Manual

102
DXi User Manual
Appendix B: Flow Sensors
Flow Limit Checking
To perform limit checking, the controller computes a Gallon-Per-Minute (GPM) flow
rate based upon the total gallons used in the previous 60 seconds.
Limit checks are performed on the following:
• Station upper limit
• Station lower limit
• Main flow limit
• Total monthly flow limit
• Unscheduled flow limit
Station limits can be automatically established by the controller or manually entered.
Station Limit
It is possible to enter a station flow limit by manuall entering the station limit, as
described in Chapter 7 or 11, or have the controller automatically set the limit during
a "learn" process as described in Chapter 5. Ensure the flow check delay is set to a
high enough value to allow for adequate hydraulic settling time for the flow meter
readings to stabilize before obtaining the nominal flow rate.
The controller compares the flowmeter reading to the station limit. If the meter value
is larger than the station upper limit, a high flow alert is raised. If the meter value is
smaller than the station lower limit, a low flow alert is raised.
The suggested upper limit flow rate should be set to the nominal flow rate for the
station +20%. The suggested lower limit flow rate should be set to the nominal flow
rate for the station -20%.
If water pressure varies greatly, upper station limits should be increased.
Main Flow Limits
Enter the Main Flow Limit, as described in the Main Flow procedure in Chapter 5.
The controller compares the flow meter reading to controller/main line station limit.
If the meter value is greater than the limit, an alert is generated.
The system default value for controller/main line limits is 500 GPM.
The Main Flow upper limit should be set higher than the total of all simultaneously
"on" stations. However, this limit should be lower than the anticipated flow rate from
a main line break.
In Flow Max systems, the total water consumption of all participating controllers is
calculated into the Main Flow limit.
Total Monthly Flow Limit
Enter a maximum monthly flow limit, as described in Chapter 4. The controller
compares the accumulated monthly flow to maximum monthly flow limit. If the
accumulated flow is greater than the limit, an alert is generated.
The system default value for maximum monthly total is 9,999,999.