.: Hot Tub electrical information

Hot tubs come in various sizes ranging from the cute, two person “Soft Tub” to the very large multiple person party units.

120 Volt Units

Some of the small tubs have a 120V 20A power requirement, which means that you can just plug them in to a handy receptacle. I have even seen large tubs set up for 120V power supply. When this is done it takes forever for the tub to warm up due to very little amount of power flowing through the heating elements, I do not recommend this way of installation for the large units.

A note of caution here is that the tub will consume most of the circuit capacity so that if you use something with appreciable draw (hair dryer, microwave or other appliance or electric tools) the circuit breaker can be tripped. This is why it is best to run a separate circuit for the hot tub no matter what size it is.

240 Volt Units

Let us start with the two fixed placements.

1) Where is the electric service panel? Preferably the main panel since we will be pulling around 50 Amps of 240 Volt power. It is usually located near a front corner of the house.

2) Where is the hot tub located? Most times this will be located in back of the house.

Power to the Hot Tub

1) Where is the hot tub? Is it on a deck connected to the house or on the ground?

2) Is the house on a slab or is there access under the house?

House and Hot Tub on slab

Let us start with the house and the hot tub on a slab. This scenario tells us that we will need to run the whole power supply line in 1” Schedule 40 PVC conduit in the ground 18 – 24 inches deep depending on jurisdiction. Above ground it has to be in Schedule 80 PVC.

We run the conduit from the main panel down into the ground to the back of the house where we come out of the ground and enter the GFCI disconnect/Spa Pack.

Note: the above is for a surface mounted panel, if yours is flush mounted (or in the wall) then you will need to use two 45 degree sweeps to get into the bottom of the panel. This is quite easily doable, and chalking fills in any excess opening created during the installation process.

The power to the hot tub is required to be Ground Fault Circuit Interrupter protected (NEC 680.22 –A5). This GFCI protection panel (Spa Pack) is to be not closer than 5 feet from the hot tub, yet within site of the unit no gates or walls (NEC 680.24 –B2b).

The conduit then runs back into the ground and out to the hot tub where it re-emerges from the ground. The power feed into the hot tub is usually on the left side of the unit facing the removable access panel. Some units have built in PVC flex conduit leading to the power panel. If your unit does not have the flex already installed then you will need to install some 1” PVC Flex.

Wire selection

Now comes the fun part, pulling in the power wire. Most of the large units require 50 Amps of 240 Volt power. To provide that we will need #6 THHN stranded copper wire. You will need four (4) pieces for each of two runs. From the main panel to GFCI then GFCI to hot tub. Be very careful to measure accurately, Measure from the inside top of the main panel to the trench bottom, the length of the trench, then up into the Spa Pack plus six (6) inches. Next is Spa Pack to hot tub. It is always better to have an extra two feet of wire that you don’t use than being 4 inches too short.

The four runs of wire are:

120 V -- Black

120 V -- Red

Neutral -- White

Ground -- Green

The colors are for identification, I do not buy #6 in all of the colors, I use colored coding tape to mark approximately two feet of each end of the wires. Inside of the hot tub control panel they are very good about identifying where each wire goes. It is also time to start filling the hot tub. Now back to the Spa Pack, the red, white and black wires attach to the bottom of the GFCI breaker with the green on the ground lug or bar. The wires from the panel attach to the ground bar (green) neutral bar (white) and the breaker feed lugs (black and red).

We are almost there, now back to the main panel and install a two pole fifty amp breaker (2P50) that is designed for your panel, connect the white and green wires to the neutral/ground bar and the red and black to the breaker. When the tub is full of water then you can turn on the main breaker, the GFCI breaker and start the hot tub from its operating panel. It will take a few hours to heat up. It is fun to check out all of the jets and other features of the tub.

Small 120 Volt tubs

If you are supplying a small tub that only requires a 20 Amp 120 Volt circuit then you use half or three quarter inch PVC conduit and three #12 gage wires, black, white and green. You can also use a standard GFCI receptacle mounted on the side of the house or post within the reach of the hot tub attachment cord.

Raised houses and decks

If you have access under your house and the tub is on a deck you can eliminate a lot of digging by just running the conduit under the house and deck. You follow the same procedure as above only no digging. If there is no flex conduit already installed, I come into the service section directly from the bottom of the deck. Using a 1” 90 degree sweep I determine where I will drill my entry hole, from inside, through the base of the hot tub and connect to the power feed conduit from the GFCI/Spa Pack under the deck. I also do not glue this last sweep until I have pulled in the power supply wires. That makes for an easier pull with less 90’s to pull through.

Now it's time to relax in your new hot tub.

* NEC = National Electric Code

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