This is the beginning... kindergarten on hot tub repair. Here we will discuss the VERY basics and lingo.
Hot Tub or Spa? I think Jacuzzi started to confusion because they were the original leader and sold both inside jetted baths and hot tubs. So it created confusion. Customers still call their indoor jetted bath a "hot tub". But most common is the unit outside is a hot tub. Spas could be either.
Where should you place a hot tub? Designers and homeowners like hot tubs dropped into a hole or built around. They look good. Repair men hate or can really love that setup. Why? The deck builder surrounds or build-in the hottub. 2 years later something is wrong. You can the repair guy... even under warranty. He comes and charges you a minimum trip/travel charge and often the first 30-60 minutes. Hot tub warranties typically do NOT cover the trip/travel charge from the shop to your house. So the repairman says "where is access?" You say the builder said it was adequete. You soon realize it is not. Repair guy charges you trip/travel/labor (even under warranty) for the trip $100-150. No repair. Blasted! Repair man happy because he really did nothing but said you don't have access. EVEN THOUGH... their is front access... Why? The issue might be on the side, or back.
So service guys like/prefer full access on all sides. Because the service guy typically will not make access, you will have a reschedule and pay for the trip.
Surface to place the hot tub. I have seen great ideas and very, very poor idea. One hot tub was placed on the deck that was suspended on the side of the mountain. No modifications to the structure. All I could do is wonder if/when the deck would separate from the house. Hot tubs are heavy when full of water. The deck or whatever surface you place it needs to be able to handle the weight.
Most common is the back patio/cement. Typically the pad will be sufficient. One thing is the pad must be FLAT. One customer had a friend pour a pad. The unit was leaking so I was sent to investigate. You could see a 2" gap between the hot tub and cement is some areas. The pad was wavy. Manufacturer voided the warranty. So pad must be flat. It can have and likely should have a slope to it to move water away from the house and pad.
Bricks, pea gravel, sand, etc can be used IF the soil below it is stable. I have very sandy soil. I brought in pea gravel and boxed it in and leveled and placed several hot tubs on it over the years. Even with water leaking the soil does not shift. Water runs right through and back to China. But other types of soil that shift and settle be very careful of a "flat" surface that settles over time. Gaps in support to the hot tub will cause damage.
Lastly in the industry are panels that snap together and provide a surface for the hot tub to sit on. As mentioned above, if you have stable soil below, they should work fine.
Electrical Power. Hot tubs operate on either 110-120vac or 220-240vac. First critical step is provide either with a GFCI (ground fault circuit interrupt) to protect you and your family. The GFCI could be built into the control box unit (not common), on the cord (110-120vac only), or most common, a subpanel or main house panel. The purpose of the GFCI or GFI is to trip when micro-amp shortage occur. In your house panel you will see breakers labeled 15a or 30a or something like that. What that means is if more than that amperage is drawn by that line it will trip. For most electrical lines thats fine. BUT there is a real danger mixing water and electricity (duh). So the electrical world came up with GFCI. Rather than sensing for 15 or 30 amps, it senses micro amps short. Most homes commonly have them in kitchens and bathrooms. They have a "TEST" button on them. So an appliance starts shorting the GFCI senses it and trips. Doing so protects you from getting shocked or worst, electricuted.
So your spa typically operates on incoming 115v or 230v gfci protected line. That said, most 115v have a heavy cord with a gfci breaker built into the cord. Plug the cord into a dedicated 115v outlet and the spa is up and running. Dedicated means that the electrical line only has the spa attached to it. An electrical line with a refrig or cooler or many lights AND a hot tub will likely damage the hot tub due to lack of current. Nice part is spas operating on 115v can often be taken home, placed, filled, plugged in, and you have a hot tub. Downside of 115v is it takes a long time to heat. Most 115v hot tubs heat about 1-2 degrees PER HOUR. So it takes days to heat your spa up.
The more common is 220-240vac. A few spas will use TWO 220v lines to the spa. Most new spas used a single line, 230vac, 50 or 60a circuit. Most warranties require 6 gauge wire. Also consider the length of the line from the house box to the hot tub. I had one customer who placed the hot tub away from the house next to a cliff. A GREAT view. I could imagine setting there in sunset hottubing. BUT.... the distance from the house to the hot tub caused the line to drop in current enough that he would damage the spa component in less than a year. Once he had the electrician come and upgrade his service to 6 gauge the problem was resolved.
220-240vac service will either be 4 wire or 3 wire. 4 wire are 2 hot, 1 neutral, and ground. 3 wire are 2 hot and ground. The difference is the needs of the spa itself. If any components in the spa require 115v, then you need a 4 wire service. If all components are 230v, then you only need 3 wire service. Either way, it must be GFCI protected.
GFCI protection is installed one of two ways. First a most common is inside the main house panel. It will be 50-60a and have a TEST button on it. The line runs from the house directly into the control box. FYI national code requires a quick disconnect box close but not too close the the spa. Its there in case the spa users needs to immediately turn power off. Consult your master electrician for code standards.
Some electricians will install a simple 50-60a breaker at the house panel and somewhere near the hot tub a "sub-panel". This sub-panel will house the gfci protected breaker. This will allow the customer to turn the spa off without going to the house panel. It will also be the likely breaker to trip.
Is your spa 115v or 230v? Most spas are 220-240v spas. Some are 115v. Many 115v can be "converted" to 230v. The control box or manual will tell you if yours can. One thing to note that the conversion on most spas ONLY affect how well the heater heats and when. When operating a spa on 115v the heater will likely turn OFF when the pump is on HIGH. Reason is the 115v can not handle enough current to feed both heater and high speed. Converting to 230v will eliminate that. One note that you usually have to do a wiring and sometimes a programing change to make this happen. Programming is normally optional but wiring is critical. So converting your heater can now stay ON when on High pump. Second and more important is the heater typically is now operating on 220-240v. This will change the 1-2 degrees per hour to 5-6 degrees per hour. So the spa will heat faster and maintain temp better.
Remember, some 115v hot tubs can ONLY be operated on 115v; you have no conversion option.