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-   -   How to install central air and sub-panel (http://www.diychatroom.com/f18/how-install-central-air-sub-panel-34223/)

Stubbie 12-22-2008 11:00 AM

How to install central air and sub-panel
 
I found this on the internet pay particular attention to the sub-panel.

http://images.google.com/imgres?imgu...%3Den%26sa%3DG

jamiedolan 12-22-2008 11:07 AM

Quote:

Originally Posted by Stubbie (Post 201297)
I found this on the internet pay particular attention to the sub-panel.

http://images.google.com/imgres?imgu...%3Den%26sa%3DG

What a mess. If people are going to be stupid with there own stuff thats one thing. But to give directions to others that are wrong just offends me. It is a nice looking site, I am sure people think he is creditable and may very well follow his directions.

Jamie

HouseHelper 12-22-2008 11:33 AM

Sad part is he says it passed an electrical inspection.

Duane 70 12-22-2008 11:56 AM

Hey guys - for us non-electricians, can you tell us what is wrong for our own information. Maybe will keep us from doing something stupid. Thanks.

Termite 12-22-2008 11:59 AM

Good god, that kind of thing makes me feel like I need to see a therapist. :laughing:

That's a baaaaaad job.

Termite 12-22-2008 12:01 PM

Quote:

Originally Posted by Duane 70 (Post 201327)
Hey guys - for us non-electricians, can you tell us what is wrong for our own information. Maybe will keep us from doing something stupid. Thanks.

The neutrals and grounds should never be on the same bar, as they're required to be electrically isolated in a subpanel. The neutral bar should not have the green bonding screw in it, which bonds the bar to the panel jacket. There should be a separate bar for grounds. All MAJOR fire and life safety issues.

That's the basics, but I could write a book of a list!

Stubbie 12-22-2008 12:06 PM

Quote:

Originally Posted by Duane 70 (Post 201327)
Hey guys - for us non-electricians, can you tell us what is wrong for our own information. Maybe will keep us from doing something stupid. Thanks.

Duane .... you bet... I don't have time at the moment but I'll transport the images here and some of the other guys can comment

http://www.howdididoit.com/AC/elecSubPanel.jpg

http://www.howdididoit.com/AC/elecSubPanelHookedUp.jpg

jrclen 12-22-2008 03:26 PM

Well Duane, lets give this a shot.

First, the number 6 wire mentioned in the text is not large enough for 100 amps. #2 copper or #1/0 aluminum of that type cable would be required.

The neutral bus must be isolated from the enclosure and have no connection to the ground bus. The bonding jumper screw must be removed (the green screw in the neutral bus). Only the neutral conductors would be landed on the neutral bus.

A ground bus would need to be installed in the enclosure for the equipment grounding conductors (the bare wires).

The lower left romex must have the outer jacket inserted at least 1/4 inch inside the enclosure.

The small metal box for the AC whip, may or may not be to small for number of #10 conductors. It looks to small to my old eyes.

Anything I missed guys?

wirenut1110 12-22-2008 03:57 PM

Grounded conductors need to be re-identified as ungrounded

Stubbie 12-22-2008 04:24 PM

Hi John

No that pretty well sums it up between you,wirenut and kctermite for the sub-panel. There are a few other viloations but they are minor.

Just to clarify for Duane....With the terminations as you see them there are parallel paths for neutral current. The sub-panel is fed with four wires H-H-N-and a bare stranded ground. That ground lug you see is incorrect and was installed on one of the two holes where a ground bar/bus should have been installed. If you look above the lug you can see the second swaged hole. Now look at the green screw in the neutral bus. That is the main bonding jumper it is only used when a sub-panel is fed with 3 wires H-H-N. Neutral current always seeks the source ( the utility transformer center tap).You never want neutral current on your equipment ground wires or on the equipment ground wire of the feeder you see connected to that lug. Neutral current will seek all paths provided to it to return to the source.
Notice this panel has the green bonding screw installed in the neutral bar. That screw threads into the metal of the panel effectively bonding the neutral bar to the metal of the panel. Now notice that ground lug where the feeder equipment ground is terminated. Electrically speaking I've created a very low impedance/resistance path from the neutral bar to the ground lug and feeder equipment ground by installing that green screw. Neutral current will now split and follow the neutral of the feeder and the equipment ground of the feeder....parallel paths. This places neutral current on the metal of the panel as it travels thru the green screw to the ground lug to get to the feeder equipment ground which is another path to the source. Simply speaking you never want system current on the ground wires. You can get shocked or electrocuted under the correct circumstances. If you think about it the neutral current uses the metal of the panel to get to that ground lug and this effectively energizes the panel which is in turn exposed to human touch.

So that green screw should not be installed and a ground bar should be installed. You would then move all the bare grounds you see landed on that neutral bar to the ground bar. This will effectively isolate neutral current to only using the neutral of the 4 wire feeder to return to the source.
The diagram below shows the parallel paths using the yellow and red arrows you do not want this. You only want the path shown in red.



http://media5.dropshots.com/photos/4...222/141323.jpg

darren 12-22-2008 04:53 PM

Typical DIY, thinks he knows everything but knows very little.

My favorite line is "6 gauge four wire is required to provide power to the sub panel. It is a beast to work with." Comments like this make me laugh, #6 is a pleasure to work with, it bends nice and stays formed for the most part. Maybe we should get him some nice thick copper for he can see what tough cable feels like.

Since when was a cable with a black and white and bare ground called 10/3.

HouseHelper 12-22-2008 05:07 PM

He says he used 6ga to wire the subpanel, but from the pictures it appears he used 2-2-2-4 SER. The duct work is pretty sloppy and poorly designed too. Also, he did not install a disconnect at the air handler/heater.

Stubbie 12-22-2008 05:11 PM

Yeah looks like #2 al ser. The whole installation is pretty shoddy.

InPhase277 12-22-2008 05:25 PM

1) Ground and neutral bonding problem/confusion
2) White conductor identification
3) Cables not strapped
4) Less than 1/4" of jacket on cable
5) 15 A double pole looks like a Siemens/ITE, not a Square D Homeline.
6) Double landed terminal at top left

junkcollector 12-22-2008 06:44 PM

Nice replies on the message part guys.:thumbsup: With all of the other replies I'm surprised that the electrical issues didn't come up sooner. Scary that that kind of crap is on the internet. Guy must have gotten his advice from the store with the orange roof.:furious:

I'm sorry but I think this whole job is something that should be left to a pro.


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