Jacuzzi Hot tub flow switch

For hot tubs that use a pressure switch, topside error messages such as FLO, FLOW or FL may appear. This leads to the removing of the filter, restarting of the spa and other home made remedies. More often than not, further investigation is required and the switch may need to be adjusted or replaced.

The pressure switch or flow switch in a hot tub, is a safety device responsible for assuring there is adequate water pressure within the heater manifold in order to avoid
a dry condition that could cause a fire or explosion. The pressure switch does not allow the spa to heat when a dangerous condition is present.

When the pressure switch is in the ON condition because water pressure is detected, the circuit to
the electric spa heater is completed and the spa is allowed to heat. If the spa pump or circulation pump becomes defective, the pressure switch should sense inadequate water pressure and not allow the spa to heat either. So even in the case where there is no leak, there is enough water in the heater tube, a pump failure without a safety device could allow water in the heater manifold to sizzle and begin boiling creating a hazerdous condition.

Another cause for the pressure switch to make sure the spa does not heat is when the filter is dirty and the resulting clog does not allow enough water to flow properly across the heater element in the heater tube.

The pressure switch itself can go bad when exposed to improperly cared for water. Abnormal ph levels can quickly degrade the pressure switch.

The Dreaded FLO Message

The FLO error when pointing to a real problem could mean a dirty filter, an obstruction in the plumbing line,
a blocked footwell suction, an air lock in the pump or a defective circulation pump.

If the circulation pump is on but the water does not appear to be moving, then there may be an actual flow related issue.

The pressure switch is often located either on a PVC plumbing part next to the spa pack or directly mounted onto the stainless steel heater manifold or tube. The heater manifold can be found either underneath, inside or attached to the power control box.

To further troubleshoot a pressure switch, a technician may turn off the power to the spa and remove both wires connected to the pressure switch. They may then place the 2 wires together with alligator clips or wrap them in electrical tape.
Shorting these 2 wires together simulates a closed pressure switch. As the power is then turned on, the heater is set to a higher temperature than the
water is currently set at and the unit is in Standard Mode so that the heat will come on.

If the heater does come on and the the FLO error does not appear on the panel, then the switch may need to be replaced, but only after being sure there is no real obstruction in the line.

The adjustment of the pressure switch means turning the black dial clockwise to make the switch more sensitive so that the
heater comes on at a lower pressure. If the switch is calibrated to be too sensitive, then the heater may not turn off as quickly as it should and OH or overheat errors may occur.