Interlock for generator

[goldstar]

Here's the key phrase

Where manual transfer equipment is used.............The user of the optional standby system shall be permitted to select the load connected to the system.

That's why the inspector is wrong.

With respect to the interlock kit, the ones made by the panel manufacturers state that they are UL listed for use with the panel. However, not all of them have a bolt-down feature . I believe the Siemens interlock kits have a metal, clip-on frame that is slid over the top 2 breakers on each side of the panel making it impossible to remove the generator breaker unless you forcibly remove that clip-on device.

Now, the kits available from www.interlockkit.com have a similar lock-down feature but use a cable tie instead of a metal clip. All the inspectors in my area will not accept these kits for that reason claiming that the cable tie is not a reliable holding device. In addition they are not UL listed with the panel.

 

[steve66]

That's exactly the point that I was trying to make, a hold down kit so the breaker can not be removed.

Maybe I'm wrong, but I thought the hold down kit had a completely different purpose. Here is what I thought the hold down was for:

For a normal branch mounted breaker, if there is a short circuit at the load, the current flows in a direction that makes the magnetic forces pull the breaker tighter onto the bus, ensuring a good low resistance contact at the breaker.

For a branch mounted main, the current flows the opposite direction. If there is a short circuit, the magnetic forces push the breaker away from the bus. Without a hold down, you get a poor connection. That bad connection creates enough heat to make bad things happen.


Steve

 

[GoldDigger]

Maybe I'm wrong, but I thought the hold down kit had a completely different purpose. Here is what I thought the hold down was for:

For a normal branch mounted breaker, if there is a short circuit at the load, the current flows in a direction that makes the magnetic forces pull the breaker tighter onto the bus, ensuring a good low resistance contact at the breaker.

For a branch mounted main, the current flows the opposite direction. If there is a short circuit, the magnetic forces push the breaker away from the bus. Without a hold down, you get a poor connection. That bad connection creates enough heat to make bad things happen.


Steve

The direction of the current flow through the breaker should not have any effect on the magnetic forces between the breaker and the bus, since both the current on the breaker side and the current on the bus side will be reversed (assuming for the moment no other current on the bus flowing past the stab.) Similarly, any forces entirely within the breaker would not reverse direction with a reversal in current flow.
My belief was that it was to prevent accidental (partial) removal of the breaker, leaving both the bus and load side terminals hot when both were expected to e cold. (That could happen with a generator, but not with PV input, although the same rule is applied to both.)

 

[templdl]

Maybe I'm wrong, but I thought the hold down kit had a completely different purpose. Here is what I thought the hold down was for:

For a normal branch mounted breaker, if there is a short circuit at the load, the current flows in a direction that makes the magnetic forces pull the breaker tighter onto the bus, ensuring a good low resistance contact at the breaker.

For a branch mounted main, the current flows the opposite direction. If there is a short circuit, the magnetic forces push the breaker away from the bus. Without a hold down, you get a poor connection. That bad connection creates enough heat to make bad things happen.


Steve

Steve, Is this just your theory at is this as a result of a study that was done?
From my perspective I have 18 years experience as a sales and applications engineer for a major molded case circuit manufacture and what you are stating is no where to be found in the rules that we played by.

 

[ActionDave]

Maybe I'm wrong, but I thought the hold down kit had a completely different purpose. Here is what I thought the hold down was for:

For a normal branch mounted breaker, if there is a short circuit at the load, the current flows in a direction that makes the magnetic forces pull the breaker tighter onto the bus, ensuring a good low resistance contact at the breaker.

For a branch mounted main, the current flows the opposite direction. If there is a short circuit, the magnetic forces push the breaker away from the bus. Without a hold down, you get a poor connection. That bad connection creates enough heat to make bad things happen.


Steve

I always thought it was to keep someone from having a hot breaker in his hand even though it was turned off.

 

[GoldDigger]

It does not exactly do that on its own. But seeing the locking device in place should, even better than a label, cause you to think twice before unscrewing it.

Tapatalk...

 

[iwire]

It's funny how some time working in the field can form ones views.

If I was asked why the hold down is required of backfed panels I would say it would be to prevent the back fed breaker from falling out of place when the panel cover is removed.

Something that can happen with plug in breakers with heavy conductors hanging from them.

 

[jcassity]

i dont want to speculate so can you describe or post a link or post a picture of your interlock?

There are interlocks that work well for "the person qualifed to deal with them"
there are interlocks that do the switching on thier own.

"IF" your MDP main breaker safety interlock "can" be manually manipulated to allow you to turn on the MDP main breaker while the genset is running, then i would have to agree with the inspector.

His way is the safest way but not the cheapest either but in single phase we are only talking a 2 more bills max to groom your selected critical circuits to a separate sub panel and a strategically placed MTS (on-off-on) with ocp.

