Go Back   DIY Chatroom Home Improvement Forum > Home Improvement > Electrical

CLICK HERE AND JOIN OUR COMMUNITY TODAY...IT'S FREE!

Reply
 
Thread Tools Search this Thread Display Modes
Old 06-03-2009, 04:32 PM   #1
Newbie
 
Join Date: May 2009
Location: Texas
Posts: 21
Share |
Default

Adding a Sub Panel for Transfer Switch


I am installing a standby generator for my home.

I am adding a 100amp sub panel adjacent to my 200amp main in my garage. I will move 22 essential circuits from the main panel to the 100amp sub panel. The sub panel will be controlled by a 100amp automatic transfer switch with a 20kw standby generator or a 100amp breaker from the main panel.

To move the circuits to the sub I must splice the circuits with wire nuts in the main panel. Wires are not long enough or accessible to reroute them to the sub

My question is: Is it OK to just move the HOTs for each branch circuit to the sub panel and leave the neutrals in the main. There is a #2 neutral from the TS to the main neutral bar and to the sub panel neutral bar (not switched)

I am trying to minimize the splices (wire nuts) required in the main panel (24 versus 45 if I move the neutrals). I am using a 2-1/2 “conduit from the main to the sub. If I move the neutrals I would have 3-#2, 1-#6(g), 5-#8, and 40-#12.

I think I know what the answer is (move the neutrals) but I just want verification and a reason.

Thanks in advance

dcopps is offline   Reply With Quote
Old 06-03-2009, 06:49 PM   #2
Electrical Contractor
 
wirenut1110's Avatar
 
Join Date: Apr 2008
Location: Chester, VA.
Posts: 1,049
Send a message via AIM to wirenut1110
Default

Adding a Sub Panel for Transfer Switch


Code requires they be routed together and terminate in the same panel.

Someone else may be able to cite a a code article.

wirenut1110 is offline   Reply With Quote
Old 06-03-2009, 07:35 PM   #3
Member
 
Join Date: Mar 2009
Posts: 780
Default

Adding a Sub Panel for Transfer Switch


Have you actually checked you usage to see if at any time you are actually using more than 100 amps?
hayewe farm is offline   Reply With Quote
Old 06-03-2009, 07:45 PM   #4
Member
 
300zx's Avatar
 
Join Date: May 2009
Location: Florida
Posts: 630
Default

Adding a Sub Panel for Transfer Switch


Quote:
Originally Posted by hayewe farm View Post
Have you actually checked you usage to see if at any time you are actually using more than 100 amps?
I was thinking the same thing. 22 circuits can add up quick.
300zx is offline   Reply With Quote
Old 06-03-2009, 10:01 PM   #5
DIY'r
 
ScottR's Avatar
 
Join Date: Oct 2008
Location: Hicksville, NY (Yes, it's an actual town).
Posts: 520
Default

Adding a Sub Panel for Transfer Switch


Quote:
Originally Posted by dcopps View Post
I am using a 2-1/2 “conduit from the main to the sub. If I move the neutrals I would have 3-#2, 1-#6(g), 5-#8, and 40-#12.
I could very well be wrong, but isn't that too much fill for 2 1/2"?*

*EDIT: At least without derating all 49 conductors.

Last edited by ScottR; 06-03-2009 at 10:06 PM.
ScottR is offline   Reply With Quote
Old 06-04-2009, 07:56 AM   #6
Newbie
 
Join Date: May 2009
Location: Texas
Posts: 21
Default

Adding a Sub Panel for Transfer Switch


Quote:
Originally Posted by 300zx View Post
I was thinking the same thing. 22 circuits can add up quick.
I checked it two ways.

First using the large loads (20amp ac, frig, ect) plus lighting and small appliances based on sf of house. Came to 79amps plus 20% overload = 95 amps.

Second by adding up all the watts assuming everything is on (Lights, coffee pot, hair drye, etc.). It came to 94 amps but i don't see this ever happening.
dcopps is offline   Reply With Quote
Old 06-04-2009, 08:03 AM   #7
My License Ain't 4 Sale..
 
Join Date: Feb 2008
Location: Atlanta, Ga/Hamilton, Al
Posts: 1,813
Default

Adding a Sub Panel for Transfer Switch


A conduit nipple can be filled to 60% before derating, but I haven't done the math. And yes, the neutrals should be routed with the hots. The grounds can stay.

P.S.: 22 essential circuits? Really? We have different definitions of essential then! The fridge, a couple lighting circuits, the furnace blower, the well pump, and a couple receptacle circuits are essential. But 22?

Last edited by InPhase277; 06-04-2009 at 08:05 AM.
InPhase277 is offline   Reply With Quote
Old 06-04-2009, 08:07 AM   #8
Newbie
 
Join Date: May 2009
Location: Texas
Posts: 21
Default

Adding a Sub Panel for Transfer Switch


Quote:
Originally Posted by ScottR View Post
I could very well be wrong, but isn't that too much fill for 2 1/2"?*

*EDIT: At least without derating all 49 conductors.
I checked it without the neutrals (28 conductors) and it was plenty but I need to recheck to include the neutrals. The conduit is less than 24” long so do I still need to meet the max fill requirements.
The main panel is recessed in sheet rock in my garage. I placed an 8x8x8 JB below the panel with a short 2 ½” nipple that resulted in 4” of the JB protruding out of the wall. That allowed me to put in a 2 ½” el to the sub panel. Each one of the conduits is less than 24”. The total length of each conductor from main to sub is 7.5’. I’ll try to take a photo tonight to show this monstrosity.
dcopps is offline   Reply With Quote
Old 06-04-2009, 08:13 AM   #9
Newbie
 
Join Date: May 2009
Location: Texas
Posts: 21
Default

Adding a Sub Panel for Transfer Switch


Quote:
Originally Posted by InPhase277 View Post
A conduit nipple can be filled to 60% before derating, but I haven't done the math. And yes, the neutrals should be routed with the hots. The grounds can stay.

