Cycle Time Calculation - Pentair FLECK 5800 SXT Installer Manual

Installer Manual Fleck 5800 - SXT - System sizing
To determine the injector size:
The velocities to be respected for brine draw and slow rinse are given on the resin manufacturer
specifications. Generally speaking, the injector has to allow a flow rate of about 4BV / h
(corresponding to the flow rate of brine being drawn added to the flow rate of raw water passing
through the injector nozzle to create the suction effect).
Q = 4 x BV / h
Inj
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 "1650 Injector
flow rates", page 33.

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.
30 / 92
DLFC
with:
Q : total flow rate passing through the injector [L/h]
inj
BV : bed volume of resin [L]
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
Ref. MKT-IM-004 / A - 18.04.2017