rtu

[mickeyrench]

can someone answer this ? we have an ac unit on the roof ,it has a disconnect switch built inside and if it is sized for short circuit protection . does the rtu need a disconnect on the outside for nec purpose? i plan to come up from the bottom of the unit from inside the roof curb and if i need the ds on the outside it maybe a problem. thanks.

 

[qcroanoke]

No, If I remember correctly,(code book is at work)
Code states disconnecting means can be mounted on OR a part of the unit.

 

[mdshunk]

The one's with the disco built in at the factory require no other local disconnect on the part of the electrician. That's the benefit of the built in disco. Some are coming through with built in recs also. Pretty nice.

 

[LarryFine]

Doesn't the allowance include a requirement that the built-in disco be accessible without having to remove an access panel or cover?

 

[mdshunk]

Doesn't the allowance include a requirement that the built-in disco be accessible without having to remove an access panel or cover?

Never really saw one on an RTU where you did have to remove a cover to get to it. Most of them have a flipper lid of some sort.

 

[charlie b]

. . . and if it is sized for short circuit protection. . . .

It need not be sized for short circuit protection. The purpose of the disconnect on or near the unit is to give the maintenance technician positive assurance that the unit is deenergized. Overcurrent or short circuit protection is the job of some other device(s), not the local disconnect.

 

[cloudymacleod]

isn't it that if u have a roof top unit that has its own disconnect inside the unit, still energized on the line side of that disconnect if u shut that disco off.so when a worker/person services that particular unit, there is still a harzard of getting electricuted by the line side of that disco inside the unit, even know the load side is dead. so by putting a disco outside the unit, to serve the manfacture units disco, could prevent any harm to that person servicing that unit. meaning that the outside disco would shut off the units manfactures disco inside, so there will be no electricity inside the unit at all. i could be wrong about this, just putting out a question.

 

[mdshunk]

isn't it that if u have a roof top unit that has its own disconnect inside the unit, still energized on the line side of that disconnect if u shut that disco off.so when a worker/person services that particular unit, there is still a harzard of getting electricuted by the line side of that disco inside the unit, even know the load side is dead. so by putting a disco outside the unit, to serve the manfacture units disco, could prevent any harm to that person servicing that unit. meaning that the outside disco would shut off the units manfactures disco inside, so there will be no electricity inside the unit at all. i could be wrong about this, just putting out a question.

I think the answer is no, but I'm not sure. I'm still reinstalling my eyeballs back in my head.

How safe do you want it? If you want to install a disco so that you can make the built-in dicso safe, why stop there? Why don't you put in a disco for your field installed disco, in case you ever need to work on that? While you at it, maybe an E-stop button too?

 

[donselectric]

i just did two and the ac guy ran his unistrut to hang the unit rite over my ko and ran his condenser lines across the access panel.. what a j/a....

 

[electrimate]

The built in disconnect is legal. If I know who the mechanical contractor is during the bid process, I can and find out if his units will have the disconnect. It can make a pretty big difference in the bid. I always state that those disconnects are provided by the mech. on the bid and that if not, I provide an adder.