Revisiting New Main Lug Install

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Old 10-07-02, 10:11 AM
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Revisiting New Main Lug Install

Hello again!

A while back I posted with questions regarding calculations for service size, etc. I found that my 150A service is more than adequate and my next phase was to begin a little-bit-at-a-time rewire of my entire 50 year old 2-wire house.

My next step was to purchase a new main lug to replace the old fuse box. My intent was (and still is) to put the new lug in a more convenient and aesthetically pleasing location, run new wire from the service to this panel to energize, then rewire old circuits (adding new receptacles) and connect them to breakers in the new box--doing these a little at a time as I get in the mood. Eventually, I will 'retire' the old fuse box completely, de-energize it and remove all wires.

Mr. Nelson recommended I get a 100A main lug, place a 100A breaker in the service panel (I have 1 space left) and run 4awg 4-wire cable from service to the new panel. Here is what happened:

On a trip to Home Depot (I live 75 minutes from the nearest one--all the local prices are sky high, so I wait until I have business "in the city" to purchase high ticket home improvement items), I found no 100A main lugs--only 100A main disconnect panels. I found a decent deal on a 125A main lug 'combo pack' that included the door, 6 - 20A breakers and 2 2-pole breakers (1 - 30A & 1 - 50A). So I bought it. I didn't buy the cable/wire because I had not measured how much I would need.

On the second trip for the wire, the person helping me was relatively new and the 'electrician types' were not there to help. Either they didn't have or he couldn't find 4 gauge, 3 wire + ground cable--he only found 6 gauge, 3 wire + ground cable. I went ahead and purchased it b/c he said I could return it.

The panel I got is a GE TLM1212CCU. I pulled it out last night and studied it. It has:

* 2 terminals (correct terminology?) to connect the 2 hot wires coming in
* 2 neutral bars--one down each side--that are isolated from the box but are connected together via a removable crossbar. There is only one terminal atop one of the neutral bars in order to connect the neutral wire coming in
* No separate ground bar

After that long intro, here are my questions:

1) I assume Mr. Nelson suggested a 100A lug because it would be cheaper than a 125A. Well, the 125A 'combo pack' at HD is cheaper than any 100A panel I can find locally. I guess it is OK to use the 125A panel and run it off a 100A breaker from the service?

2) The person who helped me purchase the panel said I could remove the crossbar that connects the 2 neutral bars and use one bar as neutral and one bar as ground. The instructions with the panel stated something of the sort. I would have to purchase another 'terminal lug' to attach to the now isolated bar in order to attach the ground wire coming in.

A) Is it OK to remove that crossbar and use this isolated bar as the ground bar rather than purchasing a separate ground bar?
B) To do so, I would have to double-up a few neutrals from different branch circuits onto the same terminal screw on the neutral bar. Is this OK to do?
C) To do so, I would have to double-up a few grounds from different branch circuits onto the same terminal screw on the ground bar. Is this OK to do?

3) Should I return the #6-4 wire cable and find some #4-4 wire? (I forgot to state that the total run of my cable from service to new panel will be less than 35 feet.)

Again, I apologize for writing novels when I post, but I like to get ALL the info in up front so extra, clarifying questions don't have to be asked and answered and waste more time before getting an answer.

Thanks for any help and info!
 
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Old 10-07-02, 11:23 AM
texsparky
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Hello Moonpie,
I couldn't locate the post where John suggested # 4 wire for the subpanel.What type of wire was suggested? Did you purchase Type NM #6? If so ,it is only rated for 55amps.
 
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Old 10-07-02, 11:50 AM
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Whoops!

I must apologize. I did not re-read my old thread and for some reason thought it was Mr. Nelson--it was Wgoodrich.

The thread is a few months old (last post 6/30/02). It is titled 'Service Panel' and I started the thread. Here is the quote from Wgoodrich:

"I would install a 100 amp sub panel as the new panel and run a 4 awg 4 wire cable from that new sub panel to a 100 amp breaker in your main panel that will replace that older 60 amp breaker now being used when you switch power to the new panel. "

AAMOF, I do not know the type wire I purchased. I will look when I get home. However, this reminds me of a question I forgot to ask:

- I will be running the wire from the service to this "sub-panel" through the crawlspace under the house. I will attach this wire to the floor joists so that it is not touching the ground. What type & rating wire must I use for this application?

