Electric service application

[Tom Veatch]

Why they want HP and not Amp per machine is beyond me.
...

Might be because tables in NEC Article 430 specify amperage requirements for dedicated motor circuits in terms of HP????

[Roger Frazee]

Don't make this harder than it is......

First you evidently are required a commercial service but have a residential need for your shop.... at least right now.

Since you prefer a separate service I won't go into all the stuff the others suggest. I also assume you are up on what they require in order to actually charge you at a commercial rate. Your load may not be big enough for them to do that in your jurisdiction. I will say that 200 amps is a ton of power for a small workshop (48 Kw) and that may be the smallest service they will allow under commercial rules. I would go ahead with the 200 amp service but that doesn't mean you have to hang a 200 amp panel in the shop. Utilities don't run around with a gillion wire sizes on their truck so what they really want to know about service size is for the transfomer rating to supply the building. From above 100 amps to 200 amps they likely will run the same size wire if it is overhead triplex. However you will have to run a 200 amp rated service entrance conductor sized to NEC rules from the mast to the panel. I would see if they will allow a stand alone disconnect as your service equipment so you can have isolation of the panel. So my point is if you say I want 150 amp service your probably going to get wire capable of 200 amps and likely the existing transformer will be checked for at least the capability to supply the dwelling and the workshop. They like to just tap existing ones if possible and voltage configurations are the same.

Anyway on to your questions

As for soft or across the line start. You don't have soft start so check 'across the line', this simply means your connecting a motor directly to line voltage. Most likely the biggest part of your equipment will be cord and plug so this is rather a commercial question for fixed in place motors.

Lighting load use 3 watts (VA) per square foot of floor space

3 x 1000 sq. ft. = 3300 Volt amps or watts resistive

For a generic on ac load use 1 ton = 3.5 kw

For generic on heating load use (if electric)...volts times amps... so 40 amps (single unit) at 240 volts would be 40 x 240 = 9.6 KW

Motors generic single phase just use 746 watts times horsepower....3hp x 746 = 2.3kw

Other loads for every receptacle outlet use 180 watts... one duplex receptacle is 2 outlets.... so 360 watts

[Anthony Watson]

I have a separate 200 amp panel in my house, and a separate 200 amp panel in my garage shop. These both feed from a junction box out in the yard, which connects to the meter out at the pole on the road. So while the garage is isolated from the house, it's all supplied on a single residential "service". (I actually have a third line running to a 60 amp panel in our pump house).

I don't know what the regulations are in your area, but you might see if you can do something similar.

Anthony

[Jim Becker]

Anthony, although the meter is at the house, my setup is similar to yours. I have a 400 amp drop which is split at the meter housing. One connection goes to the 200 amp panel for the house. The other connection goes to a 200 amp cutoff breaker which then feeds to the shop building via a conduit underground. I can completely cut off the house or the shop building separately, but only one meter and one account is involved.

[Jim O'Dell]

I ran into the commercial account stuff here in Texas when I applied for the power for the shop to be turned on 3 years ago. No discussion, commercial hookup at commercial rates. My service was already there by a previous owner, we just hadn't turned it on since I was rehabbing the building and really didn't need power at the time. It was going to be a lot more than the house was. I contemplated going the sub panel route, but digging the trench for the cable from the house's meter to the shop would have been a nightmare. Direct line, I might have been able to miss the concrete patio, but no way to miss a 25' tree! Well, I got lucky that Texas had deregulated power, and we can choose which electrical "biller" you want to pay (still comes from the same electrical supplier grid). So I talked to another company and got it hooked up at normal rates. They didn't seem to have a problem with it. I think it was just a power play by Texas Electric to try to get more money. Jim wins one for a change!!! Jim.

[Anthony Watson]

Jim,

When we first bought our property (18 years ago), we had power brought in to run the pump in our well, and power a few tools. With no buildings on the undeveloped property, and not wanting a meter reader snooping around the property later, we had the meter installed out on the pole at the road. We put a mobile home on the property and was able to run power from the original junction box in the yard. Later, I built the garage, powering it off of the same junction box. Then a couple years later we built the house, disconnected the mobile, and ran the power from the junction box. Someday we may add another building up on the hill, which would be easy to get power from the junction box. I've been very happy with the setup, despite the box in the yard. But with a little creative landscaping, we never even notice it's there.

Anthony