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Backup electrical generator hookup © D Friedman at InspectApedia.com Backup Electrical Generator Interlock Kits
Alternative to transfer switch?

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Guide to buying, installing & using interlock kits for hooking up backup electrical generators at residential properties.

This article series discusses the use of emergency generators for electrical power backup at residential properties.

InspectAPedia tolerates no conflicts of interest. We have no relationship with advertisers, products, or services discussed at this website.

- Daniel Friedman, Publisher/Editor/Author - See WHO ARE WE?

Electrical Panel Interlock Kits for Backup Generators

Manual interlock kit for connecting a backup generator to a residential electrical panel, adapted from www.interlockit.com cited & discussed at InspectApedia.coma Low-Tech Alternative to a Transfer Switch for Backup Generators

Electrical generator "interlock kits" are a simple mechanical device that permits "back-feeding" a home electrical panel from a portable generator during an electrical power outage.

Unlike a transfer switch, an electrical panel interlock kit provides a flat metal plate that is slid into position and then locked in place to assure that a main electrical panel circuit breaker remains in the OFF position so as to permit use of the backup generator.

Illustrated here: a typical electrical panel "lockout kit" used in some installations as an alternative to manual transfer switches for connecting a portable backup electrical generator to a residential electrical system.

In the event of an electrical power failure the main breaker is switched off and locked off by the interlock plate as we'll describe below. Then a backup generator, connected to the panel, can power some of the panel's circuits.

An interlock kit plate must be designed to fit the available space in specific electrical panel front plates. This illustration is adapted from interlockkit.com 's K-1010 interlock kit that can work in some Siemens, ITE, or Murray electrical panels.

To use an interlock kit typically the user must do the following

  1. Turn the main circuit breaker OFF
  2. Turn all branch circuit breakers OFF
  3. Slide the InterLock plate into position so as to block the appropriate breakers from being flopped back ON
  4. Turn the generator circuit breaker (elsewhere in the panel) ON
  5. Turn on essential circuits one at a time.

    Warning : allow appliances to start before engaging the next circuit. - Interlockkit.com instructions for kit K-1010 cited below.

Pros & Cons of Interlock Kits for Backup Generator

Pertinent Electrical Code Citations for Interlock Kits for Electric Panels

siemens electrical panel mechanical interlock for backup generators at Amazon.com cited & discussed at InspectApedia.com

Shown here: a mechanical interlock for a Siemens electrical panel, as sold on Amazon.com

Sources of Electrical Panel Interlock Kits for Backup Generators

Electric panel interlock kit for Murray electrical panels at amazon.com cited & discussed at InspectApedia.comIllustration: an electrical panel interlock kit including sliding plate and labels for a Murray electrical panel, as sold on Amazon.com - ret. 2020.02.06

Breaker Interlock kit for Challenger Westinghouse Thomas & Betts from National Ram Electronics in Alpine NY cited & discussed at InspectApedia.com

Photo: a CR-1 Generator Interlock Kit from National Ram Electronics. This inerlock fits Challenger, Westinghouse, and Thomas & Betts electrical panels. The red plate slides over to the left when the main breaker is OFF, permitting turning ON a back-fed 50A breaker powered by a backup generator.

Watch out: before trying this approach for connecting a backup generator to your electrical system, check with your local building code officials for approval and also be sure that all work is done by a licensed electrician who is expert with backup generator wiring.

 

Question: use compatible generator interlock kit on Eaton electrical panels

Since all breakers must match in a panel and by branded type, does that code requirement include branded generator interlock kits?

For an Eaton electrical panel, would it pass FL building code to have a "Genterlock" generator bypass kit installed vs the equivalent branded Eaton generator bypass kit? (i.e. using part EAT-PN200 by Genterlock vs using branded Eaton's Generator Interlock Kit 100A-125A BRMIKBR Type BR).

Thanks! - 2022/03/25

Eaton generator interlock kit compatability listing vs panel models - cited & discussed at InspectApedia.com

Moderator reply: agree: comply with manufacturer's label and interlock compatability specifications - given here

@CFB,

Bottom line: strict electrical code compliance would require that the electrician follow the panel manufacturer's requirements in choice of circuit breakers or accessories.

The BRMIKBR interlock kit is specifically for type BR electrical panels.

See the EATON TYPE BR MECHANICAL INTERLOCK KIT SPECIFICATIONSS [PDF] (2013)

[live link given above on this page]

You'll see both on this page and in that PDF several interlock models and the panels with which they're compatible, excerpted here: match the kit to the panel.

Below is the Eaton electrical panel - backup generator interlock kit compatability list by interlock kit model.

