hypothetical question

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Guys, let me pose this question to see if i understand something. Now I am just a G.C. so please don't get on me for that, I am just trying to understand something I saw.

A homeowner wired his own hot-tub. The hut-tub is 220v and 50amp. He ran 6-3 wire from the service entrance to a sub pannel put a 50 amp gfci breaker and then to the tub.

Now the service is 200amp and the tub is 50 amp, is the wiring going to be fine? Is that because the load dose not exceed what the wire is rated for? i.e.6-3 wire rated 55 amp protected by 50 breaker?

Al

[ April 19, 2004, 11:05 AM: Message edited by: ephesus56ad ]
 

hbiss

EC, Westchester, New York NEC: 2014
Location
Hawthorne, New York NEC: 2014
Occupation
EC
Re: hypothetical question

I would hope there is a 50 amp breaker in the service panel to feed that wire. You can't count on the 50 amp breaker at the other end to protect the cable. What would happen if someone cut it or put a screw through it?

Doesn't sound like this guy knew what he was doing with a sub panel anyway. Don't go in the water! ;)

-Hal
 

charlie b

Moderator
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Location
Seattle, WA
Occupation
Electrical Engineer
Re: hypothetical question

Originally posted by ephesus56ad: Now the service is 200amp and the tub is 50 amp. . . . Is the wiring going to be fine . . . because the load does not exceed what the wire is rated for?
I think you have the right basic concept. But let me phrase it a different way: At every component in the wiring system, the amount of current passing through that component has to be no more than the component?s rating. If the Service Panel is rated for 200 amps, then the total load in the house has to be less than 200 amps. If only 50 of those amps are heading in the direction of the hot tub, then the wire need only be rated for 50 amps.

But there are several possible twists and turns in the plot for this story. Hal mentioned one: You need to have a 50 amp breaker at the main panel. If the homeowner has a 50 amp breaker at the main panel to serve the sub-panel, that issue goes away. But here are a few more issues:
</font>
  • <font size="2" face="Verdana, Helvetica, sans-serif">A #6 wire is only good for 55 amps if it is made of copper, and not of aluminum.</font>
<font size="2" face="Verdana, Helvetica, sans-serif"></font>
  • <font size="2" face="Verdana, Helvetica, sans-serif">Not all types of wire are approved for underground installation. So if the homeowner ran part of the cable underground, then it becomes important to know what type of wire he used.</font>
<font size="2" face="Verdana, Helvetica, sans-serif"></font>
  • <font size="2" face="Verdana, Helvetica, sans-serif">If a load is likely to run more than 3 hours at a time, there are rules about counting it as a higher load, and therefore giving it a larger wire. This would not come into play, if the 50 amp value is the number given by the manufacturer (i.e., they would have already taken the extra factors into account).</font>
<font size="2" face="Verdana, Helvetica, sans-serif"></font>
  • <font size="2" face="Verdana, Helvetica, sans-serif">A very real, and potentially very dangerous, situation might arise, if the hot tub needs both a 220 volt and a 110 volt supply. Any external metal parts of the hot tub (and the sub-panel itself, by the way) have to have a safety ground wire going all the way back to the main service panel. That wire cannot be the same one that is used to give you the 110 volt neutral (or ?cold leg?). So if the manufacturer says that you need 50 amps of power at both 220 volts and 110 volts, then you would need four wires. If the 6/3 has a safety ground wire (typically bare copper), then it cannot be connected to the neutral wire at the hot tub or at the sub-panel.</font>
<font size="2" face="Verdana, Helvetica, sans-serif">

[ April 13, 2004, 03:14 PM: Message edited by: charlie b ]
 
Re: hypothetical question

thanks guys. Now let me add a little more information because maybe i was not clear. when i said "service entrance" i ment right off the meter. about 10' to his sub pannel. his ground is connected to the main ground outside the meter. all the wire is copper and only one connection to the 220v, no 110v. sug pannel is 125 amp G.E. only one circiut coming out althought 8 slots.

so, meter to sub with 50 amp gfci breaker to tub.
 

iwire

Moderator
Staff member
Location
Massachusetts
Re: hypothetical question

If this panel has no main breaker of it's own and is fed directly from the meter it would have to be a service rated panel.

