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Onan LT II Transfer Switch JB 7.5


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  #51  
Old 10-10-2017, 01:52:23 AM
Leon N. Leon N. is offline
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Default Re: Onan LT II Transfer Switch / JB 7.5

Only problem I see is that each tenant must remember not to draw more than 30 amps @ 120 VAC and that leaves none for you! Note they each have 200 amp service. Also note, refrigerator compressors have a relatively high starting current, but your JB can handle a temporary over load, but be cognizant of this fact. Our fridge draws 20 amps starting and only 3-4 amps running.

What you are doing is what is called back feeding. Not code compliant. Think of this scenario. What if that 240 volt dryer circuit your ATS is monitoring fails, for example, the 2-pole breaker in your panel fails and then the utility power comes back on? Talk about magic smoke! I like your idea though. You know, it all depends on your tenants and the quality of the stuff (breakers and wiring) in your 200 amp panel. Now back to bed and hoping Billy is feeling better.

Last edited by Leon N.; 10-10-2017 at 02:01:23 AM. Reason: More
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  #52  
Old 10-10-2017, 07:38:41 AM
Wayne 440 Wayne 440 is offline
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Default Re: Onan LT II Transfer Switch / JB 7.5

Quote:
Originally Posted by Leon N. View Post
...What you are doing is what is called back feeding...
He is using a transfer switch, and presumably the welder outlet as the "utility" input into same. How is that back feeding?

Quote:
...Not code compliant...
I'm sure there may be some obscure "you can't do that rule, but where?

Quote:
...Think of this scenario. What if that 240 volt dryer circuit your ATS is monitoring fails, for example, the 2-pole breaker in your panel fails and then the utility power comes back on?...
I don't see an issue. The transfer switch is designed to isolate the "normal" and emergency" feeds. The loads may see an outage, but that isn't spectacular.

I realize that there are pitfalls to designing your own appliance like this, one must consider all possible failure modes and modes of improper usage. Then try to make it fail gracefully, or at least without serious consequences. Often, it is more complicated than outside appearances indicate.
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  #53  
Old 10-10-2017, 11:58:47 AM
Steve Dawkins Steve Dawkins is offline
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Default Re: Onan LT II Transfer Switch / JB 7.5

In regards to code compliance, my concerns would be:

1. Most welding outlets are 240 volts, 3 wire. Does your utility power input to the ATS have a separate neutral and ground wire? If 4 wire, you're good.

2. The top output cord assemblies appear to be rated at 30 amps. Two of the cords terminate at boxes with quad receptacles. These receptacles will be rated for either 15 or 20 amps. Is there any fuse/circuit breaker protection to limit the 30 amps to the receptacle rating?

3. The lower output cord is rated at 30 amps, and terminates at a j-box that feeds four power strips. Do each one of these power strips have their own internal 15 amp circuit breaker? Some power strips have internal protection, and some don't.

Looking at the photos, it appears there is a circuit breaker mounted next to the quad receptacles on the transfer switch. This breaker presumably limits the current to those receptacles to 20 amps. If so, thumbs up. (no emoji)
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  #54  
Old 10-10-2017, 01:11:30 PM
Vanman Vanman is offline
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Default Re: Onan LT II Transfer Switch / JB 7.5

One technical problem would be unplugging the utility input, which would result in the loss of bonding.

That is actually a problem I have been working on (in the design phase) for a vehicle which has an inverter, a generator, and a shore power inlet. Some form of active, automatic bonding switch will need to be employed.

In this case, I don't see any harm in a local (within the transfer switch, for example) bond being established upon loss of main power, or upon transferring to emergency power.

Sure, it would be in parallel with the service bond if the input plug is still connected, but no current would flow in that path. The local bond may well serve to help clear faults, by virtue of its lower impedance, should they occur while on generator power.

In this case, ideally, a neutral switching transfer switch would be employed. Getting even more anal, I suppose that a ground rod should be driven at the plant... Though I don't think that is required for portable sets?
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  #55  
Old 10-10-2017, 01:39:04 PM
Leon N. Leon N. is offline
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Default Re: Onan LT II Transfer Switch / JB 7.5

Loss of bonding? NO way should that happen and never introduce a second earth ground connection. If so then you are really asking for trouble. The utility neutral should not be switched in the proposed set up. That ground bonding from the service entrance panel should be carried throughout the entire proposed setup including the standby generator. The ATS, in my opinion should not switch the neutral in the proposed set up.
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  #56  
Old 10-10-2017, 01:47:26 PM
Vanman Vanman is offline
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Default Re: Onan LT II Transfer Switch / JB 7.5

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Originally Posted by Leon N. View Post
Loss of bonding? NO way should that happen. <snip> That ground bonding from the service entrance panel should be carried throughout the entire proposed setup including the standby generator.
It would be, but only so long as the portable transfer switch is plugged in to the utility receptacle. Once it's unplugged, it becomes a portable generator set, and should have a local bond.
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  #57  
Old 10-10-2017, 04:46:18 PM
Steve Dawkins Steve Dawkins is offline
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Default Re: Onan LT II Transfer Switch / JB 7.5

Good point, Vanman. I hadn't considered the utility power plug being unplugged while the system was in operation, which would result in a loss of the N/G bond. Of course, anything is possible and Mr. Murphy likes to lurk around.
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  #58  
Old 10-10-2017, 06:10:28 PM
JohnnyC JohnnyC is offline
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Default Re: Onan LT II Transfer Switch / JB 7.5

Lots of comments throughout the day which I was reading, but difficult to respond due to work demands. Well., I am home so I will respond now.

