Shackled Designer
Member
- Location
- Decatur, AL USA
By way of background, in my current planning, I have a panel with about half a dozen VFDs, all of which are 2 Hp or less (5 Amps max, usually not more than 3A). When installed without line reactors, the vendor specifies that these VFDs have an SCCR of only 5 kA, regardless of the other circuit protection used. With line reactors, the rating jumps to 65 kA.
My question has to do with spacing the several line reactors. For wall mounts, one reactor vendor recommends a clearance of about 6 inches (15 cm) above and below the reactor and 4 inches (10 cm) on either side. The stated concern in the installation literature is heat. Another vendor's literature recommends a minimum of only 1 inch (2.5 cm). Naturally, with as many reactors as I need to install, I am inclined to use the lower value for saving panel space.
Now the caveat in either case is that vendors recommendations are always subject to whatever electrical codes govern at a given installation. Using the NEC, I see in 470.3 that for low-voltage (<= 600VAC) reactors, some sort of thermal insulation is required where reactors are installed with less clearance than 12 inches.
So here are my questions:
1) Does 470.3 apply to my case as described (or is more information required)?
2) If the thermal insulator requirement does apply, do the 5 to 7 VFD reactors need to be insulated from each other as well as from surrounding equipment?
3) What constitutes an acceptable thermal insulator? After all, air itself can act as an insulator.
4) Is there any difference to the application of the code if my panel is in a cooled enclosure?
5) Is there another portion of the NEC that I need to consider for this particular issue?
I appreciate any good advice.
Shak
My question has to do with spacing the several line reactors. For wall mounts, one reactor vendor recommends a clearance of about 6 inches (15 cm) above and below the reactor and 4 inches (10 cm) on either side. The stated concern in the installation literature is heat. Another vendor's literature recommends a minimum of only 1 inch (2.5 cm). Naturally, with as many reactors as I need to install, I am inclined to use the lower value for saving panel space.
Now the caveat in either case is that vendors recommendations are always subject to whatever electrical codes govern at a given installation. Using the NEC, I see in 470.3 that for low-voltage (<= 600VAC) reactors, some sort of thermal insulation is required where reactors are installed with less clearance than 12 inches.
So here are my questions:
1) Does 470.3 apply to my case as described (or is more information required)?
2) If the thermal insulator requirement does apply, do the 5 to 7 VFD reactors need to be insulated from each other as well as from surrounding equipment?
3) What constitutes an acceptable thermal insulator? After all, air itself can act as an insulator.
4) Is there any difference to the application of the code if my panel is in a cooled enclosure?
5) Is there another portion of the NEC that I need to consider for this particular issue?
I appreciate any good advice.
Shak