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Pressure Loss Ratio is determined by subtracting the resistance of the outlet
pipework and outlet fittings from the dynamic pressures of the hot and cold
water at the inlets of the mixing valve. This is at its extreme when the mixing
valve is used at its lowest flow-rate and when the maximum inequality occurs in
the pressure of the hot and cold water supplies.
Hydraulic Restriction: Flow Rate Pressure Loss Graph
(mixing valve only, equal dynamic supply pressures and mid-blend temperature
setting, rising or falling pressure loss).
250
200
150
100
50
0
0
Temperatures
Optimum performance is obtained when temperature differentials of 20
exist between blend and either supply. Blend control accuracy will begin to diminish at
temperature differentials below 12
Blend Temperature Range: between ambient cold and approximately 60
according to hot water supply temperatures.
Thermostatic Control Range: approximately 25-60
Optimum Thermostatic Control Range: 35 - 46
Recommended Minimum Cold Water Temperature: 1
Recommended Maximum Hot Water Temperature: 85
Note! If the hot water supply system does not incorporate safety devices (e.g. non self
resetting thermal cut out) to prevent this temperature being exceeded then the use of
a tempering valve may be considered to limit the temperature of the water supplied to
the mixing valve. The output temperature of this tempering valve must be set to a value
o
not less than 60
C and it must not exceed 85
the maximum possible value which may occur under fault conditions in the hot water
apparatus.
1
2
Pressure Loss - bar
o
C.
8
3
o
C.
o
C.
o
C.
o
C.
o
C if the hot water supplied to it reaches
4
5
o
C or more
o
C,
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