The essential part of any spa or hot tub is the control system. Without it, it’s much like a car with no engine. The control system is responsible for all the functions of the spa. It receives power from the main electrical circuit and then provides power to pumps, blowers, heaters, lights, etc. It’s also responsible for regulating heat levels, determining if any problems exist, and monitoring safety devices such as sensors and pressure switches. This guide explains what a control system is and what it does. We also cover how to go about choosing your replacement control system (retrofitting), as well as provide general installation instructions.
A control system or spa pack is an electronic system designed to control all the functions and power distribution for a spa or hot tub.
Here are the characteristics of spa control systems:
They use a keypad as an interface for human interaction/control.
They are responsible for providing power to pumps, heaters, blowers, ozone, lights, and other electronic components in the spa.
They are wired directly from the main incoming circuit breaker.
Most control systems can be wired 115v or 230v.
Control systems can be mechanical with air switches and relays, but most modern systems employ circuit boards and digital controls.
Here are the 2 main different types of spa and hot tub control systems
Two main types of hot tub control systems are digital electronic and old-school spa control systems. These systems work differently but essentially do the same job.
Digital control systems for spas and hot tubs (aka electronic control systems)
A digital control system is a type of automatic control system. Thanks to the built-in electronic feedback controller, it provides you with more instant information on the state of your hot tub. If any errors are detected within your hot tub's mechanics, an error message will appear on your screen, or it will automatically fix the issue.
Air control systems for spas and hot tubs (aka pneumatic control systems)
The other type of spa control system is an air control system. These are a less sophisticated type of system, mostly found on older spas or hot tubs, compared with feedback control systems as they are simply a valve with a single pipe plumbed into the jets with a knob that allows you to control the air output.
If you are wondering which control system you have, the easiest way to identify the differences between the two is to look at the keypad connection. If you have a modern digital keypad, you will generally see only one cord attached to the keypad to the main pack, whereas air systems will have additional cables attached to it.
Digital keypad for spa and hot tub electronic control systems
Pneumatic keypad for spa and hot tub air control systems
What does a spa controller do?
A spa control system is responsible for all your hot tub or spa functions. This essential hot tub component controls all other equipment, whether an old-school air control system or a more modern electronic spa controller.
Many people get confused between a spa controller and the keypad, which is on the outside of the hot tub. Although they are internally connected to each other, they are not the same thing. The keypad is the topside panel that allows you to ask your hot tub what to do, such as increase the heat or lower the pressure of the jets. However, the hidden hot tub spa control system performs these demands.
Depending on its capacity and configuration of the chosen model, a control system commands most of the equipment of your spa or hot tub.
The control system's role within a spa is evident as it keeps the entire hot tub running and allows you to enjoy your spa seamlessly.
What components are included with a spa and hot tub control system?
Not all control systems include all the items needed for a complete installation. Many only include the enclosure, circuit board, and heater.
Here are other components of a hot tub control system:
Plastic or metal enclosure box.
Most modern enclosures are water-resistant but not waterproof and must be protected from the weather. (Fig.1).
Fig. 1: Spa and hot tub control system enclosure
Fig. 2: Spa and hot tub control system with onboard heater
Onboard or remote heater.
Most systems include a heater that is mounted below, behind, or on the side of the enclosure (Fig.2). Some systems employ a remote heater that installs into the plumbing away from the enclosure and typically includes a power cord, and sensor cord (Fig.3).
Fig. 3: Spa and hot tub control system with remotely installed heater
Safety system components.
Safety system components such as sensors (Fig.4), pressure/flow switches (Fig.5), high limit switch (Fig.6).
Fig. 4: Temperature sensor for spa and hot tub control system
Fig. 5: Flow switch & pressure switch for spa and hot tub control system
Fig. 6: High limit sensor for spa and hot tub control system
Fig. 7: Keypad for spa and hot tub control system
Control system keypad.
Keypad (Topside Control) Human Interface Device (Fig.7). Often sold separately
Fig. 8: Spa and hot tub control system component cables
Bundled and retrofit control systems.
Bundled systems include items mentioned above as well as component cords for pumps, lights, blowers, etc. (Fig.8).
How does a spa and hot tub control system work?
A spa controller is designed to ensure that the user has to do as little as possible. Spas have the option to function using a closed loop control system or an open-loop control system, with most utilizing closed control loops.
This is because a closed control system automatically regulates itself, meaning it does not need humans to continuously change settings or control signals to keep the hot tub in check. A closed system also integrates feedback control systems within it, where a feedback loop will inform the system of any changes in regulation which can automatically reduce errors and general problems.
Capabilities and limitations of spa and hot tub control systems.
Every control system is designed with different capabilities. Some are built to accommodate a 115v plug-in hot tub with one pump, others are designed to accommodate swim spas with 5+ pumps. Most systems fall somewhere in the middle.
In past years, manufacturers were very specific on how many pieces of equipment their control system could run, what voltages, etc. Some modern systems are programmable to offer many different spa and hot tub configurations in a single system, making choosing the right one easier than ever.
Here are examples of capabilities and limitations of spa control systems:
Many control systems are only capable of a single configuration. For example, Dual Speed Pump #1, Single Speed Pump #2, and light.
Proprietary control systems are built to accommodate a specific configuration requested by the spa builder.
Proprietary systems are not generally compatible with generic counterparts or system components.
Universal systems offer many options to accommodate most hot tubs' specific needs and are easily retrofitted.
The first step whenever choosing a new control system is knowing what equipment is in your spa.
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