If it is you would be all set for the reasons Charlie posted.

You now have 2 service disconnects, you are allowed up to six service disconnects, although they must be grouped.
 
Re: hypothetical question

Ouch..Two services to a residence. The NEC requires that each service disconnecting means to a residence be 100A rated minimum. The second service to this residence is a violation. The owner should check the load on his main panel and, if the load permits, add the 50A/2P circuit breaker to the main panel as a branch circuit breaker.
 
Re: hypothetical question

Thanks for all the help in understanding guys. Just wanted to know what the hell he did and why. Not that I really care just trying to learn what's going on for future reference. I am just there to build a deck and arbor and got got scared of some of his other wireing.

Al

OK. I get that it is not really a sub pannel.

[ April 14, 2004, 01:00 AM: Message edited by: ephesus56ad ]
 

hurk27

Senior Member
Re: hypothetical question

I don't think there is an exception in 230.40 that would allow this type of tap on the service entrance contuctors? And the lugs in the meter unless they are a double lug they are only rated for one wire under the screw. The one thing that pop's into my mind is with the availble fault current from the transformer. This 6/3 could be a fire hazard if it were to become damaged and shorted out. Now if there was RMC (ridged metal counduit) between the meter and the disconect it would be at least safer. And the 10' tap rule I think only apply's to feeder tap's that would have short circuit protection ahead of this tap.
 

iwire

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Re: hypothetical question

230.40Exception No. 2: Where two to six service disconnecting means in separate enclosures are grouped at one location and supply separate loads from one service drop or lateral, one set of service-entrance conductors shall be permitted to supply each or several such service equipment enclosures.
If cable is acceptable or conduit is required would be an AHJ call. 230.70(A)(1)

Where I live you could use cable for this, if you kept it as short as possible, I know where Ryan inspects this would not stand a chance. :)

The NEC requires that each service disconnecting means to a residence be 100A rated minimum. The second service to this residence is a violation.
Not each disconnect, the combined rating.

230.80 Combined Rating of Disconnects.
Where the service disconnecting means consists of more than one switch or circuit breaker, as permitted by 230.71, the combined ratings of all the switches or circuit breakers used shall not be less than the rating required by 230.79.
I am not saying I would want this set up in my house but it may be code compliant, code is minimum after all. ;)

[ April 14, 2004, 04:25 AM: Message edited by: iwire ]
 
Re: hypothetical question

i don't know if ir NM, I am not familar with this term. I am a gc not an electrican. But it looks like the the same stuff you'd buy at big orange for about $100 for a 125' roll. I can just say 6/3 with a ground.

al

[ April 19, 2004, 10:58 AM: Message edited by: ephesus56ad ]
 

charlie b

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Location
Seattle, WA
Occupation
Electrical Engineer
Re: hypothetical question

Does it have black insulation on one conductor, white insulation on a second conductor, green (or no) insulation on the third condutor, and a "whitish" rubber-like insulation that surrounds all three of the others?
 

iwire

Moderator
Staff member
Location
Massachusetts
Re: hypothetical question

6/3 NM is going to have white, black, red and bare conductors.

I have only seen white or black outer jackets on this size NM.

6/3 SER will probably have 3 black conductors one with a white stripe, one with a red strip and a bare conductor.

I have only seen SE or SER with a gray outer jacket.
 
Re: hypothetical question

Black, white, red and bare all covered by black. The black, white and red are stranded and the bare is solid. And what does NM stand for?

Al
 

iwire

Moderator
Staff member
Location
Massachusetts
Re: hypothetical question

NM stands for Non-Metallic sheathed cable, many people call it Romex which is a brand name.

If it is NM then there may very well be a violation as Pierre pointed out, NM is not to be used as service entrance conductors.

The best idea if you really need an answer is to get a local electrician to look at it.

It does not sound like a great installation.
 
Re: hypothetical question

Bob,

It sounds like there is a violation, but the guy is a **** and just stiffed me on a job, so if I call anybody it just might be the local inspector. In Texas homeowners may do their wireing, but it still needs to be to code.

My whole thoughts on getting this started was to try to understand somthing. That was, to be understood better from what i've been learning in here, or at least what i think I have, what determins the amount of amps going through a wire? Is it the load at the end or combinations of loads on that wire?

Al
 
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