Need to know what is correct

Reply

  #1  
Old 05-28-06, 11:34 AM
New Member
Thread Starter
Join Date: Feb 2006
Posts: 167
Need to know what is correct

I have 6 wires for two circuits running underground through rigid PVC. One set is #6 CU for my spa and the other is #10 for my a/c compressor. I have buried most of the conduit and am at the end where I plan on running these wires up to a disconnect switch for each unit.

Since I have two curcuits here I need to know what is the correct way to run each set of wires to their disconnect switches. I thought I wouldn't be able to explain it correctly so I made a picture: http://joevb.us/images/wiring.jpg

My preference would be to do what is in figure A but my priority is to do it right, to code.

Thanks.
 
Sponsored Links
  #2  
Old 05-28-06, 11:58 AM
Member
Join Date: Jan 2004
Location: Oregon
Posts: 1,219
1) Are you still in the process of burying the conduit, and will be pulling the wire later, or have you been pulling the wire and assembling the conduit as you go along.

2) Is the conduit PVC or metal? If PVC, have you been gluing the conduit?

3) Normally you run conduit underground to an outbuilding, but usually the AC compressor is for the building being served. Are your spa and AC compressor simply alongside the building from which the circuits originate, but it was easier to run outside underground?

4) What are the circuit ratings for the spa and the AC? What breakers are you using?

5) What type of wire are you using (THWN, THWN-2, XHHW, etc.)?

6) Did you run a separate green insulated ground wire? What size?

Configuration A _may_ be possible, but your description of things has raised a number of 'red flags'. The devil is in the details.

-Jon
 
  #3  
Old 05-28-06, 12:28 PM
New Member
Thread Starter
Join Date: Feb 2006
Posts: 167
See answers in-line. And thanks.

Originally Posted by winnie
1) Are you still in the process of burying the conduit, and will be pulling the wire later, or have you been pulling the wire and assembling the conduit as you go along.
I have been pulling the wire and assembling the conduit as I go along.

Originally Posted by winnie
2) Is the conduit PVC or metal? If PVC, have you been gluing the conduit?
PVC & Yes, gluing.


Originally Posted by winnie
3) Normally you run conduit underground to an outbuilding, but usually the AC compressor is for the building being served. Are your spa and AC compressor simply alongside the building from which the circuits originate, but it was easier to run outside underground?
SPA and a/c (in their final resting places) will be along side my house, the spa being about 7-8 feet away from the side and the a/c just about a foot away. Both on the same wall.


Originally Posted by winnie
4) What are the circuit ratings for the spa and the AC? What breakers are you using?
50A for the spa and 30A for the a/c.


Originally Posted by winnie
5) What type of wire are you using (THWN, THWN-2, XHHW, etc.)?
THHN


Originally Posted by winnie
6) Did you run a separate green insulated ground wire? What size?
Yes, for each circuit, each is the same size as the other wires for the same circuit. #10 for the a/c and #6 for the spa.
 
  #4  
Old 05-28-06, 12:54 PM
Member
Join Date: Sep 2003
Location: Central New York State
Posts: 13,973
Joe,

Remove the wire and throw it away. It has been ruined by the glue. Further, THHN is the wrong kind of wire. You need THWN. Dual rated THHN/THWN is okay, but THHN (without the THWN rating) is not proper.

AFTER you place the conduit and the glue is dry, THEN you can add the wire.
 
  #5  
Old 05-28-06, 12:56 PM
Member
Join Date: Jan 2004
Location: Oregon
Posts: 1,219
Well, good news and bad news.

1) Installing the wires as you assemble the conduit is explicitly prohibited. I don't know all of the reasons for this, but NEC 300.18(A) explicitly requires that the raceway be complete between junction boxes prior to installing conductors. Among other reasons, the glue used on PVC conduit is a _solvent_ glue that works by dissolving the PVC, then evaporating so that the two pieces fuse together. This same solvent can damage the PVC insulation on the conductors. I recommend that you pull out and replace these conductors, rather than risk damage from the PVC cement.

2) Fine. Remember that you are limited to a maximum of 360 degrees of total bend (angles) in any conduit run, and are much better off less than this limit.

3) Good. You are only permitted to run _one_ circuit to an outbuilding, but since this is the same building this is fine.

4) Probably good. When you have 4 'current carrying conductors' in a single raceway, you have to 'derate' their capacity by 80%. But #10 THWN is normally good for 35A, and #6 65A, so after the derating you are fine...unless the AC compressor specifies a minimum circuit ampacity > 28.5A.

