SPLIT TYPE AC UNIT OVERCURRENT PROTECTION

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RLMJR

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Electrical Engineer
I have a project -Installation of Split type AC unit including installation of power supply , it is in the code that we need to provide a disconnect switch in the area near the ACCU or AHU , (for servicing purpose) , the disconnect switch is commonly a non fusible disconnect connected from a circuit breaker from a panel board. however i see a lot of design that the disconnect switch is fusible with dual element time delay fuse. is there a reason for adding a fuse in the switch where in fact the code only requires a disconnect switch near the unit, and fuse will be a redundant of circuit breaker from the panel board and the overload protection of the AC unit itself or the (compressor motor itself) from the unit.

-when it is required to add a fuse in the system ? when it is not?

thank you in advance for the answers.
 
1) read the HVAC unit name plate. Some specify max OCPD, but others specify 'max fuse'. If a fuse is required by the manufacturers instructions, but the electrical panel has breakers, then a fused disconnect solves the problem.

2) if the circuit feeding the unit is oversized (say for future expansion or because of a modern higher efficiency replacement) then a fused disconnect might be used to match the newer requirements.

IMHO a fused disconnect outside is never strictly required, but might be the best design choice or required by other design choices.

Jon
 
Locally our EIs have not required anything beyond a wall switch for the interior AHU as they are protected by the outdoor condensing unit.
For the most part,, our inspectors don't even require a switch citing 430.109(B)(2)
 
We would cite 440.8 to say that the interior equipment of a split system does not require its own disconnect.
 
augie47 said:
Locally our EIs have not required anything beyond a wall switch for the interior AHU as they are protected by the outdoor condensing unit.
For the most part,, our inspectors don't even require a switch citing 430.109(B)(2)
Click to expand...
Wouldn't that be 430.109(C)(2)?
Unless you have a 2020, which I don't have.
 
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