First, thanks to all for the excellent feedback on my earlier post regarding the appropriate size feeder for a 3 1/2 ton A/C compressor. I have run the #8 conductors, with 3/4 inch conduit and am now looking for some guidance on the installation of the disconnect at the compressor.
I have a few questions in regard to the disconnect box located on the side of the house, next to the A/C compressor.
Is there a standard height from grade?
Can this disconnect be installed on a pedestal or post, rather than affixed to the wall? (We will be re-siding within two or three years)
Is waterproof flexible conduit acceptable from the inside of the house to the disconnect, or must rigid conduit be used? (The old compressor used EMT conduit and a “cement tight” fitting)
Thanks in advance,
Scott
Replies
Don't know about the post issue -- probably would be legal, but it might get you into some grounding issues, etc.
What I would do though, if I was planning to reside in a couple of years, and was planning on using "permanent" (read flimsy) siding, is to make a mounting block that is cut into the existing siding (appropriately flashed) and which stands sufficiently proud of the surface that it will J-channel nicely when the time comes. The put the disconnect on that.
(If using "real" siding just surface-mount the box, and leave a little slack in the wall. It's easy to dismount the box and leave it hanging while residing. Just notch the siding around the wire and flash/caulk, or make a joint in the siding around the wire. Or, to really do it up right, take the box off entirely (with breaker disconnected) and drill a hole for the wire through the replacement siding piece.)
Our disconnect is fed through the wall by ordinary romex, going into the back of the box, then has flex running from there to the AC unit. Your local inspector may have some other preferences, however.
Thanks Dan!
I was considering a wooden post - likely a section of 4 by 6 - rather than a metal post, which could avoid the grounding concerns, and allow for easy re-siding.
I suppose simply removing the disconnect and re-installing once the siding is replaced is the most straight forward approach.
In this area, metal conduit is required, but I have seen flexible watertight as a substitute for rigid for the section from the interior of the house to the disconnect.
Thanks again, Scott
Odd that they require (relatively) rigid conduit vs flex. In the AC application, where the unit is apt to "migrate" over time, the flex would be more reliable.
I believe flex is required between the compressor and the disconnect. As someone said, vibration.
By "grounding concerns" I was referring to the possibility that some full-of-himself inspector would declare the disconnect to be a "panel" that needed its own ground rod.
Actually, an inspector would not require a grounding rod in any event. It would be viewed as a sub-panel, and as such would require a floating chassis ground, and to be grounded to the main panel.
switch has to be within five feet of compressor, in eye sight of compressor, cannot be a switch but a total disconnect, a two piece disconnect.
No, it has to be insite and within 50ft.And there are disconnects that are just switches.Note, that is by the NEC, not the RNEC.
My two compressors are set away from the house. Used a piece of cedar 4x4 left over from deck sunk into concrete (I know, the post will eventually rot out.) sticking about 3 feet out of ground. Mounted both disconnects on it. Electrical inspector had no complaints.