Sub Panel question

Reply

  #1  
Old 08-31-13, 03:51 PM
SBI
SBI is offline
Member
Thread Starter
Join Date: Dec 2004
Location: USA
Posts: 384
Sub Panel question

I plan on renovating a small room/office. It is currently used as office, but the walls are old plaster, uninsulated, so I plan on gutting everything, run wires, blue board and make it nice.
My entire 2nd floor is on one breaker and I want to isolate the office, but I probably won't be able to run multiple wires down to the panel in the basement, so I thought of taking advantage of an existing metal pipe (currently has one bx wire through it to a 20A outlet that was used for washing machine before we bought the house) to run a wire for a sub panel that I'll put flush with the wall in the room. Then feed whatever I need in the room from that sub-panel while isolating this room from the 2nd floor single breaker.
My main service was upgraded to 200A two years ago and I have plenty of room in the main panel.

My questions are:

1. I already have a sub-panel in the basement which we did during basement renovations. Could be a dumb question, but is there a limit to number of sub-panels you can have in the house ?
2. What kind of wire do I need for a 60A sub, is it 6 awg?
3. The only path I might have from that pipe to where I want the sub is through the ceiling joists. I know about the basic do's and don'ts for drilling, but can such a thick wire go through joists/studs, or is it more common to run panel feeds through cavities only?

Thanks in advance.
 
Sponsored Links
  #2  
Old 08-31-13, 04:18 PM
ray2047's Avatar
Group Moderator
Join Date: Mar 2006
Location: USA
Posts: 33,065
so I thought of taking advantage of an existing metal pipe (currently has one bx wire through it to a 20A outlet that was used for washing machine before we bought the house)
It would be unusual to run BX in conduit. BX is its own conduit. You can't reuse the metal sheath of BX if that is what you mean. If though it is conduit what is its diameter?
 
  #3  
Old 08-31-13, 04:32 PM
SBI
SBI is offline
Member
Thread Starter
Join Date: Dec 2004
Location: USA
Posts: 384
Thanks Ray.

Correction - it is not metal, it is a PVC conduit, roughly a inch and quarter diameter on the outside (so is it an inch?!).
I do not mean re-use the metal sheath of BX. What I meant was that whoever brought the line from the old panel in the basement for the washer and the 220 for the dryer, installed this conduit that goes inside the coat closet in the first floor all the way up to the floor of the 2nd floor, and inside the conduit they run the two dedicated lines to the washer/dryer.
My intention is to remove the existing bx (I already removed the 220 line years ago) and use the conduit to run a 60A wire to the sub-panel in the new room.

Sorry for the confusion.
 
  #4  
Old 09-01-13, 02:40 AM
Member
Join Date: Mar 2006
Location: Wet side of Washington state.
Posts: 18,399
Using the conduit as a sleeve for type NM cable is acceptable. Without knowing the outside dimension of the cable I cannot calculate if the conduit is large enough. If you can extend the conduit both directions (to the service panel and to the new sub-panel) you can use individual conductors rather than cable. If you need to install any pull boxes or ells they must remain accessible.
 
  #5  
Old 09-01-13, 06:20 AM
SBI
SBI is offline
Member
Thread Starter
Join Date: Dec 2004
Location: USA
Posts: 384
Thanks Furd.

The conduit is about 1.5" outside diameter so I assume it is a 1" conduit. What kind of awg do I need for 60 or 80 amps from the main panel?
Also, I am not sure I'll be able to extend the conduit to the sub location. Can I just pass it through studs and floor joists (obviously it will be one run from the main panel to the sub)?
What does it mean 'individual conductors'?
 
  #6  
Old 09-01-13, 07:23 AM
ray2047's Avatar
Group Moderator
Join Date: Mar 2006
Location: USA
Posts: 33,065
Individual conductors mean separate wires not contained in a sheath. Cable is two or more wires in a metallic (e.g. BX) or non metallic (e.g. Romex) sheath.

If you can put boxes at each end of the conduit you can run cable to it and transistion to individual conductors (THHN OR THHN/THWN) in the box. However you should be able to run one 6-3* NM-b (Romex) cable in the conduit which should be enough for your needs. You need to seal the conduit with firestop caulk if cables and no box is used.

I would suggest a main breaker 100 amp 12 space panel minimum as your subpanel. You will need to add a ground bar to it. See the third diagram (same building) at http://www.doityourself.com/forum/el...-diagrams.html for wiring diagram for how it is wired.

What is the color of the conduit? Is it gray? If not it may not be conduit. Buy a 1" and a 1" coupling if you want to be sure of the conduit size. My guess is you probably have 1" conduit.

