OEM generator interlock versus after-market

[RustyShackleford]

I'm curious about peoples' experiences and thoughts about generator interlock kits, specifically the OEM ones such as:

Product Details - Industry Mall - Siemens USA

... versus the several aftermarket ones such as:

Generator Interlock Kit / OEM Model Siemens 150 and 200 Amp Panels POST March 2020 | GenInterlock

7/8 spacing for Plug on Neutral Panels 1 1/4 spacing for NON Plug on Neutral panels

www.geninterlock.com

The price of the OEM version is not significantly higher (at least for this manufacturer), so I wonder why the after-market ones exist, unless they have some advantage.

 

[don_resqcapt19]

Right now there is actually no language in 702.5 that permits the use of interlock kits as they are not listed as transfer equipment. Yes, I am well aware that the use is a common practice that is acceptable to most AHJs. Technically the AHJ would need to give a written 90.4 permission.

This should change in the 2026 code as it is likely the term "interlock kit" will be added to 702.5, but even then there may be an issue with the type of device used.

The UL Marking Guide for Panelboards (QEUY) says the following:

Some panelboards, constructed with interlocked main switching and overcurrent protective devices, have been investigated for use in optional standby systems in accordance with Article 702 of the NEC and are marked "Suitable for use in accordance with Article 702 of the National Electrical Code ANSI/NFPA 70," or, if provided within kit form, "Suitable for use in accordance with Article 702 of the National Electrical Code ANSI/NFPA 70 when provided with interlock kit Cat No. ____

I see that as a 110.3(B) listing and labeling instruction that only permits the use of OEM interlock kits.

 

[infinity]

Around here this is something that inspectors look for. If you buy an interlock kit on Interlockkit.com you'll get a red sticker.

 

[micabay]

Around here this is something that inspectors look for. If you buy an interlock kit on Interlockkit.com you'll get a red sticker.

What difference would it make, if said interlock is preventing the main, and generator breakers from being closed at the same time?

 

[RustyShackleford]

Around here this is something that inspectors look for. If you buy an interlock kit on Interlockkit.com you'll get a red sticker.

So they're making a kit that does the same thing, for roughly the same price - the only bonus is, you get a red sticker. Doesn't quite make sense.

 

[GoldDigger]

So they're making a kit that does the same thing, for roughly the same price - the only bonus is, you get a red sticker. Doesn't quite make sense.

I would guess that one deciding factor could be availability. Suppliers like Interlockkit.com can generally ship anything in a few days while you might have to wait a much longer time to get an equivalent part from the manufacturer.

 

[infinity]

What difference would it make, if said interlock is preventing the main, and generator breakers from being closed at the same time?

I would guess that one deciding factor could be availability. Suppliers like Interlockkit.com can generally ship anything in a few days while you might have to wait a much longer time to get an equivalent part from the manufacturer.

I agree that these should be allowed especially for old panels where the panel manufacturer doesn't even sell an interlock kit because the panel is ancient. IMO any decent inspector should be able to look at the interlock kit and see if it will actually do its job regardless of a listing.

 

[LarryFine]

Interlockkit just happens to be right here in Richmond, so i can just run down and pick up one.

 

[infinity]

Interlockkit just happens to be right here in Richmond, so i can just run down and pick up one.

Do inspectors in your area except them without being listed?

 

[LarryFine]

Do inspectors in your area except them without being listed?

It has never been mentioned either way. Maybe they're used to seeing them here.

 

[RustyShackleford]

I can't tell for sure (from the links in te OP) but it looks like the OEM one works even if the panel cover is absent. The after-market ones definitely do not.