manual transfer switch

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and!ru

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I know people can use an interlock for portable generators and the owner can select whatever loads they want. I wanted to learn a little about the manual transfer switches for residential units that only have select few circuits on them. Are the loads sized so they can all be on at the same time? Or does it matter. So far I really don't understand why these units are needed.
 
and!ru said:
I know people can use an interlock for portable generators and the owner can select whatever loads they want. I wanted to learn a little about the manual transfer switches for residential units that only have select few circuits on them. Are the loads sized so they can all be on at the same time? Or does it matter. So far I really don't understand why these units are needed.
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People that like gadgets will be an easier sell. Otherwise doesn't really matter which method you use for transfer and load management. You also could add your own load metering devices to an existing setup - many those packaged load transferring panels do have meters somehow incorporated to show loading conditions.
 
The simplest is an interlock between the main breaker and a 2 pole breaker. Most mfgs have a interlocks kit for a specific panel. Another option is an interlock kit for two adjacent 2 pole breakers in a MLO panel. The main breaker would require a retaining kit.
the advantage of the above is if any breakers have gfci or AFCI that protection is retained.
In my area, we have gotten away from the “gentian” panels, as it’s breakers don’t hold up, plus if AFCI or gfci breakers are used in the main panel, that protection is lost when using the gen tran
And, you need to match the generator to the type of xfr switch for the neutral.all the above xfr switches don’t transfer the neutral, so the generator must be a floating neutral type.
Take a look at the inlet labeling requirements in Art 702.
 
and!ru said:
I know people can use an interlock for portable generators and the owner can select whatever loads they want. I wanted to learn a little about the manual transfer switches for residential units that only have select few circuits on them. Are the loads sized so they can all be on at the same time? Or does it matter. So far I really don't understand why these units are needed.
Click to expand...

Usually used more for convenience of the HO, smaller more affordable generator. And particularly when the size of the generator is insufficient for the full load of house. It allows loads to be set up to maximize potential of the limited capacity of the generator without overloading it. Similar effect to using load shedding on a whole house with an ATS. Like you stated it would be set up so that all loads desired could be on simultaneously.
 
When using a manual main panel with the interlock. We will put little red dot stickers with instructions on the panel to describe what to turn off, Such as the water heater, AC. electric heat. Only one or two burners on the stove. Maybe only use one red dot breaker at a time.
 
tom baker said:
The simplest is an interlock between the main breaker and a 2 pole breaker. Most mfgs have a interlocks kit for a specific panel. Another option is an interlock kit for two adjacent 2 pole breakers in a MLO panel. The main breaker would require a retaining kit.
the advantage of the above is if any breakers have gfci or AFCI that protection is retained.
In my area, we have gotten away from the “gentian” panels, as it’s breakers don’t hold up, plus if AFCI or gfci breakers are used in the main panel, that protection is lost when using the gen tran
And, you need to match the generator to the type of xfr switch for the neutral.all the above xfr switches don’t transfer the neutral, so the generator must be a floating neutral type.
Take a look at the inlet labeling requirements in Art 702.
Click to expand...
Thanks for the info! If the generator is a 7500W generator with a bonded neutral, do you see an issue with having an interlock? I know a floating neutral is what you want. With a bonded neutral you would have a small amount of current passing through the ground wire on the extension cord. You would loose GFI protection on the generator correct? Are there any major issues or concerns I may be missing. So far I still think you could use a small bonded neutral generator and be OK?
 
I spoke with the local inspector about geninterlock.com interlock kits. He said they are allowed but that I need a "manufacturer’s hold down accessory listed on the inside of your panel cover door to retain the back-fed breaker" Does anyone know what he's talking about?
 
Plug-in breakers that are used as back-fed must be held in place so that in the even of a fault, the mechanical forces do not pull it off the bus. The hold down method must be one provided by the manufacturer and listed for use with the specific breaker involved. If your breaker does not have one, you cannot use it. There are as many different ways this is done as there are different breakers. Just do a search on your breaker series and the term “hold down kit”.
 
and!ru said:
I spoke with the local inspector about geninterlock.com interlock kits. He said they are allowed but that I need a "manufacturer’s hold down accessory listed on the inside of your panel cover door to retain the back-fed breaker" Does anyone know what he's talking about?
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Usually one comes with the kit’s that I’ve bought. But he is probably wanting one that is listed from the panel manufacturer.
 
and!ru said:
I spoke with the local inspector about geninterlock.com interlock kits. He said they are allowed but that I need a "manufacturer’s hold down accessory listed on the inside of your panel cover door to retain the back-fed breaker" Does anyone know what he's talking about?
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Most interlock kits I've seen come with them. It basically holds your generator input breaker in place so you can't grab it and pull it out like you can a regular snap in breaker. It's actually a code requirement but I can't quote chapter and verse right now.
 
Jraef said:
Plug-in breakers that are used as back-fed must be held in place so that in the even of a fault, the mechanical forces do not pull it off the bus. The hold down method must be one provided by the manufacturer and listed for use with the specific breaker involved. If your breaker does not have one, you cannot use it. There are as many different ways this is done as there are different breakers. Just do a search on your breaker series and the term “hold down kit”.
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Thank you!
 
and!ru said:
Thanks for the info! If the generator is a 7500W generator with a bonded neutral, do you see an issue with having an interlock? I know a floating neutral is what you want. With a bonded neutral you would have a small amount of current passing through the ground wire on the extension cord. You would loose GFI protection on the generator correct? Are there any major issues or concerns I may be missing. So far I still think you could use a small bonded neutral generator and be OK?
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If the generator is gfi protected, it will not work, the gfi will trip due to the bond at the generator. It is made for job site power.
 
hillbilly1 said:
If the generator is gfi protected, it will not work, the gfi will trip due to the bond at the generator. It is made for job site power.
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You can take that bond loose but you are now limited to using it as backup power to a bonded system.
 
and!ru said:
Is it legal to disconnect the bond?
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That was a stupid question, but I do see a lot of people doing that online. Also, bonded neutral generators generally have GFCI protection on the 120V receptacles. The 30amp or 50amp plugs are generally not GFCI protected and some distributers say you don't need the GFI transfer switch if that's the case. What are your thoughts?
 
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and!ru said:
That was a stupid question, but I do see a lot of people doing that online. Also, bonded neutral generators generally have GFCI protection on the 120V receptacles. The 30amp or 50amp plugs are generally not GFCI protected and some distributers say you don't need the GFI transfer switch if that's the case. What are your thoughts?
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Forget some of code for the moment - when connecting to premises wiring with utility supply the bond is intended to be at the service equipment.

If you run separate ground and grounded conductors from generator that is bonded you will have parallel path for grounded conductor.

Ideally you want non bonded generator and the bond at the service equipment. Then the generator frame and any paths in between won't be carrying any current during normal use.

A smaller portable with no bond is just an ungrounded system when using for portable power. Unlike a utility system that is well grounded - even if you fail to ground your service correctly there is still voltage to ground because of the large grounding network that is inherent to the utility system. But this small isolated source has no ground reference. So a first ground fault is not really much of a hazard to users, it simply becomes a grounded system at this point, though not at the conventional point of the system. No fault current flows until there is a second fault. A GFCI receptacle on the generator still protects you from potential shock hazards - current still has to flow outside the protected circuit to trip, though potential for having current flowing outside that circuit is greatly lessened by not having a stout ground reference like a utility supply has.
 
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