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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Thermostat Replacement or Calibration, With Side Control Housing Previous

Note that the purpose of this section is to show you how to increase the temperature setting or replace the thermostat switch on an electro-mechanical, capillary tube type thermostat switch. This requires disassembly and reassembly of the spa side control housing, or removal of the thermostat device from a heater casing, deck mounting plate, or other switch encasement, and the reassembly of the switch and its components. 

If you have a thermostat that has a very small COPPER or Stainless Steel tube coming from it, then you should be able to perform this procedure. Note that some later model controls utilize electronic or digital thermostats which do not have this small tube, and actually looks like a black inslulated wire. With this type of control, the ONLY recommended course of action is to REPLACE the entire control box or thermostat assembly.

Recalibration is NOT an exact procedure. Since these types of thermostats only provide relative indications of hot or cold water, replacement with a new capillary type thermostat is recommended for safety reasons. 

In view of the fact that most of these types of thermostats will lose their maximum temperature sense rating over time, and recalibration is all that is typically required, this procedure is presented to show you how an experienced spa technician may solve this problem quite easily, without actually having to replace the thermostat switch.

SpaSide Controls Explained

Safety Warnings!
Remove Power from the spa/hot tub BEFORE performing this procedure.  Failure to comply with this requirement, can lead to electrical shock and/or electrocution!

Thermostats of this type provide RELATIVE indications of temperature, (ie, hot or cold only), and re-calibrating a thermostat to make the heater perform at a higher temperatures is a SERIOUS procedure. Inappropriate or incorrect calibration can lead to overheating of the equipment, fire, melt-down of plumbing or jets, injury or death to occupants of a hot-tub/spa.

The calibration procedure illustrated here is AGAINST (not in accordance with) manufacturer recommendations, and will void your warranty.
Typical Side Control This is a typical side control panel for a spa. It will have air push buttons... maybe more or less than what is pictured here. The leading manufacturers of these side controls are Len Gordon, Pres-Air-Trol, and Tri-Delta (now known as Tek-Mark), however, the spa manufacturer's logo will typically be displayed on the faceplate. Using a digital health type thermometer is the best way to determine the spa water temperature, and the calibration of the thermostat device.

Temperature Check

If you're calibrating a thermostat device that is contained in one of these types of side controls, unplug the side control plug from the spa control box. It will have 5 or 6 prongs on it. UNPLUG the SIDE CONTROL!

Removal Lift up the corner of the face plate to expose the screws that are holding the side control to the spa shell. This may require the use of a knife or other sharp thin tool to pry up the corners. Use care to avoid damage to the face plate.

On some spas, the screws may not be made of stainless steel, and may be rusted beyond recognition. Typically, on these, the corners of the face plate may already be lifted up because of the rust. Do whatever is necessary to remove the screws. In many cases, the screws will simply snap off with a little prying or twisting of a screwdriver. Try not to do any damage to the plastic side control housing.

Remove the side control assembly from the spa and you will see 4 to 6 screws holding a bottom plate in place. You may have to break the manufacturer's seal in order to gain access to the thermostat compartment. 
Disassembly Disassembly

Removing the control internals Very carefully... pull the assembly apart. If you have a side control where the thermostat won't come out of the assembly, then click here for further instructions. Watch for neon bulbs that are attached to a printed circuit board; try not to disturb them too much. Be sure that when you disassemble the box that you observe the position of all components inside for re-assembly.

Typical assembly. Note the neon glass bulbs that are attached to the printed circuit board. Normally two of these will be darker than others, the HEAT and READY indicators. This is normal for neon bulbs. 

Now, if the objective is to replace the thermostat, remove the two or three screws holding the wires in place to the thermostat switch, and remove the old thermostat. Be sure to remember which wires go where. If your heater operation ends up working backwards (on when it should be off), then you switched two of the wires; (the ones that are right next to each other. Once this is done, skip to the reassembly section below.

Control View, Disassembled

Calibration action Calibration action
At this point, the only way to determine how LOW your thermostat has drifted, is to turn the thermostat SHAFT back and forth to hear the audible click of the switch mechanism. Visualize the point in rotation where the 'click' sound occurs in the ON position, (when turning the shaft clockwise). 

Remember that the idea here is to move the ON point farther BACK in the rotation of the thermostat shaft, in order to get the heater to make the water hotter. This is NOT an EXACT procedure that requires mental judgement on the part of the individual doing the calibration. All assumption for the results of this operation are your own.

Now, using an allen (hex) wrench, turn the calibration screw (accessible through the frame of the thermostat) clockwise approximate 1/4 turn at a time, until the thermostat ON position moves BACK in the rotation to a point that is estimably lower than the original setting.

As an example, (using a typical old thermostat in use in the field), the ON point with water that is in the 80 degree farenheit range, will normally be in the late 20% of the clockwise rotation, ie, midway through the HOT indication on the control panel. What I usually do is adjust with the allen wrench so that the ON point moves midway into the WARM area indicated on the control panel. This is typically at the 55% point in the thermostat's rotation. 

To complete this operation successfully, it will require you to go through quite a few on/off switch activations by rotating the shaft back and forth while you adjust t he allen screw.

The desired end result of this operation is a thermostat that allow the water to heat to a maximum of 104 degrees farenheit. However, if you have ANY doubt as to what you are doing here, your best alternative is to replace the thermostat with a new one calibrated at the factory, and not try to calibrate it yourself.

Reassembly Re-Assembly

Is simply the reverse of dis-assembly. Very carefully insert the printed circuit board into the provided slot in the plastic housing, and the thermostat at the same time, being sure that the index (flat spot) on the thermostat shaft coincides with the index on the plastic shaft in the control box. 

Once the box is together, be sure that the neon bulbs on the printed circuit board lay in the proper indicator "slots" of the housing, and that none of the attachment wires on the bulbs are twisted or shorted with one another.

Respecting the copper capillary tube, as well as the rubber seal around the base, mate the back of the the housing to the main body, insert the screws, and tighten them down.

Be sure that when you tighten the screws that you don't squeeze out the rubber seal. The seal should only be compressed a small amount... (NOT flattened!!)

Reassembly If you were able to remove the original screws without breaking them, and if they aren't rusted or corroded, reuse them and attach the control panel back into the spa mounting hole. Otherwise, use new screws.

If you had to break off the original screws, you can either try to drill them out (definitely NOT recommended), or apply 100% silicone sealant between the control box and the spa shell. Be sure to let it cure properly before allowing moisture or water from the spa to get on the control.

When you have finished the above procedure, plug the side control back into the control box, and re-energize power. The thermostat setting should activate the heater according to your adjustment.

Metro Atlanta Spa/Hot Tub Service
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