The wonderful thing about switches and relays is...they really aren't that hard. Believe me if the Fabulous Spa Babe, in her bold beginning could somehow figure them out then it can be done! Everything you need to troubleshoot your hot tub switches and relays. You may want to print this page for a reference tool.
We start at the beginning....


First of all electricity follows a path provided by  wires and switches. A switch is simply a device that provides a bridge for electricity to cross (or not)  between two contact points or poles.  When the switch is closed it allows the electricity to follow the path through it.  When  "open"  there is no bridge, therefore no path.

A simple "single pole" switch when closed (on) allows power to go through and light a light bulb for example.  When open (off) there is no path...no light.  These switches are also known as single pole single throw switches...one way in for electricity...one way out.

There are many single pole switches to be found in any spa system.  Testing them, to be sure they are working requires being able to activate the various switch activation mechanisms found and testing for continuity through the contact points...ie where the wires connect.  Removal of the wires from these "contact"  poles is necessary so that you aren't getting feedback from up or downstream.  These are power off tests with your multimeter set on ohms.  Since knowing how to activate the switch is part of the battle, we'll go through all the single pole switches found in spa systems:

Thermostats (electromechanical) can be activated by turning them up with the power off.  If you listen carefully you will hear a faint click as you turn the temperature knob up.  That is the sound of the switch closing.  You'll also hear it as you turn it down.  If you remove the wires from each side of the T'Stat and place your meter probes across the poles you should have continuity (almost zero resistance) when you close the switch.  when you turn it down you should have no continuity after the switch "breaks."

High limit switches have a reset button that pops out when tripped.  This opens the switch allowing no path.  If the button is not popped out you should  have continuity through the poles of the high limit.

Pressure Switches, which normally operate by water pressure on a bellows that pushes up a little rod that presses on  the switch activator, must be manually activated which can be a little tricky because the activating button is underneath the microswitch.  You have to stick a little flathead screwdriver in there to activate the switch because with power off you'll have no pressure.  Don't forget to remove the wires from it to test it.

Time clocks have switches too.  If your troubleshooting a time clock on a portable spa control, First determine which wires are the time clock  motor wires.  These are not the poles you want to check.  You want the time clock switch wires.  If you look you'll see a diagram that shows the switch symbol...something like this:  --/ -- Those are the poles to remove the wires from and check.  Activate the switch by turning the knob clockwise until it clicks.

NOTE:  An important fact that may help is that usually only hot legs are switched. You'll notice that most neutrals (whites) are tied together and only serve to "complete the circuit."  Neutrals will be found on coils of contactors and relays but are rarely "switched."  That will become more clear to you as you delve into your system.

Now that you've learned about single pole single throw switches it's time to move on to another common switch type found in spa systems...single pole double throw.  The spdt switch allows for two separate paths for the electricity to follow.  Power enters this switch via a "common" pole.  When the switch is not active the bridge to the "normally closed" or NC  pole is closed.  When the switch activator is engaged the bridge to the "normally open" or NO pole is closed.  It is the spdt switch that provides the basis for the relay logic necessary to run spa systems. Air activated relays  often  use spdt switches. For instance, almost all portable spas utilize a two speed pump motor.  This motor can run on high speed or low speed but not both.  Feeding power to both the low speed and high speed windings at the same time causes a frightful noise with an overload lock out  in less than a minute.  This is prevented by the use of single pole double throw switches.  The common pole of the switch carries the power that will be used to run both high and low.  With the switch at "rest" the low speed runs.  When the switch is activated the high speed runs but never both together. Cool huh?

Now consider the fact that in a 120 volt spa you have a heater that can only run with the low speed pump,  The heater cant run with the  blower only...because there is no pump running and it will burn up. High pump and heater can't run together there isn't enough current at 120 volts/20 amp circuit  Obviously there would be an overload with high pump and blower together...Now you get a sense of why there are banks of relays to handle this logic....

The Common Microswitch is found on many different relays in an electromechanical system.  Your Pressure switch is likely to have one,  Flow switches use them, Relay banks use them. Air receiving relays have them as well.

