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A '''generator interlock kit''' (or just '''interlock kit''') is a device designed to allow safe powering of a home by a [[engine-generator|portable generator]] during a [[power outage]]. It is a less-expensive alternative to purchasing and installing a dedicated [[transfer switch]]. The kit achieves the same function by adding an external interlock onto an existing breaker panel that allows the main breaker to be turned on ''or'' one designated load breaker to be turned on, but not both at the same time. The interlocked load breaker is repurposed as the "backfeed" breaker, and a generator is connected to it (wired directly or through a power inlet).
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Under normal conditions, the main breaker is on, accepting power from the external mains into the panel, and the backfeed breaker is off, isolating the generator. The external mains feeds the panel, but the panel cannot [[backfeeding|backfeed]] the generator. [[Backfeeding]] the generator should never be done, because it serves no purpose and risks damaging the generator.
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A '''generator interlock kit''' (or just '''interlock kit''') is a device designed to allow safe [[backfeeding]] of a home through a [[engine-generator|portable generator]] during [[power outage]]s, thereby eliminating [[illegal]] and/or unsafe [[engine-generator|generator]] [[backfeeding]] situations that could potentially [[electrocution|electrocute]] [[lineman|power linemen]] or destroy the generator.<ref>http://www.nooutage.com/interlock_kits.htm</ref>
In generator mode, the backfeed breaker is on, accepting power from the generator into the panel, and the main breaker is off, isolating the external mains. The generator feeds the home by [[backfeeding]] the panel, but the panel cannot backfeed the external mains. [[Backfeeding]] the external mains is unsafe and illegal, because it can potentially [[electrocution|electrocute]] [[lineworker]]s, start fires, and overload or damage the generator.<ref>{{Cite web|url=http://www.nooutage.com/interlock_kits.htm|title=Panel Interlock Kit Kits - for safely connecting generator power without a transfer switch}}</ref>
A generator interlock kit is installed on the front cover of the home's [[distribution board|breaker panel]]. It consists of two sliding [[steel]] or [[plastic]] (depending on the brand) plates held together by three bolts. When moved down, the plate blocks the generator backfeed [[circuit breaker]] and allows the main [[circuit breaker|breaker]] to remain on; when moved up, the generator backfeed [[circuit breaker]] may be turned on, but the main [[breaker|circuit breaker]] is blocked and will remain off. The generator backfeed [[breaker|circuit breaker]] is connected to a generator inlet installed (preferrably) on the outside of the structure. A short cord connects the generator to the house inlet, usually through the use of [[Industrial and multiphase power plugs and sockets|twistlock]] plugs and [[socket]]s. ▼▲== Installation and Operation==
▲AEarly generator interlock kitkits isconsisted of two sliding [[steel]] or [[plastic]] (depending on the brand) plates held together by three bolts and installed on the front cover of the home's [[distribution board|breaker panel]] ., Ithowever, consistssome ofmodels twomade slidingby [[ steelEaton Corporation|Eaton]] or(formerly Cutler-Hammer) and [[ plasticSiemens]] (dependingfor panels manufactured by them install on the brand)adjacent platescircuit heldbreakers togetherthemselves and consist of a sliding arm for breakers installed back-to-back or a pivoting arm for breakers that are installed side-by -side threeor boltsone above the other, these arrangements remain on the breakers even if the panel cover is removed as opposed to the mechanisms installed on the panel covers. When movedthe downmain breaker is turned on, the plate or pivot arm blocks the generator backfeed [[circuit breaker]] and allows the main [[circuit breaker|breaker]] to remain on ;. when moved upConversely, when the generator backfeed [[circuit breaker]] may beis turned on, but the main [[ breaker|circuit breaker]] is blocked and will remain off. The generator backfeed [[ breaker|circuit breaker]] is connected to a generator inlet installed ( preferrablypreferably) on the outside of the structure. A short cord connects the generator to the house inlet, usually through the use ofa [[ Industrialindustrial and multiphase power plugs and sockets|twistlock]] [[AC power plugs and [[sockets|plug and socket]] s.
==Advantages==
*UsingA angenerator interlock kit allows for all of(or a panel'stransfer circuits to be energizedswitch), up toeliminates the loadneed capacityfor of[[extension thecord]]s generator;to whereas using a generatorpower [[transferhome switchappliance|appliance]] only allows a few circuits to be operateds.<ref>{{cite web |url=http://www.interlockkit.com/ |title=Home |website=interlockkit.com}}</ref>
*Like a [[transfer switch]], an interlock kit lets the generator energize the panel and all of its circuits (up to the load capacity of the generator); not just corded appliances.
*An interlock kit does not require a separate [[distribution board|panel]] to operate; it can beis installed directly on the home's [[distribution board|breaker panel]]. (provided it has an unused 2-pole breaker slot available).
*Interlock kits eliminate the need for [[extension cord]]s to power [[appliance]]s.
==Disadvantages==
*AlthoughEven theythough many are [[ULtested (safetyby an independent lab to a organization)|UL]]-approved standard, they do not carry the UL Listing mark.<ref>{{Cite web|url=http://www.nooutage.com/interlock_kits.htm|title=Panel Interlock Kit Kits - for safely connecting generator power without a transfer switch}}</ref> someWithout locala [[buildingUL code|codes]]Listing, dosome electrical inspectors will not allow the use of these interlock kits.
*RemovingWith kits installed on the [[distribution board|electrical panel's]] cover, removing the cover could allow the generator backfeed breaker to be turned on while the main is on,<ref>http{{Cite web|url=https://forums.mikeholt.com/showthread.php?t=113865&page=2|title = Wire resistance, temp, soil cond}}</ref> potentially energizing [[power line]]s or overloading the generator, if the generator is connected.
*InstallingIn some applications, installing an interlock kit requires drilling holes in the panel cover; once it is installed, it cannot be removed.
*Because the main breaker is shut off, homeowners have no way of knowing when utility power is restored, except by manually turning the generator's breaker off and the main breaker back on.<ref>http{{Cite web|url=https://www.electriciantalk.com/f2/see-if-power-restored-interlock-kit-33891/|title = See if power is restored with interlock kit?}}</ref> However there is at least one product<ref>{{Cite web|url=http://www.nooutage.com/thp108.htm|title = THP108 PowerBACK - utility power return alert}}</ref> that will produce an audible alert indicating that utility power is restored.
*Installing an interlock kit requiresuses anywheretwo fromor 2 to 3three spaces in the existing [[distribution board|breaker panel]].
*[[ transferTransfer switch]] ▼*[[UL (safety organization)]] ▼
==References==
{{reflistReflist}}
==External links==
*[httphttps://www.ulinterlockkit.com/global/eng/pages/ ULGenerator Interlock Tech] Websitewebsite
*[httphttps://natramelecwww.ul.com/ National Ram ElectronicsUL] Websitewebsite
*[httphttps://www.nooutagenatramelec.com/ NoOutageNational Ram Electronics] Websitewebsite
*[http://www.interlockkitnooutage.com/ Interlock Kit DealerNoOutage] Websitewebsite
*[https://enstorageinc.com/best-inverter-generator-review/ Best Generator Guide]{{Dead link|date=August 2025 |bot=InternetArchiveBot |fix-attempted=yes }}
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[[Category:Electrical power control]]
▲*[[UL (safety organization)]]
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