Thanks!
 
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Old 10-07-02, 12:25 PM
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I found the post dated 06/03/02 from WG.The #4 copper would only be rated for 85 amps.
IMO you should run an 1 1/4" pvc(minimum) with 3 # 3thwn and 1 #8 green(minimum) to the sub panel.You purchased a 12 circuit panel.You should have enough spaces in the neutral bar for twelve circuits.You cannot put more than 1 neutral under each terminal screw.
 
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Old 10-07-02, 07:03 PM
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Tex check 310.15(B)(6) #4 100 amps.
 
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Old 10-07-02, 07:59 PM
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aphares,I am aware of this table but 310.15(B)(6)....reads

For application of this section,the main power feeder shall be the feeder(s) between the main disconnect and the lighting and appliance branch-circuit panelboards.

I cant see that it would apply to a sub-panel feeder.This does not feed from the main disconnect;It is basically a 100amp branch circuit.

I may be wrong,but the way I interpret this is .............A main disconnect is located outside after the meter;From the disconnect to the panelboard located remote from the disconnect a feeder sized per table 310.15(B)(6)would be acceptable.
 
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Old 10-07-02, 08:05 PM
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If it goes to a subpanel, it's a feeder, not a branch circuit. Check out the definitions of these two terms in article 100.
 
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Old 10-07-02, 08:22 PM
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John,
Bad choice of words,I know.
Do you think that that the table should apply?Is this the main power feeder to the dwelling?
 
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Old 10-07-02, 08:27 PM
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The term "main power feed" is not defined. Are you talking about the "service"? In any event, I think the table applies because it seems to fit the definition of "feeder" and the table is for "services and feeders". The code lives and dies on precise language.
 
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Old 10-07-02, 09:19 PM
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John,
The way I read it,Table 310.15(B)(6), is for services.
QUOTE: Article 310.16(B)(6) 120/240-Volt, 3 Wire, Single-Phase Dwelling Services and Feeders
For dwelling units,conductors, as listed in Table 310.15(B)(6), shall be permitted as 120/240-volt,3-wire, single-phase SERVICE-entrance conductors, SERVICE lateral conductors, and FEEDER conductors that seve as the MAIN POWER FEEDER to a dwelling unit and are installed in raceway or cable with or without an equipment grounding conductor.For application of this section,the MAIN POWER FEEDER shall be the FEEDER(S) BETWEEN the MAIN DISCONNECT and the lighting and appliance branch-circuit panelboards.
 
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Old 10-08-02, 07:35 AM
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If *I* am understanding the definitions correctly, this would be a feeder as defined by texsparky's quote:

"...the MAIN POWER FEEDER shall be the FEEDER(S) BETWEEN the MAIN DISCONNECT and the lighting and appliance branch-circuit panelboards."

This is coming from the main disconnect outside (the service panel) going to this panel in the house that will be the lighting and appliance branch-circuit panel. I apologize if I was unclear in that--I may have been using the term 'sub-panel' incorrectly.

The panel that I want to install would be where all the lighting & appliance circuits would originate in my house--once I finished all the wiring and 'retired' the old 4-fuse fuse box that is serving that purpose now.

So if it does fall under the feeder definition, I could use #4 wire for a 100A panel? Referring back to my original list of questions, since I purchased a 125A panel could I use a 100A breaker in the service panel to feed this 125A panel and use #4? What if I used a 125A breaker to feed this, then what size wire should I use? Or should I nix those ideas, return the 125A panel and shop around for a 100A?

Thanks!
 
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Old 10-08-02, 09:44 AM
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If my understanding is correct, you are connecting a feeder to an existing 100 amp service panel. it's permissible to connect a feeder to a sub-panel with a rating that exceeds the rating of the feeder conductors and the feeder breaker. You can connect a 200 amp. panel to a 100 amp. feeder but you can't connect a 100 amp. panel to a 200 amp. feeder. Table 310.15(B)(6) permits a rating of 100 amps. for #4 copper conductors used as service conductors for dwellings. A temperature rating is not specified in the Table. I reason that this allows a 100 amp breaker for #4 copper feeder conductors in dwellings. The 100 amp. Main Circuit-Breaker is more likely to trip than the 100 amp feeder breaker because the tripping current of the MCB is the sum of the feeder current and the branch-circuit currents connected to the MCB. Do not make any internal modifications to the panel, and do not bond the Neutral terminal strip to the metal enclosure. Throughly bond a Grounding terminal bar to the metal of the panel and connect the bare wires on the branch-circuit cables to this Grounding bar. Good Luck!!!
 