*4-3 if you go for 80amps. That would be a bit tougher to get through the conduit as cable.
 
  #7  
Old 09-01-13, 09:47 AM
SBI
SBI is offline
Member
Thread Starter
Join Date: Dec 2004
Location: USA
Posts: 384
1. It is definitely a conduit, dark gray, but I can't tell the exact size yet. I assume 1 .

2. Why would I need/want to put box and run individual conductors instead of one cable? I cannot put box at the bottom, the bottom of the conduit reaches the basement right above the field stone foundation, about 3 ft. from the main panel.

3. Assuming Ill run one cable, is there any pros/cons in regards to BX vs. Romex? Do I still need to seal the conduit if one cable? It is not sealed now (there is one BX in it now).

4. Given the thickness of the cable (assuming 6-3 NM), am I allowed to run it in studs/floor joists from the conduit exit to the sub, which will be on the other side of the room (the room is small, 10 X 7).

5. Will I need to add a ground bar regardless of the cable that I run? How do I go about it? Is this a single ground wire and can it be run through the conduit as well?
 
  #8  
Old 09-01-13, 10:37 AM
ray2047's Avatar
Group Moderator
Join Date: Mar 2006
Location: USA
Posts: 33,065
Why would I need/want to put box and run individual conductors
Only if you couldn't use it as a cable sleeve because it was too small. Size seems adequate so that is off the table.

Assuming Ill run one cable, is there any pros/cons in regards to BX vs. Romex?
Romex is easier to pull. But you in your profile wrote:
City:
None of your business
So no one here can tell you if your city requires armored cable. Only a few do.

Given the thickness of the cable (assuming 6-3 NM), am I allowed to run it in studs/floor joists from the conduit exit to the sub, which will be on the other side of the room
Stapled if parallel hole through the center of each joist if perpendicular.

Will I need to add a ground bar regardless of the cable that I run? How do I go about it? Is this a single ground wire and can it be run through the conduit as well?
6-3 cable consists of three insulated conductors and a bare ground. All grounds in the subpanel are landed on the ground bar. Only neutrals on the neutral bar. The ground bar is bonded to the metal case. The neutral bar is isolated. (The neutral bar bonding screw or strap is not used.)
 
  #9  
Old 09-01-13, 11:51 AM
SBI
SBI is offline
Member
Thread Starter
Join Date: Dec 2004
Location: USA
Posts: 384
OK, so there will be a bare ground wire in the Romex, I misunderstood, I thought I needed an additional wire for ground.

I will have a much clearer idea of what's going on once I gut the walls. Originally I planned to put the sub right above the conduit, however this would an external wall and then I realized that installing a flush panel in an external wall means I would lose insulation, so I decided to move it behind the door on an internal wall, hence the question about feeding a thick wire through studs.

Thanks again for all your answers!
 
  #10  
Old 09-01-13, 12:47 PM
ray2047's Avatar
Group Moderator
Join Date: Mar 2006
Location: USA
Posts: 33,065
Behind a door is probably okay so long as it does block the box but remember you need 30" side to side clear space and 36" clear space in front of the panel. The panel though does not need to be centered in the 30" space.

OK, so there will be a bare ground wire in the Romex,
With in wall cable the ground is not included with the wire count. 6-3 means the size of each current carrying wire will be #6 and the 3 means there are three of them. There is always a ground so it is not part of the count. The ground will usually be smaller than the current carrying conductors on 6-3 but that is acceptable.
 

Last edited by ray2047; 09-01-13 at 03:08 PM.
  #11  
Old 09-01-13, 01:04 PM
Member
Join Date: Mar 2006
Location: Wet side of Washington state.
Posts: 18,399
... remember you need 36" side to side clear space and 30" clear space in front of the panel.
Other way around; 30 inches side-to-side and 36 inches in front. Also, nothing in the 30 inch space from floor to ceiling and 36 inches out from the face of the panel other than electrical. The panel does NOT need to be centered in the 30 inch space.
 
  #12  
Old 09-01-13, 02:52 PM
SBI
SBI is offline
Member
Thread Starter
Join Date: Dec 2004
Location: USA
Posts: 384
With in wall cable the ground is not included with the wire count. 6-3 means the size of each current carrying wire will be #6 and the 3 means there are three of them. There is always a ground so it is not part of the count.
Right, it is 6-3 with 3 wires, + a ground wire. What I meant was that the 4th ground wire can be used as ground, as you mentioned earlier.