[Click to enlarge any image]

Eaton backup generator interlock kit panel compatability list at InspectApedia.com

Details:

Thanks for the comment/question; I need a little help to answer reliably, as your question begins with a statement of "fact" that's not entirely clear.

You said "Since all breakers must match in a panel and by branded type,"

I agree that in strict compliance with the model electrical code (US NEC for example) as adopted by Florida and other states, electricians should install devices such as circuit breakers in accordance with the requirements given by the manufacturer of the electrical panel. And a strict interpretation of that would require that the brand of breaker and breaker type specified on the panel label should be respected.

Eaton CH Generator Interlock Kit at Inspectapedia.com ... Eaton CH Generator Interlock Kit at Inspectapedia.com

I don't always see that happening in practice, especially in older homes.

I also agree that electrical panel manufacturers want only their brand circuit breakers installed in their panels, but there are plenty of alternate brand and substitute brand that are marketed and that are accepted by electrical inspectors in some jurisdictions (against the manufacturer's advice or warnings) so I don't assume that all breakers will "match" by brand.

Just what will pass the Florida electrical code I can't answer for all cases - the local electrical inspector is the final legal authority. Where a backup generator is being installed, I agree that there is a rather wide range of type of lockout device and transfer switch kits sold for generator hookups, and not all will be accepted by your electrical inspector.

Eaton CH Generator Interlock Kit at Inspectapedia.com

Circuit Breaker "Types" is a Broad Term

And it's confusing to assert that all breakers must match by "type" in a panel because (for other readers) in a broader sense of the word "type" there can be various types of breakers in the same panel, such as GFCI, AFCI, and non-GFCI, single-pole, double pole, slow-trip, and other features needed on particular circuits.

A look through the Florida Building Code, Chapter V Residential Wiring, finds the word "breaker" mentioned just eight times, or nine in some versions, and in none of those citations is there an explicit reference to circuit breaker type or brand.

Below: the EAT-PN200-Generator-Interlock kit for Cutler Hammer and Challenger Panels

(The latter panel brand may be unsafe -

see CHALLENGER ELECTRIC PANELS)

Eaton CH Generator Interlock Kit at Inspectapedia.com

Also see the source code NEC 240.6

UK Circuit Breaker Types vs Fault Currents

Or for UK readers: circuit breaker types may be selected to avoid nuisance tripping such as tolerating a brief current surge on high-amp circuits such as those powering an air conditioner compressor motor

 

Question: where can we find an Interlock Kit for an old Sylvania Electrical Panel?

Sylvania electrical panel dimensions for installing an Interlock Kit for backup generator (C) InspectApedia.com Sharon ... Sylvania electrical panel dimensions for installing an Interlock Kit for backup generator (C) InspectApedia.com Sharon

We have purchased a home recently in Ontario Canada. It has a Sylvania panel, but i don't think its a Zinsco panel. However, I am having trouble finding an interlock kit for it to install our generator circuit.

And know that Sylvania became tied in with Westinghouse and then Cutler, and now Eaton sells the appropriate circuit breakers for the panel.

But, is there another panel name/model that is the same size that i can obtain an interlock to install? Most of the sites say "oooohhhh Sylvania, no, we won't touch anything Sylvania".

The 200 amp main is a vertical throw [shown below], and there is 4.25" between that main, and the top row of horizontal service breakers.

Sylvania electrical panel dimensions for installing an Interlock Kit for backup generator (C) InspectApedia.com Sharon ... Sylvania electrical panel dimensions for installing an Interlock Kit for backup generator (C) InspectApedia.com Sharon

I hate how nothing is labelled, we've gone through and traced/tested most, but not quite finished yet

Anyhow, any help would be greatly appreciated. No sense pulling permit and booking inspection etc until we source the part. Anyway, hadn't even thought that there wouldn't be an interlock available for this panel, as the last time, it was a simple acquisition - Anonymous by private email 2020/01/22

This Q&A were posted, along with more photos of this Sylvania electrical panel that is not a Zinsco-Sylvania design, originally

at IDENTIFY SYLVANIA ELECTRICAL PANELS

Reply: GTE-Sylvania Interlock Kit Panel Cover Fit details

GTE Sylvania electrical panel interlock kit key dimensions at geninterlock.com cited & discussed at InspectApedia.com

Photo: GTE-Sylvania electrical panel interlock kit key dimensions adapted from information provided by geninterlock.com cited above.

First check the dimensions in your measurement as there are certainly some interlock kit manufacturers who provide kits for some GTE-Sylvania electrical panels.

