A Guide to Hot Tub Electrics

Hot Tub Electrics

Hot Tub electrics is kind of essential. If you have opted to heat your Hot Tub with an electric heater, you are going to need electricity. Pretty obvious right? OK, but in most instances, it is not just a case of plugging into an outlet. You need to have a dedicated supply for your Hot Tub. But what does that look like? In this article, we’ll explain a bit more about the electrics and requirements for your Hot Tub.

Dedicated Breaker for your Hot Tub

When you are planning your Hot Tub electrics, it is important to take into consideration the electrical requirements. Most of the time, this is one task that you are going to need to get a professional in. Doing it yourself is dangerous and can also, in some cases, void insurance policies and the like. That said, it is important to understand what you need to ask your electrician to do for you.

Firstly, you need to have, or it is recommended that you have your own breaker. This basically means that on your fuse board, you have a dedicated fuse that is just for your Hot Tub. If the Hot Tub trips the fuse and turns off, the rest of your house is left on. This is how it should work.

The size of that breaker or fuse will depend on the kit that you put into your tub and we’ll look at that later in this article.

Dedicated Outdoor Rotary Switch

Durning the planning stage of your Hot Tub, you should consider where you are going to place the outdoor rotary switch. This is the switch that in the case of an emergency, you can turn off and kill the power to your Hot Tub. A key component in hot tub electrics.

This is simply a rotary on/off switch but should be sited more than 2 metres (6ft) away from the hot tub so that bathers cannot be in the hot tub whilst touching the switch.

hot tub electrics

The electrician should fit a suitable weather proof block connector to the end of the tail from the isolator, the hot tub supply can then be directly hard wired into the weatherproof block connector inside the hot tub. Waterproof gland packs should be used to prevent ingress of water on all electrical connections (2 at the isolation switch). Ensure that all earth cables are clearly colour coded with green/yellow insulating tape or earth sleeve.

The size, or current rating in Amps of the switch will depend on the kit that you put in your Hot Tub.

Outdoor Cable for Hot Tub Electrics

When you are running cable from your fuse board to your rotary switch and then out to your control room, you need to make sure that you are putting the right gauge and type of cable.

In order to deliver the correct amount of current and not overheat the cables, you should be as a minimum putting in 10mm cable as this should be rated for up to 65 Amps.

The 10mm size is the cross sectional area of the individual live or neutral wires. This is not the combined cross sectional area. This bit is important as if you put wire that is too thin in your system and draw too much current along it, they will overheat and in some cases, will actually melt! Hence the need for a qualified electrician. You should be asking for cable that is capable of delivering 65A.

Armoured Cable

If you are running cable outside, for safety, it really should be armoured cable. This means that if you accidentally stick a garden spade through it, you will not get through to the cable and will not get an electric shock.

In my case, I attached my own armoured cable the length of the garden to the wall. (that alternative is that you bury it but it should be 2ft down which is a lot of digging) I went for the fixed to a wall approach and also chose armoured cable as I didn’t want to worry about my kids to driving their bikes and toy cars into it.

Its more expensive for sure, but it is worth the investment for that peace of mind.

What Voltage and Frequency Do I need?

Regarding the frequency and voltage, you have to make sure that you are supplying the right amount of electricity (current) at the right voltage and at the same frequency that your heater and pumps are designed for. For example, in the UK, the voltage is 240V and 50Hz. In the USA, the standard outlet is 110V and 60Hz.

What I am emphasising here is that you cannot take a heater from the UK and plug it into the USA supply and expect it to work. Don’t worry, all the pumps and heaters that we supply are specified for the country in which they will be used!

Also with pumps, the frequency is the rotation rate which again is linked to power. Something that rotates at 50Hz is rotating 20% less than something at 60Hz. So a 50Hz pump will be rotating 20% faster than designed and will overheat on a 60Hz supply – so they need to be designed to run on the correct frequency.

I’m in the USA and being told I need a 240V Supply – is that correct?

