles]

At 15 l/m you will not get full flow from more than one shower at a time (or

1 shower + other significant demand), or maybe even just one shower if it's a deluge or full body panel type.

If you think you do need a stored water system you could consider a mains booster system e.g.

sure I've seen another (probably less expensive but lower capacity) version of this around recently but can't think where.

[Doctor Evil]

Firstly, check with the water company. Tell them about the vast pressure drop at peak times. they may have a problem which they were not ware of and get it rectified. They may have plan to uprate in say 3 to 6 months time. Find out. Is the street stop-c*ck, and your own, fully open?

If nothing can be done then 15 litre/min is really not good enough for your

2.5 bathrooms.

1. You can install an accumulator. This stores main pressure cold water at pressure, and will be fine for the couple of hours that the pressure is reduced. These work OK with unvented cylinders, but tend to be on the expensive side. They can be installed anywhere in the house. If there is mains failure the cold water is till running until the storage in the accumulator is run out. Stored cold water at atmospheric pressure; a cold water storage tank.

a) You can install a large conventional cylinder with a quick recovery coil and have power shower pumps for each shower (negative head where applicable). The upper shower room can have teh basin and shower off a negative head pump. More pipework, troublessome pumps athat make a noise.

b) Have a thermal store/heat bank off a cold water storage tank using a pump to give the pressure.

Best is probably No. 1 as the whole system is geared up main pressure hot water. When the water mains are uprated you are all prepared and nothing to do, You can leave the accumulators operating, storing cold mains water or just valve them off.

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[Emma]

Thanks for that Christian I am measuring at a kitchen mixer tap, which (apart from the washin machine pipe) is currently the only water outlet on the ground floor There is also approx 6m to 8m of 15mm copper pipe between that tap an the end of the 32mm poly pipe. Should I get the flow cup back from m plumber and try measuring the first floor bathroom and sink taps (there is probably less 15mm between them and the end of the 32mm pip , but they are obviously one floor up). Also, another poster indicate that turning on both the hot and cold taps on the kitchen mixer migh make a difference to the flow.

Many thanks Emm

-- Emma

[Doctor Evil]

Forgot to mention. An accumulator can be used witha boilermate heat bank.

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