P.S.: 22 essential circuits? Really? We have different definitions of essential then! The fridge, a couple lighting circuits, the furnace blower, the well pump, and a couple receptacle circuits are essential. But 22?
We were without power for 13 days during Hurrican Ike. After that long you want a lot of essentials. I attempted to attach the spreadsheet showing the panel. Hope it works.
SUB PANEL1Small AC (240)20120Microwave (240)3220220410Frig - Kitchen20115Master Bedroom1223Frig - Utility20215Bedroom 2 & 3136Kitchen GFI (1)20115Garage & Ulility Light57Furnace (Large)2015Bath 2, Entry & Front Light168Kitchen GFI (2)20215Family Room & Fan179Disposal/Dishwasher2015Sprinkler1811Garage GFI (Work Bench)20115Kitchen / Breafast Lights1914Master Bath GFI2015Bath Light / Floor Plug & Outside2115Washer / Dryer20215Tv/Porch/Study & Outside2024Vent Hood2015Furnace (Small)22
dcopps is offline   Reply With Quote
Old 06-04-2009, 11:25 AM   #10
Member
 
Join Date: Mar 2009
Posts: 780
Default

Adding a Sub Panel for Transfer Switch


It seems to me that you are going through a lot of extra work. Why not just install a main transfer switch. The chances of you actually using more than 20KW at one time is generally pretty slim. You can then us the breakers in the panel to turn off circuits not in use but still have them available if you need them.
hayewe farm is offline   Reply With Quote
Old 06-04-2009, 01:17 PM   #11
Newbie
 
Join Date: May 2009
Location: Texas
Posts: 21
Default

Adding a Sub Panel for Transfer Switch


Quote:
Originally Posted by hayewe farm View Post
It seems to me that you are going through a lot of extra work. Why not just install a main transfer switch. The chances of you actually using more than 20KW at one time is generally pretty slim. You can then us the breakers in the panel to turn off circuits not in use but still have them available if you need them.
This would work but I am trying to do it to code.

If I had a whole house transfer switch (without load shedding) Code would require the generator to be sized for the whole house and that includes two A/Cs, pool pump, oven, electric dryer, ect. I want this system to work automatic even when no one is home.
dcopps is offline   Reply With Quote
Old 06-04-2009, 08:34 PM   #12
Newbie
 
Join Date: May 2009
Location: Texas
Posts: 21
Default

Adding a Sub Panel for Transfer Switch


OK, here are the the photos of the project. As you can see I have already moved the a/c and microwave circuit. The main is going to take some clean up. I haven't ordered the TS yet. Let me know if I am on the right track.
Attached Thumbnails
Adding a Sub Panel for Transfer Switch-img_0433.jpg   Adding a Sub Panel for Transfer Switch-img_0436.jpg   Adding a Sub Panel for Transfer Switch-img_0435.jpg   Adding a Sub Panel for Transfer Switch-img_0437.jpg   Adding a Sub Panel for Transfer Switch-img_0438.jpg  

Attached Files
File Type: pdf Load Center.pdf (23.6 KB, 106 views)
dcopps is offline   Reply With Quote
Old 06-04-2009, 08:45 PM   #13
Member
 
300zx's Avatar
 
Join Date: May 2009
Location: Florida
Posts: 630
Post

Adding a Sub Panel for Transfer Switch


Looks good, Is that a pvc j-box or metal ? I would put a ground lug in if metal
300zx is offline   Reply With Quote
Old 06-04-2009, 09:41 PM   #14
Newbie
 
Join Date: May 2009
Location: Texas
Posts: 21
Default

Adding a Sub Panel for Transfer Switch


Quote:
Originally Posted by 300zx View Post
Looks good, Is that a pvc j-box or metal ? I would put a ground lug in if metal
It's metal. But the nipple to the main is also metalic so i figured it would do for the ground. It would be simple to add a ground for the JB (if the 2 1/2" nipple is not already full)
dcopps is offline   Reply With Quote
Old 06-04-2009, 09:51 PM   #15
My License Ain't 4 Sale..
 
Join Date: Feb 2008
Location: Atlanta, Ga/Hamilton, Al
Posts: 1,813
Default

Adding a Sub Panel for Transfer Switch


I might have done things a little different, but overall, it seems compliant. The metal box doesn't need to be bonded by a wire unless there is a splice in it, but as it is painted metal, the nipple may not be making a good connection. It would be easy to add an open lug in there and land the largest ground on it.

Also, you will save yourself a headache later if you square those wires up in both panels. Right now they are banjo'd as the crow flies. A neat panel is safer and easier to work in. Zip ties are your friend.

InPhase277 is offline   Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

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


Similar Threads
Thread Thread Starter Forum Replies Last Post
Adding a sub panel and cleaning up this mess rovers1973 Electrical 23 02-19-2009 08:35 AM
Transfer switch to main panel connection i6pwr Electrical 3 01-28-2009 06:09 AM
Light Switch to Detached Garage - Grounding Issue smitty286 Electrical 1 10-22-2008 12:17 PM
Electrical Question - adding a 3 way switch to existing Light Marcus23 Electrical 5 10-11-2008 08:52 AM
Adding a Switch and jump power Bull-37 Electrical 9 01-10-2008 05:45 PM




Top of Page | View New Posts

Copyright © 2003-2014 Escalate Media. All Rights Reserved.