WIRING QUESTION.

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NAM001

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i Am making a controller unit for my compressor, and I am stuck. the logic of ooperation is a cake walk but I want to include a 120 outlet on it to plug a fan into and be controlled by the unnit.

I have 240 single phase coming in to the controller. I am getting a step down transformer to drop to 120 vac. How should that transformer be wired on the output. one leg to case to make it compatable to house wiring ( neutral and hot. or will that put a hot on the case. I am thinking shipbuard systems where each leg of 120 is 60vac but out of phase to et 120. All that is coming in is a pair of leads making 240 and a case grounding line connected to the unit case.

With one leg on the case i only have to switch one line with the relay. If they are both hot I would have to switch both legs, than the question becomes what dies the fan do with it. If it is case grounded or gets a case ground would i get a charge touching the fan and any grounded item. I dont have 120 outlets near by the fill station.
 
If all you have coming in to the case for 240V is two leads then both of them are hot. There is a missing neutral. I would recommend hiring an electrician to do this job. It already sounds like it isn't up to code. You don't need a transformer to step 240V down to 120V, you can tie into one leg and the neutral and you'll have a two wire 120V circuit.
 
L1———N———L2
120——-0———120VAC
0———————-240VAC
 
You will want to tie the fan hot leg to the neutral so it returns the power through the neutral. The fan should be grounded/bonded to the ground from your panel. This brings the equipment that can be touched to the same potential and negates electrical shock from the panel casing becoming hot.
 
I have 240 single phase coming in to the controller. I am getting a step down transformer to drop to 120 vac. How should that transformer be wired on the output. one leg to case to make it compatable to house wiring ( neutral and hot. or will that put a hot on the case. I am thinking shipbuard systems where each leg of 120 is 60vac but out of phase to et 120. All that is coming in is a pair of leads making 240 and a case grounding line connected to the unit case.
You’ve forgotten your BEE school.

In a shipboard system, most of the equipment is 3 phase (remember lighter, cheaper, easier to maintain?). The only single phase loads are off of the lighting transformers which are 208v wye wound. So each leg is 120v to neutral, and 208v leg to leg. If using house voltage, which is 240v Delta, you have 120v to neutral and 240v leg to leg, and if you had 3 phase there would be a wild leg between 208 and 240 volts, depending on the age of your system.

To wire your fan, wire it directly to T1 OR T2 and neutral on your motor starter. If you wire it to L1 and neutral, it will run all the time.

There is no 60v AC 60hz power shipboard.

There is no need for a step down transformer.
 
And you can call me any time, I will walk you through it. If you have a single wire coming into the case that reads 240 to ground, you have the wild leg, and need to not use that one. But if you have 3 phase power, use a 3 phase motor. That’s way more better.

281-300-4748.
 
From what I have read,,,the simple option, assuming, and we all know what that means,,,he has just 240 v coming into the controller, would be purchase a 240 volt fan. Yes they are made and would stop the addition of a transformer, rewiring, and additional controls. The fan would add a small amount of current on the load side and not affect the compressor operation. Assuming, yes here we go again, it is not a large commercial fan. Keep it simple and you should not need an outside electrician to overcharge and do a major renovation on the controls or feeder.
 
I reread the initial post and using the case for a neutral is NOT allowed. Yes they used to do this with electric clothes dryers but no more, for the simple reason being it could float to potential if the ground is compromised or disconnected. What Mr Wookie is saying about high leg is usually in a commercial building. I have dealt with it when someone decides to put a restaurant in a sorta residential area and the power company is on the cheap and fast answer mode. If a high leg is there it MUST be marked as such.
 
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