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Breaker and wire sizing for long run, high amp requirements

Breaker and wire sizing for long run, high amp requirements

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  #1  
Old 02-23-17, 03:23 PM
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Breaker and wire sizing for long run, high amp requirements

I have two, 200 amp GE panels in my main residence (VA)
There is a detached garage being fed by a 30 amp double pole in one of the panels to a little 4 breaker sub-panel. When I moved in all it had was a few light bulbs and a few outlets. Weird to me, since it is three wide by 40' deep. It is inadequate for the shop gear I need to run. I plan to entirely replace this setup.

The driving factor is acquisition of a welder with input current spec of 94 amps @230V (http://www.esabna.com/literature/arc...e_15-047-a.pdf). Other items will be 240v compressor, saws, exhaust fans, dust collector etc.

The painful news is it will take 190' run to snake it out of my basement garage, under a driveway, and down to the side of the detached and up to to a new sub-panel. I found this wire size calculator indicating 2/0 (Wire Size Calculator) (AL/single Ph/240V/200'/100amp) to stay under 3% voltage drop.

There one thing about my mains: there is space for two main breakers (side by side, up-down operation) but only one is utilized. I am wondering if the other slot can be used as a feeder to the sub-panel.

Any ideas or wisdom to share on this? Thanks in advance.
 
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Old 02-23-17, 07:59 PM
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I'm not sure if it is practical, but have you considered a new 100 amp service to the garage? You would have to contact your POCO to get the details, but it may be cheaper in the long run.
 
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Old 02-23-17, 08:09 PM
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At one time there was only one meter allowed on a residential property. Now it's more about the money as I see more than one meter on many residential properties.

Now....I'm talking about in the city. Rural areas are different.

I agree with Larry.
 
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Old 02-24-17, 08:06 AM
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hmm... I am trying to avoid the nearly $2,000 cost of the new meter option.

Any advice or tips on the sub-panel route?
 
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Old 02-24-17, 10:01 AM
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Why $2000 for a new meter? Is it because the power company needs to change the transformer to supply the new load including welder?
 

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  #6  
Old 02-24-17, 11:30 AM
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Honestly I'm more worried about the transformer feeding your home and maybe the neighbors given a 96A welder and no power factor correction with a 50% pf on a residential service. Your residential service probably is simply not adequate to support this machine. First step should be to contact the power company and see if this is possible.
 
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Old 02-24-17, 03:54 PM
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The cost is their quote for the new line, conduit, and trenching from the pole to the back of the property where the structure is. My house is midway back.

I am the only one on my transformer, at the end of the road.
 
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Old 02-24-17, 05:55 PM
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Copper would be too expensive so looking at aluminum and assuming a 100 amps for the welder plus miscellaneous other loads totaling 50 amps for a load of 150a at 200 feet 4/0 would give you a 6%drop. Here is an example of cable to use: https://www.lowes.com/pd/4-0-4-0-4-0...e-Foot/3129329.

Could you live with an overhead drop from the Poco's pole to a new meter. If so what would they charge? With the cost of wire and breaker at the main panel you would be close to $1000. The Poco might do the drop instead of a latterasl for nothing or a lot less.
 
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Old 02-25-17, 01:36 PM
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The driving factor is acquisition of a welder with input current spec of 94 amps @230V
Even if you feed the garage with your existing house service, you have to contact the power company about adding such a load to their system/transformer/lines. It is the responsibility of the customer to provide all load information. Otherwise, if there is trouble at the transformer the poco will be looking for someone to blame.
 
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Old 02-25-17, 02:07 PM
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You are going to need more then 100 amps to feed your garage. That welder alone requires a 125 amp feed with 150 amp overcurrent protection. Add to that the lights, exhaust, and anything else you will be running at the same time.

I also think you need a separate service to the shop unless you pick a smaller welder.
 
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Old 02-27-17, 01:51 PM
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OK, I am going to go back to the separate meter idea, which will probably be 200 amp service. I will see how much I can get the cost down by doing the trenching work and laying the conduit instead of paying power company for that.
 
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Old 02-27-17, 01:54 PM
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I will see how much I can get the cost down....
As I suggested earlier ask the power company how much for an overhead drop.
 
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Old 02-27-17, 02:17 PM
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You may not need a separate service to the garage, but you may need to heavy up the transformer and the service entrance to the house prior to extending a subpanel to the garage.

In the first post, you mentioned you currently have two 200A panels at the house. Does one feed the other, meaning you have an overall 200A service? Do they both come from the same meter base suggesting you may have a 320A service? Do you know the size of the service and incoming service lines?

Can you post some pictures of the current service entrance and main panels? Perhaps a rough sketch of the building layouts on the property including the location of the service drop and transformer? There are probably a lot of options to consider such as mounting a service on a pole or pedestal which will decrease the cost on the power company side and allow you to do more of the work as a homeowner.
 
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Old 02-27-17, 03:11 PM
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Overhead line is not allowed by the property owners association.

Pictures below. Those mains at the bottom are 200 amp.Sorry for the rotating but you can see the info.
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Incoming to panels is 4/0.
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Tolyn: Also per the welder manual calling for 150 amp fused line disconnect, all I see for sale is 100 and 200.

The welder has a big 3 prong plug on the end of the cord, it was not "hard-wired" to a wall box/switch.
 
