Detached Shop- Residential 1PH Service

Hello,

I need advice in running service to my shop.

Current Service:
The service is 200A to an American Switch (non-feed though) 200A panel that has a limit of 100A per stab. I currently have 3 poles available and with a couple of slim breakers could easily have a two stabs free.

Shop requirements:
Though I will mainly be the only person working in the shop, I will have many motors kicking on and off, and some running simultaneously with welders, HVAC systems, compressor, rotary converters, VFD's, etc. The shop is 50' away from the service panel and I plan to bury the feeder run.

Due to the high amp demands of my work, and the short run of cable, I would like to run the largest service possible. For sizing recommendations, I am only interested in using copper cable.

My questions are:

What is the largest service I can provide through my current panel? What would be the required size and type of cable?

Are there any options to feed through my panel (or tap into before) to some sort of fusible disconnect, then to the remote panel?

I'd like to go over all of my options using my current service before I have another meter ran.

Thanks

Aaron

 

Not a pro but have you considered upping your service to 400 amp and using a double lug meter can? Then use a separate 200a main panel to feed the shop subpanel.

 

Ray,

Thanks for the reply. That's not a bad idea, but I'd really like to see what I can do without getting into my meter(which is sealed). I have already spoken to the company that owns the lines(whom I don't directly have service with) and they will run 3 phase if I switch to them and obviously with a hefty price tag. This will likely be my last resort, after I run a subpanel and determine it's insufficient. I'm a little stubborn

 

Unless you are going to be doing some pretty hefty production work it is unlikely that you will pull anything close to 100 amperes at 240 volts in a home shop. If your service (that word specifically refers to the wires from the utility through your meter and to the first disconnecting means, probably the main circuit breaker in your "main" panel) is 200 amperes then you could install a new 200 ampere circuit breaker with provisions for two sets of load conductors prior to the existing service panel. If you did this then the current service panel would become a "sub-panel" and need to have the equipment grounds and neutral bus isolated.

The cost of this would probably exceed replacing the existing panel with one that allowed a larger current flow through each stab or had feed-through capability. Alternatively, it MAY be possible to install a factory authorized four-pole circuit breaker that parallels two sets of stabs.

I'd do a comprehensive demand load study first, you likely have no need for more than 100 amperes per stab. If your study shows that 100 amperes just won't cut it AND you have a sizable three-phase load, then a new three-phase service to just the shop may be justified. Otherwise a new 200 ampere single phase-service would be less expensive than the three-phase. Yet another option would be to run two sets of feeders to the shop but such would require the written permission of the local Authority Having Jurisdiction (AHJ) aka the electrical inspection office.

 

I agree with Furd that you likely would not need more than 100 amps to your shop. You will lose some efficiency with converting single phase to three phase but since this is a one man operation I don't think that will be an issue.

For comparison my father-in-law has a shop that is fed with 100 amps, single phase, that runs:
3 phase metal lathe (static phase converter)
3 phase Bridgeport mill (static phase converter)
5 hp 12" table saw
24" belt sander
Large dust collector
Large compressor
50 amp Lincoln welder
15" planer
And all the "normal" tools found in a wood working shop (jointers, routers, chop saw, etc.)

 

I am not familiar with that manufacturer's equipment, but if I recall correctly, it is probably a 1970s vintage panel that you have which limits your options. While I see a few options for what you want to do, I am also thinking your main panel is probably approaching it's end of useful life. The least expensive and easiest option I see is to simply run a 100 amp feeder to the shop from the existing panel, but that depends on the load calculation and exactly how much power you need and as I understand it, you don't know that yet. If you need something more than 100 amps, I see a couple more options, but they involve getting into the meter enclosure and replacing the vintage panel which you have already stated you are not interested in doing. That being said, I'll not waste your time or mine with further options.

 

Thanks Furd,

Yes, my service is 200A from the pole.

I do have some very heavy loads pulling from one particular VFD, that needs to run simultaneously with some other high inrush motors, but I have reevaluated my situation and think that I will give the 100A feed a try. If it doesn't work, I'll have a nice extension cord.

Moving on with a 100A feeder breaker to a 200A subpanel. As I understand it, I would need 3 runs of #3 copper for the hots and neutral and a smaller ground. I want to bury this in 2" pvc that will run under a driveway (already cut) to the new subpanel.

Is there a 3 conductor with ground cable in this size I can get for burial in pvc conduit?

Any other cable options?

thanks

 

You don't generally use cable in conduit. You use individual conductors such as THWN. You could use also use USE quadplex (AKA mobile home cable). Under the driveway you may have to switch from schedule 40 PVC to schedule 80.

 

Toyln,

That list is very similar to mine. I have decided to give the 100A feeder a try.

CasualJoe,

You are correct, the panel is likely the original from the house, built in 71. It uses ite breakers, available from Siemens. I also agree with your assessment of the panel's lifecycle. For this particular project, I would like to leave my meter alone. Explaining to the electric company why I need to cut the seal is not something I look forward to.

 

I am not seeing the problem with that. It is not at all unusual for power companies to reseal meters following a panel replacement.

 

His location in his profile says Texas. Depending on his location within Texas and if it is city or county it could be tricky if the work isn't done by a master electrician. Also the locking bands often used just aren't that easy to remove.

 

The lock on my meter is a one time use clip. Also, the meter is not mine, it is owned by the electric company. So it is mandatory that I have them come out for any work I do between the meter and my main panel.

I just checked at the big orange store and found the 100 amp breaker I need for $38 along with # 3 THHN copper for $1.48/ft. Not bad at all. There are quite a few main breaker panels brands, I'm looking at the square D. They have a 10 yr warranty and a lifetime warranty panel. Does anyone know if there is a significant difference in quality?

Also, I will be running water in PVC as well as coaxial cable to the shop. Can these be in the same trench as the electrical conduit?

 

Square D Homeline and associated breakers are the competitive residential line and carry a 10 year warranty. Homeline exclusively uses aluminum bus bars. The Square D QO series and breakers are lifetime waaranted. QO series uses standard copper bus bars. I prefer a good copper bus loadcenter.

I am not aware of anything in the NEC prohibiting this, but I have never run into it before either. The closest I have been to a project like what you propose was utility high voltage and utility water main in the same ditch. My opinion is to use a separate ditch for the water line.

 

I just assumed the work would be properly permitted and inspected and wouldn't be a problem. If it takes a licensed master electrician to legally do the work I can see where the work would be more expensive than just doing it himself.

 

I like your idea of running 2" PVC for your feeders as it will be over-sized in case something happens, plus it is easier to pull through. You can put them in the same trench but I suggest putting the electric on the bottom and then the low voltage pipe 6-12" above it. Not sure about your risk of freezing temperatures being in TX, but of course you want to keep the water from freezing so bury that the proper depth.

Inrush current has little to do with calculating load, it is the running current you have to worry about. Unless it takes quite a long time to get things running. With most motors inrush current only lasts a few seconds.