Pentair FLECK 3150 NXT, Installer Manual

Page: 28 / 182

Installer manual Fleck 3150 NXT/NXT2 - System sizing
28 / 182 Ref. MKT-IM-010 / C - 18.10.2019
Service velocity
[bed volume per hour]
Inlet water hardness
[mg/l as CaCO
3
]
°f
°TH
°dH
8 - 40 <350 <35 <19.6
8 - 30 350 to 450 35 - 45 19.6 - 25.2
8 - 20 >450 >45 >25.2
Info
Failure to respect the service velocity will lead to hardness leakage or even total
softener inefficiency.
Note that the water supply piping size may also be useful when estimating the nominal
flow rate, since the size of the piping allows a maximum flow rate to pass. Assuming
the maximum velocity of water in pipes is about 3 m/s, a good estimation for most
common pressure [3 bar] and temperature [16°C] is:
Piping size (internal diameter) Max. flow rate
[in] [mm] [m
3
/h at 3 m/s]
0.5 12 1.22
0.75 20 3.39
1 25 5.73
1.25 32 8.69
1.5 40 13.57
2.0 50 21.20
2.5 63 34.2
3.0 75 49.2
4.2.2 Determining the required volume of resin
When sizing a softener, make sure that the volume of resin in the tank (bed volume) will
be sufficient so that even when the peak flow rate is reached, the velocity is still
between the above values depending on the hardness. When sizing a softener, always
choose the resin volume and tank size based on the peak flow rate but not on the
nominal flow rate.
Info
Sizing on the nominal flow rate without taking the peak flow rate into account would
result in choosing smaller tank size and resin volume, and may lead in severe hardness
leakage during the service cycle when the peak flow is reached.
The maximum softened water flow rate that a softener can produce is given by the
following formula: