Planning for new sub-panel in Pole Barn

[HomerGuy]

Hello,

I'm in the planning stages for a 30x40 pole barn and was hoping to get some feedback on my electrical plans.

This building will be used for storage, some light vehicle maintenance, woodworking projects, etc. My initial usage will be general lighting and small power tools. No high draw compressors, welders, fabrication equipment, etc.

The two biggest loads I can foresee are a Level 2 EV charger (48/60 amps) and a mini split to heat/cool a small 150 sq ft office space (18 amps @ 120v). I'm sure a 60 amp sub panel would be more than sufficient for my initial use, but thinking 100 amp may be the best long term option given the EV charger.

My 5 year old house has a 200 amp Siemens PN Series main panel. The wire run from the main panel in the basement of the house to the sub panel in the new barn is 275 feet (possibly as little as 265’ depending on final location of the barn sub panel, this includes vertical rise).

Here are my thoughts, please critique:

• For the 100 Amp Sub panel in barn
  • Install 100 amp breaker in main panel that will feed sub panel. Locate this 100 amp breaker as close as possible to main breaker at the top of the panel. May need to shift some breakers to make room.
  • In the barn, install Siemens PN Series 100 Amp, 20-Space, 20-Circuit main breaker panel. Keeping with the same Siemens PN series panel because why not match the main house panel.
• Feed the sub panel with three Aluminum 1/0 XHHW (2 black hot, 1 white neutral) and one Aluminum #4 XHHW (green ground).
  • At 100 amps, calculated voltage drop is 4.77%
  • At 60 amps, calculated voltage drop is 2.86%
• Use 1-½” schedule 40 PVC Conduit buried with minimum 18” cover. My soil is mostly sand, but I do contend with some rocks. Cover halfway, install buried electrical tape marker, then complete the remainder of the backfill.
  • With 1-½” conduit, the fill percentage is 27.66% with my proposed feed wire.
  • May need to transition to schedule 80 at side of house if the vertical conduit is exposed at the house.
  • Use conduit expansion coupling at transition from horizontal to vertical run.
  • I am seeing that 2” PVC may actually be cheaper (or very similar in price) to 1-½” PVC. If that is the case, I may just use 2”.
• Do NOT bond neutral and ground in sub panel
• Install Two ground rods with continuous wire at sub panel location.

Low voltage

• Install 1” PVC Conduit for data. I have no idea what this looks like yet. Still need to learn more about cable options for this long of an underground run. But I would like to have WiFi in the barn.

Finally, one last question:
I currently have a manual generator interlock kit installed on my main house panel. Is there any way I could connect the generator to the pole barn sub panel, and then back feed the house through the sub panel in the barn? When the power is out, it would be nice to move the running generator further away from the house. I cannot see a way this is possible, without running separate feeders from the main panel out to the generator inlet plug, but figured it wouldn’t hurt to ask.

 

[JuncleJohn]

That far away, and the power needed for the charger, you might need to have a separate service to your building.

We’ll see what the experts say.

John

 

[wyliesdiesels]

i would go larger on the electrical and data conduits. 2" for electrical, and 1.5" for data. I would run 2 conduits for comms. use 1 now and have one for extra in the future.

I would also go larger on the subpanel in terms of breaker spaces

275' is fine for CAT6

 

[wyliesdiesels]

Finally, one last question:
I currently have a manual generator interlock kit installed on my main house panel. Is there any way I could connect the generator to the pole barn sub panel, and then back feed the house through the sub panel in the barn? When the power is out, it would be nice to move the running generator further away from the house. I cannot see a way this is possible, without running separate feeders from the main panel out to the generator inlet plug, but figured it wouldn’t hurt to ask.

you would have to run separate feed wires from the generator inlet on the pole barn to the main panel on the house.

no way to do this via the feeder for the pole barn as the interlock would need to have the pole barn breaker in the off position when the main service panel breaker is on to prevent utility backfeed

 

[wyliesdiesels]

That far away, and the power needed for the charger, you might need to have a separate service to your building.

We’ll see what the experts say.

John

why?

 

[JuncleJohn]

That’s why I said let’s see what the experts say. I’m not an electrician. I was wondering if maybe that would be too many amps to rob from the house.

John

 

[Cruzan80]

That’s why I said let’s see what the experts say. I’m not an electrician. I was wondering if maybe that would be too many amps to rob from the house.

John

No reason that the subpanel couldn't be a 200A if required. The only restriction that I know of is that the sub can't be bigger than the main (pesky math stuff means it can't supply more than it has total... /s).

