Swim Spa Load Calcs Question

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dhood

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I'm trying to add a swim spa to my duplex home and need help with the calcs to see if I need a panel swap or not. Briefly there is 3 phase service with a 4 wire 2/0 UG feeder in 1 1/2inch PVC. Each unit has its own single phase 125 A panel and one additional 100 A panel for house common load like 600 W of outdoor lighting and a few service outlets. The spa would be added to the house common panel. The spa mfg says I need one 40 A and one 60 A breaker to serve the four 5 HP and one 4 HP motors and an 11kw elec heater. Its all 220 V. My question is on the load calcs; can someone please confirm that all spa loads are figured at 100% demand, and if I need to figure any of the motors at 125% as well? Thanks alot, this is my first time post and the website looks great!
 
The first thing I seen was 4 2/0 in 1 1/2" PVC. I believe 3 would be the max.

Is the service panel voltage 120/208?

Quote: The spa mfg says I need one 40 A and one 60 A breaker to serve the four 5 HP and one 4 HP motors

Are you sure about that?

A 5 HP 1P 208 motor full load is 30.8a
Sorry no 4 HP listed. Figure it will be more than a 3 HP at 18.7a but less then 30.8a.

11 KW @ 308v is 52.8v

That's allready over the 100a.
 
Yeah, its a Sunbelt Spa model SS-OLY-9-15 Olympia. Its huge. Got the specs off the internet on this model, and the mfg speced the 40/60 A breakers. Sorry, the conduit is 2 inch dia. The local utility said I could pull 4/0 thru this conduit. Engineer confirmed this for 3 conductors, not counting the 4th nuetral. But can the nuetral can be ignored per code in a 3 wire 3 phase setup. There are three meters so the service is roughly balanced except for the load differences on each meter.
 
Mr Hood . If your 100 amp three phase house panel has as little load on it as you say. Then chances are your spa/ hot tub will be fine on that panel. With out any modifications.
Get the exact specs for the spa / hot tub. Hire a qualified electrician and he or she can make the call very quickly. :wink:
Good Luck
 
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being you're the architect, i would let the EE do these calculations, since that is in fact the job they are trained for.
 
After looking at the manufacture site I think it is two 5HP & 1 4HP pumps. They don't provide the actual load that I could find. It is just a slightly bigger hot tub. Tring to figure the load off the pump size will probibly give you an unrealistic number. Reason is depending how it is programed and jumper settings it will vary what is working at the same time. Such as it may not heat with 2 of the pumps working. Or not all the pumps work at the same time. I kinda wonder if the HP advertised is not the actual running HP. More of a locked rotor amprage equils this many HP. A way to make it seem more than it is. That may explain where they came up with a 4HP motor.


Figuring the amps off the CB sizes I would guess the running load tops out at about 80 amps. I would not concider it a continous load of 80 amps. While the house panel may cover this I think they need to calculate the entire building. You did not say how many units. But it does not matter because we are just guessing at all the details.
 
Thanks for all the input. I am a retired architect and all the EE's I worked with are also retired or gone. So without a board like this I am feeling kinda isolated. I hired an EE who turns out doesn't understand spas, pools or worked with that part of the NEC, and two licensed elec contractors who couldn't answer the load questions I had or knew how to balance 3 phase (wow!), so thought I'd post here before throwing myself at the mercy of the building dept. What you all say makes sense and I think I need to really question the mfg on the loads for this spa.

Calcs for the rest of the duplex (only two units) affect the service entrance, they are similar at 75 A and 101 A after demand reductions after the first 10k, and figuring HVAC at 100%. So the question was is the spa figured at 100% (or more)? If I add a future load to the house common panel like a garage, then I probably would have to know this answer to calculate total load for the service entrance. Until then I agree the 100 A main for the house common probably is big enough and if 80 A is the max actual load then any particular service feed conductor of the three hot legs would be under 200 A. If using 3 condutors in the conduit (nuetral is ignored) then would the 2/0 copper in 2 inch dia conduit be big enuf? I WILL look for another electrical contractor or engineer next week, your input is great since it helps me to ask educated questions and I am really impressed and appreciative that so many have taken an interest so quickly!
 
Dhood, fire those EC's if they can't figure this out. If you don't even do a load calc you should still be able to figure this out. Have you considered what the heating source is going to be? I figured if it's electric you're pulling another 46 amps on this thing. If it's gas thats another matter.
 
I called the mfg who didn't know the answer. I guess they hire an EE who does the calcs, writes a spec and goes away when the design is done. The mfg installers only know rule of thumb for breaker sizes but can't do load. Any EE I hire would have to call the mfg. So I opened up the spa and read all the id plates. Two 230V 5hp motors for the spa massage jets. They are two speed rated 12 and 4.4 A. One electric heater at 11 kw (volts ?). One 4 hp motor for the swim jets rated 208-240V 21 A. The circuit can be set to lock out the heater when the swim jets are operating. I have 208V service. I'm just guessing the minimum continuous load would be about 16000 watts / 208V or 77 A. Will find a better EE tomorrow. Thanks for the suggestions.
 
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