Yes, this is correct. To run a Hot Tub in the USA you are going to need 240V @ 60Hz.

You may see if you Google around pumps and heaters that are rated at 110-120V, 60Hz. To be honest, trying to take a short cut here and not making the right adjustments in your electricity supply is not going to work. Spa Packs (heaters) and pumps that will run on 110-120V are just not powerful enough. At 120V, you will only get something like 1.4KW of power to heat your Hot Tub which is not enough. Switch that over to 240V and it will now provide you with 5.5KW of power which is more more useful to heating your Hot Tub. 

Don’t Worry, the chances are you already have 240V into your home!

The USA electrical supply is 120V and 60Hz as standard (sometimes is referred to as 110-115V). However, most homes in the USA actually have a split system 120V supply into your homes in the USA. This means that there are two supplies of 120V into your home, again, this is the case in most cases.

hot tub electrics

Image Credit – www.signatureinspectionshawaii.com
  • What this means for your Hot Tub supply is that you can take a feed from your main consumer unit/meter from 120V L1 (line/hot 1) and 120V L2 (line / hot 2) which supplies a total of 240V @ 60Hz which is what you need. Some domestic appliances do this already like cookers and washing machines that need more power. The red circle above shows hot this outlet for our Hot Tub would be wired to get 240V.
  • Your electrical contractor will be able to tell you more about this. In summary, the chances are you already have the 240V supply that you need into your home and your electrical contractor just has to wire this up correcty for your Hot Tub.

Why Do I need 240V?

This comes down to a current versus power thing. It is very hard to generate a powerful pump at 110-120V the amount of current needed would be astronomical and arguably dangerous. This would add up across the total system when you add all the individual parts all drawing current which is why the parts are designed to run at 230-240V.

How do I calculate the amount of Current that I need?

All of the electrical components that will be in your “Control Room” will have a current rating. We’ve already established that they are going to be running on 240V @ 60Hz, but how much current do we need?
Each component’s manual or spec sheet will tell you how much each component will draw current wise on full power. For example, a pump might only draw 2A on low speed, but will draw 20A on full speed. (we note down 20A)
  • Your blower might draw 5A on full speed (we add that to the 20A + 5A)
  • Your Spa Pack on full heat might draw 32A (we add this to the 20A+5A+32A)
  • Anything else that you have connected to that supply will all draw current. Lights, TVs, Stereos, you need to add these onto this number.
In our example above, we are at 57A. To be on the safe side, I would be asking my electrician for a 63-65A supply so I know that I will not be at the limit when all components are running on full. Also, when pump kick into full power, there is a bit of a spike on the current draw so you need a bit of extra head room.
Generally, you will need a 60-65A supply for any components that we supply you. We will of course be able to advise you exactly what you need if you purchase the kit through us.

Check List for your Hot Tub Electrical Supply

Here is what you are going to need your electrical contractor to put in place for you
  • 240 V Supply @ 60Hz
  • 60-65A Fuse / Breaker
  • 60-65A Rotary Switch / Isolator
  • 10mm core Armoured Cable (capable of delivering 65A of current)

Final Thought

Please, please please get an electrical contractor to do this work for you. Get it wrong, with the levels of current we are taking about in a Hot Tub setup and the mistake could be very costly indeed, and I don’t mean in the wallet.

Happy ‘Tubbin


Can I Help You?

If I can help you in any way I would love to hear from you. You can get in touch using the form below.

Thanks - Andi


Hi, Andi here. I own Buildahottub.com and also write all of the articles and info pages on the site. Some years back now, I built my own hot tub but struggled to find the information I needed. So, once my tub was complete, I started this website to help others in their own pursuit of hot tub and plunge pools DIY building information.

Today, I've helped over 1000 DIY customers just like you all over the world build hot tubs and pools. Have a good look around the site, there are lots of resources here. Please do get in touch if I can help you. - Cheers, Andi

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