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Old 08-11-2020, 10:41 AM
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Default The definitive shop electric service thread

Im about to get back on working on my building its self.

A discussion that keeps coming up with a friend of mine is I should go with a 208/120 three phase service. Myself I think I should go with 240 delta. I've got enough panels I can keep single and three phase loads seperate and not have to worry about the high leg on 240 single phase loads.

Am I right in thinking it takes more amperage at 208 then 240 for motor loads?
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Old 08-11-2020, 10:51 AM
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Originally Posted by OldRedFord View Post
Im about to get back on working on my building its self.



A discussion that keeps coming up with a friend of mine is I should go with a 208/120 three phase service. Myself I think I should go with 240 delta. I've got enough panels I can keep single and three phase loads seperate and not have to worry about the high leg on 240 single phase loads.



Am I right in thinking it takes more amperage at 208 then 240 for motor loads?
208... I don't know everything... But I thought house power regardless phase doesn't work like that...

120 - one leg
240 - two legs

I've got typical house pwr, the equipment I use 2 legs for 240v and have added 30amp cbs. All equipment 240v 30amp are on their own cb, never sharing power.

I don't know if I'm even close to what your asking
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Old 08-11-2020, 11:14 AM
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What’s the biggest loads you plan to be able to handle? Welders? Machines?

What’s the cost of 3ph service versus single where you are? Both to run the service and on a monthly basis.

Some utilities charge a base rate just to have a connection, even with zero use.

Do you have to run two services to have both?


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Old 08-11-2020, 11:33 AM
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I would think if you got 3 phase, you should be covered for any load. It will have two 110v single lines, with a Wild 240V leg.

But like others have mentioned, what is your electric company’s rate for having the Three Phase meter there. My electric company charges me $30 every month wether or not I use any electricity, just to cover the cost of bringing me the power lines to have electric available when I need it. I can imagine that the 3 phase meter could be upwards of $60 a month base.

Ultimately, equipment does run more efficiently on Higher voltages, but you are still buying the electricity by the watt, and you will be using close to the same wattage wether you are running your air compressor on 120v or 240 volts. The difference is you are splitting the amperage draw on two lines vs one line, so you can use smaller wires with the higher voltage.

I know you are collecting tools to use, but are you going make this an expensive hobby, or going to turn this into a business someday.

If you have the option to get 3 phase now, it will probably be the easiest to work with the rest of your life, and be the cheapest to put in now than later, but only you can answer the question whether you can have that meter sitting there year round costing $$.




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Old 08-11-2020, 11:39 AM
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Go with the 120/208 as it has the advantage of balancing the 120 volt loads leaving you with the most 3 ph available.
With the delta system if you load up the single phase panel with machines and lights when they are running at for example a total of 100 amps the third leg can only supply three phase up to the remaining available amps on the other legs for a total load of at best about 75 % of service capacity
with 120/208 you can easily get 85-90% utilization.
Not real critical in a one man shop but add employees and it gets important
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Old 08-11-2020, 06:45 PM
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Originally Posted by toprecycler View Post
I would think if you got 3 phase, you should be covered for any load. It will have two 110v single lines, with a Wild 240V leg.

But like others have mentioned, what is your electric company’s rate for having the Three Phase meter there. My electric company charges me $30 every month wether or not I use any electricity, just to cover the cost of bringing me the power lines to have electric available when I need it. I can imagine that the 3 phase meter could be upwards of $60 a month base.

Ultimately, equipment does run more efficiently on Higher voltages, but you are still buying the electricity by the watt, and you will be using close to the same wattage wether you are running your air compressor on 120v or 240 volts. The difference is you are splitting the amperage draw on two lines vs one line, so you can use smaller wires with the higher voltage.

I know you are collecting tools to use, but are you going make this an expensive hobby, or going to turn this into a business someday.

If you have the option to get 3 phase now, it will probably be the easiest to work with the rest of your life, and be the cheapest to put in now than later, but only you can answer the question whether you can have that meter sitting there year round costing $$.




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My hope is to provide additional income. I feel like im already beyond your average hobby machine shop and I don't even have a lathe yet. Even as a hobby shop it's expensive.

Equipment and horsepower so far
Cincinatti Bickford Super service 21" drill. Belived to be a 5 horse 3 phase motor. Could be 3 too.

Cincinatti 21" Camel Back 3 or 5 hp 3 phase

Gorton mill 3 hp spindle motor

Lincoln MK 250 DC welder....32 amps full load

Chicken house fan 7.5 hp

I do have a 300 amp multi process welder but it's 480/600 only.

Shop lighting could be as much as a total of 60 amps if I domt go with a 54 watt equivalent lumen output led bulb in my high bays.

Been suggested if I can to go.three phase on my HVAC equipment and well pump.

First lathe will probably be 7.5-10 hp

I've got one air compressor that needs a 20 horse motor and a second one that needs a 15.

A shaper and horizontal mill are on the short wish list.

Right now I have a 200 amp mobile home service out there that I ran a "temporary under the radar" feed off of down to the shop. Meter base, main breaker and small breaker box are all mounted on a pole. Base charge is $20 a month. Have not used over $40 a month yet.


Service at my trailer runs about 120 a month. Between that and the shop id say a total of $160-170 a month combined right now.

Ideally if I can keep my monthly bill with three phase near $200 a month I can live with that.

If I get to where im beyond one part time helper I'd probably look at renting commercial space at that point.
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Old 08-11-2020, 06:57 PM
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For what I see, I’d say stay single phase and run a phase converter and vfd’s.

15 and 20 hp piston compressors are huge as piston units go, and compared to some of the new small rotary compressors are definitely obsolete.


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Old 08-11-2020, 07:29 PM
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Originally Posted by greywynd View Post
For what I see, I’d say stay single phase and run a phase converter and vfd’s.

15 and 20 hp piston compressors are huge as piston units go, and compared to some of the new small rotary compressors are definitely obsolete.


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Phase converter and VFDs are my plan B

I missed a question.

I can only have one service.
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  #9  
Old 08-11-2020, 08:47 PM
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With 3 phase there is some kind of power factor. The square root of 3 is involved somewhere. It caught me once when I was ordering a piece of equipment, and I hadn’t factored it in. Bottom line was that the existing service was too small for the equipment.
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Old 08-11-2020, 08:49 PM
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Originally Posted by OldRedFord View Post
Phase converter and VFDs are my plan B

I missed a question.

I can only have one service.


Ok, to clarify, you can have only one electric service to your property?

And right now you have a single phase 200 amp service?

But, the question is, are you positive that you can get 3 phase service at your property? And how much will that cost up front, and what is the monthly service charge before any power usage?



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