Need help wiring Generator to a transfer switch.


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Old 12-28-12, 10:07 AM
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Need help wiring Generator to a transfer switch.

I bought my house a year ago and have lost power enough times to save up and buy a generator and transfer switch. I got sick of borrowing my fathers generator and having to pull my main box apart with get things powered as needed. I didn't have much money but i got a good deal on a Milwaukee 4778 generator and a Gentran Reliance 30310.

The person I bought it from had it set up where he would pull out the generator and go from the 3 prong 250 volt outlet on the generator to a 3 prong Male receptacle on the outside of his house with a heavy three prong wire. From that receptacle to the GenTran switch is a mystery. The receptacle on the GenTran switch is a 4 prong 240 twist lock male receptacle.

My plan is to duplicate what he had set up.

My question comes around the neutral bonding on the generator and how to wire the three prong outside receptacle to the 4 prong twist lock on the GenTran switch. I know a lot depends on either having a neutral bond on the generator. I looked through the manual and I looked the generator over and can't find bonded or floating anywhere on either. Please let me know where I can go from here.

I want to plan ahead and do this properly ahead of time so I am not forced to back feed through the dryer when we lose power and the hardware stores are out of supplies!
 

Last edited by ray2047; 12-28-12 at 10:52 AM. Reason: Correct typo.
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Old 12-28-12, 10:41 AM
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For reference. I think this is yours. Both versions are bonded. Do you have the full power switch?

Not an electrician so the pros will take over. The three wire 240v outlet is way out of my knowledge area.


http://genuinemilwaukee.yolasite.com...58-01-0961.pdf

http://genuinemilwaukee.yolasite.com...54-00-2401.pdf

Or this one.

http://genuinemilwaukee.yolasite.com...58-01-0960.pdf

http://genuinemilwaukee.yolasite.com...54-00-2400.pdf
 
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Old 12-28-12, 11:32 AM
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I'm not sure what you mean by the "Full Power Switch" That looks like my generator. If it is bonded then it should not have worked for the previous owner the way he had it hooked up unless they unbonded it, correct?
 
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Old 12-28-12, 11:53 AM
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Would it make sense to replace the 3 prong receptacle on the generator with a four prong? How would I go about wiring that?
 
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Old 12-28-12, 12:16 PM
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One of the gens in the pdf I linked to has a 120v only switch. Does yours have this?

It would be my opinion to have that gen rewired properly with a L14-30? Possibly a L14-20...not sure.

The issue is it has no neutral for the 240.... IMO you would need to unbond the gen and rewire for connection to that transfer switch.

Again I am no electrician and base it on what I did with my gen. I run 120v only outlet. Although my gen is only 3250 watts.

What for the pros but if you can define what model schematic yours is that will help.
 
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Old 12-28-12, 01:37 PM
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U have a hodgepode/mismatch on the transfer switch. The Gentran you listed is a 30 amp 120/240. From what I can see the Generator has 120V 30 Amp outlet and then a 20 Amp 240 Outlet. Not one that is *combined*.

There is no clean cut way of wiring into the Transfer Switch the proper way....you got to pick your poison and choose the 120 side or the 240 side ....depending on what you want to power up. Obviously, if you choose 240, you can only have the 240 on the Transfer switch you have linked...

Then comes the cords as the inlet on the Gentran is a 120/240 Combo. So you need to either bridge the 2 Hots if you choose the 120 and ...or just the 240. Still a mish mosh of plugs if as the turnlock on the generator will be mated to a different on on the inlet.

This all starts going down a weary path.
If you just pick the 120 route off the generator, I'd just buy a 120 30A transfer switch so all the inlets, turnlocks, etc are in theory all L6-30
 
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Old 12-28-12, 02:13 PM
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my generator does not have the 120 only switch. The 240 outlet is only 240 there is a separate 120 twist lock outlet. The transfer switch is up to 30 amps. The generator puts out 20 amps on the 240 side. Yes that is not an exact match but the transfer box is designed to accept an upgraded generator with out having to change the transfer switch. I need to have 240 due to the jet pump for our water. I was looking at the generator and there is a lug that is labeled ground and there its a cut wire on it. I wonder if someone went through the generator and un-bonded it so it would work with the transfer switch. Ill post pics later.

