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Water Flow (Pressure) Switch Adjustment
Occasionally, plumbing system design features will create a situation whereas the heater will abnor-
mally cycle on the water flow circuit. This situation will be evident if the circulator pump is operating,
the filter is clean, and all water valves are set to flow water through the heater– but the error code:
“FLO” remains displayed (or displays intermittently). In these rare instances where the factory water
pressure switch (WPS) setting will not satisfy site conditions, a WPS adjustment, to enable normal
heater operation, is possible.
WPS adjustment procedure to be performed by experienced service personnel only; procedure is
NOT a homeowner-based task, and must not be attempted by individuals lacking adequate electrical
and mechanical experience. BEWARE: ROTATING FAN PROP HAZARD: fan may start during
water switch adjustment. Keep hands clear of fan blade at all times.
Failure to heed the following may result in permanent injury
or death.
WARNING !
Locate Water Pressure Switch and Identify Type:
1. Before proceeding with switch adjustment, be absolutely certain the heater is receiving correct
water flow. Leave circulation pump operating during water pressure switch (WPS) adjustment
process.
2. Remove heater front cover and locate the water pressure switch. The switch will be found
attached outside of the electrical enclosure, at lower edge; exact location will vary by heater
model (see photo P-1, on following page).
3. AquaCal heat pumps may come equipped with either of two (2) water pressure switches: “Len
Gordon” or “TecMark” brand (see photos P-2 and P-3, on following page, to determine which
brand pressure switch is installed). The adjustment procedures differ slightly between the two
brands.
To Adjust a “Len Gordon” Switch:
1. Locate the black, rectangular plastic tab, located on the forward-facing side of the switch
(reference P-2 on page following). The black rectangle is a wheel lock tab; slide the tab fully
LEFT to unlock the adjustment wheel.
2. With water pump operating, and electrical power supplied to the heater,
slowly rotate the top of
the adjustment wheel TOWARDS you until the FLO code (just) disappears. WARNING: watch
for rotating fan blade; depending upon the state of the control circuit time delay, the heater may
start simultaneous with the WPS adjustment.
3. Once the adjustment has been completed, slide the wheel locking tab fully back to the right-
hand, locked position.
To Adjust a “TecMark” Switch:
1. (Reference photo P-3 on page following.) TecMark switches do
not have an adjustment wheel
lock.
2. With water pump operating, and electrical power supplied to the heater,
slowly rotate the top of
the adjustment wheel AWAY from you until the until the FLO code (just) disappears. WARNING:
watch for rotating fan blade; depending upon the state of the control circuit time delay, the heater
may start simultaneous with the WPS adjustment.
Controls Configuration & Adjustments...