Hot Tub, Continuous Load

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jmellc

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Durham, NC
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Facility Maintenance Tech. Licensed Electrician
A former coworker asked me if a hot tub should be wired at 125% for continuous load. I haven’t done a hot tub in 9 years but I think I just followed the numbers on the nameplate. But it could well be used 3 hours or more. I recall that being the standard for motor loads. He said the literature called for #6 wire & 50 amp breaker. We discussed if continuous load was already figured in. I suggested checking for actual nameplate info & seeing if the numbers there indicate it.

Thanks for any feedback.
 
retirede said:
When I had one, it would run full heat for 6-8 hours to get up to temp after an initial, cold water fill.
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By NEC definition it still isn't a continuous load unless every single component of the tub (lights, blowers, etc.) were running simultaneously for more than 3 hours.
 
Be careful with the info on some tubs. I almost got in trouble on some that said it drew 48A and another that drew 42A. They didn't factor in for the motor @125%. I had to search to find the specs and they were 60A and 50A respectively.
48 x 125% = 60
40 x 125% = 50
Most literature have that figured in but some don't. All the nameplates should have. What I was facig was just looking at literature before the tub was there and couldn't see the nameplate. It's not for continuous loads, it's for the motor.
 
Little Bill said:
Be careful with the info on some tubs. I almost got in trouble on some that said it drew 48A and another that drew 42A. They didn't factor in for the motor @125%. I had to search to find the specs and they were 60A and 50A respectively.
48 x 125% = 60
40 x 125% = 50
Most literature have that figured in but some don't. All the nameplates should have. What I was facig was just looking at literature before the tub was there and couldn't see the nameplate. It's not for continuous loads, it's for the motor.
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How big are the pumps in these things? Maybe I'm calculating this incorrectly but adding 25% to a 1 HP pump only adds a few amps to the calculation.
 
infinity said:
How big are the pumps in these things? Maybe I'm calculating this incorrectly but adding 25% to a 1 HP pump only adds a few amps to the calculation.
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You add 25% to the listed total amps
48A x 25% = 12
48 + 12 = 60
OR
48A x 125% = 60A
That makes it sound like it's for a continuous load but the specs I read said it was for the motor. Regardless, if you see specs that say 40A or 48A for a hot tub you know it should be on either a 50A or 60A breaker. Thankfully, most will give you corrected amps upfront.
 
Little Bill said:
You add 25% to the listed total amps
48A x 25% = 12
48 + 12 = 60
OR
48A x 125% = 60A
That makes it sound like it's for a continuous load but the specs I read said it was for the motor. Regardless, if you see specs that say 40A or 48A for a hot tub you know it should be on either a 50A or 60A breaker. Thankfully, most will give you corrected amps upfront.
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Bill, I'm trying to figure this one out, what code section shows this calculation?
 
I don't believe their is anything specific to hot tub but, in general resistant heat is figured at 125% based on 422 & 430
 
infinity said:
How big are the pumps in these things? Maybe I'm calculating this incorrectly but adding 25% to a 1 HP pump only adds a few amps to the calculation.
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3HP is typical, with a 1.5-5 HP range. Two or three two speed pumps plus a blower is common.

The primary pump is used to pull water through the filter and push it through the resistive heater. It automatically runs at low speed for several hours a day, perhaps 1 hour every 6 hours, if just filtering.

Additional pumps and blowers are used for controlled jets. They usually are turned on by users and eventually shut off using a timer and wouldn't be considered a continuous load.
 
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infinity said:
Bill, I'm trying to figure this one out, what code section shows this calculation?
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I know of only two places for this, one is for the motor and the other is for a continuous load. It may be a mfg thing on some of these tubs. All I can tell you is some of the tubs info I was sent said something like "48A current draw" and then I see the specs and nameplate and they said 60A. The only way to come up with 60A from 48A is to multiply by 125%, the same for one saying 40A and nameplate saying 50A.
As I said earlier, it's good that most go ahead and give you the actual OCPD to be used.
Also. some of them give you the option of two different current draws depending on what all equipment you want to run at one time, such as both pumps and heater, one pump and heater, pumps and no heater, etc.
 
Dennis Alwon said:
I don't believe their is anything specific to hot tub but, in general resistant heat is figured at 125% based on 422 & 430
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But we're talking about the nameplate on an appliance. I don't see where any consideration needs to be made when appliance has a motor, heater and other controls if it is not a continuous load. Are you saying that a hot tub with a 48 amp nameplate current cannot be on a 50 amp circuit?
 
infinity said:
But we're talking about the nameplate on an appliance. I don't see where any consideration needs to be made when appliance has a motor, heater and other controls if it is not a continuous load. Are you saying that a hot tub with a 48 amp nameplate current cannot be on a 50 amp circuit?
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You won't find a nameplate on a hot tub that says 48A, it will be in the literature. The nameplate is what we go by and it will say 60A.
 
infinity said:
But we're talking about the nameplate on an appliance. I don't see where any consideration needs to be made when appliance has a motor, heater and other controls if it is not a continuous load. Are you saying that a hot tub with a 48 amp nameplate current cannot be on a 50 amp circuit?
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I am not convinced that the load should not be considered continuous. I will say I have hooked up many hot tubs and they were all 50 amps but I cannot say that the load was 48 amps. My guess is the load was less than 48. I believe the manufacturers are using 125%
 
Dennis Alwon said:
I am not convinced that the load should not be considered continuous. I will say I have hooked up many hot tubs and they were all 50 amps but I cannot say that the load was 48 amps. My guess is the load was less than 48. I believe the manufacturers are using 125%
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It is possible that they are adding 125% but if it says 48 amps then from everything that I've read in this thread a 50 amp circuit is code complaint.
 
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