This appears to be the proper one.

http://genuinemilwaukee.yolasite.com...58-01-0960.pdf

If you look at the dedicated 240 outlet it appears to be two hots and a ground. No neutral.

Could I take the two hots a neutral from the 120 plugs and a bare ground from the frame and connect them to a 4 prong 20 amp outlet to replace the 240 three prong outlet?
 
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Old 12-28-12, 02:20 PM
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What type of pump do you have?

The money spent to set that up would be better spent on a new gen.

I dont think that 5000 watts will start your pump.
 
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Old 12-28-12, 05:14 PM
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Here I drew this up. This I believe is what you need to do or have an electriian do so you can connect to the transfer switch.

The circle is the bond that needs to be removed when hooking to the home cant have two from what I know.

Need an L 14 20 I believe for that gen. Do away with the 30 amp 120. You can wire to the duplex as I show but I would change it to a 20 amp.

Hope the electricians will chime in. Possibly they know a better solution with that 250v outlet with no neutral.

The black and red are the hots and the grey the nuetral. You need to get another 20 amp breaker.

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It would seem logical that the hots go on the right on the duplex outlet. Funny on my original schematic it shows the opposite. I drew the one above how I perceived it but possibly it should be like this.

Geez I should have just posted this schematic for you... Duh....

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Last edited by lawrosa; 12-28-12 at 06:29 PM.
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Old 12-28-12, 08:36 PM
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that schematic looks easy enough to do. Now of course thats what I say now sitting in my warm living room on the lap top. Well see about that tomorrow when I'm out in the cold with the box apart.

What would happen if:
1: I made a cable with a three prong male plug on one end. black wire to one prong, red wire to another prong, and a white and green to the third prong. Then on the female end of the wire I do four prong female plug with one red wire hot, black wire hot, white wire to neutral, and green to ground.

2: I unbonded the generator. Left the three prong in place. ran red, black, and white to transfer switch. Put a grounding rod in the ground where I will use the generator and wire the generator frame to the ground rod.

This is just out of curiosity and to be better educated in the subject. I plan on doing Lawrosa's wiring configuration.

The jet pump is 3/4 hp and when I run it it will be the only circuit open. It will be for toilet flushing, showers, and maybe to do some dishes.


0.75 (hp) * 746 (watts/hp) / 0.8 (efficiency) / 240 (volts) / 0.9 (power factor) = 3.2 (running amps).
Starting amps can be up to 5 times the running amps. 3.2 (running amps) * 5 = 16 (starting amps).
3.2 (running amps) * 240 (volts) = 768 (va).
16 (starting amps) * 240 (volts) = 3840 (starting va).
 
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Old 12-28-12, 09:07 PM
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What would happen if:
1: I made a cable with a three prong male plug on one end. black wire to one prong, red wire to another prong, and a white and green to the third prong. Then on the female end of the wire I do four prong female plug with one red wire hot, black wire hot, white wire to neutral, and green to ground.
Well where would you get the white wire from on the gen side? It would be essentially bonded, no? I dont think you can do that without rewiring the gen as I stated.

2: I unbonded the generator. Left the three prong in place. ran red, black, and white to transfer switch. Put a grounding rod in the ground where I will use the generator and wire the generator frame to the ground rod.


I dont think thats a good idea.... Does not sound right from my knowledge.

3/4 shallow pump probaby 12 amps.... You should be good.


I dont know where the local electricians are to give input here. I am not an electrician remember... I would wait for feed back from them....

Possibly they are on strike or something??????







 
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Old 12-28-12, 09:24 PM
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You're doing pretty good all by yourself

At this point do we know if generator is unbonded ?
 
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Old 12-28-12, 09:24 PM
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Is this Reliance Controls 30-Amp (120/240V 10-Circuit) Indoor Transfer Switch the box you bought? If so, that's a transfer panel, not a transfer switch. It appears to be set up for 6 120V circuits and four 240V circuits.

