Subpanel cable in open ceiling with steel joists

[DanielVetpath]

Hi folks: I recently bought a decades old commercial building to use as shop space. The ceiling is open and the construction includes steel joists. The existing subpanels are pushmatic fed by three wire SER cable threaded through the joists. The main service panel was upgraded to a Square D 200 amp service. The electrician tied in the existing subpanel cables, each to a 100 amp breaker. I am starting to replace the subpanels as I work my way through the building. The run to the first subpanel I want to replace is 80 feet. What size cable should I use (assume aluminum) and can it be SER or should I use MC or something else as it runs through the exposed joists? Thanks for any insights. Daniel

 

[Terry D]

To keep them at 100 amps, i would use a #1 aluminum 4 -wire MC cable or EMT

Looks like you have alot of clean up in that ceiling

 

[mike93lx]

When you price out the wire and conduit, I would think about how much power you really need. You can step down in wire size by going to a 90a breaker (#2 AL instead of #1) or even #4 for a 60a breaker. 60a breakers are cheap, too.

 

[DanielVetpath]

To keep them at 100 amps, i would use a #1 aluminum 4 -wire MC cable or EMT

Looks like you have alot of clean up in that ceiling

Thanks for the info. A lot of clean up for sure, but I am grateful that everything is open and very accessible.

 

[Norcal]

When you price out the wire and conduit, I would think about how much power you really need. You can step down in wire size by going to a 90a breaker (#2 AL instead of #1) or even #4 for a 60a breaker. 60a breakers are cheap, too.

15-60A breakers are the same price, then at 70A it jumps up in price, then 80-100A, goes up again, then 110-125A goes up even more. 80A & 110A breakers are not real common.

 

[mike93lx]

15-60A breakers are the same price, then at 70A it jumps up in price, then 80-100A, goes up again, then 110-125A goes up even more. 80A & 110A breakers are not real common.

I know, that's why I mentioned 60a breaker costs.

Didn't want him to run #2 and be surprised at the cost of a 90a breaker. IMO, either stick with 100a or drop to 60a

 

[theoldwizard1]

In residential buildings horizontal feed from/to the panel must be in conduit or behind a covering (plywood/drywall) up to the top plate.

Subpanel must be connect to main by 4 wires. As others have said, stick with the lowest amperage breaker possible in the main. Saves money on wire also.

 

[sparky 1971]

How many sub panels are there total? I know the first is 80' away, but what about the rest? It may be more cost effective to get a roll(s) of mc cable that is long enough to do everything. You could probably get by with 60 amps to each sub, but since the 100 amp breakers are already in place, it's going to come down to cost which will be based on footage of wire needed, which changes just about every hour. Just figure out what the length of cables you are going to need, find the price of the cable and fittings and compare.

 

[alfredeneuman]

Hi folks: I recently bought a decades old commercial building to use as shop space. The ceiling is open and the construction includes steel joists.

NEC 334.10

3) Other structures permitted to be of Types III, IV, and V construction. Cables shall be concealed within walls, floors, or ceilings that provide a thermal barrier of material that has at least a 15-minute finish rating as identified in listings of fire-rated assemblies.
******************************************************************************
Type 1 and 2 are for residential
You'd have to drywall the entire area if NM and SER were to be used

 

[DanielVetpath]

How many sub panels are there total? I know the first is 80' away, but what about the rest? It may be more cost effective to get a roll(s) of mc cable that is long enough to do everything. You could probably get by with 60 amps to each sub, but since the 100 amp breakers are already in place, it's going to come down to cost which will be based on footage of wire needed, which changes just about every hour. Just figure out what the length of cables you are going to need, find the price of the cable and fittings and compare.

Nice. Pretty much what I was thinking. Thanks

 

[wyliesdiesels]

Hi folks: I recently bought a decades old commercial building to use as shop space. The ceiling is open and the construction includes steel joists. The existing subpanels are pushmatic fed by three wire SER cable threaded through the joists. The main service panel was upgraded to a Square D 200 amp service. The electrician tied in the existing subpanel cables, each to a 100 amp breaker. I am starting to replace the subpanels as I work my way through the building. The run to the first subpanel I want to replace is 80 feet. What size cable should I use (assume aluminum) and can it be SER or should I use MC or something else as it runs through the exposed joists? Thanks for any insights. Daniel

That was not done to code. subpanels need to be fed with 4-wire feeders especially when the main is in the same building

EDIT: i zoomed in real close on the pic and see that there is indeed a ground wire so disregard

 

[alfredeneuman]

That was not done to code. subpanels need to be fed with 4-wire feeders especially when the main is in the same building

SER cable is the same as NM as the ground wire isn't counted. 6-3 SER has 4 wires
https://www.platt.com/platt-electric-supply/Service-Entrance-Wire/Service-Type-SER-Aluminum/search.aspx?q=6/3+ser+cable&SectionID=15&GroupID=197&CatID=761&SubCatID=1464

 

[wyliesdiesels]

SER cable is the same as NM as the ground wire isn't counted. 6-3 SER has 4 wires
https://www.platt.com/platt-electric-supply/Service-Entrance-Wire/Service-Type-SER-Aluminum/search.aspx?q=6/3+ser+cable&SectionID=15&GroupID=197&CatID=761&SubCatID=1464

all the SER ive ever dealt with had the ground wire counted including on the jacket. but alas i zoomed in on the picture and see that there is a ground wire....

