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04-29-2010, 12:21 PM
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#1
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Member
Join Date: Jan 2010
Location: Grand Rapids Mi
Posts: 30
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50 amp hot tub feeders
I usually install #6 feeders for a hot tub with a 50 amp rating but I cant figure out why. Can I use# 8 thhn . if not why. I have never clamped a hot tub drawing more than 30 A thats with all pumps and heaters on. referances please
Thanks
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04-29-2010, 03:36 PM
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#2
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not THAT old!
Join Date: Mar 2010
Location: Quebec Canada
Posts: 359
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If it asks for 50 amp. Install 50 amp and # 6 feeders or your warranty will be void. 
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04-29-2010, 05:55 PM
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#3
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Chairman of the Bored
Join Date: Oct 2008
Location: Atlanta, Ga.
Posts: 8,955
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Quote:
Originally Posted by myenergy
I usually install #6 feeders for a hot tub with a 50 amp rating but I cant figure out why. Can I use# 8 thhn . if not why. I have never clamped a hot tub drawing more than 30 A thats with all pumps and heaters on. referances please
Thanks
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you need to remember the spike in current when that motor starts to wind up.
__________________
I'd rather be sleeping.
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04-29-2010, 05:57 PM
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#4
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Chief Electron Relocator
Join Date: Sep 2007
Location: Cornpatch USA
Posts: 31,265
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Quote:
Originally Posted by Electric Al
If it asks for 50 amp.........
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50 amp what? Minimum branch circuit rating, or over-current protection, or both?
Look on the nameplate for MCA and OCD ratings.
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In winter, why do we try to keep the house as warm as it was in summer when we complained about the heat?
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04-29-2010, 10:33 PM
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#5
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Master Plumber
Join Date: Aug 2007
Location: In your attic.
Posts: 8,104
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Since we are on the subject - is it required to pull a full size ground for a 50A spa circuit, or can I run a #10 ground?
~Matt
__________________
Poor planning on your part does not constitute an emergency on my part.
Advertising space available. Inquire within. 
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04-29-2010, 10:44 PM
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#6
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Chairman of the Bored
Join Date: Oct 2008
Location: Atlanta, Ga.
Posts: 8,955
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Heel I'd think a #12 might suffice but I'd go with #10
__________________
I'd rather be sleeping.
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04-30-2010, 12:28 AM
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#7
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Senior Member
Join Date: Dec 2009
Location: Nebraska
Posts: 296
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If you have 75 degree terminals and 75 degree conductor you can use #8 copper @ 50 amps. Remember that NM cable must be sized to 60 degree temperature rating so you can not use #8 if using NM cable. If equipment instructions state #6 minimum then you also cannot use #8.
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04-30-2010, 07:07 AM
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#8
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Moderator
Join Date: May 2009
Location: Chapel Hill, NC
Posts: 11,988
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Many tub manufacturers spec that a full size egc must be used. I believe it is worded to say that the egc must be the same size as the ungrounded conductors.
I have given up using nm cable and now I run conduit so that the egc is not an issue.
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04-30-2010, 07:08 AM
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#9
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Moderator
Join Date: May 2009
Location: Chapel Hill, NC
Posts: 11,988
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Quote:
Originally Posted by BuzzKill
Heel I'd think a #12 might suffice but I'd go with #10
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Buzz how could #12 suffice? Check Table 250.122 for EGC-- it is based on the breaker size.
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04-30-2010, 08:22 AM
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#10
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Chairman of the Bored
Join Date: Oct 2008
Location: Atlanta, Ga.
Posts: 8,955
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Quote:
Originally Posted by Dennis Alwon
Buzz how could #12 suffice? Check Table 250.122 for EGC-- it is based on the breaker size.
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I said "I think" it would suffice. What do I know? Enough to use #10, though. It's a pretty simple question with a pretty simple solution: check the code book. I'd be interested to see test results of how well certain size wires carry the fault current before disintegrating.
__________________
I'd rather be sleeping.
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04-30-2010, 10:00 PM
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#11
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Senior Member
Join Date: Dec 2009
Location: Nebraska
Posts: 296
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Quote:
Originally Posted by BuzzKill
I said "I think" it would suffice. What do I know? Enough to use #10, though. It's a pretty simple question with a pretty simple solution: check the code book. I'd be interested to see test results of how well certain size wires carry the fault current before disintegrating.
