Need help identifying my home power

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  #1  
Old 01-19-15, 02:03 PM
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Need help identifying my home power

Hi!

I'm trying to find out what kind of power supply setup do I have in my apartment, and I was hoping I could get some help finding out here!

First, some background info:

I live in a three level/12 unit apartment building, and I have a Square D fuse box installed. Here's a pic:

Name:  fusebox.jpg
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Voltage measured between the two fat black wires to the right (mains?) leading to the main breaker is ~240v.

My outside meter is an Itron CL200 C1SR (photo found online):

[ATTACH=CONFIG]45186[/ATTACH]

There is also no visible electrical wiring outside of the building.

Now, the questions and problems that I have, are as follows:

1. I'm trying to find out if this is a single phase two/three wire system, or three phase system with just one phase panel in my unit, that is being fed to the building. The fact that it's a small residential building and that the voltage reading between these two wires is ~240v, instead of ~208v, makes me think it's a single phase (split phase?) system, but I need confirmation.
2. The right hand side breakers are responsible for appliances such as the furnace, ac, range. I see two wires coming out of each one of them. Is the purpose here to have 2x120v hots to provide 240v output?
3. Conversely, the small breakers on the left hand side use only a single wire each, so these must be 1x120v lines, correct?
4. I can identify the ground bar and ground wires in my fuse box, but what about neutral? Is there no neutral/return wire here? Shouldn't each breaker circuit here have a return channel?
5. Is it safe to measure voltage between one of the main hots and the ground bar? I would assume it is, and it should read ~120v, is that correct? I just don't want to cause any issues (arc, shorts, etc.)
 
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  #2  
Old 01-19-15, 02:44 PM
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Unless you OWN the apartment you have no business in that panel. Even if you own the entire building it is possible, maybe even likely, that only a licensed electrician may do any work because it is a multi-family dwelling.
 
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Old 01-19-15, 02:55 PM
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I agree with Furd. You live in an apartment in the Chicago area. You have what you have. If it's inadequate, talk to the landlord or move. Stay the hell out of the panel. And don't even think about making any modifications.
 
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Old 01-19-15, 03:17 PM
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Thank you for your sound advice. I should have stated at the beginning of my post that I was not planning on making any alterations whatsoever. The wiring installed in my unit fits my needs well.

I am, however, interested in how household electrical systems work and I have read up on wiring in U.S. based dwellings. To confront my very basic knowledge with reality, I decided to open my breaker box and see if the setup looks similar to what I have seen and read so far. Hence the questions.
 
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Old 01-19-15, 03:34 PM
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First you do not have a Square D fuse box. You have a Square D breaker box. Two different things. It is single phase 3 wire supply consistent with older rules for sub panels. You might want to look for the book Wiring Simplified for a entry level education on residential wiring.
 
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Old 01-19-15, 03:40 PM
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Yeah,
Stay out of the panel. You don't need to be poking around in the panel to see how it works.
You have your picture, close up the panel and let it be.
Looking at your picture, the top bar with white wires connected is your neutral buss bar. (you called them ground wires). Your particular panel doesn't have a separate bar for bare grounds.

So your panel is about as simple as it gets. You don't need to study it.
You have hot wires coming off breakers, either singles (120V) or doubles (240V).
You have your neutrals. The conduit serves as ground at the wiring boxes inside the dwelling.

You already knew most of this and you don't need to confirm it by measuring "big fat wires".
Those fat wires will kill you.
 
  #7  
Old 01-19-15, 03:40 PM
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Thank you, I misspoke, this is clearly a breaker box. And thank you, I will definitely look for that read! And thank you Handyone!
 
  #8  
Old 01-19-15, 03:43 PM
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You have a single phase, 240/120 volt three-wire service. You could still have three-phase to the building although it is doubtful.

You do NOT feed a 240 volt circuit with two 120 volt circuits. The 120 volts is derived from the 240 volts supplied. Two-pole circuit breakers supply 240 volts and single-pole circuit breakers supply 120 volts. The different voltages are the result of the utility transformer having a center tap mid way between the ends that supply the 240 volts, 120 volts being available from the center tap to either end tap.

You have no "ground" bar in this panel. The white wires are neutrals and are the returns from the 120 volt circuits. The large white is connected to the center tap of the utility's transformer.
 
  #9  
Old 01-19-15, 07:10 PM
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Thank you! Now after reading some more and going through your answers, it makes a lot more sense.
 
  #10  
Old 01-20-15, 07:24 AM
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A somewhat unique feature to your panel is the lack of ground wires (green or bare) and a ground bar. The entire electrical system is run in metal conduit and metal boxes, which is legally allowed to be the ground in place of dedicated ground wires. You typically won't find an entire residential electrical system run in metal conduit outside of Chicago. The local codes there are quite restrictive with regard to what kinds of wiring are allowed compared to other areas of the country where you will see various flexible cables like Romex, BX, etc.
 
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