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Old 08-08-2012, 09:17 AM   #16
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Outdoor A/C compressor cut-off safety


My take on this is, the black, red and green wire come from a premade whip that is feeding the AC unit.
The incoming power is connected to the bottom of the disconnect.

This is way past time for diy help, and needs to be professionally repaired before some poor AC tech gets his di** knocked into the dirt!

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Old 08-08-2012, 07:20 PM   #17
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Outdoor A/C compressor cut-off safety


JB, that's what it's looking like to me.

After researching it a bit more, I believe the main breaker is three-phase, strangely (it's residential, but this house was built 50-60 years ago). It used to have some brand of main breaker that was known for causing fires, so that was replaced 10-20 years ago with a new main panel. The main 200A breaker is a powerpact qdl32200, not a qdl22200, which I think indicates 3-phase. http://i.imgur.com/xJeCV.jpg

This one a/c compressor at issue is the only three-phase appliance in the house, but I think it's a legit 3-phase circuit and the compressor says 3-phase on the label.

For the image above, the two sides (black) are 120v, and the middle (red) is 208v (sum of two 1/3 out of phase feeds), measured vs ground. ALL differentials (right to middle, right to left, middle to left) are 240v. (These are valid numbers, it's a true rms multimeter). That seems like it could work, but I don't understand why the middle conductor feeding into the main breaker from the top (the red one) is smaller.

Furthermore, the three wires (my previous post, picture) coming out of the three-slot breaker, the top and bottom (black, red) are 120v, the middle (white) is 208v. So that must be getting converted to 3 120v wires somewhere between the breaker box and the cut-off switch, I guess.

What I don't get is why the feed whip from the A/C unit doesn't have a ground to be tied into the ground from the house breaker box. However, since it must have come with the compressor which was made in 2004, I'm going to assume the people involved knew what they were doing even though I don't understand it.
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Old 08-08-2012, 07:23 PM   #18
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Outdoor A/C compressor cut-off safety


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Originally Posted by mike31 View Post
JB, that's what it's looking like to me.

After researching it a bit more, I believe the main breaker is three-phase, strangely (it's residential, but this house was built 50-60 years ago). It used to have some brand of main breaker that was known for causing fires, so that was replaced 10-20 years ago with a new main panel. The main 200A breaker is a powerpact qdl32200, not a qdl22200, which I think indicates 3-phase. http://i.imgur.com/xJeCV.jpg

This one a/c compressor at issue is the only three-phase appliance in the house, but I think it's a legit 3-phase circuit and the compressor says 3-phase on the label.

For the image above, the two sides (black) are 120v, and the middle (red) is 208v (sum of two 1/3 out of phase feeds), measured vs ground. ALL differentials (right to middle, right to left, middle to left) are 240v. (These are valid numbers, it's a true rms multimeter). That seems like it could work, but I don't understand why the middle conductor feeding into the main breaker from the top (the red one) is smaller.

Furthermore, the three wires (my previous post, picture) coming out of the three-slot breaker, the top and bottom (black, red) are 120v, the middle (white) is 208v. So that must be getting converted to 3 120v wires somewhere between the breaker box and the cut-off switch, I guess.

What I don't get is why the feed whip from the A/C unit doesn't have a ground to be tied into the ground from the house breaker box. However, since it must have come with the compressor which was made in 2004, I'm going to assume the people involved knew what they were doing even though I don't understand it.
You have a high leg delta service... I never understood why these were installed at a residential property...

Phase to phase you get 240 volts, phase to neutral you will get 120v except on phase "B" this is the bastard leg, or high leg... NEVER, EVER use this leg for Line to Neutral loads....

Looking at the Main breaker picture indicates a "open-delta high leg" meaning you have two transformers, instead of three for a true "open delta"

Last edited by stickboy1375; 08-08-2012 at 07:31 PM.
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mpoulton (08-09-2012)
Old 08-08-2012, 07:27 PM   #19
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Outdoor A/C compressor cut-off safety


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What I don't get is why the feed whip from the A/C unit doesn't have a ground to be tied into the ground from the house breaker box. However, since it must have come with the compressor which was made in 2004, I'm going to assume the people involved knew what they were doing even though I don't understand it.
Someone hacked the installation, I dont know why, but its hacked. And you really need to call a licensed electrician to come and repair all the insane violations.

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Old 08-09-2012, 04:22 AM   #20
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Outdoor A/C compressor cut-off safety


This is a three phase circuit. The white wire on the breaker is the third phase, and is improperly colored. That yellow tape on that wire in the panel should be orange, and indicates that it is the "high leg" of the service (208V to ground). The worst part (hopefully) is that they switched to green for the third phase in the disconnect! That's awful. Hopefully that green conductor isn't connected to the chassis of the condensing unit...

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