Spa Wiring Conductor Sizing Long Run

Status
Not open for further replies.
3

395Garrison

Member
Location
Temecula
Occupation
General Contractor/Superintendent
I purchased a spa and I am planning on pulling the conductors over the weekend. The spa requires a 50 amp 240v four wire set up. From the house panel to the GFCI disconnect the run is 175’, from the disconnect to the spa is another 35’. Looking at conduit calculations with a long pull of 4 awg in mind, I installed 1 1/4” schedule 40 underground for the long run and 1” for the shorter run. My question is, after the disconnect am I able to step down to 6 awg or should I run 4 awg all the way to the spa connection? Haven’t laid my eyes on the spa connection yet, but imagining 4 awg might be a pretty tight fit. On top of the 4 awg, the spa’s wiring diagram designates the use of an equal sized ground wire as the conductors.

Thanks,
Garrison
 
Last edited:
What is the actual full load current when this spa is running? Using 40 amps according to the Southwire voltage drop calculator if you ran #6 AWG the entire way (210') with a 40 amp load your voltage drop would be 3.09%. #4 AWG for the entire length would have a VD of 2.01%. Your proposed combination of #4 and #6 will get your VD below 3% if that's what you're aiming for. You could get away with #6 if you like. Even with a 3.09% VD the only real downside is that the heater will take a little longer to heat the water.
 
I would use #2 aluminum conductors for the long run to the disconnect, four of which will fit in the 1-1/4" PVC, and the #6 copper from there to the spa.
 
Last edited:
infinity said:
Using 40 amps according to the Southwire voltage drop calculator if you ran #6 AWG the entire way (210') with a 40 amp load your voltage drop would be 3.09%. #4 AWG for the entire length would have a VD of 2.01%.
Click to expand...
How do you tell it to use a different wire gauge? :unsure:
 
From the panel to the disconnect is a feeder, and isn't subjest to mfg brach circuit requirements (which is part of Larry's answer).

I wouldn't use a full-size ground or neutral on the feeder.

If copper, you could pull 4-4-6-6
If aluminum, you could pull 2-2-4-6

That would make it a whole bunch easier to pull
 
infinity said:
There is a drop down menu for different parameters.

Click to expand...
I didn't realize that I should select Voltage Drop as the calculator option before.

Using #2 al to the disconnect, I get 1.71% drop , and 0.52 for #6 cu to the spa.

That would be a total of 2.23% and cost less than using copper for the long run.
 
infinity said:
He did state that the EGC is required by the manufacturer to be the same size as the ungrounded conductors.
Click to expand...
He said full size, but that's only on the branch circuit.

Mfg probably requires copper only as well - on the branch circuit.

Whatever happens with the feeder is not subject to those branch circuit requirements
 
James L said:
He said full size, but that's only on the branch circuit.

Mfg probably requires copper only as well - on the branch circuit.

Whatever happens with the feeder is not subject to those branch circuit requirements
Click to expand...
Got it. I missed the feeder to the GFCI part. I agree.
 
Thanks for the replies, I wasn’t sure how to calculate the voltage drop over both legs. Sure would be easier to hook up #6 on the second leg.

From the owners manual. Also states warranty will be void if not hooked up in this fashion. But do side with the feeder argument.


“The power supplied to the spa must be on a dedicated GFCI protected circuit as required by NEC 70 with no other appliances or lights sharing the power.
Use copper wire with THHN insulation. Do not use aluminum wire.
Use the table below and on the next page to determine your GFCI and wiring requirements.
Wires that run over 100 feet must increase wire gauge to the next lower number. For example: A normal 50 amp GFCI with four #6 AWG copper wires that run over 100 feet would require you to use four #4 AWG copper wires.”

Looking at the the available GFCI load centers and it looks like they are only designed for up to #6, going to be a joy stuffing it with #4 and terminal pins.

Thanks,
Garrison
 
I have never ran a full size ground for a hot tub. I know what the mfg says but NEC says a #10 EGC is all that is required. IMO, the mfg is just CYA!
It's hard enough to get 2-3 #6 in those small wiring compartments, much more with 4 #6!
 
Little Bill said:
I have never ran a full size ground for a hot tub. I know what the mfg says but NEC says a #10 EGC is all that is required. IMO, the mfg is just CYA!
It's hard enough to get 2-3 #6 in those small wiring compartments, much more with 4 #6!
Click to expand...
I wouldn't run a full-size neutral, either.
I do kinda like to have it one size larger than the ground, just so they don't have to be identified (taped) until the time it guts cut and landed
 
Little Bill said:
I have never ran a full size ground for a hot tub. I know what the mfg says but NEC says a #10 EGC is all that is required. IMO, the mfg is just CYA!
It's hard enough to get 2-3 #6 in those small wiring compartments, much more with 4 #6!
Click to expand...
Same here, plus I often have run 8 AWG instead of 6 AWG. Most those spa control panels don't really have room to bend 6 AWG :confused:

Brand new spa- I will more seriously consider following the details of the instructions. Used spa and no warranty - I don't care and will do what NEC otherwise allows.
 
kwired said:
Same here, plus I often have run 8 AWG instead of 6 AWG. Most those spa control panels don't really have room to bend 6 AWG :confused:

Brand new spa- I will more seriously consider following the details of the instructions. Used spa and no warranty - I don't care and will do what NEC otherwise allows.
Click to expand...
I remember one where I pretty much had to line the conductors up to the terminals and gently push them all at once to get them in the terminals. It was almost impossible to grab one conductor and put it in, then grab the next. There was only an inch or so between the entry to the control panel and the terminals.
 
James L said:
I wouldn't run a full-size neutral, either.
I do kinda like to have it one size larger than the ground, just so they don't have to be identified (taped) until the time it guts cut and landed
Click to expand...
Don't forget that smaller than #6 must be white, not re-colored white.
 
Status
Not open for further replies.
Top