conductor sizing vs. breaker sizing

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lkapigian said:
Ok, they faxed me Article 240.4 item 2 as the reason we have to match breaker with wire size- I don't understad how this comes into play with 440

Thanks

Larry!!
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FAX 240.5(G) back to him with Table 240.4(G) and circle the part where 440, Parts III and IV are shown to apply to air-conditioning and refrigeration equipment circuit conductors.
 
Here, cut'n'paste this:

240.4 Protection of Conductors. Conductors, other than flexible cords, flexible cables, and fixture wires, shall be protected against overcurrent in accordance with their ampacities specified in 310.15, unless otherwise permitted or required in 240.4(A) through (G).

(G) Overcurrent Protection for Specific Conductor Applications. Overcurrent protection for the specific conductors shall be permitted to be provided as referenced in Table 240.4(G).



Next, find a way to copy this image:

Table%20240.4G.jpg




Then, copy'n'paste this:

III. Branch-Circuit Short-Circuit and Ground-Fault Protection
440.21 General. The provisions of Part III specify devices intended to protect the branch-circuit conductors, control apparatus, and motors in circuits supplying hermetic refrigerant motor-compressors against overcurrent due to short circuits and grounds. They are in addition to or amendatory of the provisions of Article 240.
 
You guys are amazing- Thanks so much for all the help- I have sent all the info applicable, and will wait and see the outcome---- Thanks again!!!
 
Well the final verdict- we are not allowed to over size the OCP- Size the wire to the MCA and match the OCP to that and no more- They say just make sure we are using HACR breakers which all breakers now are HACR------We have had this issue put on the agenda with the chief building inspector and do my best- Our market is mainly A/C upgrades ( no new construction) been adding/ replacing units for years and only had this problem now- I know the MCA gies us a litle cushion from the real FLA but I am sure we are going yo have some trip issues
 
lkapigian said:
Well the final verdict- we are not allowed to over size the COP- Size the wire to the MCA and match the OCP to that and no more- They say just make sure we are using HACR breakers which all breakers now are HACR------We have had this issue put on the agenda with the chief building inspector and do my best- Our market is mainly A/C upgrades ( no new construction) been adding/ replacing units for years and only had this problem now- I know the MCA goes us a Little cushion from the real FLA but I am sure we are going yo have some trip issues
Click to expand...


I feel sorry for you since you have to deal with officials who have such poor knowledge of the electrical code. If they really want to learn something they should try posting here, but my guess is that they really don't want to learn anything since they likely know it all.

If they can so easily screw up something as rudimentary as OCPD for AC units I can't imagine what they would do with an installation that was actually complex.
 
310.16 Asterisks

310.16 Asterisks

OK I have read the sections enough to make my mind numb-------The asteriskx on table 310.16 whiche directs us to 240.4 (D) the wire size listed are 14,12 and 10----- am I sill alowed to use 240.4(G) on wires over that size?-----I just want to make sure all I have learned here will apply in most of what we see- Residental HVAC units up to 5 tons-Thanks again
 
Rob,

"my guess is that they really don't want to learn anything since they likely know it all."

Well, I used to but I've forgotten most of it and now have to relearn some things again and again and again and again.:grin: :D
 
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