Heater Will Not Fire - B - Pentair MT125 Installation And User Manual

Section 3. Troubleshooting
52

Heater Will Not Fire - B

Start
Is ERR PS displayed
on LCD?
NO
CONTINUE
MASTERTEMP 125 Pool and Spa Heater Installation and User's Guide
YES
Verify that pump is on, filter is
not blocked, and the water
flow is above the minimum
requirement.
With pump running, adjust
Water Pressure Switch to
lower pressure until ERR PS
goes out. Then verify that
ERR PS goes on with pump
off.
Check that water pressure is
within the adjustment range of
the Pressure Switch (0-5 psig)
Verify that switch wiring is OK
and Pressure Switch port is
not blocked, and replace
water Pressure Switch.
Check if any of the other
Alarms are activated.
Go to ALARMS Diagnostics
(Pages 53 and 54)
YES
NO
YES
YES
NO
NO
YES
YES
NO
Service pump/filter and elimi-
nate other flow obstructions.
Heater should fire on call for
heat. Re-verify that water flow
is above minimum requirement
Minimum Flow Requirements
Model Flow (min/Max)
125 20 gal/min (70 GPM)
If water pressure is outside of
adjustment range that will
open switch with pump off
and close switch with pump
on, replace with flow switch
set above minimum flow
requirement.
Minimum Flow Requirements
Model Flow (min/Max)
125 20 gal/min (70 GPM)
Go to "Diagnostic.
(Pages 53 and 54)
460906 Rev. D 8/2020