Indeed your panel appears to have an inch more space between the main breaker and the highest circuit breakers than do later GTE-Sylvania panels

About the "wont-touch Sylvanias" - informed inspectors and electricians may have told you, as you put it "oooohhhh Sylvania, no, we won't touch anything Sylvania" because of the failure rate associated with a subset of Sylvania electrical panels, in particular those sporting Zinsco-design circuit breakers and panel buses.

If your panel is not one of those then at least it isn't suffering from that issue.

At IDENTIFY GTE SYLVANIA-ZINSCO PANELS we show the problematic GTE Sylvania Zinsco panel labels.

Geinterlok.com sells interlock kits for GTE-Sylvania electrical panels - as you'll find in the resources we list at

INTERLOCK KITS for BACKUP GENERATORS

Though you'll want to give them a call; it's possible that you may not find an interlock add-on for some older panels like this Sylvania Electric model.

If there is no perfect fit, check with the kit manufacturers as you may find that they have one that fits or they can even make one for you; it's a simple flat metal cutting operation to fit the measurements of your specific electrical panel.

Just be sure you buy equipment that's UL or CSA tested and listed and locally approved, and that it's installed by a licensed electrician, permitted, approved.

Those steps are for your own safety.

In the standard backup generator hook-up you would use a transfer switch, IMO safer than an interlock kit; in that approach you won't need another 200A main, just a sub panel big enough to
contain the key circuits that you want to power by generator in an emergency, + the transfer switch. I discuss these

at DOUBLE THROW TRANSFER SWITCH

IMO it's also not clear that interlock kits as a means of backup electrical generator use are entirely safe;

And you don't really have the option of just switching which ever circuits you want over to the generator as you can overload that device.

I think an electrician ought to be able to install a sub-panel off this one that can handle other brands and provide an appropriate either-or switch.

Reader follow-up:

The interlock is the simplest safest way to connect portable a portable generator and let you have control over what you power at any given time.... (do not want to get into pulling "selected" circuits out to a generator panel, this is older home and some of the circuits are a bit weird/not how I would do them with a new-build, want to be able to send power where its needed when its needed).

Are you suggesting a sub-panel with another 200amp main and the "gennie" breaker (30amp or 50amp depending on which generator we go with), with that sub-panel then supplying the power to the existing main panel? I'll have a look at the other section of the website you mention as well, thanks.

That's why you have to know what's on each circuit and what the limit is for gen load. Not for the "average" homeowner, but if you have a clue and are sensible, its perfectly safe. They are still legal and meet code in Canada. We've never bogged down the generator, err on side of caution with load.

But until we find the CSA or UL pieces of metal that make up the safety device/interlock, we can't pull the permit and call for the inspection, no point.

They take next to no time to install, physically prevent the utility main being on at the same time as the generator breaker, and the inspectors seem happy with them (they meet code, so they better!) its a rural area, and I think the inspectors are just happy to see the interlock on there and not seeing people modify without the interlock.

Reply: safety hazards in some electrical panel transfer switch interlock methods

Agreed, but using an interlock kit instead of a transfer switch as you describe requires that anybody who ever uses the electrical system in the future needs to understand the overload and safety issues; we prefer to design and install electrical equipment such that no special knowledge is required on the part of the building occupants, as we don't count on future building occupants having the same level of expertise as you.

A standard electrical transfer switch is simple and safe for future building occupants to use as it makes it unlikely that occupants can make a mistake, overloading a circuit or causing an electrical fire or shocking an electrical worker outside your home who is up at a pole and doesn't know that by error a homeowner is back-feeding power into the electrical lines.

Reader follow-up:

Generac 6333 60-A single load double pole manual transfer switch for backup generators cited & discussed at InspectApedia.comThe standard transfer switch is the set-up we don't want, the transfer switch set- up. we need the flexibility to power up circuits when needed, and not have to decide "permanently" what circuits will be able to be powered.

Between elderly family members/medical equipment, and just life in general changing, we need the flexibility to direct power anywhere its needed and not have to move selected circuits to a sub panel that can be powered.

We know what draw is on a given circuit, and can leave the circuits not needed turned off, and then turn on when needed, balancing load and generator rating. we had a similar setup at a previous home, and it worked fantastic.

Utility company power goes off - turn off Main breaker and all service breakers (including the generator breaker in the panel), start generator, stabilize it, plug it into the house, turn on generator output, go downstairs, turn on generator breaker on the panel, and then turn on desired service breakers.

You get to control where the power is going, and can move that around as needed.

Anyway, hadn't even thought that there wouldn't be an interlock available for this panel, as the last time, it was a simple acquisition.

Something like the Generac 6333 60-Amp Single Load Double Pole Manual Transfer Switch for Portable Generators [shown above as for sale at Amazon) is our back-up plan, if we can't find an interlock.


...

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