Class 2/UL 1585

[jemsvcs]

Although not stated directly in the NEC, UL 1585 limits Class 2 transformers (and therefore Class 2 circuits) to 30 V RMS. 725.2 for a Class 2 Circuit states "...Due to its power limitations, a Class 2 circuit considers safety from a fire initiation standpoint and provides acceptable protection from electric shock ."

My question regards the choice of doorbell button equipment. Do doorbell buttons that will be located in wet locations need to be listed for wet locations? With the exception of some newer wireless buttons, I haven't found a wired button that states it is for wet locations. Is there such a thing? Isn't it possible (even at 30 V) that under the right conditions a significant shock could occur?

Take this into account. According to NIOSH literature, wet skin can have a resistance of only 1000 ohms and 30 milliamps is enough to cause a loss of muscular control. Therefore, a short in 30 V circuit in a wet location could result in a 30 mA current flowing through some unfortunate person's body.

I know this scenario is not probable...but as far as safety is concerned, I'm only interested in the possible.

 

[hbiss]

Re: Class 2/UL 1585

Neither side of a doorbell secondary circuit is normally connected to ground. Therefore if the shell of the button were to become connected to one of the conductors there could be no shock hazard.

 

[pierre]

Re: Class 2/UL 1585

Because one side of the button is not connected to ground does not mean that a shock potential is not possible. I myself have never seen a doorbell rated at 30v, but that doesn't mean there are not any available. I would say that a shock hazard for a 30v doorbell button could be possible, especially during stormy weather in exposed locations. Most doorbells that I know of are 12 - 16 volts and I believe this is intentional for safety reasons just as Jem has mentioned.

Pierre

 

[jemsvcs]

Re: Class 2/UL 1585

I agree Pierre. Especially since the person's body would be acting as ground. I also realize that most doorbells are in the 12 to 16 V range. However, NIOSH still list the muscle 'freezing' range from electric shock at 9 to 30 mA for men so it would still be possible.

Still trying to find if there are any wired doorbell buttons rated for wet locations.

 

[hbiss]

Re: Class 2/UL 1585

Yes, I left out that most doorbell circuits operate at 12-16 volts not 30. You would really have to have some unusual circumstances for someone to get a tingle.

I suppose if you really wanted a water proof button get an oil tight button and put it in a NEMA box and be sure to run an equipment ground to the enclosure.