I don't see a 4778 generator at the Milwaukee Tools site. The closest match I found to your description is their Heavy-Duty 5,000 watt gas-powered generator, Model # 4950-20.

The problem, if my guesses are correct, is that you have a transfer panel that will handle quite a few loads but is limited to 30 amps total, and a job-site generator that is designed to have tools plugged into it, but not to be a backup generator for a residential service.

All that said, you may be able to do what you need with what you have. If you follow lawrosa's suggestions for maximizing the 120V supply from your generator, if you connect the power to only one of your transfer panel's two hot buses, and if you have all gas appliances, you might be able to provide power to the controls for your gas furnace and range, to your refrigerator and your microwave, and to one lighting circuit.

The greater problem is the generator. If you can trade the one you have for one that is made to supply 120/240V power, that would help a lot. If it would run on natural gas, that would help even more.

If you haven't already done so, reading Congratulations! You have a Generator might help answer many of your questions.
 
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Old 12-28-12, 09:31 PM
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Out of the box.......the generator has the neutral and ground tied together. (bonded)

It is already wired for max 240vac output. Leave current receptacle in it. Connect white and green together in plug.
 
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Old 12-28-12, 09:54 PM
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.the generator has the neutral and ground tied together. (bonded)


You cannot have two bonds.... You either need to unbond gen or get a neutral switching transfer switch.


The problem, if my guesses are correct, is that you have a transfer panel that will handle quite a few loads but is limited to 30 amps total,


Not sure why its called a transfer panel. It states transfer switch. I belive this is it and good for 7500 watts. I think your good there. Your whole issue is the gen. Needs to be rewired IMO.

And once again....I am not an electrician but wired a few gens in my day.




30310A Pro/Tran | Product Details | Reliance Controls Corporation



 
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Old 12-28-12, 10:44 PM
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Not sure why its called a transfer panel. It states transfer switch.
It does, but calling a mule a horse won't shorten its ears or make it capable of breeding.

Seriously, we call those boxes that combine both a switch and some breakers "transfer panels" to distinguish them from true transfer switches, which transfer the incoming feed from the utility supply to the backup or standby supply, and feed out to the system load.
 
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Old 12-29-12, 12:31 AM
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Most people, and also many manufacturers, don't know the difference between a transfer switch and a transfer panel. If it is a single switch to select between utility and generator power then it is a transfer switch. If it is some kind of panelboard that contains multiple utility/generator selector switches along with circuit breakers that are only used with the generator then it is a transfer panel.
 
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Old 12-29-12, 02:20 AM
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Yes that is the transfer panel. They make a relay looking device that goes in the panel that makes it a switching bond panel. i have to take mine apart to see. Also I have to take the generator apart to see if someone has already un-bonded it. Until I can verify that it is un-bonded i am assuming that it is bonded.

with my grounding rod idea it would leave the three prong receptacle in place and i would run hot, hot, neutral from the un-bonded generator. I would tap the third leg, white neutral wire, to the neural side of the jumper wire that I have to cut to un-bond it. Then ground frame to grounding rod.

How can i test if it is unbonded?
 
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Old 12-29-12, 04:40 AM
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Originally Posted by Biglurr54
How can i test if it is unbonded?

With the generator off, check for continuity between the generator's neutral receptacles and the generator's chassis ground.
If the receptacle neutrals and chassis ground are connected, it's bonded.
If there is no continuity between neutrals and chassis ground, it's not bonded.

Earlier discussion about bonding solutions is here
http://www.doityourself.com/forum/el...d-neutral.html

Simplest bonding solution is here
http://www.doityourself.com/forum/el...ml#post2024634
To break the neutral-ground bond loop when wiring the exterior power inlet;
connect the ground wire to the box only, not the receptacle ground pin.

My two cents - my gut feeling is that all receptacles should be wired correctly; my solution would be to physically remove the ground pin from the plug that plugs into the generator.
Thus, generator is safe for worksite use, receptacle is safe for later re-use (say electric car charger) and it is only the cable which is non-standard.
 

Last edited by Hal_S; 12-29-12 at 05:13 AM.
 

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