I think the inspector see's the possibility i described as "possible". if it is, and you look close and agree, i want you to imagine someone other than yourself trying to operate our genset or get it turned up.

im not taking the inspectors side,, but i have to deal with this every day because in reality its the local juristiction having governing authority that you have to satisfy, and realize that the NEC is not really the law of the land,, its the reference guide and universal language. your gen install in your area may not be compliant in another area simply by preference.. inspectors play these games all the time,,no disrespect intended. For the most part they want to implement thier designs or thier experince into thier market they manage.

tell us more about your interlock, can it be overridden when the gen is running?
if it can,, perhaps he will accept it if you place a placcard on the panel board with step by step instructions such as what we find on kirk key manual transfer switches.

 

[ActionDave]

It's funny how some time working in the field can form ones views.

If I was asked why the hold down is required of backfed panels I would say it would be to prevent the back fed breaker from falling out of place when the panel cover is removed.

Something that can happen with plug in breakers with heavy conductors hanging from them.

Kind of another way a sayin' the same thing I was thinking, only a little different.

 

[John120/240]

I always thought it was to keep someone from having a hot breaker in his hand even though it was turned off.

Exactly This has been my interpretation

 

[iwire]

Kind of another way a sayin' the same thing I was thinking, only a little different.

Yes.

 

[hudsonvalleyelectrician]

Inspector Randomness

Inspector Randomness

I pulled a permit for recently installed portable generator for my home with an interlock. I placed an 30A double-pole breaker to backfeed from generator to the panel. The interlock was screwed to the cover of the panel to prevent turning on the main breaker while generator is running. When the inspector came to inspect the work, he wanted me to put the circuits in a subpanel for the generator because the 30a generator is not sufficient to power the whole panel. I explained to him I am not intended to power the whole house and will only power what I need for that time.

Does anybody know if this is a code violation? The interlock is UL listed. If I separate out the circuits in sub panel that means I have to use transfer switch. Thanks for any advice you can provide.

I would phone other inspectors and ask them about Generator interlocks first, to see how the feel about them and how they feel about the main panel being used as a manual transfer switch. IT IS code compliant, BUT there are some inspectors that still fail jobs like yours. You are always free to politely inquire also as to what code section he is using to fail your install.
We use the Interlocks here in NY and have no issues with them or most inspectors.

 

[stew]

Most jurisdictions including all State inspectors Iknow of here in Washington will not allow aftermarket UL listed interlocks. Although they are listed by UL as a device that meets the intent of the code they are NOT listed for use in any manufacturers panels. The only devices that are acceptable here are the ones that are supplied specifically by the panel manufacturer and designed and listed for that makers panel. That all being said the 2 aftermarket ones I have seen are nearly exactly like the ones some panel manufactures supply and will work just as well.

 

[electrofelon]

Most jurisdictions including all State inspectors Iknow of here in Washington will not allow aftermarket UL listed interlocks. Although they are listed by UL as a device that meets the intent of the code they are NOT listed for use in any manufacturers panels. The only devices that are acceptable here are the ones that are supplied specifically by the panel manufacturer and designed and listed for that makers panel. That all being said the 2 aftermarket ones I have seen are nearly exactly like the ones some panel manufactures supply and will work just as well.

That is ridiculous. Who says they need to be listed for specific panels? Do they require NM cable, 2 screw clamp connectors, emt connectors, pvc TA's, etc to be listed for use in specific panels?

 

[electricmanscott]

Genius inspectors. This is why people avoid permits and inspections.

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[goldstar]

That is ridiculous. Who says they need to be listed for specific panels? Do they require NM cable, 2 screw clamp connectors, emt connectors, pvc TA's, etc to be listed for use in specific panels?

I tend to agree with you but I think this is a CYA type of thing with inspectors. If the device (it's actually a type of appliance to be specific) doesn't have a UL listing with the panel and is not made by the panel manufacturer inspectors generally won't accept them for fear that if some unauthorized person or homeowner gets injurerd while misusing this device it's their tail in the ringer. Another bunch of crap as far as I'm concerned. Many inspectors also don't like the ones that come with a cable tie that holds the two adjacent breakers together the generator breaker so that the generator breaker won't fall out, citing that the tie may become dried and break apart over time. More crapola IMHO.

 

[goldstar]

Genius inspectors. This is why people avoid permits and inspections.

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Bingo !!! That's the long and short of it. I'd rather see the job get inspected for a proper and safe installation rather than flat and outright denying the use of an interlock kit. Most homeowners will just avoid getting the interlock kit, shut their main breaker off and back-feed thru their AC disconnect.

 

[iwire]

Genius inspectors. This is why people avoid permits and inspections.

Couldn't we use that very same excuse to argue against every code rule?

 

[electricmanscott]

You could. Doesn't necessarily equal this particular situation.


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[goldstar]

Couldn't we use that very same excuse to argue against every code rule?

I suppose, if you really wanted to, you could apply that excuse to all Code rules as you described. However, most Code rules are made to prevent misuse or miswiring that may potentially cause a dangerous situation. What's dangerous about using a non-UL interlock kit that is designed and works exactly like the ones manufacturers make for their own panels ?