Neutral sizing for hot tub

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What does instructions for hot tub say? Many will tell you to run same sized neutral as ungrounded conductors even when the load just isn't there:blink:
 
you tell us the cost diff between #6 and #8 for the full installation.

HD #6 THWN 73c/ft
HD #8 THWN 46c/ft

lets say 200ft
#6 $146
#8 $92

diff $54 (retail box store, +tax)

unless you are asking for some pull issue or box or fitting or "have to install 1,000 of these" reasons, i would spend the extra ~$50 for #6.

what say you?
 
FionaZuppa said:
you tell us the cost diff between #6 and #8 for the full installation.

HD #6 THWN 73c/ft
HD #8 THWN 46c/ft

lets say 200ft
#6 $146
#8 $92

diff $54 (retail box store, +tax)

unless you are asking for some pull issue or box or fitting or "have to install 1,000 of these" reasons, i would spend the extra ~$50 for #6.

what say you?
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It's only money. 30 years ago the difference was maybe only $20.
 
FionaZuppa said:
you tell us the cost diff between #6 and #8 for the full installation.

HD #6 THWN 73c/ft
HD #8 THWN 46c/ft

lets say 200ft
#6 $146
#8 $92

diff $54 (retail box store, +tax)

unless you are asking for some pull issue or box or fitting or "have to install 1,000 of these" reasons, i would spend the extra ~$50 for #6.

what say you?
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Thank you, actually it was the space, it seems every tub I connect has a 3/4 inch knockout and we use 3/4 conduit. I just thought it might be a little easier pulling, by downsizing. But I haven't looked yet at this tub for manufacture recommendations, I will tomorrow. With the advice so far, it doesn't sound like I will chance downsizing.
 
The problem I see is that the code allows dropping the neutral size on a feeder but other than ranges and dryers there is no allowance for downsizing the neutral for branch circuits.
 
Dennis Alwon said:
The problem I see is that the code allows dropping the neutral size on a feeder but other than ranges and dryers there is no allowance for downsizing the neutral for branch circuits.
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I see, that's true. A question; I usually use romex 6-3 to the disconnect that has #6 neutral, but # 10 ground. What about the ground size? Thank you.
 
Stevenfyeager said:
I see, that's true. A question; I usually use romex 6-3 to the disconnect that has #6 neutral, but # 10 ground. What about the ground size? Thank you.
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The #10 ground is NEC code compliant however I have seen some tubs that require a full size equipment grounding conductor-meaning a #6 in your case.

I avoid this issue and just pipe it all the way
 
Dennis Alwon said:
The problem I see is that the code allows dropping the neutral size on a feeder but other than ranges and dryers there is no allowance for downsizing the neutral for branch circuits.
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That is not how I see it. 210.19 basically says conductors need to be sized no smaller then the load served, subpart 3 does give a minimum size for ranges and cooking appliances though.

If OP's hot tub requires more then 8 AWG neutral it would be 110.3(B) that would be violated if he didn't comply.
 
kwired said:
That is not how I see it. 210.19 basically says conductors need to be sized no smaller then the load served, subpart 3 does give a minimum size for ranges and cooking appliances though.

If OP's hot tub requires more then 8 AWG neutral it would be 110.3(B) that would be violated if he didn't comply.
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Think about it. Those are the hot conductors.. According to your statement then I could run a #14 equipment grounding conductor when the branch circuit is on a 50 amp overcurrent protective device. There are rules for feeders and the neutral being sized not smaller than the equipment grounding conductor but where is that rule for branch circuits?
 
Dennis Alwon said:
Think about it. Those are the hot conductors.. According to your statement then I could run a #14 equipment grounding conductor when the branch circuit is on a 50 amp overcurrent protective device. There are rules for feeders and the neutral being sized not smaller than the equipment grounding conductor but where is that rule for branch circuits?
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210.19 applies to branch circuit conductors. Is the neutral conductor not a branch circuit conductor? In a two wire circuit both conductors carry same current and will be required to be same ampacity. In a multiwire circuit neutral may never carry same current as the ungrounded conductors in some instances, but they still give a minimum size for for cooking appliances/ranges, I do not see a minimum size for other applications. 210.19(A)(4) does give a minimum size of 14 AWG but that basically means they don't want you to use 18 AWG even thought the load is only 3 amps, and applies to both grounded and ungrounded conductors.