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Old 02-27-17, 03:53 PM
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Overhead line is not allowed by the property owners association
Why I would never buy property with an HOA or unlapsed deed restrictions. Maybe they will go half and half with you on the cost since they want to be so high and mighty with you... yeah, when a flock of pigs flying north for the summer fly overhead.

Seriously the POA might see the building as commercial. Have you given that consideration?

What type of plug? No pro but I though above 60 amps they used pin connections.
Also per the welder manual calling for 150 amp fused line disconnect, all I see for sale is 100 and 200.
It is for a disconnecting means only, not overload protection, so that is only a minimum requirement. A 200 amp would be okay. (Like using a 15 amp switch on a circuit with a 60 watt bulb.)
 
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Old 02-27-17, 04:41 PM
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hmm.. I thought the difference between fused and non-fused disconnects was that the fused combined overload protection with disconnect.
 
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Old 02-27-17, 04:58 PM
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Fused disconnects are used for both overload and short circuit protection. You would need a 200 ampere disconnect with 150 ampere fuses, not at all uncommon but it will be expensive.
 
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Old 02-27-17, 05:23 PM
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You should be able to use a 150A breaker in the panel and a 200A non fused disconnect.
 
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Old 02-27-17, 06:45 PM
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iBooks: From what you said and the pictures, looks like I have the 320A doesn't it? Does that open up any new options?
 
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Old 02-27-17, 07:49 PM
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The size of the wires in the gutter below might shed some light on the service you have at your house. Your existing meter socket looks to be a 200 amp to me.

The other issue you have is you will not find a 200 amp breaker for those panels. One option is to install a fused disconnect next to the panels and tap into the feeder in the gutter. (assuming there is a single feeder)
 
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Old 02-28-17, 07:58 AM
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"One option is to install a fused disconnect next to the panels and tap into the feeder in the gutter. (assuming there is a single feeder)"

This is sounding promising.

Why "assuming there is a single feeder"? If two, wouldn't I just choose one?
 
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Old 02-28-17, 12:37 PM
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I confirmed that the gutter under the main panels is splitting three 4/0 into six for feeding each panel.
 
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Old 02-28-17, 12:59 PM
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The #4/0 conductors in conjunction with the meter socket lead me to believe you have a 200A service that is probably pretty heavily loaded given that you have two completely full 30 space panels.

The good side is that it looks like an upgrade to 400A would be pretty straightforward using a 400A meter/main exterior box from which you can feed each of the interior panels and run a feeder to the outbuilding.
 
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Old 02-28-17, 02:32 PM
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re: " it looks like an upgrade to 400A would be pretty straightforward using a 400A meter/main exterior box from which you can feed each of the interior panels and run a feeder to the outbuilding"

to repeat for my clarification, this approach would entail:
1) a new meter
2) pulling more, or bigger, wire to the gutter??
3) splitting feeder three ways (1 for each main panel, 1 for garage sup-panel)

The old heating system was all electric, since replaced with heat pump. There are still several big circuits used for wall space heaters and electric baseboards. Very little use, maybe 4-6 weeks a year, and during those times I'm not in my garage. Just saying, I think not being able to work on a big AL tig job during dead cold of winter would a reasonable limitation for me (no heat in the garage). Of course as soon as I think I want heat in the garage so I can work in winter, I'd be screwed. Would have to go with propane.
 
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Old 03-01-17, 04:06 PM
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IMO upgrading the house service to 400 amp so that it can carry the garage as well is not worth the hassle. Anything can be done for a price, but I believe your money would be better spent elsewhere.

Since you "only" have a 200 amp service in the house I suggest going back to the original idea (well, my and Ray's) of a separate service for the garage. Perhaps the PoCo could set a pedestal with a meter/breaker near the transformer. That way you could do the rest of the work yourself.
 
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Old 03-01-17, 06:12 PM
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Tolyn, just wondering if assuming the Poco offers high side metering if he could use a single wire feed to a center tapped 240v transformer at the shop or would the cost of the transformer offset any savings?
 
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Old 03-01-17, 06:40 PM
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I hope I understand the question correctly.

I kind of doubt it as normally a customer does not pay for the transformer, and I would doubt they do that metering for a residential customer. They may have to pay to have it installed but the power company still owns the transformer. That, and I also doubt a person could buy a 7200v to 120/240v transformer.

At my house the PoCo just changed my transformer. I have a 1/4 mile driveway and the power is run from the road underground to a ground transformer. It is 7200 volts coming to it, then 120/240 on the secondary to my meter on my house. This was done for me for free because their line running underground was starting to have failures which would trip the overcurrent device on the pole. I'm sure the wire/cable rated for 7200 volts is not cheap!
 
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Old 03-01-17, 07:40 PM
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Only brought it up because there was a thread a while ago from a guy having a single line run to a transformer at his cabin. Really not something I'm familiar with.
 
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Old 03-02-17, 10:37 AM
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I really appreciate the continued insight and ideas, and I want to thank you.

I agree at this point that best option overall is to just get new 200A service at the garage. This will spare me all the work in the house with a sub-panel install, routing big wires out the basement, through the wall, trenching through or under driveway to garage, etc.

Another thing is that I would so hate to hit a limitation later on that prevents simultaneous use of equipment, or even worse, starts tripping the house breakers because I'm welding in the garage while a compressor and fan are operating.

Investigating all the options is part of the research, and I actually enjoy it; thanks all for sharing knowledge and opinions to help me come to a conclusion!!
 
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