Buzzer and bell transformer

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hhsting

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I have buzzer and bell transformer 120VAC to 24VAC. Below is what engineer sent.

0862bbf7705f9808872b014a83a5100e.jpg




I have following questions:

1. Would that require system bonding jumper? I am not sure if NEC 2017 Article 250.30 applies or not.

2. Would that require grounding electrode conductor secondary?

3. Would that require secondary overcurrent protection?
 
It would depend on the specific details of "T-1" but normally "No" to all your questions.
 
hhsting said:
I have buzzer and bell transformer 120VAC to 24VAC. Below is what engineer sent.

0862bbf7705f9808872b014a83a5100e.jpg




I have following questions:

1. Would that require system bonding jumper? I am not sure if NEC 2017 Article 250.30 applies or not.

2. Would that require grounding electrode conductor secondary?

3. Would that require secondary overcurrent protection?
Click to expand...
The rules for Power Limited Circuits are very different. Please check Article 725.
 
This is no different than a standard doorbell transformer.120 volts go in, 24 volts come out.
Chances are that the transformer will be installed on a metal box and will be "grounded" by proxy.

Ron
 
rc/retired said:
This is no different than a standard doorbell transformer.120 volts go in, 24 volts come out.
Chances are that the transformer will be installed on a metal box and will be "grounded" by proxy.

Ron
Click to expand...

Yes it used for bell or buzz type application.

Anything in NEC 2017 that says grounding electrode conductor and system bonding jumper not required for these types of transformer?
 
hillbilly1 said:
It won’t hurt anything bonding it, usually just a bond jumper wire. You don’t have to use a grounding electrode if that’s your question.
Click to expand...

I don’t see where in NEC 2017 it says bonding jumper is required or not required for this type
of transformer? I got it wouldn’t hurt
 
hhsting said:
Yes it used for bell or buzz type application.

Anything in NEC 2017 that says grounding electrode conductor and system bonding jumper not required for these types of transformer?
Click to expand...
In this application, no special bonding is required.
I, like every other electrician on this site have installed hundreds of these.
As an inspector, I've inspected hundreds.
You are good to go!

Ron
 
augie47 said:
Yes and 250.20(A)
Click to expand...

Transformer is 100va primary 120V and secondary 24V used for door bell or buzzer application in cash registers or front of door.

So according 250.30(A)(1) exception 3 system bonding jumper is required but then 250.20(A) system bonding jumper is not required?
 
250.20(A) says its not required to be grounded, so its permitted to be an ungrounded system.
250.30(A) applies to grounded systems.
 
hhsting said:
Yes it used for bell or buzz type application.

Anything in NEC 2017 that says grounding electrode conductor and system bonding jumper not required for these types of transformer?
Click to expand...
Start with 250.20(A) that tells you the 24 volt system is not required to be a grounded system. If it is not a grounded system, there cannot be a system bonding jumper as that only exists on grounded systems.
 
I guess if you really want to over think things technically 250.30(B) would apply to a ungrounded class 2 xformer, but then 251.121 Exception permits a wire type branch circuit equipment ground.
 
don_resqcapt19 said:
Start with 250.20(A) that tells you the 24 volt system is not required to be a grounded system. If it is not a grounded system, there cannot be a system bonding jumper as that only exists on grounded systems.
Click to expand...
But 250.20(A) allows it to be a grounded system, and the schematic posted shows a grounded secondary.

250.30(A)(1) Exception 3 then provides relief on the System Bonding Jumper size in this application. Does anything provide relief for a GEC connection for such an installation?

Cheers, Wayne
 
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