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Old 10-08-02, 10:00 AM
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A correction is in order-----Moonpie has a 150 amp. MCB. But my essentail point stands---he can connect #4 copper feeder conductors protected by an 100 CB to a sub-panel rated at 125 amps. with the Neutral terminal insulated from Ground and with a Grounding bar bonded to the metal enclosure and connected to the feeder Equiptment Grounding Conductor.
 
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Old 10-08-02, 11:30 AM
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Thanks, everyone, for the replies.

So now and added question ("Joy!", you say.):

Suppose I sell the house and the next owner wants to add some circuits and looks and says, "Well lookee there, it's a 125A main lug, so I can just change that 100A breaker in the service panel to a 125A breaker and I'm good to go!"

And let's suppose he doesn't have the foresight to look at the feeder wire, or he does and says, "That's pretty thick and in good shape--I'm good to go!" instead of logging on here and asking questions.

In that case, #4 wire is probably not rated for 125A? If not, what is b/c I should probably run that instead. I was thinking of taking the panel back and getting a 100A, but that was the problem in the first place--finding a 100A main lug. So I should probably just buy the correct wire for 125A whether I use a 100A or 125A breaker.
 
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Old 10-08-02, 12:45 PM
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Originally posted by texsparky
John,
The way I read it, Table 310.15(B)(6), is for services.
QUOTE: Article 310.16(B)(6) 120/240-Volt, 3 Wire, Single-Phase Dwelling Services and Feeders
For dwelling units, conductors, as listed in Table 310.15(B)(6), shall be permitted as 120/240-volt, 3-wire, single-phase SERVICE-entrance conductors, SERVICE lateral conductors, and FEEDER conductors that serve as the MAIN POWER FEEDER to a dwelling unit and are installed in raceway or cable with or without an equipment grounding conductor. For application of this section, the MAIN POWER FEEDER shall be the FEEDER(S) BETWEEN the MAIN DISCONNECT and the lighting and appliance branch-circuit panel boards.
You are right. This section is often misunderstood. The increased ampacity permitted under that table is dependent on the diversity of the entire dwelling load for safety. When the load imposed on the conductors is only part of the dwelling load that level of diversity can not be assumed. The language in that section was meant to cover the feeder between any dwelling units remote service disconnecting means and the panel in the unit itself. It applies to apartments and condos as well as to one and two family dwellings. In each case the feeder in question must be carrying the power from the main disconnect to the lighting and appliance panelboard that serves the dwelling. The principal reason for the feeder provision is to avoid requiring feeders that are larger than the service conductors supplying them.

310.15 Ampacities for Conductors Rated 0?2000 Volts.
(A) General.
(6) 120/240-Volt, 3-Wire, Single-Phase Dwelling Services and Feeders. For dwelling units, conductors, as listed in Table 310.15(B)(6), shall be permitted as 120/240-volt, 3-wire, single-phase service-entrance conductors, service lateral conductors, and feeder conductors that serve as the main power feeder to a dwelling unit and are installed in raceway or cable with or without an equipment grounding conductor. For application of this section, the main power feeder shall be the feeder(s) between the main disconnect and the lighting and appliance branch-circuit panelboard(s). The feeder conductors to a dwelling unit shall not be required to be larger than their service-entrance conductors. The grounded conductor shall be permitted to be smaller than the ungrounded conductors, provided the requirements of 215.2, 220.22, and 230.42 are met.
--
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Last edited by hornetd; 10-08-02 at 04:18 PM.
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Old 10-08-02, 03:24 PM
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Thank you. I stand corrected. Learn something new every day (although I think I learned this before and subsequently unlearned it and now I've relearned it).
 
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Old 10-08-02, 05:06 PM
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Moonpie,
# 1 thwn is rated for 130 amps. You can't base your decision on what some future owner may or may not do.
 
