Doorbell Transformer Inside Main Panel

[Wes Stevens]

I am looking for a code reference to give a licensed electrician that shows a doorbell transformer and it's associated low voltage wiring are not allowed inside main or auxiliary breaker panels. He says it is allowed and I have been saying it is not, but I can't find the information to support my view.

Thanks four you help:

Wes

[hausdok]

Isn't that as simple as looking on the listing and labeling for the panel and saying, "Show me on this label where it says that it's ok to install that transformer in here, or point me to the specific code reference that says it's ok to install such devices in this panel?"

OT - OF!!!

M.

[jgclancy]

It's a debatable point.Nothing directly against transformers in the cabinet. If Class-2 wires are correctly rated and kept the correct distance ( I think 1/4 " ) from the higher voltage wires in the cabinet it's okay.

Usually, they are not and usually you can't know the rating of the wires.A lot of times they are double taped and wires not desgnated for voltage.

It's not a good idea due to the hazards of overheating or the possibility of the two types of wiring touching and sending the wrong voltage through doorbell wiring.

The safest way would be to have it next to the cabinet in a box that keeps anyone from touching the exposed terminals.

Not illegal but just not a good idea to have it in the panel.

Jim C.

Jim C.

[Jim Katen]

Originally posted by Wes Stevens

I am looking for a code reference to give a licensed electrician that shows a doorbell transformer and it's associated low voltage wiring are not allowed inside main or auxiliary breaker panels. He says it is allowed and I have been saying it is not, but I can't find the information to support my view.

Thanks four you help:

Wes

Mike & Jim Clancy hit on the relevant issues.

110.3(B) tells us that listed or labeled equipment has to be installed in accordance with the instructions. Panel enclosures generally come with a label that tells you what equipment, in addition to breakers & wires, you're allowed to put in the enclosure. Doorbell transformers are not on that list. So the code reference you're looking for is 110.3(B).

The rules that Jim Clancy brought up are in 725.136(D). It's a long, complicated passage that I won't type out here, but Jim summarized it pretty well. It allows Class 2 wiring in a panel enclosure if certain conditions are met. This is where the debatable part comes in. The conditions include allowing these wires in the enclosure if "they are introduced solely to connect the equipment connected to Class 2 and Class 3 circuits and where (1) or (2) apply. "

(1) is the 1/4" separation thing Jim mentioned.

(2) requires that they use special cables to protect the Class 2 conductors.

The whole 725.136(D) thing is on very sketchy ground.

Is that any clearer?

- Jim Katen, Oregon

[Steven Hockstein]

How much work is involved with relocating the transformer? It seems to me that it would take the electrician less time to move it out of the panel than to argue about it.

[jgclancy]

Thanks for the actual Code citings Jim K. I remembered generally where they were but not the exact numbers and didn't want to give incorrect information.

Now, to be clear, i think the transformer should never be in the cabinet and when mounted outside should be protected from the

exposed terminals. I feel any electric shock is dangerous and can affect the heart.

Almost every transformer in a cabinet is usually just sitting inside with wires going every which way and unlabeled. HI's can note them as incorrect just about every time they see one in there.

As far as what is listed on a panel. So many old panels do not have that information and other times it's incomplete. To be pedantic, I can use wire nuts in a cabinet but I've never seen them actually listed on a panel.

Jim C.

[kurt]

I'm the philistine. I tell folks it's "wrong", why, then explain how I've only seen it about 5000 times, and nothing bad is going to happen if remains.

Or something like that. Honestly, this sort of stuff rarely, if ever, makes it's way into one of my reports.

[Scottpat]

I have never seen a doorbell transformer that did not create a "double tap" issue on a breaker. Add that to the fact they are not suppose to be in the panel enclosure and you have two good reasons to say somthing about them.

[kasterko]

Quote: Originally posted by Wes Stevens

I am looking for a code reference to give a licensed electrician that shows a doorbell transformer and it's associated low voltage wiring are not allowed inside main or auxiliary breaker panels. He says it is allowed and I have been saying it is not, but I can't find the information to support my view.

Thanks four you help:

Wes

id="quoteN">

Mike & Jim Clancy hit on the relevant issues.

110.3(B) tells us that listed or labeled equipment has to be installed in accordance with the instructions. Panel enclosures generally come with a label that tells you what equipment, in addition to breakers & wires, you're allowed to put in the enclosure. Doorbell transformers are not on that list. So the code reference you're looking for is 110.3(B).

