Cycle Time Calculation - Pentair FLECK 9100 SXT Installer Manual

4.2.5. Cycle time calculation

From this point, the volume of resin, the tank size and the capacity of the softener are determined.
Next step is to calculate the regeneration cycle duration, which depend on the valve configuration and
once again on the resin specifications.
Note
Preprogrammed cycle times are only factory default programming that need to be adjusted
to fit the system requirements).
For cycle time calculation the valve configuration must be known, which depends on:
• the tank size;
• the resin volume previously determined;
• the salt amount used per regeneration;
• the resin specifications for the velocity and volume of water to use for backwashing the resin
bed;
• the velocity and volume of water for brine draw and slow rinse;
• the velocity and volume of water to use for fast rinse.
To calculate the backwash duration:
T = (N x BV) / Q
backwash
BVbw
Note
The typical value of the volume of water to be used for backwash is between 1.5 and 4 times
the bed volume, depending on the inlet water quality.
To calculate the brine draw duration:
Knowing the injector flow rate at the working pressure:
T = V / Q
brine draw brine inj
Note
Multiply the amount of salt in kg by 3 to get a approximation of the brine volume to draw.
Ref. MKT-IM-004 / A - 27.10.2016
DLFC
Installer Manual Fleck 9100 - SXT - System sizing
with:
T : backwash duration [min]
backwash
N : number of bed volume needed for backwash
BbwV
BV: bed volume [L]
Q : drain line flow controller size [L/min]
DLFC
with:
T : brine draw duration [min]
brine draw
V : brine volume to be drawn [L]
brine
Q : injection draw flow rate [L/min]
inj
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