 

[DanielVetpath]

Follow up question. One of the other pushmatic subpanels is fed with three wires (no ground) through EMT from a shut off. If the conduit is large enough (I will have to measure it), can I just pull a ground and replace the subpanel with an upgraded (non-pushmatic) version? If so, how do I bond the ground coming from the main panel to the ground going to the subpanel? Get a double lug?

 

[PCustoms]

Follow up question. One of the other pushmatic subpanels is fed with three wires (no ground) through EMT from a shut off. If the conduit is large enough (I will have to measure it), can I just pull a ground and replace the subpanel with an upgraded (non-pushmatic) version? If so, how do I bond the ground coming from the main panel to the ground going to the subpanel? Get a double lug?

Is this what you are calling a "subpanel"?

Is this fed from the top, or the bottom?

 

[DanielVetpath]

Is this what you are calling a "subpanel"?

Is this fed from the top, or the bottom?

This is the shut off coming from the main panel (coming in bottom) and heading out (wires leaving top) to one of the pushmatic panels. Note: this is a different subpanel than the one I originally mentioned. The previous panel is fed by SER cable. There are three others that are fed via these shut offs with EMT.

 

[mike93lx]

I would think a dual lug and then adding a egc would work, although if it is EMT end to end, I think that should cover you. I am not an electrician though

 

[alfredeneuman]

fed with three wires (no ground) through EMT from a shut off.

If EMT is used all the way you don't need a ground wire.
The EMT serves as the ground.

 

[wyliesdiesels]

Is the EMT complete from panel to panel? if so, no need to add an EGC. the conduit is your ground

 

[Terry D]

This is the shut off coming from the main panel (coming in bottom) and heading out (wires leaving top) to one of the pushmatic panels. Note: this is a different subpanel than the one I originally mentioned. The previous panel is fed by SER cable. There are three others that are fed via these shut offs with EMT.

I might be more concerned how they tapped power to feed those disconnects. I do see (4) 2-pole breakers, but seems redundant to feed a fused disconnect off a breaker, Might have been the easiest thing to do when they replaced that panel. Those disconnects obviously have been there longer than the panel.

 

[DanielVetpath]

I might be more concerned how they tapped power to feed those disconnects. I do see (4) 2-pole breakers, but seems redundant to feed a fused disconnect off a breaker, Might have been the easiest thing to do when they replaced that panel. Those disconnects obviously have been there longer than the panel.

You are correct - the electrician that just replaced the main panel maintained the 100 amp breakers and fed them to the pre-existing disconnects.

 

[DanielVetpath]

Is the EMT complete from panel to panel? if so, no need to add an EGC. the conduit is your ground

You are correct - there is continuous emit from the disconnect to the subpanel

 

[sparky 1971]

No need to worry about the three panels that are utilizing continuous EMT. You can replace the panels if you want, but I don't see a reason to unless there is a problem, it's not like they are Federal or Zinsco panels. I believe the panel posted in the OP has a four wire feeder. I see an insulated neutral and a bare ground, but can't tell if the ground goes to the cable for sure, don't know where else it would come from though. If it were my building for my own personal use, I wouldn't lose a bit of sleep over it being as is until I got around to fixing it.

 

[Norcal]

The big problem with Pushmatic panels is they are obsolete & replacement breakers are freaking expensive but if don’t need to replace them now, might wait & replace as needed. They are not like Zinsco/Sylvania, or FPE.

 

[alfredeneuman]

The big problem with Pushmatic panels is they are obsolete & replacement breakers are freaking expensive but if don’t need to replace them now, might wait & replace as needed. They are not like Zinsco/Sylvania, or FPE.

I'll say!
How about a 2 pole 20A C/B for $60.98????
https://www.homedepot.com/p/Pushmat...acement-Circuit-Breaker-VPKUBIP2020/100175741

 

[Bert_]

Jeez. Didn't know pushmatic breakers sold for big bucks. I've got a couple boxes of used pushmatic breakers that I grab from whenever I need one. If a friend needed one I'd give it to them for free.

 

[nadogail]

Jeez. Didn't know pushmatic breakers sold for big bucks. I've got a couple boxes of used pushmatic breakers that I grab from whenever I need one. If a friend needed one I'd give it to them for free.

