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#36498 - 04/08/04 05:03 AM Rooftop unit follow-up
Redsy Offline
Registered: 03/28/01
Posts: 2138
Loc: Bucks County PA
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.


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#36499 - 04/08/04 06:07 AM Re: Rooftop unit follow-up
Bomzin Offline
Registered: 03/25/04
Posts: 27
Loc: Utah
Yes it's ok, usually mounted right on the unit itself. Why would it be a bad idea, worse idea not to have one.

#36500 - 04/08/04 07:49 AM Re: Rooftop unit follow-up
Mean Gene Offline
Registered: 10/20/03
Posts: 137
Loc: Ohio, USA
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 - 04/08/04 08:11 AM Re: 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 - 04/08/04 09:07 AM Re: Rooftop unit follow-up
Ryan_J Offline
Registered: 08/19/03
Posts: 1355
Loc: West Jordan, Utah, USA
Ryan Jackson,
Salt Lake City
#36503 - 04/08/04 04:15 PM Re: Rooftop unit follow-up
DougW Offline
Registered: 06/08/03
Posts: 1083
Loc: North Chicago, IL
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 - 04/08/04 04:25 PM Re: Rooftop unit follow-up
triple Offline
Registered: 04/01/02
Posts: 182
Loc: Wisconsin
Kentvw said it best. Follow those directions and you can't go wrong.

If you wire/ground correctly, how can the "case" become hot? If it is not wired correctly then no procedure for disconnect placement is going to make the set-up safe.
#36505 - 04/08/04 04:35 PM Re: Rooftop unit follow-up
maintenanceguy Offline
Registered: 12/02/01
Posts: 303
Loc: Southern NJ, USA
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 - 04/08/04 04:37 PM Re: Rooftop unit follow-up
triple Offline
Registered: 04/01/02
Posts: 182
Loc: Wisconsin
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 - 04/08/04 04:48 PM Re: Rooftop unit follow-up
Redsy Offline
Registered: 03/28/01
Posts: 2138
Loc: Bucks County PA
I was thinking in terms of replacing the condensing unit, and having the disconnect flopping around on the ground in the meantime.
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