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I am adding a mini split from the sub panel of my home to additional room I am adding . Mini split of 120 v, 9000 btu and 20 Ampacity. From panel to disconnect fuse box,my contractor installed 8/3 ( 8 gauge??) wire but mini split require 20 amp ( 20 ampacity) which should be Ok with 12 or 10 gauge wire. Is it ok to connect the this mini split with this 8 gauge wire to pass Vito inspection ? Wire length may be 20 ft.

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  • The only problem should be if the device connections are not made for(does not fit) or marked for 8 gauge.
    – crip659
    Nov 5, 2022 at 12:31

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Using the larger size wire will be OK. Make sure to use a 20 amp breaker or whatever the instructions call for. If the breaker or mini split connections won't handle the #8 AWG wire, use wire nuts and splice a piece of #12 or #10 to the #8 and connect the smaller wire to the devices

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  • Thanks .. is there any city code or national rules or code link I can read for more details ?
    – Zia
    Nov 5, 2022 at 13:02
  • @Zia you haven't specified which city or country you're in, so ...
    – brhans
    Nov 5, 2022 at 13:51
  • The NEC is sometimes difficult to read even for professionals. Try this: wiresizecalculator.net It will show you that the #8 wire chosen by your contractor is well over the minimum size for your usage.
    – RMDman
    Nov 5, 2022 at 13:52
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    Wires can always be larger than required for the current (but you may need to join to smaller wires depending on device terminal largest capacity - or not.)
    – Ecnerwal
    Nov 5, 2022 at 14:09
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    @Zia NEC 250.122(B). It specifically authorizes using larger wire than needed, but it specifies the ground wire being enlarged in proportion. On paper that would require #8 ground, but if you read the Handbook for the reason for the rule, it clearly does not apply here, and the AHJ should waive it. (the reason is that if you're enlarging hot wires to reduce voltage drop on a Very Long Run, you want ground to be able to flow enough current to trip the breaker.) Nov 5, 2022 at 18:43

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