Doorbell transformer fuzes

[Gibbs]

I see on some blogs inspectors are requiring fuzes (NEC 450.3(B)) to be on the primary of doorbell transformers. Aren't they excempt from fuze requirement by NEC 450 excption#2?

 

[Dennis Alwon]

They are not required to be fused.

 

[raider1]

Correct, Article 450 does not apply to Class 2 and 3 transformers that comply with Article 725.

Check out 450.1 Scope Exception #4.

Chris

 

[hurk27]

all doorbell transformers that have been manufactured in the last 15 to 20 years have a fuse built into the windings, this fuse is opened from both temperature and overload, and is one of the main reasons not to put these transformers in hot attic spaces, this also applies to most small fractional motors such as bath fans, range hoods etc...

 

[gar]

110108-1420 EST

hurk27:

Is the protection device really a non-resettable thermal fuse?

.

 

[hurk27]

110108-1420 EST

hurk27:

Is the protection device really a non-resettable thermal fuse?

.

Yep, dug a few out trying to figure out what failed, same thing with a bath fan but at least they bring the fuse terminals out to pegs where you can jump them. the fuse is actually under the paper cover over the windings, will look like a bump.