qcroanoke
Sometimes I don't know if I'm the boxer or the bag
- Location
- Roanoke, VA.
- Occupation
- Sorta retired........
generator interlock switch
- Thread starter journeyman0217
- Start date
- Status
mjf
Senior Member
Nope, after looking at their site again it appears they only comply with UL 67.
Inspectors here are accepting that.
Reliance
Member
- Location
- Racine, WI
Which is better than nothing, but I think we can agree that when the cover is removed, having the interlock still maintain its isolation is even better.
The functionality is similar yes, but I disagree when you say "either way, they are defeated by removing the cover". That is not true and a proper interlock should not fail in its main purpose with a dead front cover off.
Both UL and NEC address this. That is why UL will list certain panel board interlocks and not others, and that is why inspectors will pass certain inspections and not others.
NEC article 408.36 (D) Back-Fed Devices (from part III. Panel Boards)
"Plug-in-type overcurrent protection devices or plug-in type main lug assemblies that are backfed and used to terminate field-installed ungrounded supply conductors shall be secured in place by an additional fastener that requires other than a pull to release the device from the mounting means on the panel"
UL 1008 7.1.18
"The operating mechanism of an open transition transfer switch shall be interlocked to reduce the possibility of simultaneous connection to both normal and alternate supplies. Removal of the doors or access panels shall not result in defeating the interlocking mechanism."
When there is a massive power outage where hundreds, thousands, hundreds of thousands, or millions of home owners all at once are setting up portable generators, we probably should think about it a great deal.
- Occupation
- Licensed Electrician
I think they will be focused on getting the generator going. I seriously doubt they will be using their time and energy to look for a screwdriver in order remove their deadfront.
goldstar
Senior Member
- Location
- New Jersey
- Occupation
- Electrical Contractor
The reason we install these devices is for safety. We also install a panel cover for safety. When we use the word IF along with "the cover is removed" we're implying that whomever is removing the panel is intentionally doing so at the risk of their own safety. Unless we start installing tamper-proof locks on breaker panels I don't see any way we EC's can prevent someone from removing the covers.
Now, we have to ask the question "Why would someone want to remove the cover during a power outage"?
Now, we have to ask the question "Why would someone want to remove the cover during a power outage"?
kwired
Electron manager
- Location
- NE Nebraska
- Occupation
- EC
FIFY
I don't know UL standards, but would guess these interlock devices are just that - an interlock device and not listed transfer equipment that is likely covered by a different standard.
Reliance
Member
- Location
- Racine, WI
I agree in that I doubt anyone will jump right up to remove the cover unless they have a reason. However I can certainly think of a lot of reasons myself, the main one being that something isn't working that they think should be working. In the age now with GFCI's in both generators and homes, it's not hard to imagine that someone will experience an issue with a single circuit and try to address it themselves one way or another. What if it's very cold and their heating system is not kicking on? If there is a large outage, how available will EC's be in their area and how quickly will they come to these homes on call with these types of issues? I think it's reasonable to assume that there could definitely be instances of home owners trying to address an issue by opening their cover when their main power fails and they are having some type of problem getting something to work. Are we that confident that most HO's that get an interlock installed actually test their portable generator with it prior to a power failure?
If the panel is opened of course always a safety risk, but if the reason for opening the panel has nothing to do with the interlock, and the interlock comes right off with the cover, it should be clear that it adds even more potential for deadly situations than if the interlock stayed intact. This is why UL and the NEC say almost the same thing about these devices and what their requirements should be. It's not that hard to make one that doesn't come off with the cover, it's been done correctly for nearly 20 years by multiple OEM's.
kwired
Electron manager
- Location
- NE Nebraska
- Occupation
- EC
Do you have pictures of interlocks that stay on when deadfront is removed - in particular for the "loadcenters" that are typical in residential appliactions?
Only one I can think of is the one they make for QO series that attaches to two side by side QO breakers. Cat # QO2DTI. But that only works with typical 125 amp and less QO breakers, and only certain panels will accept the hold down kits for the back fed mains that would be necessary as well. Haven't seen anything for interlocking a QOM1/QOM2 breaker (or similar designs in other manufacturers) and breaker in a branch position in same panel that doesn't attach to the deadfront.
Reliance
Member
- Location
- Racine, WI
Not of any field install kits, sorry.
I don't know which of the big name panel makers offer proper kits in this context, how many variations or for which panels, that are field installed only and would meet the requirements I've been stating in reference to UL and the NEC. I'm sure there are some considering how many different possible kits are available both by the aftermarket companies and the panel companies.
The OEMs I was referring to are the mgf's that focus on transfer equipment and don't compete with the big panel makers. They have always used general panel boards or make their own, make their own mechanism and have it factory installed (and listed) and sell it as a combination panel board and transfer panel. Sometimes they preload them with breakers and wires to ease the install if it's a smaller panel intended to be setup as a sub panel (60A-100A).
The list is not very big, when I said multiple OEMs I probably should have said "a very small list" of OEMs have been doing this for a long time.
My speculation would be the big panel makers don't care much about this since it's unlikely the sales volumes are significant enough for them to care.
kwired
Electron manager
- Location
- NE Nebraska
- Occupation
- EC
Most of what I can think of that fits what you are describing have an automatic transfer switch in them, or if using back fed main breakers maybe are limited to 60 - 100 amps and only maybe a dozen poles for branch breakers. A QO2DTI like I mentioned before in a small loadcenter will yield about same outcome. But I have never seen a 150-225 amp main breaker that can interlock with a generator breaker in similar fashion.
mjf
Senior Member
I think the only interlock I've ever personally seen that doesn't remove with the cabinet cover are manufactured by Reliance Controls.
(BTW.....what's your forum name?)
Reliance
Member
- Location
- Racine, WI
Right, along with other manufacturer's that build this equipment with regards to the NEC and UL requirements, such as Generac (including Gen-Tran who they had acquired), Milbanks, and a few others. And some of the panel makers aftermarket brackets but I don't know how many, apparently there are some that don't remove with the cabinet and some that do.
- Location
- Massachusetts
Like the Square D one that I mentioned, it bolts to the cover.
But here is the deal, once the untrained break out their tools there is nothing that can stop them from making a safe installation dangerous.
Even a commercial ATS can often be made unsafe by just the removal of a few screws and removing the interlock.
Heck even Kirk key interlock systems only bolt to the switchgear covers
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