The Beta 240 is a (long discontinued) hot-tub spa-pak made by Aqua Spa Pak.   There is limited information about this unit available online, and the intent is to provide as much information as possible as I troubleshoot and repair a unit that came with a house I bought.

For good background information about spa components, testing, and troubleshooting, I recommend the Spa Repair Handbook from Central Spa Supply.  I have also received helpful information and advice from Poolside  Spa Sales & Service.

Safety Precautions

The standard precautions for working with electricity apply, especially as this is a 240V unit and is usually located near water. Don’t even consider opening up your spa-pak if you don’t know what you are doing around high-voltage electricity.

Check water temperature with a thermometer, especially when troubleshooting issues with the thermostat and/or high-limit switch and use extreme caution around water hotter than 104F.

General Description

All components in this spa pak use 240VAC supplied through the “panel” side of a GFCI breaker.  The load-neutral leaving the GFCI breaker is not used as none of the components require 120V, but the line-neutral (white pigtail) must be connected for proper GFCI protection.

The two-speed pump runs whenever the pak has power.  The motor is protected by two 20A fuses on L1 and L2.  A latching air-operated switch connects L2 to either the low-speed or high-speed windings of the pump’s motor.  Pumping the plunger (mounted tub-side) forces air into the switch and toggles between speeds.

The heating element will turn on, and the lamp will illuminate only if:

  • the high-limit switch is below the max temperature (normally closed) – somewhere around 120F
  • the pressure sensor detects adequate water pressure around the heating element (normally open)
  • the thermostat is calling for heat (depends on the dial setting)

The pressure sensor is in series with the thermostat, requiring both be Closed/ON before the main contactor will close.  The high-limit switch controls the second contactor, which is normally closed unless an over-temperature condition is encountered.

Schematics and Drawings

The only information I could find online is the Aqua Spa Diagram, which in my opinion is not an accurate diagram nor one that is easily interpreted, so I drew a proper schematic.

Aqua Spa Pak Beta 240 Schematic

Beta 240 Schematic – Click for PDF.  The symbol used for the motor indicates 3-phase, but in fact the motor is single phase 240V with high and low-speed windings.

Here is a photo which has been annotated to show the locations of all the components:

spa pak photo

Click for PDF

Test Measurements

  • Heater:  11 ohms
  • Contactor Coils: 900 ohms
  • High-Limit Switch: normally closed, opens when bulb heated with blow torch.
  • Pressure Sensor:  normally open, closes when pressure is applied (use a bicycle pump)
  • Thermostat: open when rotated fully counter-clockwise.  Should close when rotated clockwise.
  • Contactors:  normally open.  #2 should close immediately when power is applied, #1 should close when pressure is present and thermostat calls for heat.

Component Details


  • Switching Voltage: 240V AC
  • Switching Current: 20A (min)
  • Coil Voltage: 240V AC (min)
  • DPST
  • Normally-open
  • Chassis-mount

GFCI Breaker

  • 50A breaker
  • 240V
  • 2-pole
  • 5mA ‘trip’ current

Quick Fixes

  • Use sandpaper to clean up the contacts on buzzing contactors.
  • Use gas line to replace old/cracked pressure tubing for the Hi/Lo switch or the pressure switch

Go Digital

After a while messing around with these “analog” components, I decide to replace one of the contactors, the theromstat, and high-limit switch with a temperature-controlled relay.  I built one myself using an Arduino and a 1-Wire temperature sensor (details here).  It has the added feature of transmitting temperature readings over a wireless network, which I send through an XBMQ gateway to Thingspeak for logging and graphing.

Hot Tub Temperature Graph

Bringing fresh water up to temperature.

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