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sizing equipment ground conductors is not about sizing them to prevent the ground wire from overheating it about sizing it large enough to lower its impedance enough to operate the overcurrent device quickly.
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04-30-2010, 10:37 PM
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#12
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PGW Professional
Join Date: Jan 2007
Location: Rahway, NJ
Posts: 12,776
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Quote:
Originally Posted by TOOL_5150
Since we are on the subject - is it required to pull a full size ground for a 50A spa circuit, or can I run a #10 ground?
~Matt
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That would depend on both 110.3(B) and Table 250.122. 
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05-01-2010, 12:00 AM
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#13
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Circumcised Member
Join Date: Jul 2009
Location: Sebring, FL
Posts: 275
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Quote:
Originally Posted by TOOL_5150
Since we are on the subject - is it required to pull a full size ground for a 50A spa circuit, or can I run a #10 ground?
~Matt
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Only if the power used for the spa is from a transformer or other seperately derived system.
I think.
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05-01-2010, 04:15 AM
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#14
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Master Plumber
Join Date: Aug 2007
Location: In your attic.
Posts: 8,104
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Quote:
Originally Posted by Magnettica
That would depend on both 110.3(B) and Table 250.122. |
Thanks, but I knew this part - it was post 8 from dennis I was unsure about. I am thinking it would be wise to just run a full size EGC to the spa disco. Unless I can check out the specific spa before I get the line ran.
~Matt
__________________
Poor planning on your part does not constitute an emergency on my part.
Advertising space available. Inquire within.
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05-01-2010, 09:46 AM
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#15
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Senior Member
Join Date: Dec 2009
Location: Nebraska
Posts: 296
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Quote:
Since we are on the subject - is it required to pull a full size ground for a 50A spa circuit, or can I run a #10 ground?
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~Matt
Quote:
Originally Posted by idontknow
Only if the power used for the spa is from a transformer or other seperately derived system.
I think.
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I don't know of any requirement like this and I fail to see any logic as to why that would be a requirement.
Voltage (assuming an unlimited capacity in the supply) and impedance of the circuit are the same no matter what the source is. So why should you need a different size conductor on one vs the other?
If anything the SDS will likely have higher impedance and lower available current so you would want the larger conductor on it to allow more current to flow during a fault to allow faster operation of overcurrent device.
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05-01-2010, 09:50 AM
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#16
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Fried Bologna um um good!
Join Date: Jan 2010
Location: nc
Posts: 8,092
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Some of the hot tubs I have done said to use #6 in the instructions.
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The more I learn the less I seem to know...... 
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05-02-2010, 09:10 AM
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#17
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Senior Member
Join Date: Dec 2009
Location: Nebraska
Posts: 296
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Quote:
Originally Posted by jwjrw
Some of the hot tubs I have done said to use #6 in the instructions.
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then you must follow them instructions, if not in the instructions then follow NEC.
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05-02-2010, 09:17 AM
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#18
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Moderator
Join Date: May 2009
Location: Chapel Hill, NC
Posts: 11,988
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Quote:
Originally Posted by idontknow
Only if the power used for the spa is from a transformer or other seperately derived system.
I think.
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It would be good to back this up with an article number. Never heard of it before.
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05-02-2010, 09:27 AM
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#19
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Fried Bologna um um good!
Join Date: Jan 2010
Location: nc
Posts: 8,092
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Quote:
Originally Posted by kwired
then you must follow them instructions, if not in the instructions then follow NEC.
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Thats why I said some say to use #6. 
__________________
The more I learn the less I seem to know......
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05-02-2010, 09:37 AM
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#20
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Senior Member
Join Date: Dec 2009
Location: Nebraska
Posts: 296
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Quote:
Originally Posted by idontknow
Only if the power used for the spa is from a transformer or other seperately derived system.
I think.
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Quote:
Originally Posted by Dennis Alwon
It would be good to back this up with an article number. Never heard of it before.
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The only thing I find like this is 680.25 (B)(1) but it is in 680 part II for feeders for permanently installed pools and does not apply to hot tubs.
The only parts of 680 that apply to hot tubs and spas are Part I general and part IV spas and hot tubs
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