One Man's Trash is another mans Treasure.

 

[sparky 1971]

Wow. I haven't bought a Pushmatic in years. I have several interiors with the breakers still mounted in them along with a couple of boxes of them. The last I had to buy one, I think it was a Siemens. That was probably 15 years ago.

 

[Norcal]

Wow. I haven't bought a Pushmatic in years. I have several interiors with the breakers still mounted in them along with a couple of boxes of them. The last I had to buy one, I think it was a Siemens. That was probably 15 years ago.

I have some NOS, P2100's, & P270's, been procrastinating about putting them on eBay for years, I pity anyone with a 3 phase Pushmatic panel, they were discontinued long before the single phase panels, I would almost be willing to bet that 3-pole breakers would be even more costly then Zinsco bolt-on breakers, which are both only available as used items.

 

[DanielVetpath]

All of your input is really helpful. You can see in this picture that there are multiple boxes and wires for old telephone service. There were up to two businesses downstairs and two apartments upstairs at one time or another. I am interested in continuing to remove old, obsolete and unused wires and pipes to simplify and update things as I go. Can I simply cut the wires and remove those telephone interfaces without causing problems to the telephone service that feeds them? I have tried to contact our local land line service provider, but get caught in the phone tree as I am not a customer (catch 22 - have to become customer to get them to access my account to help me). Thanks for any thoughts. Really, I just want to simplify and clean things up. I will probably just get rid of these fused disconnects and run typical four wire through EMT (I know I don't need a ground, but for the relative cost and peace of mind) to upgraded Square D subpanels as there are already 100 amp breakers in place. It gives me better access to the side of the main panel in this picture and gets rid of more moving parts.

 

[mike93lx]

I would have no qualms with cutting anything inside my building and that shouldnt cause any upstream issues.

 

[Terry D]

I have some NOS, P2100's, & P270's, been procrastinating about putting them on eBay for years, I pity anyone with a 3 phase Pushmatic panel, they were discontinued long before the single phase panels, I would almost be willing to bet that 3-pole breakers would be even more costly then Zinsco bolt-on breakers, which are both only available as used items.

I had a box of them. I ended up selling most of them on Ebay. Kept a few for my self. They sold quick. Also sold some wadsworth. I guess people are still trying to keep the old panels going

 

[DanielVetpath]

I would have no qualms with cutting anything inside my building and that shouldnt cause any upstream issues.

Thanks - didn't want to create issues for someone else. I know how frustrating that can be. If I can get the maze of wires leading from the telephone service cables on the outside of the building, it will really help clean things up. When the electrician upgraded the main panel, he removed five old electric meters taking me from six accounts to one account with the electric service provider.

 

[Norcal]

All of your input is really helpful. You can see in this picture that there are multiple boxes and wires for old telephone service. There were up to two businesses downstairs and two apartments upstairs at one time or another. I am interested in continuing to remove old, obsolete and unused wires and pipes to simplify and update things as I go. Can I simply cut the wires and remove those telephone interfaces without causing problems to the telephone service that feeds them? I have tried to contact our local land line service provider, but get caught in the phone tree as I am not a customer (catch 22 - have to become customer to get them to access my account to help me). Thanks for any thoughts. Really, I just want to simplify and clean things up. I will probably just get rid of these fused disconnects and run typical four wire through EMT (I know I don't need a ground, but for the relative cost and peace of mind) to upgraded Square D subpanels as there are already 100 amp breakers in place. It gives me better access to the side of the main panel in this picture and gets rid of more moving parts.

Are those safety switches being fed from that SQ D panel? If so, they are reverse fed & someone is in for a rude & deadly experience if they try to remove a fuse.

 

[DanielVetpath]

I had a box of them. I ended up selling most of them on Ebay. Kept a few for my self. They sold quick. Also sold some wadsworth. I guess people are still trying to keep the old panels going

Thanks - I thought I might try to sell these as well and use the money to offset some expense with the current upgrades.

 

[Terry D]

Are those safety switches being fed from that SQ D panel? If so, they are reverse fed & someone is in for a rude & deadly experience if they try to remove a fuse.

Good catch. I didn't even catch that. That should be addressed, good thing you can turn the breaker off upstream

 

[DanielVetpath]

Are those safety switches being fed from that SQ D panel? If so, they are reverse fed & someone is in for a rude & deadly experience if they try to remove a fuse.

Wow - never even noticed. Interestingly, they were originally fed from the bottom from the electric meter on the other side of the wall (you can see the hole filled in below each disconnect). The electrician that upgraded the main service panel removed the extra electric meters and wired these disconnects to 100 amp breakers in the panel. Many thanks for pointing this out.

 

[DanielVetpath]

Are those safety switches being fed from that SQ D panel? If so, they are reverse fed & someone is in for a rude & deadly experience if they try to remove a fuse.

Yes! ouch.