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Rooftop unit follow-up #36498 04/08/04 08:03 AM
Joined: Mar 2001
Posts: 2,056
Redsy Offline OP
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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Re: Rooftop unit follow-up #36499 04/08/04 09:07 AM
Joined: Mar 2004
Posts: 28
Bomzin Offline
Yes it's ok, usually mounted right on the unit itself. Why would it be a bad idea, worse idea not to have one.


Re: Rooftop unit follow-up #36500 04/08/04 10:49 AM
Joined: Oct 2003
Posts: 152
Mean Gene Offline
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.

Re: Rooftop unit follow-up #36501 04/08/04 11:11 AM
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 [Linked Image].

Re: Rooftop unit follow-up #36502 04/08/04 12:07 PM
Joined: Aug 2003
Posts: 1,374
Ryan_J Offline

Ryan Jackson,
Salt Lake City
Re: Rooftop unit follow-up #36503 04/08/04 07:15 PM
Joined: Jun 2003
Posts: 1,143
DougW Offline
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.

Re: Rooftop unit follow-up #36504 04/08/04 07:25 PM
Joined: Apr 2002
Posts: 189
triple Offline
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.

Re: Rooftop unit follow-up #36505 04/08/04 07:35 PM
Joined: Dec 2001
Posts: 300
maintenanceguy Offline
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. [Linked Image]

Re: Rooftop unit follow-up #36506 04/08/04 07:37 PM
Joined: Apr 2002
Posts: 189
triple Offline
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.

Re: Rooftop unit follow-up #36507 04/08/04 07:48 PM
Joined: Mar 2001
Posts: 2,056
Redsy Offline OP
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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