IIRC, the subpanel can have a master breaker higher than the feeding breaker in the main panel, because the subpanel "master" simply becomes a means of disconnect, and the feed wiring is protected by the breaker in the main panel.

 

[JuncleJohn]

No reason that the subpanel couldn't be a 200A if required. The only restriction that I know of is that the sub can't be bigger than the main (pesky math stuff means it can't supply more than it has total... /s).

IIRC, the subpanel can have a master breaker higher than the feeding breaker in the main panel, because the subpanel "master" simply becomes a means of disconnect, and the feed wiring is protected by the breaker in the main panel.

Thank you. Still learning new things everyday.

John

 

[wyliesdiesels]

That’s why I said let’s see what the experts say. I’m not an electrician. I was wondering if maybe that would be too many amps to rob from the house.

John

without knowing what electrical loads the house has, how many people, and doing a load calc, there is no way to know such a thing. which is why suggesting such a thing is a waste of time.

most houses pull hardly any load except during thanksgiving and christmas when the oven stove microwave and AC are on full tilt and someone is hanging out in the hot tub.

 

[matt_i]

I would definitely run 2". Easier to pull and larger LBs if you are using those.

Also I am not a fan of using anything other than copper wire. Just a personal preference. I believe it to be the best engineering material for the job.

 

[JuncleJohn]

Good to know.

John

 

[dscheidt]

you would have to run separate feed wires from the generator inlet on the pole barn to the main panel on the house.

no way to do this via the feeder for the pole barn as the interlock would need to have the pole barn breaker in the off position when the main service panel breaker is on to prevent utility backfeed

The other way this can be done is to move the utility service to the barn, and have the house be a subpanel. That doesn't often make sense, but there are situations where it does.

 

[wyliesdiesels]

The other way this can be done is to move the utility service to the barn, and have the house be a subpanel. That doesn't often make sense, but there are situations where it does.

easier said than done if the panel in the house is a meter main or has a bolted neutral bus

 

[mike93lx]

I would definitely run 2". Easier to pull and larger LBs if you are using those.

Also I am not a fan of using anything other than copper wire. Just a personal preference. I believe it to be the best engineering material for the job.

Copper only serves to allow use of smaller diameter wires, which isn't needed in a new install, and to lighten your wallet (very significantly in this case). It will not function better.

Aluminum is perfectly safe and will work great.

 

[mike93lx]

IIRC, the subpanel can have a master breaker higher than the feeding breaker in the main panel, because the subpanel "master" simply becomes a means of disconnect, and the feed wiring is protected by the breaker in the main panel.

Correct

 

[theoldwizard1]

That far away, and the power needed for the charger, you might need to have a separate service to your building.

why?

The decision is up to the inspectors and PoCo !

If it is really a "barn" (capable of housing animals) the power company may require a separate service. (Happened to my buddy.) More expensive to install, but he gets an "agricultural rate" from the PoCo.

Also, most local codes for "barns" require that all electrical be in EMT.

 

[mm08822]

No reason that the subpanel couldn't be a 200A if required. The only restriction that I know of is that the sub can't be bigger than the main (pesky math stuff means it can't supply more than it has total... /s).

Don't confuse connected loads with simultaneous loads.

As long as the feeder connecting to the sub panel is properly ocp'd, the sub panel could be 200A rated and connected to a 100A service panel.
Worst case, the sub panel simultaneous loads increase over time and either the feeder cb or the main cb trips.

 

[mm08822]

The decision is up to the inspectors and PoCo !

If it is really a "barn" (capable of housing animals) the power company may require a separate service. (Happened to my buddy.) More expensive to install, but he gets an "agricultural rate" from the PoCo.

Also, most local codes for "barns" require that all electrical be in EMT.

Unless the load size increases for the house service AND the POCO can't provide for that increase, then maybe a proposed solution by the POCO is another service. It begs the question then, "How can you provide enough power for another service (load) but not accommodate my house 200' away?" (Different voltages and whether single vs 3 phase is needed becomes a different story.)

No way can POCO regulate anything past the meter. If I wanted to attach 6 100A feeders to my main panel, they can't say anything. Nor could the inspector if my load calcs don't require a service upgrade.

Unpainted emt in an ag building with livestock will rust out. Well protected pvc conduit or uf cable is more common, IME.

Where do these written local codes exist that you speak of?

 

[sparky 1971]

The decision is up to the inspectors and PoCo !

