Hot Tub Pump and Heater Control

Electrical Circuit Control for a Hot Tub Heater and Pump – Install a relay that would be activated when the pump is turned on by the Intermatic Time Clock. The HydroQuip electric heater circuit would be connected through the set of contacts of the relay.

How To Control The Heater and the Pump
Electrical Question: Can I interconnect the heater and the pump with a switch or relay to ensure that the heater fires only when the pump is in the low-speed “on” cycle?

• My 500 gallon cedar hot tub is heated by a Hydro Quip 11 kw electric heater (230v 60 amp). The pump is a SuperFlo 1.5 hp two-speed (230v 20 amp).
• The heater and the pump are wired completely independent of each other and are not interconnected. As a result, the heater high-temp limit switch frequently trips if the heater fires when the pump is in the “off” cycle of the time switch (The Intermatic time switch is simply set for pump to cycle on/off every four hours).
• Eventually, the high-temp switch fails and needs to be replaced, I suspect this is due to heat spikes occurring when the pump is in the off cycle (?) My question is: Can I interconnect the heater and the pump with a switch or relay to ensure that the heater fires only when the pump is in the low-speed “on” cycle?

Thank you!

This electrical wiring question came from: John, a Handyman from Ridgefield, Connecticut.

Additional Comments: Excellent; Very Informative.

Dave’s Reply:
Thanks for your electrical wiring question John.

Electrical Circuit Control for a Hot Tub Heater and Pump

Application: Hot Tub Heater and Pump.
Skill Level: Intermediate to Advanced – Best performed by a Licensed Electrician.
Tools Required: Basic Electricians Pouch Hand Tools and Voltage Tester.
Estimated Time: Depends on personal level experience and ability to work with tools.
Precaution: Identify the hot tub circuit, turn it OFF and  Tag it with a Note before working with the wiring.

• Johns questions are  specific to his application, so for the benefit for everyone else here is a summary of the solution.
• Install a relay that would be activated when the pump is turned on by the Intermatic Time Clock.
• The HydroQuip electric heater circuit would be connected through the set of contacts of the relay.
• The relay coil voltage must match the pump voltage and the relay contact rating must match that of the heater specs.
• IMPORTANT NOTE:
  • In freezing temperature areas a freeze stat could also be added to override the time switch to prevent possible freezing of any parts. Insulating wherever possible will help as well.
• All of the hot tub electrical equipment must be GFI protected.

More about Wiring a Hot Tub

• Hot Tub Wiring
• Wiring Diagrams

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Wiring a Light Switch – Diagram 1

Electrical wire

• Electrical Wire for the Home
• Complete listing of electrical wire types and parts used for home projects with electrical code information serves as selection guidelines.

Hot tub wiring

• Hot Tub Wiring Diagram Information
• Electrical Codes and Details for Spa and Hot Tub Wiring. Essentials for your installation, including the required GFCI ground fault protection and circuit wire size.

Electrical relays

• Electrical Relay Articles
• This section will cover the use of relays that are sometimes needed to control special device loads such as Air Conditioners and other high demand equipment from starting at the same time.

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