Adding compressor to 220v in my garage

arlen4720 · Jun 26, 2013

LD1 said:
I'm not an electrician so forgive my ignorance, but I have been told that 4-wire is only needed IF the appliance has 220v AND 110v circuits within it. Like a stove that has 220 heating elements and a 110v digital display.

But things such as a compressor or welder that are 220 ONLY, 3-wire is okay??

There is no ignorance to forgive....You are 100% correct on all counts. I AM a master electrician, and an electrical engineer, and there is so much BS on this thread it is funny. What the OP is proposing is OK. A sub panel does not need a neutral if you are only supplying line to line loads. A service needs a neutral, even if you don't need it, but it is not required to be extended beyond that point unless needed to supply line to neutral loads....which is almost always.
All you really need to do is ask the local inspector before he comes...He is right, even when he is wrong. The inspector will be so **** happy that you thought it through this far:thumbsup:

EE_Bota · Jun 26, 2013

I was glad someone reminded us that breakers are for wire protection.

I was glad PF got dropped too.

arlen4720 · Jun 26, 2013

arlen4720 said:
One point we are all missing is that since both of the items that the OP are refering to are packaged, listed equipment, is that the branch circuit capacity and overcurrent device selection needs to be based on the manufacturers requirements.

I "bumped" this since nobody seemed to pay attention to it the first time I posted it. It is a very important point...when dealing with listed (UL or otherwise)equipment.

buickanddeere · Jun 27, 2013

Gator6x4 said:
The plugin you are currently using is for a 110 volt AIr Conditioner. The plug and the pig tail on the AC unit are designed like that to prevent someone from plugging into a regular outlet. I am surprised you haven't enjoyed some hot times using it to power a 220 volt unit.

You need four (4) wires going to a 220 plug in. Most 220 wires with four wires have a red, black, green and white wires. the red and black each carry 110 volts, the green is for ground and the white is the neutral safety ground. 220 volt appliances require a minimum of number 10 wire. Most compressors require number eight (8) wire. Some require number (6).

Neutral Safety Ground?
There is no such thing as a neutral safety ground.
The white is an insulated current carrying load conductor which is held to earth potential in order to keep the 120,277 or 347 lines from exceeding 120,277 or 347 to earth.
The ground system and there is only one. Is usually a bare conductor which holds the chassis of equipment to earth potential.

EE_Bota · Jun 27, 2013

The center tap of the pole transformer secondary provides a nice way to give the customer 240 without having any single line exceed 120 by much so long as the primary is connected to the correct voltage.

hr3 · Jun 27, 2013

Lots of discussion but nobody has quoted in the code book that a remote panel has less then 4 wires...I'll agree it will work and it will be safe for now,, but we don't live forever and the next person that moves into his house and doesn't want a welder outlet and the compressor is long gone.. Guess what he is going to use this nice little remote panel for..

arlen4720 · Jun 27, 2013

hr3 said:
Lots of discussion but nobody has quoted in the code book that a remote panel has less then 4 wires...I'll agree it will work and it will be safe for now,, but we don't live forever and the next person that moves into his house and doesn't want a welder outlet and the compressor is long gone.. Guess what he is going to use this nice little remote panel for..

I think you have it backwards. You're supposed to Recite the code that says that you can't do it.

hr3 · Jun 28, 2013

I already found were where it says you can't this is why I called you on it.. Oooo and while your looking where in the book is the term sub panel ever used,, I would think with your training and background you would use the proper terminology..

arlen4720 · Jun 28, 2013

hr3 said:
I already found were where it says you can't this is why I called you on it.. Oooo and while your looking where in the book is the term sub panel ever used,, I would think with your training and background you would use the proper terminology..

The suspense is killing me...What is your code reference?

hr3 · Jun 29, 2013

Ok lets start with the wire that is feeding the existing welder outlet it's type SE..

ARTICLE 338
Service-Entrance Cable: Types SE and USE..

338.10 Uses Permitted.

(A) Service-Entrance Conductors. Service-entrance cable shall be permitted to be used as service-entrance conductors and shall be installed in accordance with 230.6, 230.7, and Parts II, III, and IV of Article 230.

(B) Branch Circuits or Feeders.

(1) Grounded Conductor Insulated. Type SE service-entrance cables shall be permitted in wiring systems where all of the circuit conductors of the cable are of the thermoset or thermoplastic type.

(2) Use of Uninsulated Conductor. Type SE service-entrance cable shall be permitted for use where the insulated conductors are used for circuit wiring and the uninsulated conductor is used only for equipment grounding purposes.

Exception: In existing installations, uninsulated conductors shall be permitted as a grounded conductor in accordance with 250.32 and 250.140, where the uninsulated grounded conductor of the cable originates in service equipment, and with 225.30 through 225.40.

To me the circuit as run now is legal but as soon as you put the existing wire into a panel then it changes to a remote panel feeder..