Pentair ThermalFlo, User Manual, Page: 28 / 40

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ThermalFlo Installation and User’s Guide
Water Pressure Switch Adjustment
CAUTION — The water pressure switch should be adjusted to turn the heater off when the pump is off. Setting the
switch to close at too low of a flow can damage the appliance. Adjust the switch to turn the heater off,
not on.
The pressure switch is preset at the factory for activation at 2 psi [14 kPa]. This is the minimum setting for the
water pressure switch and works for all basic installations as shown previously on
pages 7, 9-10 in this manual.
Only adjust the water pressure switch if the heat pump does not operate when the proper flow is applied to unit
or if the heat pump does not shut off when the filter pump is off. Occasionally, unusual plumbing configurations or
necessary restrictions in the plumbing may cause pressure sensing problems. In these rare situations, the plumbing
system configuration may require adjustment of the water pressure switch.
Adjustment of the pressure switch may be necessary if any part of the filter system piping is 3 feet [0.91 m] or
more above the top of the heat pump jacket.
Do not adjust the pressure switch if the heat pump is installed more than 15 feet [4.57 m] above or
6 feet [1.83 m] below the pool surface. Consult your local Pentair Water representative for recommendations.
On some installations, the piping from the heat pump to the pool is very short. The back pressure could be too low
to trigger the pressure switch. If this happens, it may be necessary to install a directional fitting or elbows where
the return line enters the pool. This will increase back pressure enough for the heat pump to operate properly.
If this configuration is necessary, be sure to check that the system flow is above the minimum requirement of
30 gpm after the direction fitting or elbow has been installed.
Make sure the pool filter is clean before making any pressure switch adjustment: A dirty filter will restrict the
water flow and the pressure switch cannot be adjusted properly.
To adjust the pressure switch:
1. Be sure that all valves in the system are set to allow water flow through the heat pump. Start the filter pump.
2. Set the heat pump control to call for heat. Set the On/Mode switch on the heat pump control to the “ ON ”
position.
3. If the heat pump control water pressure indicator LED is Off , then the flow in the system may be below the
minimum flow of 30 gpm needed for the safe operation of the heat pump. Investigate and correct any flow
problems before adjusting the water pressure switch. If the flow is above 30 gpm and the light is
Off , adjustment
is required.
4. Remove the heat pump’s left front panel and remove remaining right front panel. The water pressure switch
is located in the water plumbing in the lower right corner of the heat pump.
5. Slowly rotate the 7/64 in. Allen head set screw on the water pressure switch in a counterclockwise direction
until the “ Water Pressure Indicator ” LED is On . Remember that there is a time delay before the heat pump
compressor will start.
6. Once the heat pump is running, turn off the filter pump. The heat pump should turn off immediately.
7. If the heat pump continues to operate when the filter pump is off, turn the Allen head set screw on the water
pressure switch in a clockwise direction until “ Water Pressure Indicator ” LED is Off and the heat pump
stops.
8. Check the setting of the water pressure switch by starting and stopping the filter pump and checking the control
display and operation of the heater between each flow change.
9. If the water pressure switch cannot be adjusted to accommodate the conditions listed above, an external flow
switch must be added to the plumbing system to ensure that the heat pump will not operate without the proper
flow through the heat exchanger.