Hot Tub Technical guide on:
How to test and adjust a pressure switch
The following guide relates directly to pressure switches, what they do, how to test them and how to adjust them. They are normally found connected to the heater tube inside the hot tub but can also found fitted to the plumbing near the heater as well.
Images of pressure switches. (hover over image for name and link).
What does the switch do?
Pressure switches are specifically a safety device that will restrict electricity getting to a heater or element in a hot tub if a lack of pressure is available. They can save expensive parts getting damaged and even fires, it is important to note at this point their are also 2 other safety devices that also restrict power to the heater which are the thermostat in the tub and the high limit strapped to the heater tube its self all of which control relays on the PCB (Printed Circuit Board)..
Testing a Pressure Switch
The easiest way to test a pressure switch is with a multi meter, simply disconnect the spade connections connecting to it and dial your multi meter to buzz test, when the pump is switched of it should give you an open circuit (no buzz) and when the pump is on and its working correctly a buzzing noise on both low and high speed, if it only buzzes on high speed you have a low pressure issue.
The other ways to test this are not as accurate and could also indicate other issues, for example disconnecting the pressure switch whilst the pump is on should give you a flow error (FLO or ...) but simply this could also mean that you have a restriction of flow i.e.. a blockage, dirty filter scale issues or a faulty pump.
Using visual fault codes like flo on the control panel
The problem with pressure switches are that they are an indication of pressure, and their fore a safety device that says something is wrong, their are so many possibilities from dirty filters to badly engineered hot tubs that cause errors on a hot tub, even air in the pipe work via low water level will cause the switch to fail. So make sure you have covered all the basics first, remove the filter, check the pump is working correctly, check water level, look for blockages and compare the pressure coming out of the jets so on...
Note just the bends and restrictions of plumbing will give enough back pressure to trigger 1 bar of pressure which is also the same amount a pressure switch is usually set to.
Adjusting a switch
Most pressure switches can be adjusted by turning a dial or rotating a nut, but this is not advised due to masking other errors in a hot tub.
If you must adjust then here is how to adjust a Tecmarc or Balboa pressure switch.
To adjust the Tecmark Pressure switch screw inwards to reduce the amount of pressure required and on the Balboa switch screw out to reduce the gap between the button and the switch.
Note on Balboa switches - you can test the switch is working correctly by pushing it upwards, and if the switch is leaking or heavily corroded replace it.
Types of pressure switches
The most common switches on the market are made by Balboa and Tecmark who make switches for Gecko as well as allot of swimming pool manufacturers.
This guide was written by Jon Pennington @ Hot Tub Help Ltd for the Website www.hottubdiy.co.uk.