Now that you're feeling more comfortable with switches lets move on to relays.  While essentially a switch is a relay it does "relay" power along, some relays get a little more complicated in that they usually serve as a mount for several switches and can be powered by air (air receiving relays) or a magnetic coil.

Air receiving relays receive the air that is passed through the tube connected to your button spa side.  They are of two types...latching and non latching (or momentary.)  Latching air receiving relays actually run equipment.  They will directly feed pumps, blowers, lights and even heaters. They can come with one microswitch or two or three.
There are four function "cam" action air receiving relays that can run every piece of equipment in a 120 volt portable spa.  Pump...pump and blower... blower only.... and low speed/heat with T-stat demand.  When you  press your button on the spa the force of the air moves an arm that comes up and turns a cam that activates the microswitches in sequence.

Momentary air receiving relays generally send a pulse of electricity to the coil of a coil activated relay.  This causes a rod or plunger to move and in various ways activate a switch or switches on the relay.  When you push your button again it again sends a pulse which will cause the relay to move to another position or move back to the original position.

A word about coil voltages... while 240 volt coils and 12 volt coils are not unheard of most likely your coil voltage will be 120 volts.  Be sure of it though. It should say on the coil what the rating is.  It will also say what the switch rating is... study it to be sure you know which is which.  On potter brumfield coils the number at the top is the coil rating.

Contactors are a heavy duty relay that allow for heavier current flow, like to a heater.  Supply wires to a heater are large wires.  Contactors have the capacity to handle the wire size and the current flow but are activated by coils.  This allows for smaller wires to be used through the control loop: T-stat, hi limit, pressure switch to the coil of the contactor.

Many spa systems utilize cube relays which are type of coil activated relay that does not use a microswitch.  They are hard to troubleshoot because you often cant see what they are doing.  The coil poles are at the very bottom.  Common poles in the middle and normally open on top of that.  Often the normally closed poles are snipped off but sometimes present...they are at the top. USUALLY but not always left and right is electrically isolated.  These can be replaced with Potter Brumfield S 87 R 11 which is a coil activated relay with 2 microswitches.

Basic troubleshooting of switches and relays requires  understanding the above and knowing how your spa works.  If your complaint is no heat for instance and you have established that you have flow and know your high limit isn't tripped you must isolate the circuit and backtrack through it.  Knowing that your heater and low pump will work together helps.  If turning up your t-stat activates your low pump but not your heater contactor then start at the coil of the contactor.  Power on...call for heat..meter set on volts:  Measure voltage across the coil of the contactor.  If you have 120 volt there then your contactor should be activating.  If it's not  its bad.  If you measure no voltage at the contactor then your problem is upstream of it.  Look for where it stops.  Do you have power to the t-stat? Out of it? to the high limit?  Out of it? to the pressure switch? out of it?  Just trace the path.  If you have power in but not out... that will be your problem component.

The big thing to remember when you open up your box and the words "oh God" come unbidden to your lips is that you will be tracing individual problem circuits.  Sometimes I do sit for awhile and contemplate the why did they do it like that concept but if I've got a heater not working I'm only working with the  heater circuit and maybe the low pump circuit.  You can easily isolate each component by following it's power cord into the box.  Two speed pumps have 4 wires...red black white and green.  Red is usually low.  Blowers have 3 wires. lights have 2., heaters may have two or more see heater troubleshooting for clarification.  Spa side controls with Thermostats and air buttons  have 6 wires. The ones you are concerned about are the red and the black.  Black is power to the thermostat... red returns it to the contactor or heater relay. Just FYI the other wires of the 6 White neutral, green ground, yellow indicator light for jets, orange indicator light for blower.

There are some manufacturers out there that really do like to confuse us. Systems that have a lot of cube relays jumping from one to another  can be difficult to troubleshoot... even for me!  The relay activates another relay and you can't visibly see the action of the dern thing.  that's why I really like the NuWave.  Clean Reliable easy to troubleshoot. Easy to see.  Check it out... specially if you have one of those cube relay nightmares!
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