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Helpful guidelines
Cold water supplies and storage
Recovery of cold storage
Ensure that there is sufficient water recovery to cover the water usage by the appliance
Aeration of pump and cylinder from a cold water storage cistern
This occurs when the incoming cold mains ball valve is positioned above the cold feeds
to the cylinder and to the pump – aerated water is drawn into the pump as illustrated.
Chronic aeration of the pump occurs when
this problem is combined with inadequate
storage capacity and/or when the volume
of water is drawn by the pump and other
services exceeds the refill rate and creates
a vortex which draws air and possibly debris
into the pump.
Water starvation protection
In systems where it is absolutely not possible to increase the usable cold water storage capacity
to meet the increased demand of a pumped system; a water starvation protection unit (WSP)
may be considered (See fig 11).
The WSP is a Salamander level switch which must be positioned 102mm higher than the highest
outlet from the cold water storage cistern. When the water level drops too far the WSP will
switch off the pump until the cold water storage level is recovered.
Cold storage usable capacity
The usable capacity of cold storage is easily calculated as the capacity of water in the cold cistern
above the cold feeds to the cylinder, the pump and other outlets – see formula.
Formula for calculation on rectangular cistern:
Water above inlet (15”) x width (23”)
x length (36”) = 12,420 cu inches
Volume cu inches (12,420) x 0.01639
= 203.56 litres
Volume litres (203.56) x 0.22 = 44.78 gallons
Outlets
to pump
Vortex
Reposition
cold mains
ball valve here
The bottom
of the cold
tank must
be checked
& cleared
of debris
Wi
dth
Length
Depth
of water
Useable capacity
Figure 9: Aeration
Figure 10: Water capacity calculations
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