Really?

If it is really a "barn" (capable of housing animals) the power company may require a separate service. (Happened to my buddy.) More expensive to install, but he gets an "agricultural rate" from the PoCo.

Go back to post number one and read the second paragraph. Then, read it again.

Also, most local codes for "barns" require that all electrical be in EMT.

Again, really? How many different municipalities with written amendments are you familiar with?

 

[Cruzan80]

Don't confuse connected loads with simultaneous loads.

As long as the feeder connecting to the sub panel is properly ocp'd, the sub panel could be 200A rated and connected to a 100A service panel.
Worst case, the sub panel simultaneous loads increase over time and either the feeder cb or the main cb trips.

I didnt. If you read the rest of the post, you would see where I said that the subpanel could have a "master" breaker rated higher than the feeding breaker from the main. Which I think is what your reply was saying.

However, if the main breaker only receives 100A, their is no way it can supply 150A to the subpanel. That was the part where the sub CAN'T be bigger. Hence the "pesky math" part and the /s for sarcasm...

 

[HomerGuy]

Well this took a turn and started some interesting side discussions....lol.

So far the major take-aways that I see:
- Recommend 2" PVC conduit instead of 1-1/2". Looks like this only adds about $90 in pipe cost, so not too bad.
- Run two 1-1/2" PVC instead of one 1" PVC (one for data, one spare).
- Consider a larger sub-panel than the 20 space model. To be honest, I hadn't given this much thought. 20 spaces seems like plenty off the top of my head, but I haven't really put pen to paper on this one.
- I'm going to stay with the aluminum wire. Comparative copper (even with smaller gauge than AL) is literally 3x the price of the aluminum. I'm already looking at about $1k in aluminum wire.
- As suspected, I cannot connect my portable generator through the sub-panel in the pole barn.

Can someone please sanity check my wire sizes, particularly the ground?

 

[mike93lx]

Well this took a turn and started some interesting side discussions....lol.

So far the major take-aways that I see:
- Recommend 2" PVC conduit instead of 1-1/2". Looks like this only adds about $90 in pipe cost, so not too bad.
- Run two 1-1/2" PVC instead of one 1" PVC (one for data, one spare).
- Consider a larger sub-panel than the 20 space model. To be honest, I hadn't given this much thought. 20 spaces seems like plenty off the top of my head, but I haven't really put pen to paper on this one.
- I'm going to stay with the aluminum wire. Comparative copper (even with smaller gauge than AL) is literally 3x the price of the aluminum. I'm already looking at about $1k in aluminum wire.
- As suspected, I cannot connect my portable generator through the sub-panel in the pole barn.

Can someone please sanity check my wire sizes, particularly the ground?

#4 for egc is fine.

I'd probably go 2/0 for L1 and L2, and drop the neutral to #1. Probably cost neutral and gets you to right about 3% at 100a (although hitting 100a would be very difficult). Or 1/0 for hots and still #1 for neutral.

You could use your portable generator for just the barn.

If you want to feed it back to the house, #4 Al would get you 30a. 4-4-4-6 would work

 

[mm08822]

Well this took a turn and started some interesting side discussions....lol.

So far the major take-aways that I see:
- Recommend 2" PVC conduit instead of 1-1/2". Looks like this only adds about $90 in pipe cost, so not too bad.
- Run two 1-1/2" PVC instead of one 1" PVC (one for data, one spare).
- Consider a larger sub-panel than the 20 space model. To be honest, I hadn't given this much thought. 20 spaces seems like plenty off the top of my head, but I haven't really put pen to paper on this one.
- I'm going to stay with the aluminum wire. Comparative copper (even with smaller gauge than AL) is literally 3x the price of the aluminum. I'm already looking at about $1k in aluminum wire.
- As suspected, I cannot connect my portable generator through the sub-panel in the pole barn.

Can someone please sanity check my wire sizes, particularly the ground?

I think your plan is fine. Since you are liking the idea of 2" conduit, I would go with the 2-2/0, 1-#1, and 1-#4 into a 200A main cb 40 space panel. Feed the 2/0's with a 125A cb in your main panel. Even with fully the feeder fully loaded (unlikely), the vd is just @3%. (Cry once and you'll always have enough power w/o ever redo'ing anything.)

The only question I have is, what is the likelihood you will have 2 EVs charging in the pole barn at the same time? If these are daily drivers, are you going to walk a football field's length to get the car each day? Wouldn't one (or two) EV chargers more likely be at the house?

