HVAC wire sizing question

[SlackJawedYokel]

I have RTU that has a rating of 52 amps with an MCA of 52 amps. Going by the code it looks like I can use #6 thhn dual rated because the 75 degree rating is 65 amps and for a continuous load of 52 amps it meets the 80% correction factor. Is there something I am missing or does this work out just perfectly?

 

[SlackJawedYokel]

Sorry the MCA is 65 amps

 

[infinity]

Sorry the MCA is 65 amps

You'll need a conductor with a minimum ampacity of 65 amps. What is the wiring method? If it's conduit and wire or MC cable you can use #6 which has a 75° C rating of 65 amps. NM cable (60° C) would require #4 AWG conductors.

 

[Strathead]

I have RTU that has a rating of 52 amps with an MCA of 52 amps. Going by the code it looks like I can use #6 thhn dual rated because the 75 degree rating is 65 amps and for a continuous load of 52 amps it meets the 80% correction factor. Is there something I am missing or does this work out just perfectly?

What do you mean by the 80% correction factor?

 

[roger]

What do you mean by the 80% correction factor?

Another way of saying 125%

 

[infinity]

What do you mean by the 80% correction factor?

Another way of saying 125%

Neither of which are applicable to the conductor sizing in this a installation (but you both knew that).

 

[Deltaforce]

Temperature correction factor to apply still if ambient more than 30C

 

[Dennis Alwon]

I have RTU that has a rating of 52 amps with an MCA of 52 amps. Going by the code it looks like I can use #6 thhn dual rated because the 75 degree rating is 65 amps and for a continuous load of 52 amps it meets the 80% correction factor. Is there something I am missing or does this work out just perfectly?

The 65 amps mca has already calculated the 125% factor for the a/c unit. 52 amps x 1.25 = 65 amps. If the unit states 52 amps mca then you do not multiply by 125%. I am assuming the mca stated on the unit is 65 amps so your wire should match that based on either 60C or 75C depending on your wiring method.

 

[Strathead]

Neither of which are applicable to the conductor sizing in this a installation (but you both knew that).

And that is what I meant. What is it in this context.

 

[Little Bill]

I have RTU that has a rating of 52 amps with an MCA of 52 amps. Going by the code it looks like I can use #6 thhn dual rated because the 75 degree rating is 65 amps and for a continuous load of 52 amps it meets the 80% correction factor. Is there something I am missing or does this work out just perfectly?

What is the MOCP listed on the nameplate on the unit?