Dennis Alwon said:
Look at exception 2 of 210.19(A)(3)
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Exactly the subpart 3 that I mentioned. It only applies to ranges/cooking appliances.

We don't provide overcurrent protection to grounded conductors - so in the OP's hot tub installation the fact there is a 50 amp breaker (a hypothetical fact here) on the ungrounded conductors has no meaning on sizing the grounded conductor.

Outside of any other rules that would give a minimum size for that grounded conductor 210.19 only says it must be able to carry the connected load, but be no smaller then 14 AWG. Those "any other rules" would likely come from instructions with the hot tub, unless you can produce something for this specific application that I have missed.
 
I am not sure what we are arguing. I did make a typo (thinking one and wrote the other) when I wrote dryers as I really meant cooking appliances.

210.19 says the branch circuits conductors must have the capacity to carry the load however in (3) it gives an exception for the neutral for cooking units... that is the only exception I see.

IMO, and I will leave it at that, the neutral cannot be downsized for a tub, in spite of what the installation instructions state. Would you allow a multiwire branch circuit with a 14 wire on a 20 amp circuit if the neutral would never see more than 15 amps? Maybe you would I just don't read it that way.
 
Does your hot tub even require a neutral? Quite a few 50 amp hot tubs will not even utilize the neutral you just need a neutral to the Disco for the GFI breaker. If you put the GFI breaker in the panel you wouldn't even need a neutral to the disconnect assuming the hot tub does not need a neutral if it does I'd run same size circuit conductors as the ungrounded. I believe the ground wire can be number 10
 
Dennis Alwon said:
I am not sure what we are arguing. I did make a typo (thinking one and wrote the other) when I wrote dryers as I really meant cooking appliances.

210.19 says the branch circuits conductors must have the capacity to carry the load however in (3) it gives an exception for the neutral for cooking units... that is the only exception I see.

IMO, and I will leave it at that, the neutral cannot be downsized for a tub, in spite of what the installation instructions state. Would you allow a multiwire branch circuit with a 14 wire on a 20 amp circuit if the neutral would never see more than 15 amps? Maybe you would I just don't read it that way.
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Dennis Alwon said:
btw, how would you account for table 310.15(B)(16) for the neutral
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You have to deterine maximum load the neutral will see.

If only neutral load is that pump motor and the pump motor is rated for 10 amps - how do you overload the neutral without also drawing enough that the motor overload cuts it out of the circuit? Said conductor must have minimum ampacity of 10 amps according to 210.19, but in (A)(4) it also says it can't be no smaller then 14 AWG. No way this conductor ever sees 50 amps in normal operation, and we don't need 50 amp conductor just because the ungrounded conductors have a 50 amp breaker on them.

This is no different then reducing the neutral for a service or feeder, there is no overcurrent protection on the neutral, we must figure out what the maximum load is that it may carry and size accordingly, unless there is some other requirement that gives a minimum size. Otherwise for branch circuits that absolute minimum is the already mentioned 14 AWG from 210.19(A)(4), feeders it must be no case can it be smaller then the EGC required for that feeder, for services it can be no smaller then the required GEC.

No instructions stating otherwise with the tub, I likely run 10 AWG neutral - though I truly believe it could be as small as 14 AWG if the connected neutral load is low enough.
 
K wired, I agree with you however 110.3(B) will most likely be the deciding factor here. Knowing the manufacturer and model of hot tub would help significantly in answering the original posters question. As I wrote before there is a decent chance that this hot tub does not even require a neutral. If it does number 8 would be more than sufficient the neutral would never see more than 40 amps, it's unlikely that , even if needed, it would see 15 amps. Article 680 installs are nothing to Monkey around with however I do not see a problem here with running a number eight neutral to the hot tub
 
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