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Old 10-08-02, 07:26 PM
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Thanks, texsparky.

I reckon the easiest thing to do at this point is just get some #1 and go from there.

On Thursday I should be going in 'to the city' to take someone who is delivering a truck to where I work, to the airport to catch his flight back. Tomorrow I will search the online yellow pages for electrical supply houses 'in the city' and I'll go there rather than Home Depot and see what I can find.

Who knows what I'll come home with?
 

Last edited by Moonpie; 10-23-02 at 11:09 AM.
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Old 10-23-02, 11:08 AM
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Update:

I got the cable a couple of weeks ago. Two weekends ago I spent most of one day moving some studs and mounting the new main lug panel in the hall wall where the wife and I finally decided for it to go.

This past Monday evening I finally ran the cable through the crawlspace, securing it to the floor joists. Yesterday evening I connected all 4 wires in the new main lug panel. Next step is to connect the other end in the service panel.

New question:

The instructions with (and the label in) the new main lug panel give torque specs for the different lugs and screws in the panel. I have only ever seen big torque wrenches (like when working on an automobile), so how do I go about making sure I have the screws properly torqued when I'm tightening these screws with a screwdriver or a hex driver?

Thanks!
 
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Old 10-23-02, 12:59 PM
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You will have to spend a little more money!!!!!

Go here.... http://www.mytoolstore.com/klein/57035.html
 
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Old 10-23-02, 04:29 PM
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<gulp!>

 
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Old 10-29-02, 03:39 PM
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...continued...

The power company is coming tomorrow at 9:00 AM to pull my meter so I can hook up that end of my new service cable for my new main lug in the house. (Good thing I often come in to work early, stay late and work through lunch sometimes so I can take a few minutes to run home. )
Tonight I'm planning to go ahead and connect the 2 hots to the 2 screws on the double pole 100A breaker (outside the panel--just leave the breaker lying loose) so all I have to do when they pull the meter is connect the 'neutral' and the ground wires to the bar then insert the breaker into its slot.

Here comes a couple more questions I haven't thought about until now:

1) Does it matter which hot wire is connected to which pole of the breaker when considering which hot wire is connected to which lug in my new panel? (In my mind, I would think it doesn't matter as long as the 2 hots are getting their power from the 2 different lugs and not both getting power from the same.)

2) Both my hot wires in my cable that is running from my service panel to this main lug in the house are black. Do I need to put tape or paint or anything on one of them to designate it as the second hot wire? (Or would I only need to do something of the sort in a branch circuit (for example the switch loop) where the normally 'neutral' white wire is being used for a hot and has to be marked?)

Thanks!
 
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Old 10-29-02, 05:44 PM
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Order of operations for cut over.

Why are you having the meter pulled or the service equipment deenergized? Is it to permit you to work safely in the panel, is it to deenergize the existing fuse panel during cut over or is it both? You may want to change the steps you laid out to size the wires, prepare the conductors for length, tie down the back fed main breaker using the manufacturers kit, then terminate all conductors during the outage. Have your emery cloth, wire brush, and anti oxidase compound at the ready if you are using aluminum. If you can buy the lock out devices to fit the breakers you are using at both ends of the feeder you could terminate both ends and lock out the breakers to preclude a hazardous back feed. Two locked out breakers in series are considered a perfectly adequate safeguard. This is only necessary if the panel has a source of power now. If it does not then such precautions are unnecessary and you could terminate the entire feeder in advance of the outage. You could wait for the outage to terminate the new feeder at the supply end if you are uncomfortable working in the energized main service. If both this new MLO and the pole mounted service have yet to be energized you can tie everything down now.
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Old 10-29-02, 07:20 PM
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hornetd - thanks for the reply. I don't believe I completely followed your whole reply, but I'll answer what I could keep up with.

I have installed my MLO in the house, connected all 4 of my feeder wires in the MLO and run the cable under the house. The other end is dangling loose beside my service panel waiting for me to connect all 4 wires in the service panel. My service panel is existing and energized--I am installing and energizing a new MLO and will slowly rewire existing circuits & transfer them to this new MLO, eventually 'phasing out' the old screw-in, 4 fuse, fuse box that currently supplies all the old 2-wire circuits in the house.

