Why won't my pool heater turn on?

A pool heater that will not turn on is usually missing one of four things: power, water flow, a call for heat, or a clean ignition. A few of those you can rule out from the equipment pad in ten minutes. Once they are ruled out, a gas heater that still will not fire needs a licensed pro, because what is left is in the gas, ignition or safety circuits.

Start with what the heater needs

Power. If the display is dark, look at the breaker first. Raypak's manual says that if you have no electrical power, it may be that your circuit breaker has tripped.^[1] A breaker that trips again straight away is a wiring or component fault, not a reset problem.

Water flow. The heater will not fire in still water. The heater requires water flow and positive pressure to fire and operate properly.^[1] Raypak's own list for a heater that will not fire says the pump strainer basket may be full, the filter may be dirty, or the pump may have lost its prime and be running dry.^[1] A filter pressure gauge reading higher than usual, or no pressure at all, tells you which.

A call for heat. The heater only runs when the controls ask it to. Raypak says the time clock must be in the "ON" position,^[1] and the thermostat or setpoint has to be above the current water temperature. Its default setpoint range is 50-104°F,^[1] so a setpoint at or below the pool temperature is the simplest reason of all. If a solar system or another heat source feeds the heater, note that with an additional source of heated water, such as a solar system, that provides adequate heat to maintain the setpoint, the heater will not fire.^[1] It is working as designed.

Read the display

A digital heater tells you what stopped it. Raypak's status messages include Water Sw Open for an open water pressure switch, Hi Limit for an open high limit, Rollout Sw Open for an open rollout switch and Ignition Failure when the pilot flame is not established.^[1] Three more details help a technician:

• After repeated pilot flame losses the heater will lock out for 60 minutes before retrying,^[1] so a heater that went quiet may simply be waiting.
• Cold water can stop it. Raypak lists a Low Temp Lockout when the water temperature is below 36°F.^[1]
• The control keeps a fault history of up to ten faults,^[1] so write down the messages before anyone clears them.

Photograph the display and the fault history. It saves a diagnostic visit's worth of guessing.

What the messages usually point to

A water switch or flow message points back to the pump, filter, valves and the pool's water level. A limit message points to water flow, and Raypak's troubleshooting chart for a rollout message says to check for a blocked heat exchanger and soot, which is a heater problem rather than a pool one.^[1] An ignition message points to the gas supply, the pilot or the igniter. None of those are repairs to try yourself. The gas valve, pressure switch, igniter and control board are replaced as parts, and the work is done with the gas and power isolated.

For what a technician actually does on arrival, read what a technician checks when a pool heater will not fire. If the diagnosis is a failed part, should I fix my pool heater or buy a new one helps you weigh the repair against replacement, and how much a pool heater repair visit costs tells you what to ask in a quote.

When to call a licensed pro

Call once the breaker, time clock, pump, filter and setpoint are ruled out, or at once if you smell gas. Raypak says its gas heater must be installed and serviced by a qualified installer, service agency or the gas supplier.^[1] Virginia's licensing law draws the same line. In Virginia no individual may engage in work as a liquefied petroleum gas fitter or natural gas fitter provider unless licensed under that article of the Code.^[4] The definition of a liquefied petroleum gas fitter excludes hot water heaters, boilers and central heating systems, which require a heating, ventilation and air conditioning or plumbing certification,^[3] so ask the business which DPOR licence it holds for your heater.

Permits matter if the repair becomes a replacement. Virginia's building code permit rule covers installations or alterations involving fuel supply systems, mechanical systems or electric wiring.^[2] DPOR also says that if the work is valued at $1,000 or more, a valid Virginia contractor's licence is required for the licence category in which the contractor is to work.^[5] Check the licence before you pay a deposit.

Give the technician what you found: the display message, the fault history, when it last worked and what you already checked. More answers are in pool and spa answers, and you can find pool and spa businesses near you.

To get the heater looked at, describe the pool heater problem and licensed local businesses reply.