Heat bank mains flow rate

[Tim S]

Would anyone with knowledge of thermal stores (or any direct from mains HW system) be able to reckon if 50l/minute supply is enough for a house with 1 bathroom, one shower room plus kitchen and 4 people?

Just measured it though the garden tap which is teed straight off water main just after the house stopcock.

The only datasheet indicator I can find is this, from Gledhill, with kind of quotes the wrong things (flow would have been helpful)

"A 15mm copper or equivalent external service may be sufficient for a small

1bathroom dwelling (depending upon the flow rate available), but the minimum recommended size for new dwellings is 22mm (25mm MDPE). For the BMA 225 model we recommend a 28mm (32mm MDPE) supply pipe."

I looked, we don't have MDPE, we have plastic coated 15mm copper to the street stopcock about 10m away. Flow measured though garden tap teed straight off water main at house. Better than expected flow seems attributable to the massive pressure (not measured that, but it seems pretty high).

I would run 22mm from the house c*ck, to minimise further losses and to be "upgrade ready" should it ever become necessary, but it would be nice to know if the supply is likely to be OK as is.

Cheers

Tim

:)

[Tim S]

Tim S coughed up some electrons that declared:

Hi,

Quick follow up.

Just found this:

a rough guide it looks reasonable (I'm going to measure my shower at home with a bucket tonight, that's the one device I most care about).

Looking like 50l/m is acceptable - though it would be sensible to put some balancing valves on the bath supply at least to limit the flow there.

I'll plumb the core runs in 22 anyway, which at least leaves the options for a mains upgrade if it ever proves necessary.

Cheers

Tim

[Doctor Drivel]

That is more than enough!!!! Have a "dedicated" 22mm pipe from the stoptap to the heat bank. Just before the heat bank's cold inlet, tee off and run the cold for the shower off this. Just after the DHW oulet on the heat bank, tee off and run the hot for the shower from this. This reduces flunctuation influences on the shower. Have a shower mixer with a pressure equalisation valve in it, or fit an external valve.

Many "heat banks" can handle up to 10 bar, as they use plate heat exchangers and flow switches rated to 10 bar too. Lowering the pressure will reduce the 50 litres/min you currently have. What is the static pressure? Measured with no taps on.

Thermal stores tend to be around 3 to 3.5 bar, so a pressure reducer may be required with a store.

[Doctor Drivel]

25 to 30 litres/min would be fine for that.

The shower is king. The system must be balanced to give all flow and pressure to this. If the bath is in the bathroom no need to balance the bath taps, as both will not be on at once. When the shower is on, the influences are kitchen tap, other toilets, dishwashers, etc. These don't need to be full force.

Good.