Is it OK to mount the disconnect on the rooftop unit? I think it is a bad idea, even if permissible. But, there is no existing mounting rack on the roof, and fabricating one would mean securing it to the roof, which would potentially cause leaks in the future.
I think John's reasoning for it not being a good idea is in the event the chassis of the unit were to become energized or the unit were to catch fire the disco may become untouchable.
#36501 - 04/08/0411:11 AMRe: Rooftop unit follow-up
Not that it makes it right or wrong but I have mounted a gazillion disco's to RTU's. Mounted directly to the unit on large units and various strut set-ups on others. The only issues I have had are: Do not mount to access covers. Do not mount over name plates. Do not screw into internal coils .
#36502 - 04/08/0412:07 PMRe: Rooftop unit follow-up
When I worked at a local grocery store chain, I remember seeing several disco's mounted towards the corner of the units - the idea being, if the case becomes "hot", one can D/C the power by using a hot stick / "broom" stick, or other nonconductive means.
The D/C is also visible from 2 sides, and I've seen the units labeled with yellow and black "caution" style labels as to where the D/C's were, as well as information as to which panel they were being fed from.
Not a code requirement, of course, but a good idea nontheless.
#36504 - 04/08/0407:25 PMRe: Rooftop unit follow-up
Triple beat me to it. If everything's grounded properly, the disconnect's housing would be hot if the RTU cabinet was no matter how far away it was mounted.
And if it's right on the unit, The HVAC guy (That's usually me) never has to wonder if he's turned off the right switch. And do us a favor, mount your switch right above the equipment's data plate. When they're exposed to the sun and rain they fade so bad we can't read them but everytime I see a data plate under the disco, the plate looks like the day it was made.
#36506 - 04/08/0407:37 PMRe: Rooftop unit follow-up
I do, however, like to mount the disconnect separate from the unit to facilitate that units removal/replacement in the future. Most of the time this is not very practical without a good deal of additional labor. Thus the disco gets screwed to the side of the rooftop unit.
#36507 - 04/08/0407:48 PMRe: Rooftop unit follow-up