HVAC general duty disconnects

[electro7]

I wanted to get opinions on if general duty disconnects are okay for HVAC units on top of a commercial roof? I don't see it being an issue myself for this application since they aren't subject to physical damage but wanted to get second opinions.

Thanks ahead of time!

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[electro7]

I read another post and started wondering about the start up amperage of the HVAC units exceeding the disconnect amperage rating which could possibly cause a failure in the future. Any thoughts?

 

[ron]

Typically disconnects for HVAC are selected based on the horsepower rating, not amperage.
Standard duty disconnects are code acceptable, but I typically choose heavy duty

 

[petersonra]

I wanted to get opinions on if general duty disconnects are okay for HVAC units on top of a commercial roof? I don't see it being an issue myself for this application since they aren't subject to physical damage but wanted to get second opinions.

Thanks ahead of time!

Sent from my SM-S918U using Tapatalk

what does "subject to physical damage" have to do with it?

 

[electro7]

Typically disconnects for HVAC are selected based on the horsepower rating, not amperage.
Standard duty disconnects are code acceptable, but I typically choose heavy duty

Got it, thanks.

 

[electro7]

what does "subject to physical damage" have to do with it?

I thought the Heavy Duty disconnects had a thicker gauge metal and were used in locations such as industrial manufacturing plants where they could be subject to physical damage. And I thought the general duty had a thinner gauge metal and could be damaged easier. Does that make sense? I must be mistaken. Let me know.

 

[grich]

I've had several general duty switches break on me. Nothing sadder than pulling a handle and having one phase blade still stuck in the jaws. I insist on heavy duty, assuming the innards are more robust than a general duty switch.

 

[petersonra]

I thought the Heavy Duty disconnects had a thicker gauge metal and were used in locations such as industrial manufacturing plants where they could be subject to physical damage. And I thought the general duty had a thinner gauge metal and could be damaged easier. Does that make sense? I must be mistaken. Let me know.

I think the HD switch are probably heftier than general duty switches. I don't think the code ever says anything about a HD switch being a requirement. it is a design choice.

 

[jim dungar]

I thought the Heavy Duty disconnects had a thicker gauge metal and were used in locations such as industrial manufacturing plants where they could be subject to physical damage. And I thought the general duty had a thinner gauge metal and could be damaged easier. Does that make sense? I must be mistaken. Let me know.

There are no NEC nor UL differences between Light Duty, General Duty nor Heavy Duty. These are simply marketing terms by manufacturers.

But, general duty are typically 250V max with limited enclosure selections such as Type 1 and Type 3R. Heavy Duty come in 250V and 600V and usually have more selections of industrial options like field accessories, defeatable door interlockles and enclosure like Type 12 and Type 4X. Light Duty are often cost reduced, such as thinner metal, targeted to 120/240V residential use..

These terms are similar to cords with 600V SO being called extra hard usage vs 250V SJ being called hard usage.