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Pump hunting protection
In negative head systems all the discharge pipework after the pump is pressurized.
In such systems there exists the possibility the pump will hunt ON-OFF-ON etc at intervals.
This will happen:
•
if all outlets are not fully closed
•
if there is a leak at a connection
•
if boosted toilets are not fitted with equilibrium ball valves
•
or as residual hot water contracts in long pipe runs.
Stored hot water volume
In calculating the volume of the stored hot water requirement it is important to consider:
•
number of bathrooms, with particular attention to the size of the bath
•
number of persons in household
Stored hot water temperature
Extract from BS5546:1990 (Current)
“The mean temperature of the stored water should not normally exceed 60ºC and in a
combined central heating and domestic hot water system it is recommended that the stored
water temperature is controlled independently from that on the primary circuit”.
Extract from BS6700:1997
“Under normal conditions the temperature of stored hot water should never exceed 65ºC.
A stored hot water temperature of 60ºC is considered sufficient to meet all normal requirements
and will minimise scale deposits in hard water areas”.
Effective control of stored hot water is simply achieved by use of a cylinder thermostat or direct
acting thermostatic valve (e.g. tapstat).
Maximum water temperature for CT Xtra, CT Bathroom & CT FORCE pumps is 60ºC.
In systems where the stored hot water temperature cannot be controlled e.g. Aga solid fuel
appliance or very crudely by the boiler thermostat, a Salamander approved HWS TMV must
be used.
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