The door is 30" wide so I'll definitely have the 30" side to side, and I will have 36" in front when the door is open
 
  #13  
Old 09-01-13, 03:07 PM
ray2047's Avatar
Group Moderator
Join Date: Mar 2006
Location: USA
Posts: 33,065
Dang! Furd is going to make me stand in the corner for the rest of the day because of that one. My post will be corrected. (Hey, mods have perks.)

 
  #14  
Old 09-01-13, 03:37 PM
SBI
SBI is offline
Member
Thread Starter
Join Date: Dec 2004
Location: USA
Posts: 384


Thanks! Will have all that (when the door is open
 
  #15  
Old 09-01-13, 04:28 PM
Nashkat1's Avatar
Member
Join Date: Mar 2012
Location: USA
Posts: 8,470
Will have all that (when the door is open
When the door is open? Are you planning to put your subpanel in a closet?

1. I already have a sub-panel in the basement which we did during basement renovations. Could be a dumb question, but is there a limit to number of sub-panels you can have in the house ?
No.

2. What kind of wire do I need for a 60A sub, is it 6 awg?
60A? I thought you were only going to use this for your office and separate the rest of the loads on the second floor from it. What are you planning to install in your office that will require 60A?

3. The only path I might have from that pipe to where I want the sub is through the ceiling joists. I know about the basic do's and don'ts for drilling, but can such a thick wire go through joists/studs, or is it more common to run panel feeds through cavities only?
If your attic is unfinished there's no need to drill through the joists to run cable. It can just lay across them.

If the PVC sleeve is 1-1/2" OD it should be 1-1/4" ID. That's plenty of room for your cable.

I use a 7/8" auger bit to drill through framing. That hole is plenty big enough for your feed cable. Just make all holes in the center of each member (like the top plate).

Does your jurisdiction require residential wiring to be done in metal conduit?

Note: This job requires a permit in most jurisdictions.
 
  #16  
Old 09-01-13, 05:18 PM
SBI
SBI is offline
Member
Thread Starter
Join Date: Dec 2004
Location: USA
Posts: 384
When the door is open? Are you planning to put your subpanel in a closet?
No, sorry...the door to the room , so it will be a flush mount on inside wall behind the door when the door is open.

60A? I thought you were only going to use this for your office and separate the rest of the loads on the second floor from it. What are you planning to install in your office that will require 60A?
I am, but I'd like to over-prepare instead of going short and find myself with an issue. According to my over-kill calculations (including three high wattage computers, two monitors, office shredder, maybe a window a/c, a small baseboard heater for supplemental heat, chargers, modem, routers, switches [I know they are small consumers, but still] ) I am at around 46A.
Also, as I mentioned this room was used as a laundry room by the previous owner and we kept all infrastructure in the room (it will be closed in behind 2X4 and sheetrock with panel access) just in case we would like to convert this room back to a laundry room when we get too old to go down to the basement
Hoping it won't happen before I retire, if/when this happens, I'll be able to 'convert' all my office electronics to a one 30A outlet for dryer and 20A for the washer.

Does your jurisdiction require residential wiring to be done in metal conduit?

Note: This job requires a permit in most jurisdictions.
Not sure, I'll have my electrician deal with that. In my city I cannot pull a permit for electrical work, only a licensed electrician (however, contrary to the local inspector, according to MA laws, anyone can perfom electrical work, they just can't pull a permit if they are not licensed (per MA's chief electrical inspector).
 
  #17  
Old 09-01-13, 07:26 PM
Nashkat1's Avatar
Member
Join Date: Mar 2012
Location: USA
Posts: 8,470
OK, got it on the sizing of the sub and its feed. One question: No printer?

Originally Posted by Nashkat1
Does your jurisdiction require residential wiring to be done in metal conduit?

Note: This job requires a permit in most jurisdictions.
Not sure, I'll have my electrician deal with that. In my city I cannot pull a permit for electrical work, only a licensed electrician (however, contrary to the local inspector, according to MA laws, anyone can perfom electrical work, they just can't pull a permit if they are not licensed (per MA's chief electrical inspector).
The law is written that way so that 1> they have done what they could to restrict issuing permits to people who are trained, experienced, bonded and licensed to perform the work properly and, 2> those people are free to hire whom they like to work for them. Gotta train helpers and apprentices somehow, otherwise we don't have a next generation of masters.

The chief inspector's interpretation sounds entirely in alignment with this.
 
  #18  
Old 09-01-13, 09:18 PM
SBI
SBI is offline
Member
Thread Starter
Join Date: Dec 2004
Location: USA
Posts: 384
One question: No printer?
Absolutely , a Multi Function device and at its pick it draws around 24 watts. It was included in the calculations, but I forgot to mention it above.

Thanks!
 
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