Pentair Siata V132 SFE, Installer Manual

Page: 29 / 88

Installer manual Siata V132 - SFE - System sizing
Ref. MKT-IM-003 / B - 19.04.2017 29 / 88
4.2.5. Cycle time calculation
From this point, the volume of resin, the tank size and the capacity of the softener is determined. Next
step is to calculate the regeneration cycle time, which depends 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 desired per regeneration;
• the resin specifications for the volume of water to use for backwashing the resin bed;
• the velocity and volume of water for brine draw and slow rinse;
• the volume of water to use for fast rinse.
To calculate the backwash duration:
T
backwash
= (V
resin
x N
BV
) / Q
backwash
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
brine draw
= V
brine
/ Q
inj
Note

Multiply the amount of salt in kg by 3 to get a correct approximation of the brine volume to
draw.
A
with:
T
backwash
: backwash duration [min]
V
resin
: volume of resin [L]
N
BV
: number of bed volume needed for backwash
Q
backwash
: backwash flow rate which is controlled by the
DLFC [L/min]
A
with:
T
brine draw
: brine draw duration [min]
V
brine
: brine volume to be drawn [L]
Q
inj
: injection flow rate [L/min]
A