spa parts, hot tub parts and repair help
spa parts, hot tub parts and repair help
spa parts, hot tub parts and service help
spa parts, hot tub parts and repair help
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Spa System Diagrams,
Air Side Controls
Diagrams Index


Spa and Hot Tub side control diagram, typical

This is a diagram of a conventional air control spa-side control panel using a capillary style thermostat.  Newer versions utilize an electronic thermostat and will have more components inside--namely, a larger PC board with integrated circuits and such onboard.

While not "exact" in nature, the diagram does represent the principles of spa side controls manufactured by Len Gordon's "Aqua-Set," Press-Air-Trol "Patrol," and Tri-Delta (now Tek-Mark).


Spa and Hot Tub Side Control Plug, typical This is the standard J&J Electronics-brand plug usually employed on these types of controls.  Newer versions will not have a ground lug. 

The wire colors and designations correspond to the wire terminations as shown in the above side control diagram.

Tech-Notes:
The ONLY active component in this spa side control is the thermostat.  The light indicators, air push-buttons, and thermostat have nothing to do with each other; it is simply a conglomeration of 3 different functions in 1 box.  Meaning, that if your indicator lights fail, and the thermostat gives out, the air buttons will still continue to activate the air switches in the spa control box.

(If your side control has an electronic thermostat, then the blower indicator (orange wire) will not be used for a blower light.  See the electronic version of this control online for details (-available soon-)

1.  The air push buttons.  They send air pressure through the tubes to activate and deactivate the air switches in the spa control.  These air buttons simply allow for electrical isolation between the user in the hot-tub or spa, and the control system.  They do NOT affect the thermostat's operation or the indicator lights.

2.  The indicator lights.  The indicator lights are simply neon bulbs.  These can  be found at Radio Shack, or techamerica.com.  Usually, when you disassemble one of these control boxes, the "Ready" indicator will be very black, and the "Heat" indicator will be running a close second.  Since neon bulbs effectively "short-out" when power is applied to them, current limiting resistors are used in series with them.  This is the primary difference between a 115V version of a spa side control versus a 230V type.  The resistors will be a higher rating on a 230V control, to prevent burning out the neon bulbs.

The way that the indicator lights work is that the air switch, or  relay in the control box, sends power back to the side control, to either the jets or the blower indicator  lines.  This will be the yellow wire for jets, and orange wire for the blower.  This is the de-facto standard in this industry.

3.  The thermostat.  The thermostat is a single pole, double throw switch (SPDT), activated by pressure effects in the sensing bulb.  When the pressure in the bulb is reduced (a cooler condition), the switch activates, sending power to the N.O. or "normally open" terminal on the switch.  This will have 2 effects on the control.

  • It will send a voltage signal to the spa control, (usually 115 or 230V), telling the spa control that it's time to get the heater turned on.  Using relays, this also turns on the low-speed pump, or the main pump in low speed mode.  (Not all control systems use the same method).
  • It will also send voltage to the "Heat" light on the spa side control, telling the user that the heater has been told to get the spa warmer. (But this does NOT mean that the spa is actually doing this!)
When the temperature gets to its high point, the switch in the thermostat will revert to the N.C. or "normally closed" position.  This, is the opposite condition. What happens is that the thermostat will...
  • Remove the "call for heat" signal to the spa control system, which turns off the heater, and if not in the filter mode, it will turn off the spa pump motor if it is operating in low-speed mode.
  • Revert to sending voltage to the "Ready" indicator on the spa side control, telling the user that the set temperature has been reached.


The spa heats up to 98 degrees (F), but won't go higher. I used to be able to get it up to 104 or 105 degrees.

In most cases, this can be resolved by resetting the set screw in the thermostat itself.  Here are some ideas on solving this problem.  This usually occurs because the capillary tube and the copper sensor has weakened over time and has expanded a small amount, causing the "top end" of the thermostat's setting to be lower than what was originally set by the factory.

Metro Atlanta Spa/Hot Tub Service
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