5) Possibly bad. THHN wire is _not_ rated for use in wet conditions, and conduit underground is considered a wet location. However _most_ THHN is 'dual rated' THWN (and a few other specifications). If your wire says THWN on it, then you are fine. If it only says THHN, then you need to replace it.

6) Excessive. You only need a single #8 insulated grounding conductor. The grounding conductors from both circuits would need to be spliced together in box A.

The good news is that you could run things as per diagram A as long as box A is large enough, which most certainly are.

-Jon
 
  #6  
Old 05-28-06, 04:40 PM
ray2047's Avatar
Group Moderator
Join Date: Mar 2006
Location: USA
Posts: 33,125
Minor suggestion if you are going to remove the existing wire use it to pull your new wire.
 
  #7  
Old 05-28-06, 05:26 PM
New Member
Thread Starter
Join Date: Feb 2006
Posts: 167
Originally Posted by winnie
5) Possibly bad. THHN wire is _not_ rated for use in wet conditions, and conduit underground is considered a wet location. However _most_ THHN is 'dual rated' THWN (and a few other specifications). If your wire says THWN on it, then you are fine. If it only says THHN, then you need to replace it.
It is dual rated, thanks for the info.

Originally Posted by winnie
I recommend that you pull out and replace these conductors, rather than risk damage from the PVC cement.
Yeah, good luck with that
 

Last edited by JoeVB; 05-28-06 at 06:13 PM.
  #8  
Old 05-28-06, 08:49 PM
Member
Join Date: Jan 2004
Location: Oregon
Posts: 1,219
No, this was not a 'I recommend that you pull these wires out *wink wink* cover my rear'.

This was a 'You run the risk of having a short circuit between the wires feeding your spa. You have _published_ that you performed this installation incorrectly and you _know_ that it is an incorrect installation. Fix this.'

-Jon
 
  #9  
Old 05-28-06, 09:41 PM
New Member
Thread Starter
Join Date: Feb 2006
Posts: 167
Originally Posted by winnie
No, this was not a 'I recommend that you pull these wires out *wink wink* cover my rear'.

This was a 'You run the risk of having a short circuit between the wires feeding your spa. You have _published_ that you performed this installation incorrectly and you _know_ that it is an incorrect installation. Fix this.'

-Jon
Actually I read the can and it is PCV cement, I honestly didn't know there was a difference so I just answered. I also confirmed with a friend, that it is OK to use what I am using.
 
  #10  
Old 05-29-06, 05:13 AM
Member
Join Date: Sep 2003
Location: Central New York State
Posts: 13,973
What you did is wrong on all accounts. The cement has damaged the wire and your technique was improper even if the wire would not be damaged.

You don't have a choice. You have advertised here for the world to see that you did something incorrect, dangerous. Now you are stating that you have no regard for the safety of yourself, your family and your neighbors.

Can you tell me the name of your insurance company? I want to let them know what kind of a customer they have. They will want to drop you like a bad habit.

Please, do the right thing. Admit your mistake (to yourself and whoever else will know) and redo it.
 
  #11  
Old 05-29-06, 10:21 AM
nap's Avatar
nap
nap is offline
New Member
Join Date: May 2006
Location: north
Posts: 4,163
Originally Posted by JoeVB
Actually I read the can and it is PCV cement, I honestly didn't know there was a difference so I just answered. I also confirmed with a friend, that it is OK to use what I am using.

Joe, it's not that you used the wrong cement (glue). The problems is as racraft and winnie has told you several times; the glue melts the insulation on the wire just like it does to the pvc pipe. The glue you used sounds to be the correct glue but that is not the point.

That is why you need to wait until the glue in the entire pipe has dried before pulling in any wire.

You may have caused enough damage to the wire to be a serious situation. If the isulation is not good enough to do it's job, you will end up with a short circuit situation, potentially exposing you and others to a deadly situation or a situation that may cause a fire and remove your house from your life.

The other guys sound so serious because they take electricity very seriously, and so should you. It can kill and/or destroy property. It isn't worth the money to risk that type of scenario.

Definately better safe than sorry.

As a bit of relief, I have been told that stripped copper scrap wire is worth over $4 a lb.
 
  #12  
Old 05-29-06, 04:09 PM
New Member
Thread Starter
Join Date: Feb 2006
Posts: 167
I realize the gravity here, I have pulled the wires and replaced them. Wasn't fun but it is done.
 
Reply

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Thread Tools
Search this Thread
Display Modes