Cycle Time Calculation - Pentair FLECK 5600 SXT Installer Manual

Installer Manual Fleck 5600 - SXT - System sizing
Note
This value does not correspond to the brine draw flow rate but to the total flow rate passing
through the injector. Then refer to the injector diagrams for the chosen tank size and at the
inlet pressure in order to check if the injector will give a correct flow rate. See "Salt amount
definition", page 32.

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
30 / 92
DLFC
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
Ref. MKT-IM-013 / A - 21.12.2016