The rules that Jim Clancy brought up are in 725.136(D). It's a long, complicated passage that I won't type out here, but Jim summarized it pretty well. It allows Class 2 wiring in a panel enclosure if certain conditions are met. This is where the debatable part comes in. The conditions include allowing these wires in the enclosure if "they are introduced solely to connect the equipment connected to Class 2 and Class 3 circuits and where (1) or (2) apply. "

(1) is the 1/4" separation thing Jim mentioned.

(2) requires that they use special cables to protect the Class 2 conductors.

The whole 725.136(D) thing is on very sketchy ground.

Is that any clearer?

- Jim Katen, Oregon

[Jeff Remas]

I am looking for a code reference to give a licensed electrician that shows a doorbell transformer and it's associated low voltage wiring are not allowed inside main or auxiliary breaker panels. He says it is allowed and I have been saying it is not, but I can't find the information to support my view.

Thanks four you help:

Wes

I personally don't flag them as a problem for existing homes. I don't see it as a defect.

On new construction as a code inspector I can't allow it due to 101.3(B) if it is not listed on the panel.

From a home inspection standpoint, there are bigger fish to fry than something like that. It is more of a "prove you are right" than a concern or actual defect.

Agree, moving it outside the panel now that you flagged it is easier than arguing about it.

[enigmapaul]

Doorbell transformers usually have threaded collar and a nut to mount them to a spare knockout. As far as I know these are ok to install to the OUTSIDE of the load panel. If that is the case, then how does that square with 101.3(B)? If its on the onside edge, do we feel it does not apply?

I am looking for a code reference to give a licensed electrician that shows a doorbell transformer and it's associated low voltage wiring are not allowed inside main or auxiliary breaker panels. He says it is allowed and I have been saying it is not, but I can't find the information to support my view.

Thanks four you help:

Wes

I personally don't flag them as a problem for existing homes. I don't see it as a defect.

On new construction as a code inspector I can't allow it due to 101.3(B) if it is not listed on the panel.

From a home inspection standpoint, there are bigger fish to fry than something like that. It is more of a "prove you are right" than a concern or actual defect.

Agree, moving it outside the panel now that you flagged it is easier than arguing about it.

[Jim Katen]

Doorbell transformers usually have threaded collar and a nut to mount them to a spare knockout. As far as I know these are ok to install to the OUTSIDE of the load panel. If that is the case, then how does that square with 101.3(B)? If its on the onside edge, do we feel it does not apply?

I'm not sure it's an issue. 110.3(B) just says that listed equipment has to be installed in accordance with its instructions. So you'd need to look at the instructions.

We throw around the term "panel" a lot, but for this discussion, we should probably be more careful with our terms. The thing that most of us call a panel is really a load center. A load center comprises a metal box (or enclosure) with a panelboard mounted inside. The instructions usually deal with what you can and can't do with the panelboard and what you can & can't put inside the box. I don't recall reading too much about what you can & can't do with the outside of the box. My suspicion is that you could mount a doorbell transformer, an enclosed relay, a lightning arrestor, and other such things on the outside of the box with impunity.

- Jim Katen, Oregon

[John Kogel]

I am looking for a code reference to give a licensed electrician that shows a doorbell transformer and it's associated low voltage wiring are not allowed inside main or auxiliary breaker panels. He says it is allowed and I have been saying it is not, but I can't find the information to support my view.

Thanks for you help:

Wes

All the above comments are relevant, but it may come down to this - If the Authority Having Jurisdiction in your area says it is OK, then that may be why the electrician is arguing with you. Check with the authority first, (get an e-mail from him if possible to print off and show people).

In my area, the double taps were allowed for many years, but the transformer had to be mounted on the outside of the load center. So I don't mention those older installations, unless it's laying loose inside.

The thinking is that the soft stranded wire does not compromise the branch circuit wire connection the way a hard copper wire could.

See Jim's comment below. []

New installations in my area - the tranny is in a closet or in the crawlspace on the side of a junction box. The new AHJ's don't allow it to be double-tapped. Correctly so.

[Jim Katen]

. . . The thinking is that the soft stranded wire does not compromise the branch circuit wire connection the way a hard copper wire could.. . .

And this is how folklore is born.

It was just as wrong then as it is now. If you make up the connections carefully, it doesn't matter whether the wire is stranded, fine stranded, or solid; a carefully made connection performs just fine while a poorly made one burns up. The problem with putting two wires under a lug that's only approved for one is just that -- it's only approved for one -- and that hasn't changed over the years. There really isn't anything more to it.

- Jim Katen, Oregon