the ones i have used before have been very consistent.....but i have always checked several from and compared ....as with anything online some online calculators may have glitches etc...i do prefer ones that have a temperature component to them and give them higher precedent....i am a bit suprized anyone publishes a calculator online without a sign -in liability release form attached anymore
Wire sizing for sub panel
Is it just me, or has anyone else using online wire sizing calculators get multiple answers across different sites? I've tried to keep everything the same (insulation temp, direct burial, distance, alum conductor, voltage drop of 3%, etc) and can never seem to have them agree.
Does anyone recommend a go to calculator?
Does anyone recommend a go to calculator?
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Thanks. I'm trying to plan a 360ft 100A subfeed and am coming up with 2/0 all the way to 250 MCM with online calculators.the ones i have used before have been very consistent.....but i have always checked several from and compared ....as with anything online some online calculators may have glitches etc
im not a electrition....but i checked a lot of electrical work over the years as a contractor........one rule of thumb is checking the wire ampicity then adding one wire size for each hundred foot of one way run for a quick check if the calculator doesnt get close to that something is wrong........i did a quick check the rule of thumb as i understand your parameters would put you between 4/0 and 250Thanks. I'm trying to plan a 360ft 100A subfeed and am coming up with 2/0 all the way to 250 MCM with online calculators.
I thought the nec code book has a chart, and the same 1size/100’ caviot.
I required 1 upsize for a 125’ run
I required 1 upsize for a 125’ run
They do. And there are sites that interpret the code into layman's terms. You have to decide if you are going copper or aluminum, conduit or direct burial.
I ran a service to a barn with almost the same specs as the op....(don't remember what wire size I used)...but I ended up going with conduit and copper to keep the wire size small enough to fit into the connecting lugs on the supply side breaker...
2/0 if copper or alum 250 is what i came up with , based on your parameters 240v, single phase, 90* insulation temp. , 100 amp ,360' , direct burial and 3% voltage drop.Thanks. I'm trying to plan a 360ft 100A subfeed and am coming up with 2/0 all the way to 250 MCM with online calculators.
Full disclosure , I'm not an electrician .
I installed a 100 amp sub panel in a barn probably 10 years ago, that run was similar at around 350'. I used 4/0, aluminum, direct burial and installed a junction box at each end. Used the junction to extend each end of the wire with #2 so the wire could fit into the breaker at the feed end and the sub panel at the barn end. You can buy numerous types of connectors or buy a junction panel with lugs to make the size change. Depends on your code compliance requirements.
You can't even seriously consider a run of that size and length using copper these days, you'd probably have over $4000 in wire alone.
You can't even seriously consider a run of that size and length using copper these days, you'd probably have over $4000 in wire alone.
How did you make your CU to AL connections in your JBs? Good grief, I just looked at the wire prices. Why is copper wire so freaking expensive?
I used these:
Morris Products Black Insulated 2 Conductor Splice Connector – 250-6 Wire Range, 5/16 Allen Hex – 2.2”L x 2.41”W x 2.22”H – Easy Dual Entry – Pre-Filled, Rubber Vinyl Coating, 2 Screws 97118: Conduit Fittings: Amazon.com: Industrial & Scientific
Morris Products Black Insulated 2 Conductor Splice Connector – 250-6 Wire Range, 5/16 Allen Hex – 2.2”L x 2.41”W x 2.22”H – Easy Dual Entry – Pre-Filled, Rubber Vinyl Coating, 2 Screws 97118: Conduit Fittings: Amazon.com: Industrial & Scientific
www.amazon.com
As a retired linemen when we used alum & copper. No matter what type of connector we always coat both feeds with yuck n puck, it's a inhibitor.
Trade name” noalox “As a retired linemen when we used alum & copper. No matter what type of connector we always coat both feeds with yuck n puck, it's a inhibitor.
Seasled,
That might be the real name, but I or most linemen used that name they would say, what the H is that and I kept it clean. But you are right.👍
That might be the real name, but I or most linemen used that name they would say, what the H is that and I kept it clean. But you are right.👍
Yeah you are right. No way I could do this in copper. Even aluminum will probably be over $1500 just in wire (for the aluminum only). Here is what I am doing, or planning on doing. I'm gathering info before I present my plan to local codes:I installed a 100 amp sub panel in a barn probably 10 years ago, that run was similar at around 350'. I used 4/0, aluminum, direct burial and installed a junction box at each end. Used the junction to extend each end of the wire with #2 so the wire could fit into the breaker at the feed end and the sub panel at the barn end. You can buy numerous types of connectors or buy a junction panel with lugs to make the size change. Depends on your code compliance requirements.
You can't even seriously consider a run of that size and length using copper these days, you'd probably have over $4000 in wire alone.
I'm actually daisy chaining 2 sub panels. I'm going from the house to our barn 140' away with a 110A sub feed to a outdoor 200A feed-thru panel mounted to outside of the barn. I'm going to re-breaker the main to 100A instead of 200A (I'll have to buy it separately) Square D makes the homeline panels that you can downsize the breaker. The outdoor box is only 16 circuit, which is fine.
