[dcopps]

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

 

[wirenut1110]

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

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

 

[hayewe farm]

Have you actually checked you usage to see if at any time you are actually using more than 100 amps?

 

[300zx]

circuits

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.

 

[ScottR]

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.

 

[dcopps]

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.

 

[InPhase277]

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?

 

[dcopps]

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]

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 PANEL 1Small 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

 

[hayewe farm]

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.

 

[dcopps]

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]

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.

 

[300zx]

Looks good, Is that a pvc j-box or metal ? I would put a ground lug in if metal :thumbsup:

 

[dcopps]

Looks good, Is that a pvc j-box or metal ? I would put a ground lug in if metal :thumbsup:

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)

 

[InPhase277]

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.

 

[dcopps]

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.

I agree it needs a cleanup. My biggest worry is how to trace which neutral to move over to the sub panel. With all the clutter it will be difficult. Any suggestions?

 

[InPhase277]

I agree it needs a cleanup. My biggest worry is how to trace which neutral to move over to the sub panel. With all the clutter it will be difficult. Any suggestions?

Man, honestly, since you are doing all that work any way, just disconnect everything and go from there. Pull all the wires off the ground and neutral bars, label or mark the wires on the breakers, and start fresh. Find the neutrals you need and get them out of the way, then re-terminate everything nice and neat. Then make your taps and tie everything up. You will be much more satisfied when you're done.

 

[dcopps]

Well, I finished the sub panel over the weekend. Took a lot longer than I thought. The main panel is cluttered more than I would like but what can you say with 45 wire nuts. I attached a finshed. Next project will be the transfer switch. Thanks for the help.

 

[masterklu]

I have just aquired a Kohler 12res generator and a Asco 165 100amp ATS . I also have a 200 amp service., I am not a electrician but have some elec. understanding, but would like more. My intent is to do the same install as yours, with the help of a elctrician friend. Have you installed the ATS yet ? I would like to hear and see the install, follow up with some pictures if possible. I would like to do the wiring and set up myself if possible with help of course. Your post is much appreciated. Thanks

 

[dcopps]

I just finished the intall yesterday. Everything works great. I also installed a watt meter below the TS. You can see the current transformers in the photo of the TS.