The reason I am having the service panel de-energized is because I do not have a main disconnect in my service panel--I have slots for 6 double-pole breakers, so I am good with the 'no more than 6 swipes of the hand' rule.

I figured (correct me if I'm wrong) that I could connect the 2 hot wires on the service end of the feeder to the 2 screws on the breaker then install the breaker into the service panel all with the panel energized (especially since this breaker is going in the slot furthest from the lugs).

However, since I've never done work in a service panel before, and since I have no main disconnect, I figured (correct me if I'm wrong) that I should have the panel de-energized before I stick my hands and a screwdriver (or other appropriate tool) in there to connect the neutral and ground wires of the feeder to the bar in the service panel. It would not be safe, would it, for me to be trying to connect the neutral and ground wires with the panel still energized? (That was NOT meant as a smart-aleck question if it sounds that way--I meant it as an honest question.)

Bottom line Reader's Digest(tm) version:
- MLO is installed and feeder wires all connected on MLO end
- Other end of feeder needs to be connected to breaker and bar in service panel
- Service panel has no main disconnect

Am I going about this correctly to have the PC cut the power, or should I do something differently?

Thanks!
 
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Old 10-29-02, 08:07 PM
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You are taking the right approach. In the absence of insulated tools and flash protective clothing you would be foolhardy to undertake the cut over in a hot panel. Experienced electricians usually want to have another electrician present during hot work.

Before the utility people arrive check out the panel and its feeder with a meter to make sure it is free of shorts and ground faults.

Good Luck.
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Old 10-30-02, 06:54 AM
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I don't know if you will read this in time to reply before I have to go meet them, but are you talking about checking the new MLO and it's feeder for shorts and ground faults?

How would I go about doing that? I have a multimeter, is that sufficient or would I need something else?

Thanks!
 
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Old 10-30-02, 11:02 AM
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Your multimeter will be fine. Just make sure that with all breakers except the MLO's back fed main open there is no continuity between any two conductors of the feeder.
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Old 10-30-02, 03:49 PM
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Thumbs up UPDATE

UPDATE - PHASE 2 COMPLETED!

Unfortunately, I did not get hornetd's reply in time to check for shorts and/or ground faults.

At 9:00 AM sharp (maybe even a few minutes before), the PC showed up and in a matter of a few short seconds, pulled my meter.

Long story short (y'all know how 'loquacious' I can be)...feeder neutral & ground were connected to appropriate places on bars (which are connected), breaker was inserted & 2 hots connected. Mess cleaned up, tools put away then back to my 'job' work. Made phone calls: inspector inspected, OK given, PC put meter back. WOOHOO!

Wow, last year I wouldn't have even BEGUN to try something like this. But thanks to EVERYONE'S help & input on this forum I was able to do this thoroughly, safely and COMPLETELY!

I have not 'flipped the breaker on' yet to energize the MLO (I don't even have any breakers in it yet)--I will do that this evening when I get home and can test everything with my meter before and after doing so. If all seems good, I might even start on Phase 3 (the circuit by circuit rewire of the house) tonight by finishing the run of 12/2wG from a new GFCI receptacle I installed in a bathroom remodel and connecting everything in the new MLO. It'll be my first equipment grounded receptacle in the house!

(Those of you who've done this for awhile, please forgive my 'giddyness', but DANG what a good feeling it is to have done this!)

Thanks again everyone!
 
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Old 10-30-02, 07:11 PM
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Congratulations!
 
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Old 10-31-02, 07:23 AM
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Update to the update:

Yesterday evening I got out the multimeter (it is analog, so I'm sure there is some margin of error).

With breaker off, I tested the MLO:
- Hot1 to Neutral: 0V
- Hot2 to Neutral: 0V
- Hot1 to Ground: 0V
- Hot2 to Ground: 0V
- Hot1 to Hot2: 0V

With breaker on:
- Hot1 to Neutral: 120V
- Hot2 to Neutral: 120V
- Hot1 to Ground: 120V
- Hot2 to Ground: 120V
- Hot1 to Hot2: 245V

(Unfortunately I didn't even think to check Neutral to Ground just to make sure--I just thought of it as I was writing this.)

Thanks again everyone--y'all all rock!

I'll shut up and stop posting to this thread now.
 
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