"Emma" wrote in message
...
Hi - can anyone help?
We've just had our water supply pipes (from mains to meter and from
meter to stop-cock) changed from lead to 32mm blue poly pipe, in
anticipation of fitting a heat bank/ thermal store.
For most of the day the flow has improved dramatically - although my
plumber's flow-cup only goes up to 17 litres a minute, the flow is well
over that and my rough tests of timing the filling of a 12 litre bucket
make me think we now have around 30 litres a minute.
However, at peak times (particularly between 7 and 8 am - when we need
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 at
peak times.
What I need to know, is whether 15 litres a minute will be enough if we
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 5
bedrooms and three bathrooms (One shower room, one with shower over
bath, and one with separate shower and bath). The likely peak needs are
a shower, bath, washing machine and dishwasher all going at the same
time.
We were thinking of going for a Gledhill Boilermate (probably
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're
going to have to put in a conventional system. We have a crappy combi
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 the
lower part of the attic (higher front part of the attic is being
converted and will have a shower room, so we would need a negative head
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?
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-cock, 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.
http://www.gah.co.uk/
http://www.rcmgroup.co.uk/stainless_...ster/index.htm
2. 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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