Air handler unit in closet disconnect 2

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Trowbridge - Martin

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This is an update to earlier post:
An A.H.U. air handler unit is in a second floor hall closet space for itself. There is a disconnect (circuit brkr) in the garage main panel not within sight and more than 50 feet away from AHU. The AHU has a built in disconnect (circuit brkr) accessable on front of unit. Does there need to be an additional disconnect on the wall of the closet space prior to the unit also? The AHU built in disconnect works good for sevicing the unit but not at all when unit is replaced.
Please give code sections or just great comments. Thanks
 
There is nothing in the NEC that says you have to be able to replace unit by pulling disconnect. The same situation gets discussed every time someone mounts a disconnect on a rooftop unit. Thus meaning the unit cannot be changed by simply pulling the disco. I see no reason to have an additional disco,when your unit came with one
 
mcclary's electrical said:
There is nothing in the NEC that says you have to be able to replace unit by pulling disconnect. The same situation gets discussed every time someone mounts a disconnect on a rooftop unit. Thus meaning the unit cannot be changed by simply pulling the disco. I see no reason to have an additional disco,when your unit came with one
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I agree. When the unit gets replaced, LOTO breaker.
 
To me, the appropriate Code Article would be 424.19.
If that is the case one would have to select the appropriate section, A, B or C.
Guessing, I would say 424.19(C) is in play here and would permit the unit switch to be the disconnecting means but then one needs to select what type premises is involved per (C)(1) - (C)(4) as far as the need for additional disconnects.
 
augie47 said:
To me, the appropriate Code Article would be 424.19.
If that is the case one would have to select the appropriate section, A, B or C.
Guessing, I would say 424.19(C) is in play here and would permit the unit switch to be the disconnecting means but then one needs to select what type premises is involved per (C)(1) - (C)(4) as far as the need for additional disconnects.
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Good play Gus. So is the OCPD in the unit supplementary?
 
Dennis Alwon said:
Good play Gus. So is the OCPD in the unit supplementary?
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Million dollar question :)
Larger units will have true "supplementary overcurrent protection" where the heat banks are divided as required in 422.22(B) and are mentioned in 422.22(C).
IMHO, I look at the single device units we see everyday as having "unit switches" as every unit I have seen comes with a 60 amp size regardless of the OCP required.
Unfortunately the "is or is not" only muddies the water.
 
On smaller units the OCPD comes with the heat strip kits that are installed by the HVAC installer. If he installs a 10kw heater then you will have 60 amp breaker. If he installs a 5kw heater then you will have a 30 amp breaker. Or depending on the unit you can have a combination of 10s and 5s or 10s and 10s. Or he can go the cheap route and buy heaters without breakers (depending on the brand).
 
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