120/240V question

[Mildoc]

Getting a Nordic Hot Tub that needs a dedicated line that must be installed. It can run on either:
120V / 20A or 240V / 50A.

1. Why is the amperage needed for 240V so much higher?
2. Which would be the best line to run, with lower elec. bills?
3. If a 240V line pulls the full (or close to) 50A, wouldn't that be more expensive to run?

[LCHIEN]

One of those amperages must be incorrect. There should be only a small difference in total watts (volts times amperes).

usually the 120V amperage figure is twice the 240V amperage figure.
The economic consideration is that you'll need two breakers for 240V but you can use smaller (less costly wire).

You should get the correct values from the manufacturer before making a decision.

[mpc]

Many hot tubs are available with different sized heater units. For 120 volt operation they usually come with a small heater; for 240 volt operation the heater is often 4 times stronger... ergo twice as many amps even with twice the working voltage.

With the 240/50 setup the tub will be able to heat up more quickly. Values I've seen (including my own unit) are roughly 3 degrees temp increase/hour for the 240/50 units on large (10+ person) tubs. For 120 volt setups it can take much longer to heat up or recover after "topping off" the water level. Since the circulation pumps must run whenever the heater is running a larger heater can actually be more efficient: heat the water faster = less pump run time.

See if Nordic's web site lists the heater wattage/KW... I'll bet you see something like "Heater KW (120/240): 1/4" which is 1 kilowatt heater for 120 volt installations, 4 kilowatts on 240 volt installations.

mpc

[cabinetman]

My suggestion would be to have a licensed electrician make an on site assessment, so your existing electrical can be evaluated with respect to your new project and its requirements.

.

[Mildoc]

One of those amperages must be incorrect. There should be only a small difference in total watts (volts times amperes).

That's what I thought, but 220/50 is listed for all their spas in the brochure.

You should get the correct values from the manufacturer before making a decision.

Plan to. Going tomorrow 2PM for their sale that will save us $1900.

[Mildoc]

My suggestion would be to have a licensed electrician make an on site assessment, so your existing electrical can be evaluated with respect to your new project and its requirements.

.

Already done, but we do not have the HT yet. When the electrician looked at the brochure, he was the one that pointed out the possible discrepancy.

[Mildoc]

With the 240/50 setup the tub will be able to heat up more quickly. ....Since the circulation pumps must run whenever the heater is running a larger heater can actually be more efficient: heat the water faster = less pump run time.

Yes, I know a 220V line can be more efficient because the water will heat faster, etc. Did not know about the circulating pump.

See if Nordic's web site lists the heater wattage/KW... I'll bet you see something like "Heater KW (120/240): 1/4" which is 1 kilowatt heater for 120 volt installations, 4 kilowatts on 240 volt installations.mpc

Plan to ask a lot of questions tomorrow and check the data plate on the unit.

But I still don't get why a 120V line requires 20A while a 240V line needs 50A.

[Mildoc]

Just checked the Nordic web sit. It says:

VOLTS: 120/20 or 240/50
Amps: 50

So I guess that means the 240V would be the best overall, as the 120V would not only run longer, but perhaps use MORE electricity to run the heater, circulating pump, light?

Electrician says he would need to run 8 gauge wire for a 240/50 line. Correct???

[LCHIEN]

i was assuming it could be wired to run either in a configuration like motors where you either series or parallel the windings, or in the case of a heater, the heater elements to keep constant power.

If in fact, the high voltage is set with the same heater elements and no reconfiguration, the same heaters (assuming they're rated for the higher power) would pull twice the current and four times the heating power. in which case 50A might be the correct rating (the not being 40 due to increased motor current from increased pump rate or maybe 40 is not a standard breaker?)

[Stytooner]

The other consideration between the two is the initial cost of materials. The 220 will likely be about 4 times the cost. Just been running some wiring in my new shop and have several 220 circuits. It sure does hurt when you have to buy those plugs and receptacles.

[woodturner]

The economic consideration is that you'll need two breakers for 240V but you can use smaller (less costly wire).

Just to clarify, two breakers ganged together - also called a double pole breaker.

I know that is what you meant, just expanding for less technical readers.

[Mildoc]

Turned out that with a 110V line you could not operate jets & heat together. So, despite the cost, had a 220/50 line installed for $695. Oh well..... Saved $2400 on the tub itself so we're still ahead!

BTW, LOVE IT!

[toolguy1000]

nothing like it up here in NY when it snows.

[Mildoc]

When I first mentioned getting a hot tub LOML said "You'll never use it."

Guess who has been in it every single night?

Still don't know what temp. I really like. Started at 95F and have been upping it 1 degree every 2 days or so. Now at 98F. Guess we'll see, and I bet it will be 104F in the winter!