Honeywell SMV800 - Page 63

Revision 1.0 SMV800 Modbus User's Guide Page 51
Continued ..
Reverse Flow
ON
OFF
With Reverse flow OFF, flow value will
be zero flow when Flow is negative
(when Differential Pressure is < 0) for
Algorithm Options = Advanced
Algorithms or 1989 Algorithms
With Reverse flow ON, flow value will
be negative when Differential Pressure
is < 0 for Algorithm Options =
Advanced Algorithms
With Reverse flow ON or OFF, flow
value will be 0 when Differential
Pressure is < 0 for Algorithm Options =
ASME 1989 Algorithms
So, if Reverse flow is expected, select
Algorithm Options = Advanced
Algorithms, set Reverse Flow
Calculation parameter: ON
Example:
When Reverse flow is ON, PV4 is
calculated considering the absolute
value of DP (when Differential Pressure
is < 0) and resulting Flwo value will be
negative.
Example When Reverse Flow OFF:
DP = -100 inH20
SP = 14.45 psi.
PV4 (Flow) = 0
Example When Reverse Flow ON:
DP = -100 inH20 (-3.612 psi)
SP = 14.45 psi.
PV4 calculation will consider 100in H20
in calculation.
SP value, SP=SP-DP.
SP = 14.45-(-3.612)=18.062 psi will be