 

[mm08822]

I didnt. If you read the rest of the post, you would see where I said that the subpanel could have a "master" breaker rated higher than the feeding breaker from the main. Which I think is what your reply was saying.

However, if the main breaker only receives 100A, their is no way it can supply 150A to the subpanel. That was the part where the sub CAN'T be bigger. Hence the "pesky math" part and the /s for sarcasm...

I've read your post 4x in its entirety. Each time I remained uncertain about what you meant by "bigger". That word hangin by itself, is somewhat vague/elusive when talking about several ratings, capacities, etc. at the same time. I can think of several ways that "bigger" can be used talking about this setup and not a problem.

Only in your last post, did you then splain precisely what you meant. Now other readers know for certain what bigger refers to.

 

[Cruzan80]

I've read your post 4x in its entirety. Each time I remained uncertain about what you meant by "bigger". That word hangin by itself, is somewhat vague/elusive when talking about several ratings, capacities, etc. at the same time. I can think of several ways that "bigger" can be used talking about this setup and not a problem.

Only in your last post, did you then splain precisely what you meant. Now other readers know for certain what bigger refers to.

Ok, so you did not get my humor. I didn't "leave it hanging by itself", but rather added "supplied more than it has", along with an entire paragraph afterwards.

I am glad you now understand the full context of my posts.

 

[sparky 1971]

My 5 year old house has a 200 amp Siemens PN Series main panel. The wire run from the main panel in the basement of the house to the sub panel in the new barn is 275 feet (possibly as little as 265’ depending on final location of the barn sub panel, this includes vertical rise).


Finally, one last question:
I currently have a manual generator interlock kit installed on my main house panel. Is there any way I could connect the generator to the pole barn sub panel, and then back feed the house through the sub panel in the barn? When the power is out, it would be nice to move the running generator further away from the house. I cannot see a way this is possible, without running separate feeders from the main panel out to the generator inlet plug, but figured it wouldn’t hurt to ask.

As suspected, I cannot connect my portable generator through the sub-panel in the pole barn.

Since the house is only five years old, do you have a meter/main with breaker spaces outside? If so, you could feed the pole barn from there if you want as well as put the interlock in it with the generator inlet at the barn. Or, you could still put the inlet at the barn and leave the transfer interlock where it is. Assuming the whole point is to have the generator at the barn where it's easier to store.

I have a meter main on a pole with an interlock; I buried #6 USE conductors in the same trench as my garage feeder with the inlet mounted on the garage exterior next to the LB. I haven't had to use it in the 10 years I've lived here but when I do, I can fire up the genny and plug it in, then it can be warming up while I do the 250' walk of shame to make the transfer. I'll leave the generator in the garage and I have a cord long enough to run through the back door and reach the inlet.

 

[bob smith1]

I'd reach for MHF cable, Aluminum is the only right answer, oversize sub for more space, bigger sub OCPD is super fine, it only serves as a main disconnect in a sub. Reduce neutral size, don't need full size. "technically" running generator in detached to serve home is not legal due to you needing an ATS at the home, or some other transfer means. However, I live in illegal land and do it all the time. Just have to switch off the main in the home.

Run bigger conduit, you will appreciate when pulling, plus you have options if ever needed. Oversize conductors a bit. Lost count how many people buy what they need today, skimp all the way, then get to rip it all out in a year because they cheaped out did direct bury.....lol

 

[mike93lx]

I'd reach for MHF cable, Aluminum is the only right answer, oversize sub for more space, bigger sub OCPD is super fine, it only serves as a main disconnect in a sub. Reduce neutral size, don't need full size. "technically" running generator in detached to serve home is not legal due to you needing an ATS at the home, or some other transfer means. However, I live in illegal land and do it all the time. Just have to switch off the main in the home.

Run bigger conduit, you will appreciate when pulling, plus you have options if ever needed. Oversize conductors a bit. Lost count how many people buy what they need today, skimp all the way, then get to rip it all out in a year because they cheaped out did direct bury.....lol

Why would you advocate for using MHF when running conduit?

 

[bob smith1]

Why would you advocate for using MHF when running conduit?

Because it's common, thus cheaper, all conductors in the cable, no jacket. yeah, send it into the conduit, no prob. I guess you can compare to a spool but what the OP wants to do is not typical. White full size conductor. Just pull same color and tape. I'm all for reduced neutral. I also like to combine/incorporate MWBCs to aid in ensuring balance is honored.

