SCCR and Voltage question

[RexV24]

Hi Guys,

I have a question. I am currently working in the HVAC field and ETL told me that we need to tag our units with a nameplate stating the SCCR and maximum voltage.

I don't know much about this topic, but I figured out our SCCR is 5 KA, but am unsure what to put for the maximum voltage. Even though our units are mainly 460 volts, I am guessing the V Maximum is at 600V.

Could you guys please clarify for me. I would need to order a lot of plates and it is costly so i do not want to make a mistake.

Thanks,

 

[Jraef]

Hi Guys,

I have a question. I am currently working in the HVAC field and ETL told me that we need to tag our units with a nameplate stating the SCCR and maximum voltage.

I don't know much about this topic, but I figured out our SCCR is 5 KA, but am unsure what to put for the maximum voltage. Even though our units are mainly 460 volts, I am guessing the V Maximum is at 600V.

Could you guys please clarify for me. I would need to order a lot of plates and it is costly so i do not want to make a mistake.

Thanks,

Your nameplate must show the maximum voltage it is intended to operate at, not the maximum rating of the components inside.

By the way, 5kA SCCR is the "freebie" rating that can be applied without testing or even much thought. That sort of thing drives electricians nuts when it arrives in the field, because that is hardly EVER adequate, especially on a 480V installation. That means the poor electrician must go through gyrations and extra cost to find a way to limit the AFC to less than 5kA. Be a man and get your stuff listed at a more reasonable level. Most power components are capable of more if you use the right combinations of devices and hire someone who knows how to calculate the overall SCCR correctly.

 

[augie47]

"That sort of thing drives electricians nuts when it arrives in the field"
Amen ! and inspectors.
I have 3 industrial jobs in progress where there have been numerous industrial control panels supplied with 5k rating. The customer has no idea and it ends up being that "damned inspectors fault."

 

[RexV24]

It is not like am trying do this the easy way. I wouldn't call it a freebie. We had claimed it to be something else, but ETL saw that we have a relay and circuit breaker in the system which is rated for 5KA so he said you have to go with a 5KA rating. I run 120V through the breaker from a transformer and the breaker says 5KA 277VAC. Since ETL has told me that my KA rating must be according to the lowest rating that I have, so he went off our circuit breakers. He said we need a nameplate on each unit specifying this amount and the maximum voltage. However, I do not know what the maximum voltage would be. Would it be the voltage of the unit motors which i usually run at 460V or would it be the voltage that i run that component off of which is 120V? I am not sure, and that is why i came to this forum for some help.

Thanks,

 

[Jraef]

It is not like am trying do this the easy way. I wouldn't call it a freebie. We had claimed it to be something else, but ETL saw that we have a relay and circuit breaker in the system which is rated for 5KA so he said you have to go with a 5KA rating. I run 120V through the breaker from a transformer and the breaker says 5KA 277VAC. Since ETL has told me that my KA rating must be according to the lowest rating that I have, so he went off our circuit breakers. He said we need a nameplate on each unit specifying this amount and the maximum voltage. However, I do not know what the maximum voltage would be. Would it be the voltage of the unit motors which i usually run at 460V or would it be the voltage that i run that component off of which is 120V? I am not sure, and that is why i came to this forum for some help.

Thanks,

Control circuit components don't count. Your ETL guy should have known that. The SCCR only relates to the POWER components in the panel. So if it is for 480V equipment, it is only the 480V circuit components that matter. When it comes to the Control Power Transformer for example, the PRIMARY fuses count, the secondary do not.

 

[bluesmoke...oops]

Control circuit components don't count. Your ETL guy should have known that. The SCCR only relates to the POWER components in the panel. So if it is for 480V equipment, it is only the 480V circuit components that matter. When it comes to the Control Power Transformer for example, the PRIMARY fuses count, the secondary do not.

In my experience that's fine as long as the control components are isolated from the power components with a barrier. If they are exposed to each other, the 5kA gets used.

And I so enjoy when that happens as well. Had an industrial 1000A, 480V furnace controller that was rated for 5kA. Near as I could figure it they wrapped the feeder around the 100,000 sq ft building about 5 times they would get the current down to an acceptable level using impedance. :lol:

 

[GoldDigger]

They would have gotten a better air core inductor if they just ran the feeder a lot more times around a small room.
But they would have to separate the phases for that to work
Underground duct bank maybe, with the two loops 20' apart?

 

[big john]

...Underground duct bank maybe, with the two loops 20' apart?

Only if they backfill the trench with iron ore.

 

[GoldDigger]

Only if they backfill the trench with iron ore.

Oh, this is California. I thought it was Minnesota where everything is iron ore.

 

[Jraef]

In my experience that's fine as long as the control components are isolated from the power components with a barrier. If they are exposed to each other, the 5kA gets used.

And I so enjoy when that happens as well. Had an industrial 1000A, 480V furnace controller that was rated for 5kA. Near as I could figure it they wrapped the feeder around the 100,000 sq ft building about 5 times they would get the current down to an acceptable level using impedance. :lol:

Don't laugh, but although that example is pretty extreme, I have to admit that I did this a few years ago, albeit at a much lower level. I ordered an MCC with 42kA bracing, 30kA AFC, for a greenfield project based on the transformer impedance and sizes of the 2 unit substations given to me. The MCCs got on site, we hooked them up, tested them etc. We were getting the final inspection and the AHJ caught a mistake. The HV contractor couldn't get the transformers in time, so he substituted larger ones for the same cost, but didn't think to let anyone else know and the AFC was now 45kA. All of the starters were rated 100kAIC and the Mains were 65kAIC thank goodness, but all of the smaller feeder breakers were at 35kAIC. I had to change out all those feeders, but I still had 42kA bracing on the bus bars, which is something that cannot be changed in the field. So I did dig a trench around the buildings and ran the feeder cable in loops, just to add the cable length for more wire resistance. It was expensive of course, (2 x 1200A feeds, more VD, etc.), but there was no room anywhere to put air core reactors, my only other viable option. The HV contractor ended up getting the bill for that, but it was a fight.