This allows me to feed #2 copper on the top coming from house (I'm using copper here because of limited room in house panel) and continue on with 4/0 by connecting right to the main lugs at the bottom of the outdoor panel. It'll eliminate all the junction, splicing crap. It will then be 4/0 at 350-360 ft to another 200A indoor panel to be able to fit the 4/0 directly to the lugs.
The only part I'm not sure about is if I can use a main lug 200A panel or if it needs to be a main breaker panel. I suppose I could do the same as the other panel and downsize the main breaker. Need to do some more investigating here...
I crimped extremely heavy duty ring terminals on each wire and then bolted them together. The connection was insulated with a layer of tape, then a sticky rubber electrical insulation and another layer of tape. Same method (and materials) we use to connect every 480v motor at work, up to several hundred HP. Totally a coincidence.How did you make your CU to AL connections in your JBs? Good grief, I just looked at the wire prices. Why is copper wire so freaking expensive?
That's what I had and it didn't cost anything. Today I'd just use the connectors linked in the above post, they are pretty slick and a lot easier if you need to take them apart.
As long as the initial breaker feeding the circuit from your main panel is sized for the wire you use, the main breaker amperage in the sub panels doesn't really matter. That initial breaker is what will protect the entire circuit, the mains are just acting as a switch.Yeah you are right. No way I could do this in copper. Even aluminum will probably be over $1500 just in wire (for the aluminum only). Here is what I am doing, or planning on doing. I'm gathering info before I present my plan to local codes:
I'm actually daisy chaining 2 sub panels. I'm going from the house to our barn 140' away with a 110A sub feed to a outdoor 200A feed-thru panel mounted to outside of the barn. I'm going to re-breaker the main to 100A instead of 200A (I'll have to buy it separately) Square D makes the homeline panels that you can downsize the breaker. The outdoor box is only 16 circuit, which is fine.
This allows me to feed #2 copper on the top coming from house (I'm using copper here because of limited room in house panel) and continue on with 4/0 by connecting right to the main lugs at the bottom of the outdoor panel. It'll eliminate all the junction, splicing crap. It will then be 4/0 at 350-360 ft to another 200A indoor panel to be able to fit the 4/0 directly to the lugs.
The only part I'm not sure about is if I can use a main lug 200A panel or if it needs to be a main breaker panel. I suppose I could do the same as the other panel and downsize the main breaker. Need to do some more investigating here...
Believe you need to have a main breaker unless the main and sub are located within the same building.
Make sure you're running 4 wires to the sub panel(s), two hots, neutral and a ground. Bonding screws need to be removed and all grounds and neutrals kept separated.
I believe you are correct about the main breaker in each panel. I just need to check with local code as it can differ from NEC. For example can I breaker everything at 100A or would I need to be progressively smaller in amperage for each? I heard this needs to be done, but unsure exactly. Need to do more research here..As long as the initial breaker feeding the circuit from your main panel is sized for the wire you use, the main breaker amperage in the sub panels doesn't really matter. That initial breaker is what will protect the entire circuit, the mains are just acting as a switch.
Believe you need to have a main breaker unless the main and sub are located within the same building.
Make sure you're running 4 wires to the sub panel(s), two hots, neutral and a ground. Bonding screws need to be removed and all grounds and neutrals kept separated.
Yes, 4 wire. I'll need to install grounding rods as well.
when i made my long barn run (seperate buildings) the MASTER electrition that did the final work did it with 3 wires but the box on each end was grounded to ground rods......are you sure it requires a ground feed on seperate building sub feed ??As long as the initial breaker feeding the circuit from your main panel is sized for the wire you use, the main breaker amperage in the sub panels doesn't really matter. That initial breaker is what will protect the entire circuit, the mains are just acting as a switch.
Believe you need to have a main breaker unless the main and sub are located within the same building.
Make sure you're running 4 wires to the sub panel(s), two hots, neutral and a ground. Bonding screws need to be removed and all grounds and neutrals kept separated.
when i ran a sub panel in my home to my garage (same structure) i did a 4 wire feed with ground back to panel (master electrition did final hook up on that one too)
could you clairify your stated requirement for the 4 wire feed
Used to allow a three wire service if the building was at least a certain footage away, (no idea how far) and as long as no other utilities, pipes or wires of any kind ran between the two buildings. Can't say for certain that is no longer possible, but it's usually easier to just run a fourth wire and not worry about failing inspection or your insurance company having some issue with the install in the future.
My shop was built in 1990 and is only about 50' from the house. They allowed 3 wire at that time, so that's what I did. Only a couple years later they failed a friends inspection with an identical situation. Almost immediately I decided I needed phone, natural gas and a few years later network connection.
My shop was built in 1990 and is only about 50' from the house. They allowed 3 wire at that time, so that's what I did. Only a couple years later they failed a friends inspection with an identical situation. Almost immediately I decided I needed phone, natural gas and a few years later network connection.
1 - 20 of 30 Posts
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