 

[wyliesdiesels]

deleted

 

[mm08822]

Individual conductors are also cheaper than mhf per w&cyw.

 

[bob smith1]

Individual conductors are also cheaper than mhf per w&cyw.

Apparently that can be a locale issue because most times round hur, MHF is cheaper, has a superior jacket, and is twined and ready to install. Will admit, it's less fun to pull, but you toss that **** butter down the hole and she will take it.

I'm a fan of PE jackets. Good stuff.

Either way, the shopping should prove the best value, but Copper is NOT the path! I'm still pissed about a family adventure they did before I got involved, running 60A Copper, when I could have served it with 100A Aluminum at HALF the price! Dicks said, "Oh Aluminum burns houses down". Then I walk their sorry asses to their own main panel, served with ALUMINUM for 30+ years. "Has your house burned down yet????" F'n crickets........

Just watch, Aluminum is going to largely take over the electric conductor market and the code will change to accept it......AGAIN, because the alloy is totally different now, and processes just need changed.

 

[mm08822]

Apparently that can be a locale issue because most times round hur, MHF is cheaper, has a superior jacket, and is twined and ready to install. Will admit, it's less fun to pull, but you toss that **** butter down the hole and she will take it.

I'm a fan of PE jackets. Good stuff.

Either way, the shopping should prove the best value, but Copper is NOT the path! I'm still pissed about a family adventure they did before I got involved, running 60A Copper, when I could have served it with 100A Aluminum at HALF the price! Dicks said, "Oh Aluminum burns houses down". Then I walk their sorry asses to their own main panel, served with ALUMINUM for 30+ years. "Has your house burned down yet????" F'n crickets........

Just watch, Aluminum is going to largely take over the electric conductor market and the code will change to accept it......AGAIN, because the alloy is totally different now, and processes just need changed.

Pulling 4 single straight conductors will always be easier than a twisted mass. Much easier bending through LBs as well.

 

[bob smith1]

Pulling 4 single straight conductors will always be easier than a twisted mass. Much easier bending through LBs as well.

Just a secret I learned in Nam.... no one said you have to keep the conductors twisted! I have both opened the entire cable length, or immediately at an LB. Even have a fun roller that straightens them right out.

But whatev.

 

[mm08822]

Just a secret I learned in Nam.... no one said you have to keep the conductors twisted! I have both opened the entire cable length, or immediately at an LB. Even have a fun roller that straightens them right out.

But whatev.

Plenty of other ways to waste time instead.

 

[bob smith1]

Plenty of other ways to waste time instead.

I will just continue saving cash. Thx. I guess if you have weak arms, every pound is a struggle but doing a push/pull, you're dreaming about MHF being a problem.

 

[mike93lx]

cheap insurance. if a rock nails a direct buried cable you have to redig the trench or find the bad spot and repair. if you have conduit, unlikely you would need to pull the cable out but if you do, easy....

I'm not questioning the conduit.

I'm questioning putting mhf in conduit

 

[bob smith1]

This is just a head to head comp, excluding the superior XLP insulation. I very much realize some people (especially electricians) chose based on ease of install. this is easy. I am not saying use these conductor sizes, I was just comparing at a national supplier.

 

[HomerGuy]

#4 for egc is fine.

I'd probably go 2/0 for L1 and L2, and drop the neutral to #1. Probably cost neutral and gets you to right about 3% at 100a (although hitting 100a would be very difficult). Or 1/0 for hots and still #1 for neutral.

You could use your portable generator for just the barn.

If you want to feed it back to the house, #4 Al would get you 30a. 4-4-4-6 would work

Thank you. Upsizing the hot and shrinking the neutral is definitely something I will consider.

Also a good point on the feeders for the generator should I decide to go that route. The wire could be significantly smaller than the feeders to the sub-panel. Since I can't use the same sub-panel feeders it's probably not worth the time or money to run a separate set of feeders for the generator that will only be used very occasionally. But a good option to consider nonetheless.

 

[mike93lx]

Thank you. Upsizing the hot and shrinking the neutral is definitely something I will consider.

Also a good point on the feeders for the generator should I decide to go that route. The wire could be significantly smaller than the feeders to the sub-panel. Since I can't use the same sub-panel feeders it's probably not worth the time or money to run a separate set of feeders for the generator that will only be used very occasionally. But a good option to consider nonetheless.

It's a long distance to run the generator from, unless it's an automatic standby. I'd much rather have it by the house.

If you need power backup at the shop, you can always do a separate interlock in that panel and have a generator just for that