Generator transfer switch question(s)

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Old 07-29-18, 01:17 PM
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Generator transfer switch question(s)

A question about the transfer switch that I bought (got it new, never-opened, from Craigslist for $75). It is a kit, so it comes with two switch boxes (it's an older Generac kit, it comes with 2 transfer switch boxes rated for 7200 W each, 6 circuits per box, 1 circuit pre-wired for 240V), an outdoor outlet, and a generator cable. The outdoor outlet and generator cable are both wired for a 50-amp outlet (L14-50).

Here's the problem--my current panel was installed in 1966 so it surely doesn't meet code today. I don't have the side-to-side clearance required, although I do have enough space in front of the panel.

I'm just wondering what types of work are allowed to be grand-fathered in. Does it differ from city to city? Would adding the switch mean that I have to bring the rest of the panel up to code?


It is this kit but it has two transfer switch boxes and a 50-amp outdoor outlet instead of 30A. https://www.amazon.com/Generac-Porta...ct_top?ie=UTF8
 
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Old 07-29-18, 01:50 PM
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Two boxes could be tough to install if you're short on room.
A picture or two of your panel setup would be most helpful.....How-to-insert-pictures
 
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Old 07-29-18, 01:58 PM
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Thank. I definitely don't think that I can install two boxes. Right now I'm planning in installing just one. That will meet my needs with 1 240V circuit and 4 120 V circuits. Since I don't have any room on the side of the panel, I was planning on installing the switch underneath it, with the junction box (from the outdoor outlet wiring) right next to it. I'll try to take some pictures.
 
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Old 07-29-18, 02:40 PM
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Panel has walls on both sides, unfortunately. But I can add the transfer switch directly under.
 
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Old 07-29-18, 04:40 PM
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You can install the transfer switch box a little further away but you will need a junction box to splice in jumper wires since the wires that come with the transfer switch box might not be long enough.

I am guessing that each of the transfer units will require splicing on about fifteen mostly #12 and #14 wires and a junction box of about 70 cubic inches.
 

Last edited by AllanJ; 07-29-18 at 05:05 PM.
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Old 07-30-18, 07:46 PM
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As a follow-up, I'm having trouble understanding how this transfer switch supports a 240V/30A circuit. In a normal 240V circuit with two hot wires, the current will just make a loop from one 120V conductor, through the load, to the other 120V conductor that's 180 degrees out of phase. So if you have a 30A breaker and 10 gauge wire on that circuit, you would have 30A flowing from one hot wire, through the load, back on the other hot wire. Right?

Now, with the transfer switch that I have, I'm not sure how that 240V circuit is supported at the 30A rating. I do see how the 240V is generated from the two different hot wires. But in this switch, there are only 15A breakers. So how does the wiring support 30A? It would appear to me that there can only be 15A in the circuit. What am I missing?
 
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Old 07-30-18, 08:46 PM
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In a normal 240V circuit with two hot wires, the current will just make a loop from one 120V conductor, through the load, to the other 120V conductor that's 180 degrees out of phase.
There is no "120 volt conductor". 120 volts is derived from either leg of the 240 volts supplied to your house and neutral. For the transfer panel you need both legs of the hot plus the neutral, counting ground four wires.
 
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Last edited by ray2047; 07-31-18 at 02:56 PM.
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Old 07-31-18, 09:11 AM
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I'm not sure that I agree....your picture shows a 480 V potential between the two hot wires. Right? Isn't it supposed to be 120V @ 0 deg and 120V @ 180 deg?
 
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Old 07-31-18, 12:47 PM
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No. Your house is-- supplied from a transformer with a 240v secondary and a grounded center tap.
 
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Old 07-31-18, 01:05 PM
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Describing the transformer diagram here, you have to add the words "from" and "to" when mentioning degrees.

Notably we would say 120 volts @ 0 degrees from top to center terminals along the right side and 120 volts @ 0 degrees from center to bottom but we would say 120 volts @ 180 degrees from bottom to center..

Also "240 volts" should also be shown with two arrows pointing to the respective terminals between which 240 volts is measured. In the diagram "240 volts" should be written further out to the right with its two arrows pointing to the top and bottom terminals.
 
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Old 07-31-18, 02:59 PM
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Alan thanks for the input. Revised diagram:

------------------------
 
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Old 08-01-18, 05:01 AM
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Ok, thanks.

I'm still unsure of how my transfer switch supports 30A in the way that a house circuit supports 30A. In a house circuit you can have 30A running down each hot leg, but it would appear that my switch has 15A running down each hot leg due to the fuses. What am I missing?
 
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