120v or 240v for Hot Tub?

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chetwynd

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General Contractor with electrical and plumbing classifications.
I'm installing a hot tub that can either be wired for 120v or 240v. It's interchangeable by using a jumper wire between two of the lugs.

Anyway, other than the water heating up substantially faster, what are the other advantages to hooking it up to 240v as opposed to 120v?

Does it consume less electricity to maintain the heat once it's heated up?

Just hoping to hear some feedback on whether it's worth hooking up to 240v, when costs are considered. To give you an idea of what I'm looking at, it's either a rather inexpensive extension cord (GFCI protected, dedicated circuit) for 120v, or cutting open a concrete patio, digging a massive trench for quite a distance, to bury the 220v in conduit, etc.

Also, if 120v is used, does it still require a full-fledged disconnect like I usually do with 240v installations? Could it just essentially be a heavy-duty high quality extension cord?

Thank you!
 
Chet, 680.42(A)(2) would allow the cord for a hot tub, but I'd say it would have to be listed that way, looking at 680.42(A).

That aside, I'd say it would require one of the wiring methods described there or in Part II of that Article.

Edit to add: the biggest bonus to 240V would be that the ampacity of the conductors could be reduced accordingly.
 
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Watts are watts that is how the cost for electrical use is going to be billed. It is no cheaper to heat at 240 or 120 volt. You should not use an extention cord for this type of install as it will be there a long time and get worn and become dangerous. It would be in your best interest to get a qualified electrician to look at it for you. Have a happy and safe tub time:smile:
 
most of the dual voltage tubs that I am familiar with will not run the heat and jet cycle together on 120 volt but will on 240 volt. your heat cyclr does not function on 120 volt the entire time you are using the tub, hence it takes awhile for the water to heat back up after use. since a watt is watt regardless of voltage, this means a longer average run time for the heat cycle. My brain says it would be cheaper to operate @ 240 volts.
 
georgestolz said:
Edit to add: the biggest bonus to 240V would be that the ampacity of the conductors could be reduced accordingly.
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Actually, for this particular installation, operating at 120V _reduces_ the ampacity of the conductors required. The reason is that the 240V heating element is not actually reconnected for 120V operation, but instead simply connected across the 120V supply; halve the voltage applied and you halve the current that it draws. Of course the heating element is now only operating at 1/4 of its original power rating.

chetwynd said:
Anyway, other than the water heating up substantially faster, what are the other advantages to hooking it up to 240v as opposed to 120v?

Does it consume less electricity to maintain the heat once it's heated up?
Click to expand...

As others have said, watts is watts. To maintain a steady state temperature, the power input via the heating element must be equal to the thermal power lost. Because you have a thermostat, the heater is turned on and off to keep the correct average power input. If you use the heater at 120V, and thus at lower power, then the heating element will need to be on for a proportionately longer time. The same total watt-hours will be used.

The choice of 120V lower wattage operation or 240V higher wattage operation will depend upon a large number of factors.

If the insulation is poor or the outside temperature extremely cold, then the heater may not be able to provide sufficient power input to maintain the desired water temperature. In this case the heater will use less power at 120V than at 240V, but only because it is not providing enough power to meet your customer's use requirements :)

If your customer tends to turn the thermostat way down to conserve energy when the tub is not used, then the 120V element will require a substantially longer pre-heat time, and may result in more total energy consumed. If the pre-heat time is too long, then they may simply leave the hot tub on all the time, wasting lots of energy.

If the building service is near its maximum capacity, then the lower wattage connection will put less strain on the electrical system.

etc. etc.

-Jon
 
chetwynd said:
To give you an idea of what I'm looking at, it's either a rather inexpensive extension cord (GFCI protected, dedicated circuit) for 120v,
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A tub can be cord and plug connected but you can not run it on extension cord permanently.

I am going to close this thread as you do not appear to be an electrical contractor.

If I am mistaken send me a PM and explain what you do.
 
A lot depends on usage and where you live.For a 15 minute use here in Florida (not this morning at 44) it will be fine on 120.Main down fall is it does not heat while using it.240 would be a better job but now cost is involved.
 
chetwynd said:
it's either a rather inexpensive extension cord (GFCI protected, dedicated circuit) for 120v, or cutting open a concrete patio, digging a massive trench for quite a distance, to bury the 220v in conduit, etc.
Click to expand...

OK I re-opened your thread as you asked, now will you explain what you mean by 'extension cord'?

And why the voltage will change the need to cut the slab?
 
rcarroll said:
FWIW, I would wire 240v to it.
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Same here. Whether for equipment that uses more power, like the hot tub here (for performance reasons), or the more typical higher-voltage/lower-current situation (for efficiency/economic reasons), I almost always go for the higher voltage connection.
 
iwire said:
OK I re-opened your thread as you asked, now will you explain what you mean by 'extension cord'?

And why the voltage will change the need to cut the slab?
Click to expand...

I am bit curious as to why a cord across the floor would be ok but some pvc would not be ok.
 
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