What’s a Hot Tub without a Heater? A Cool Bath!
In the second post in our “Help!” series, we take a look at the water temperature in your spa or hot tub, specifically, when it is lower than you want!
Temperatures of 100° to 104° are preferred by most hot tubbers, and nothing is worse than checking your spa temperature, and finding your thermometer dropping!
Troubleshooting a hot tub heater is a step-by-step process, to determine if you have a pressure problem, a power problem or a part problem.
Spa heaters need to have enough water flow, or more specifically, enough water pressure to operate. That is why your spa has a pressure switch, a simple device that senses the water pressure, or flow rate. When the water flow is high enough, the switch is open, or ON, which allows the heater to operate. When the pressure falls below the minimum set point of the pressure switch, it flips closed, or OFF, which breaks the circuit, and the heater won’t come on. Pressure switches are important safety devices, to keep a spa heater from running when there is not enough water running through the heater to absorb the heat being produced.
The high limit switch can also be tripped by low pressure or water flow. When the water slows down in the heater, this raises the temperature of the water as it exits the heater. Most high limits are set to trip when they sense water temperatures of around 140° . Tripping high limit switches can be another symptom of a pressure problem.
What can cause pressure (flow) problems? First, clean the spa filter cartridge, or replace if it’s over 2 yrs old. If your circulation pump has a strainer basket, check that it is clean. Obstructed suction inlets, clogged pipes, or clogged pump impellers can also cause flow problems, as can obstructed outlets, closed valves or closed jets.
Is the pump moving water at all? An Air Lock in the pump after draining and refilling is not uncommon. Is the pump on low-speed? Most heaters will only operate with the pump on high speed.
Rule out pressure problems first by making sure water is flowing as fast as it should be to operate the heater.
Power to the heater is the next thing to check. Specifically wires and connections. Locate your heater, and the wires that are connected, which should be very tight. Loose connections on the heater can cause overheating and hi-limit tripping, and even failed circuit boards. Inspect the wires for any frayed, chewed or burned wires.
Checking Voltage: If you are comfortable and cautious with testing voltage, you can check the volts on the heater terminals with a multi-meter, or AC volt meter. With the meter set onto AC volts, with a setting higher than 240V. With the thermostat turned up, and the pump running on high, touch or clip each meter lead to each terminal (at the same time), and you should see 220 volts, or something pretty close (215-225v).
If you do get 220V while touching to each heater terminal, but no heat, this usually means that the heater element is bad. Inspect the coating around the filament of the heating element, any cracks or chips and the element should be replaced.
If you don’t get any volts while testing the heater leads or terminals, check that a GFCI outlet is not tripped, as well as any circuit breakers. Make sure the thermostat is turned up. If you still get nothing, the circuit board is likely bad.
Checking Continuity: With power off, the two heater terminals can be tested for continuity. Place your multi-meter on the lowest Ohms setting, and touch each lead to each terminal at the same time. If the meter doesn’t move, the element is bad. If the meter does move, and shows steady resistance, the element is probably good, but could still have a short – inspect the element for cracks or chips.
Rule out power problems by testing for voltage coming into your spa pack, and verifying that voltage is reaching your heating element.
Heater Element: Heater elements can fail if the outer coating becomes cracked, corroded or chipped. And, they can also fail without any visible signs on the heater element. Checking for voltage and continuity, as described above can help determine your elements condition. Average lifespan: 5-10 years.
Filter Cartridge: Filter cartridges are not really a heater system part, but so crucial to heater operation. Clogged spa filters may look normal, but be full of small crystallized minerals covered in oily gunk. Average lifespan: 1-2 years.
Pressure Switch: When your spa filter, or suction intakes, or return jets are clogged, blocked or obstructed, the pressure switch will stay closed and keep the heater from working. The same if your pump is on low speed, or if valves are closed. A pressure switch can be easily jumped out with a wire and two alligator clips. Many spa pressure switches are adjustable from 1-5 psi, and sometimes the internal diaphragm fails, requiring replacement. Average lifespan 5-10 years.
High Limit Switch: The hi-limit switch often has a reset button located near the heater. You may experience occasional nuisance tripping, but repeated tripping indicates either low flow or a malfunctioning heater element. High limit switches can also be bad. They can often be jumped out, using a wire and alligator clips, to bypass the component temporarily, for testing purposes. Average lifespan: 10-15 years.
Thermostat: Older spas will have a manual thermostat that is turned with a knob. Often this is on the side of the heater unit. Some very old spa thermostats are adjustable with a small Allen key, but use caution not to turn up the heat to more than 104°. Newer spas will use potentiometers and sensors to control the temperature regulation via the circuit board. Average lifespan: 10-15 years.
Contactor: This is a switch before the heater, which confirms the voltage is regular. When so, the contactor closes and allows power to continue to the heat4er element. Some contactors are loud enough to be heard clicking into place when power is sent to the element. Contactors can become insect infested or can pop a spring occasionally. Average lifespan: 10-15 years.
GFCI: Your spa should have a GFCI breaker in the panel, and also may have a GFCI outlet connected to the spa pack. Ground fault circuit interrupters are very sensitive and they can become overly sensitive. These are safety devices which sense current going to ground, so when they trip repeatedly, this indicates that some small amount of voltage is leaving the circuit. They can also fail from time to time. Average lifespan 10-15 years
PCB: This is an abbreviation for Printed Circuit Board, the circuit board that controls the functions of your spa. Failures of the board are unfortunate and not too unc0mmon. They can result from improper or loose wiring, excessive moisture or heat, voltage spikes which ‘fry’ the board. Troubleshooting a pcb is difficult even for a knowledgeable person with equipment. Spa circuit boards can be repaired, but replacement can often be a cheaper, faster solution. Average lifespan: 10-15 years.
Rule out parts problems by testing each component individually. When a spa heater is not working, there is one or more component to the system that is keeping it from operating. And, as I’ve heard many electricians say, …“the problem lies, where the power dies! “
Happy Hot Tubbin’
Hot Tub Works