Leon, I believe Wayne 440 answered correctly to your questions in post #52.

--------------------------------------------------------------------------------
Steve Dawkins concerns:
In regards to code compliance, my concerns would be:

1. Most welding outlets are 240 volts, 3 wire. Does your utility power input to the ATS have a separate neutral and ground wire? If 4 wire, you're good. Yup, I got a 4 wire setup as seen in the first attached picture of my mig welder wall outlet. I got 2 hots, neutral and ground

2. The top output cord assemblies appear to be rated at 30 amps. Two of the cords terminate at boxes with quad receptacles. These receptacles will be rated for either 15 or 20 amps. Is there any fuse/circuit breaker protection to limit the 30 amps to the receptacle rating? These outlets are rated at 20 amps. I have one duplex outlet wired to one leg and the other duplex outlet wired to the other leg. The breaker you see in the second picture is a double pole breaker. I want to kill power from both legs if one leg or the other is overloaded or shorts out

3. The lower output cord is rated at 30 amps, and terminates at a j-box that feeds four power strips. Do each one of these power strips have their own internal 15 amp circuit breaker? Some power strips have internal protection, and some don't. Yes, each of those power strips has a built in 15 amp breaker and they do work. These power strips are rated for continuous 125 vac 15 amp duty. Each tenant would get a power strip and if they over load it, the breaker will trip. 2 power strips are connected to one leg and the other two power strips are connected to the other leg. In total 30 amps per leg.

Looking at the photos, it appears there is a circuit breaker mounted next to the quad receptacles on the transfer switch. This breaker presumably limits the current to those receptacles to 20 amps. If so, thumbs up. (no emoji)
--------------------------------------------------------------------------------

Leon stated:
Only problem I see is that each tenant must remember not to draw more than 30 amps @ 120 VAC and that leaves none for you!
Each tenant will get one 15 amp power strip and that will be sufficient for a fridge, TV and lights. I did this already back during Hurricanes Irene and Sandy. They will not be able to exceed a 15 amp draw.

--------------------------------------------------------------------------------

As for the ground bonding issue, I intend to keep the portable ATS plugged into the utility power source (in my case the mig welder outlet) which is a 4 wore setup. I assume grounding would not be a issue in that case since the ATS is actually working as designed where as the load end is properly grounded through the genny and ATS and then to the utility house ground. If the utility power input plug mysteriously "falls out" of the receptacle I would assume then the setup will then fully function as a portable generator would. The power strips and what's plugged into them are totally independent of the house wiring as a true portable setup should be. Correct me if I'm wrong.

--------------------------------------------------------------------------------

There is ONE issue that I need to implement to make this setup safe that no one has mentioned yet which I am surprised. Anyway, many thanks for the comments and if need be lets further discuss the grounding issue if needed. As we all know, grounding issues seems to open many cans of worms and debate.


JohnnyC
New Jersey

***** I just reread the comments on the grounding and now I assume the issue is over the neutral to ground bonding, not necessarily a grounding issue, right???? -- It has been a long day at work...
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  #59  
Old 10-10-2017, 07:09:59 PM
Leon N. Leon N. is offline
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Default Re: Onan LT II Transfer Switch / JB 7.5

OK now I sort of get it. Each tenant will have to pull his fridge out from the wall and plug it into your to be supplied power strip. So you are going to run a cable from your ATS up the stairs to each apartment. You can keep the incoming panel earth ground as the single point earth ground even if the utility cable from the pole to the house is severed. Yes I guess that will work.

I thought you were going the use the in-house wiring and only power the dedicated branch circuit powering the fridge with all other breakers turned off.
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  #60  
Old 10-10-2017, 08:26:46 PM
JohnnyC JohnnyC is offline
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Default Re: Onan LT II Transfer Switch / JB 7.5

Quote:
Originally Posted by Leon N. View Post
OK now I sort of get it. Each tenant will have to pull his fridge out from the wall and plug it into your to be supplied power strip. So you are going to run a cable from your ATS up the stairs to each apartment. You can keep the incoming panel earth ground as the single point earth ground even if the utility cable from the pole to the house is severed. Yes I guess that will work.

I thought you were going the use the in-house wiring and only power the dedicated branch circuit powering the fridge with all other breakers turned off.
Leon, I thought about using the in-house wiring, but the simplest solution would be two ATS and a second generator. If I add on or modify any of the house wiring, it may be hard to justify when it comes time to sell the house.

As for pulling out the fridges, that is not a problem. Actually it may be good as it would be the perfect time for them to clean the year(s) of dust and whatever rolls under the fridges. Also, I did this routine for Hurricanes Irene and Sandy. Not a problem. The advantage of the ATS vs. no ATS is I can set things up before the storm hits and if the utility power goes out, the ATS will automatically wake up the JB and transfer the load to the JB. When power is restored, the ATS will retransfer back to the utility power and automatically shut down the JB and I won't have to be there for this to happen.

Now, back to the neutral / ground bonding issue: Should both the neutral and ground wires be bonded together INSIDE the ATS??????

JohnnyC
New Jersey
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