Roof Top Unit Local Disconnect

Status
Not open for further replies.
Our local city elcetrical inspector is interpreting NEC 440.11 to say that a local disconnect needs to be installed such that the entire air conditioning unit can be removed, including the housing. He insist that a separate disconnect be installed beyond the integral disconnect permitted in 440.14 to allow the roof top unit be pulled while avoiding the need to lock out the circuit breaker at the main panel.

Our interpretation of the NEC permits the iuse of an integral disconnect as stated in 440.14 which provides a local disconnect to service and remove the equipment that has been electrically connected but not the housing itself.

Can you help us determine which interpretation is correct?
 

mcclary's electrical

Senior Member
Location
VA
I believe he is misreading 440.11. I kinda see where he could stretch this article to THINK that's what it means, however, I think he's misinterpreting the wording.
 
Our local city elcetrical inspector is interpreting NEC 440.11 to say that a local disconnect needs to be installed such that the entire air conditioning unit can be removed...

By mounting the disconnect onto some other construction independent of the RTU sheetmetal?

This may be a local thing or a job spec, but in some parts of the country (NC and points south) this seems to be a common expectation whatever the NEC may be interpreted to say on the topic.
 

chris kennedy

Senior Member
Location
Miami Fla.
Occupation
60 yr old tool twisting electrician
Welcome to the Forum Bryan.

440.11 General.

The provisions of Part II are intended to require disconnecting means capable of disconnecting air-conditioning and refrigerating equipment, including motor-compressors and controllers from the circuit conductors.
If your disco is mounted the the RTU's enclosure, whats the problem.

Enclosure. The case or housing of apparatus, or the fence or walls surrounding an installation to prevent personnel from accidentally contacting energized parts or to protect the equipment from physical damage.
440.14 Location.
Disconnecting means shall be located within sight from and readily accessible from the air-conditioning or refrigerating equipment. The disconnecting means shall be permitted to be installed on or within the air-conditioning or refrigerating equipment.
I think this is poor design, but thats why we have LOTO.

Where are you located Bryan?
 

skeshesh

Senior Member
Location
Los Angeles, Ca
Disco means

Disco means

I'm pretty sure, as the other guys pointed out, that it's permitted per 440.14, but I usually like to mount the disconnect on a wall or pole close-by. I think in this way while the cost of wiring doesn't changes significantly, there is the advantage of disconnecting the unit from a distance should there be some major malfunction that causes flames, heat or fumes. Also, I'd like to ask the more experienced guys to correct me if I'm wrong, since maybe such a highly hazardous failure doesnt happen often enough to justify this practice.
 

nakulak

Senior Member
if someone wants you to go beyond the call of duty and make a safer installation which exceeds the requirements of the NEC, then that's great. but for the prices we are doing things, they get a feeder up thru the curb and any disco that will work. I like the integral discos and gfi's that the newer units have built in. your inspector is all wet.
 

skeshesh

Senior Member
Location
Los Angeles, Ca
if someone wants you to go beyond the call of duty and make a safer installation which exceeds the requirements of the NEC, then that's great. but for the prices we are doing things, they get a feeder up thru the curb and any disco that will work.

Yea I hear ya. Still in a bunch of project (i.e. gov't project, military projects) I do have a bit of a leeway and I'm talking about a short run to the closest wall or just a run to a pole-mount disco 6ft away or something like that. What I'm trying to figure out is if the scenario I'm thinkin of is completely out of the ballpark and its an absolute waste of money to do this, or does that kind of malfunction/failure happen often enough to justify the practice when the owner has the monetary means.
 
Yea I hear ya. Still in a bunch of project (i.e. gov't project, military projects) I do have a bit of a leeway and I'm talking about a short run to the closest wall or just a run to a pole-mount disco 6ft away or something like that.

Like on larger jobs with multiple RTU's being fed through conduit coming through it's own pitch pocket as opposed to the one offs like Nakulak described with feed coming up through the curb?


What I'm trying to figure out is if the scenario I'm thinkin of is completely out of the ballpark and its an absolute waste of money to do this, or does that kind of malfunction/failure happen often enough to justify the practice when the owner has the monetary means.
 

benaround

Senior Member
Location
Arizona
Yea I hear ya. Still in a bunch of project (i.e. gov't project, military projects) I do have a bit of a leeway and I'm talking about a short run to the closest wall or just a run to a pole-mount disco 6ft away or something like that. What I'm trying to figure out is if the scenario I'm thinkin of is completely out of the ballpark and its an absolute waste of money to do this, or does that kind of malfunction/failure happen often enough to justify the practice when the owner has the monetary means.

We are talking about roof top units with built-in disconnect(s), I don't see justification to

add another disconnect six feet away. You mention "closest wall or pole-mount" , so I

don't think we are on the same subject. If on the ground, the way you mentioned would

work for me !!
 

skeshesh

Senior Member
Location
Los Angeles, Ca
Disconnect

Disconnect

We are talking about roof top units with built-in disconnect(s), I don't see justification to add another disconnect six feet away. You mention "closest wall or pole-mount" , so I don't think we are on the same subject. If on the ground, the way you mentioned would work for me !!

Well, the OP was asking if its permitted to mount disconnects on the unit enclosure, which we all agreed on per 440.14. Then I extended a question about if failures that cause flames/heat/fumes/etc. happen often enough in a typical install to justify having the disconnect further from the unit enclosure. A lot of mfg's offer units with VFD+disconnect options which, you're right, are regularly mounted on the unit. However if your request, as I do sometimes, they will ship the starter/disconnect control box seperately if there's a preferrence other than unit-mount. What I'm tryin for figure out is have I been doing a good practice (meaning such failures as described above happen at least some of the time to justify the practice) or have I just been wasting money since such failures of equipment pretty much never happen.
 

benaround

Senior Member
Location
Arizona
Skeshesh,

To answer your question, it's a waste of time and money, the disconnect is not there for

emergency use, it is there as a service disconnect. If a RTU was on fire ( in over 40 yrs. I

have not seen it ) the last thing to do would be getting closer to the unit. I hope this is

not too harsh for you, it is not intended to be.
 

skeshesh

Senior Member
Location
Los Angeles, Ca
To answer your question, it's a waste of time and money, the disconnect is not there for emergency use, it is there as a service disconnect. If a RTU was on fire ( in over 40 yrs. I have not seen it ) the last thing to do would be getting closer to the unit. I hope this is not too harsh for you, it is not intended to be.

Yea, I figured I may be assuming a situation that pretty much never happens. Although my theoretical understanding of electrical engineering is decent, as a fresh-out-the-oven engineer (2 years exp. <<< 40 yrs.) I get schooled on daily bases by persons of greater experience, which pretty much includes all of my coworkers, contractors, clients and AHJs. Not only am I not offended, but I absolutely welcome ALL comments that can help me fill in the gaps in experience that is impossible to learn in school, so please don't hesitate to let me know anytime I'm making an assumption that is proven wrong by experience in the field.
 

raberding

Senior Member
Location
Dayton, OH
Occupation
Consulting Engineer
RTU disconnects

RTU disconnects

gotta always check the local codes and amendments. Somewhere in TX (San Antonio, maybe) the local amendments require the disconnecting means to be independently supported and in sight of the equipment. That means ot integral disco; no disco attached to the unit housing.
 

jusme123

Senior Member
Location
NY
Occupation
JW
make sure the integral disc opens all ungrounded conductors within the RTU,because sometimes the integral disc does not accomplish this and a separate disc is required
 
Status
Not open for further replies.
Top