Shop Wiring Q's ,Please Help!

Reply

  #1  
Old 01-08-12, 01:23 PM
Member
Thread Starter
Join Date: Jan 2012
Location: USA
Posts: 2
Shop Wiring Q's ,Please Help!

Ok, so I'm wiring up a new commercial auto shop that we're moving into, and I have a few questions. I'll try to lay them out in an orderly fassion, since I have so many. And thanks in advance for your time and responses.

1. If wiring a 220v system, and the appliance says 30A, does that mean I treat it as 2x 15 amp systems (double 15A breaker) with the wiring to support 15A or 2x 30A wiring? (2x 120v lines). Like since 220v is just 2x 120V, is it 2x15A =30A?

2. When I use wire calculators on the net here, they pretty much tell me anything over 20ft needs some ungodly wiring. If I'm running a 30A 220V service 140ft (+40ft up and down the walls if you want to get technical) away from the box what size wiring is really needed? Its for a Dyno w/eddy load break. So the full 30A will be VERY rare, and when it is only 15-30sec at a time.

3. Genericly speaking in an office environment, how many outlets do can you generally run from one 15A circut? How bout 20A?

4. The shop is 140ft long. From the opposite side of the pannel is where I'm running 3x lifts (220V) and the Dyno. Would it generally be cheaper to run wiring to each, or run a sub pannel (50A) at the other end, and then run off of it. What size wiring should be needed for 140ft run on 220v and 50A service?

Thankyou in advace,
CK
 
Sponsored Links
  #2  
Old 01-08-12, 01:31 PM
pcboss's Avatar
Forum Topic Moderator
Join Date: Jul 2002
Location: Maryland
Posts: 14,359
Many areas would prevent a DIY from working on a commercial building. Check with your building officials.

A 30 amp circuit will use a 30 amp breaker, not 2x15.

Designing a circuit takes into account of what will be used on that circuit. A copier may need its own circuit, whereas a couple of pcs may run fine on the same circuit.

I would not waste time on a 15 amp circuit on a commercial job.
 
  #3  
Old 01-08-12, 01:48 PM
Member
Join Date: Feb 2002
Location: port chester n y
Posts: 2,117
A 30 amp , 220 volt load = a 30 amp 2-pole circuit-breaker.

A 30 amp 220 volt load 150 ft from the breaker = a #6 copper conductor.

A 50 amp "Feeder" , 150 ft in lenth = a #4 copper conductor

A 100 amp Feeder similar in lenth = a #2 copper conductor. Because of the relatively small increase in wire guage ; #4 -to-#2 ; a 100 Feeder gives twice the power -capacity of a 50 amp Feeder which would well justify the cost difference between #4 / #2 conductors.
 
  #4  
Old 01-08-12, 02:43 PM
Tolyn Ironhand's Avatar
Group Moderator
Join Date: Nov 2007
Location: Twin Cities, MN
Posts: 11,982
Besides the liability of doing your own commercial wiring (which you have pulled a premit for I assume ) you are also wiring in a potentially hazardous location which has their own set of special rules. This is not a place you will want to be DYIing it. Based on some of the questions you asked, you might want to consult a pro.
 
  #5  
Old 01-08-12, 02:47 PM
Member
Join Date: Dec 2008
Location: Northeastern, MN
Posts: 175
shouldnt you be saying.............

120v x 2 = 240volts not 220v
 
  #6  
Old 01-08-12, 02:51 PM
Member
Join Date: Apr 2006
Location: USA
Posts: 133
Your questions are very basic information that a qualified electrician would know. Do you self a favor and get someone who knows what they are doing. You may burn the whole place down.
 
  #7  
Old 01-08-12, 03:01 PM
Member
Thread Starter
Join Date: Jan 2012
Location: USA
Posts: 2
Thanks for the clairification. I just wanted to make sure a 30A double pole wasn't actually suppling a total of 60A before it would blow. I don't want to overpower a circut incase there is a short.

So if it calls for 30A, even thought its a 220v system, and splits the load between 2 lines, use wire and breakers rated for 30A on each?

Is there really a difference between the 220v breakers? I thought they were just 2x 110v breakers connected together with a pin?

And I'm not looking to do this myself, I'm just looking to get pricing and schematics sorted out so I know what I'm up against before I see an electrician. This way I'm edjucated, and know what "needs" to be in place, so I don't get schooled.
 
  #8  
Old 01-08-12, 03:27 PM
Tolyn Ironhand's Avatar
Group Moderator
Join Date: Nov 2007
Location: Twin Cities, MN
Posts: 11,982
There is many of us here right now so if I repeat what others have said just ignore me.

A circuit breaker is rated by the number, in amps, on the breaker. That breaker will trip when it reaches (or there abouts) that amount of current on either leg. There is no splitting the current. If you had motor drawing 20 amps, on a 30 amp 240 volt circuit, and you put an ammeter on each leg. It would read 20 amps on both. This is because current in on one leg, is current out on the other.

They are similar to single pole breakers but are joined with the handle tie and are physically attached together as one unit. They are also rated differently for the voltage they will encounter. This is also the same with three pole breakers for three phase circuits.

On a circuit, the wire is sized to handle the load, and the breaker is sized to protect the wire from overheating (among other things)
 
  #9  
Old 01-08-12, 03:29 PM
ray2047's Avatar
Group Moderator
Join Date: Mar 2006
Location: USA
Posts: 32,659
Is there really a difference between the 220v breakers? I thought they were just 2x 110v breakers connected together with a pin?
First off assuming a single phase supply it will be a 240v not 220v feed which can be split into two 120v sources not 110v. However a commercial shop may have 3 phase power with voltages of 120 and 208 or 277 or even 480.

Many two pole breakers have internal trips not just the handles tied together.
 
Reply

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Thread Tools
Search this Thread
Display Modes
'