Electrical assistance please

D+C4106 · January 23, 2009, 06:04:16 AM

Some time ago there was a post with a 50 amp outlet wiring diagram and a procedure to check it for proper output. I have installed a 100 amp line from the house to the barn, (grounded in the house panel). Now I am running a 50 amp line from the sub panel to an outlet for the bus and would like to check it before I plug the bus into it. I tried the search feature without much luck. Any help will be appreciated. Thanks, Denis

Sean · January 23, 2009, 06:32:08 AM

Your 50-amp outlet has four holes -- one round or u-shaped, and three slots.

Assuming it is mounted with the round or u-shaped hole "up" (the correct mounting orientation), let's call the round hole the "12-o'clock position," the three slots are thus at 3 o'clock, 6 o'clock, and 9 o'clock. Get out your AC voltmeter and check as follows:

Between 3 o'clock and 9 o'clock should read between 220 and 250 VAC
Between 3 o'clock and 6 o'clock should read half of that, between 110 and 125 VAC
Between 6 o'clock and 9 o'clock should also read between 110 and 125 VAC
Between 12 o'clock and 6 o'clock must read zero
Between 12 o'clock and 3 o'clock should read between 110 and 125 VAC
Between 12 o'clock and 9 o'clock should read between 110 and 125 VAC

Now set your meter on Ohms and check the following:

Between 12 o'clock and the metal case of the box should read zero ohms
Between 12 o'clock and 6 o'clock should read more than zero, but a relatively small number -- less than half an ohm or so

HTH.

-Sean
http://ourodyssey.blogspot.com

bobofthenorth · January 23, 2009, 07:28:46 AM

As usual, if your question is electrical Sean has the right answer. If you want a graphic illustration use this:
http://www.myrv.us/electric/

This page has all you really need:
http://www.myrv.us/Imgs/PDF/50-amp%20Service.pdf

Len Silva · January 23, 2009, 09:18:55 AM

Using Sean's instructions, I would caution that you turn off the breaker supplying the outlet before proceeding with the ohm meter checks. Just in case something is wrong, you won't destroy the meter.

D+C4106 · January 23, 2009, 12:42:48 PM

Sean, Bob and Len, THANK YOU, That is the information I needed. If all goes well I hope to have this done within a day or so. Again, Thank you for your help. Denis

Sean · January 23, 2009, 01:49:22 PM

Quote from: Len Silva on January 23, 2009, 09:18:55 AM
Using Sean's instructions, I would caution that you turn off the breaker supplying the outlet before proceeding with the ohm meter checks. Just in case something is wrong, you won't destroy the meter.

Good advice. I should have stated that the order of the tests as I posted them is important -- if you don't get the zero voltage reading in step 4, then you should not proceed to any of the further steps until that problem is corrected.

-Sean
http://ourodyssey.blogspot.com

gm4106 · January 23, 2009, 02:00:22 PM

May be this will help you.

D+C4106 · January 25, 2009, 04:16:38 PM

All went well until the OHM test, my reading would be as high as 09.6, then it would drop, another time it may have been 04.5 then drop to the lower reading of 00.5 range. Does temperature affect the meter? It is only 11 degrees here. Any suggestions ? Thanks, Denis

Sean · January 25, 2009, 05:08:36 PM

Is that the reading between the case and the ground (12 o'clock) or between the ground and the neutral (6 o'clock)?

-Sean
http://ourodyssey.blogspot.com

JackConrad · January 25, 2009, 05:11:36 PM

Are you sure you are maintaing a good contact with both the the test probes? An intermittant poor connection here will give different readings. Jack

D+C4106 · January 25, 2009, 07:17:49 PM

Jack, it was cold and I may have been shivering !! I will try it again tomorrow in the daylight.
Sean, that reading was between ground and neutral.
Thanks for your help, Denis

buswarrior · January 25, 2009, 07:31:47 PM

I've noticed digital meters don't like the cold.

Keep it in the house, and put it in your jacket for the trip outside, then yank it out and get on with it before the cold creeps back into the case, to see if you get anything different.

happy coaching!
buswarrior

Sean · January 25, 2009, 07:50:09 PM

Quote from: D+C4106 on January 25, 2009, 07:17:49 PM
... that reading was between ground and neutral.

OK, let me know what gauge wire you used, and about how far from the receptacle back to the main panel, and I can tell you approximately how many ohms it should read. But half an ohm would be the max for, say, 6-gauge at less than 500' run.

Once you get a steady reading by either not shivering

or warming up the meter, or both, if it is significantly higher, say more than an ohm or two, you should check all your ground and neutral connections for tightness, broken strands, etc.

-Sean
http://ourodyssey.blogspot.com