Disconnect at flat roof.

[Prince Kuhio Plaza]

Aloha,
Our facility has a large number of roof mounted AC units.
Our question is:

Is there a minimum distance requirement from the bottom of the disconnect switch to the roof?

Most of the disconnects are more than 24" above the roof. However, there are a couple that are less than 12". One is 3" from the roof to the bottom of the switch. I've attached a picture of one in question.

Mahalo,
Tom

 

[iwire]

No minimum height requirement.

I doubt they will end up under snow.

 

[qcroanoke]

No minimum height requirement.

I doubt they will end up under snow.

Maybe lava.... ;0)

 

[kwired]

No minimum height requirement.

I doubt they will end up under snow.

Maybe lava.... ;0)

Gee guys, I read OP and before reading on, had same two thoughts, then saw those thoughts were already posted. I don't know if that is a good thing or a bad thing either.

 

[GoldDigger]

Gee guys, I read OP and before reading on, had same two thoughts, then saw those thoughts were already posted. I don't know if that is a good thing or a bad thing either.

I think the good thing is that you read the other replies before posting.

 

[mgookin]

I disagree. The mechanical code requires vertical clearance, that clearance being a function of the width of the equipment. And for this purpose, I would consider that disconnect to be part of the mechanical equipment, or system. The reason for this clearance is to allow the roofing contractor to replace or maintain the roof and to allow air & water to wash down the roof so you don't end up with a rotten area of roof. Consult the mechanical code. If it's not there it's in the building code, or maybe both. But I remember it originating in the mechanical code circa 2001-ish.

 

[iwire]

The mechanical code requires vertical clearance, that clearance being a function of the width of the equipment. And for this purpose, I would consider that disconnect to be part of the mechanical equipment, or system.

In my opinion the field installed disconnect is not under the mechanical code.

 

[mgookin]

I looked it up. Here's what I found in the Florida Building Code, the basis of which is the ICC codes.

1509.7 Mechanical units.

Roof mounted mechanical units shall be mounted on curbs raised a minimum of 8 inches (203 mm) above the roof surface, or where roofing materials extend beneath the unit, on raised equipment supports providing a minimum clearance height in accordance with Table 1509.7.

TABLE 1509.7 CLEARANCE BELOW RAISED ROOF MOUNTED MECHANICAL UNITS

WIDTH OF MECHANICAL UNIT (in.) / MINIMUM CLEARANCE ABOVE SURFACES (in.)
< 24 --- 14
24 < 36 --- 18
36 < 48 --- 24
48 < 60 --- 30
> 60 --- 48


For SI: 1 inch = 25.4 mm.

I think if you asked ICC or any other qualified interpretor of the code if a disconnect mounted on that mechanical equipment can be 1/2" above the roof, they're going to tell you to use this table. And common sense will tell you that as well.

Width of course is the narrower of the two horizontal dimensions (the other would be length which does not matter).

But this is for new construction. The photo in the OP shows about a 5" curb and it appears the disconnect is at or near the same elevation as the bottom of the mechanical equipment; common sense saying that's fine.

In new construction or new installs, please don't cut the roofer short; you'll be doing the owner a disservice.