AC requires 40amp breaker but ac company installed a 35amp breaker

[olporr]

HVAC equipment doesn't specify min breaker sizes. Only min circuit sizes and max breaker sizes—what are those? The wire should be sized based on the MCA and the breaker based on the MOCP.

[Gregoire_Brun]

hello @olporr 

Could you please give us more details about your question ?

From where are you ? 

What are type of product you speak?

Thanks in advansed .

[Yarom · Accepted solution]

The AC might not require the maximum 40A of the type of HVAC unit. It could be a series of and you have a specific model of the series. For this reason, it is important to know the specific model so that you can know how much current is required.

As for the mcb rating, that depends on the wiring.  Breakers are designed to protect wiring from overheating. Based on the load (your HVAC unit), the correct wiring should be laid. This comes from the local or regional standards, following a table.

If your specific model only requires 35A, then the current draw on the cable will stop if there is an issue in the unit, causing a higher draw.

The correct way to look at the required breaker is to know the requirement of the load (HVAC unit in your case), the installed cabling data (AWG, length, type of cable) and use the data in the regional standards table (UL/NEC, or IEC or whatever it is if in some other country).

[johnfernandez]

The Minimum Circuit Ampacity (MCA) determines the wire size, and the Maximum Overcurrent Protection (MOCP) determines the breaker size. Ensure the wire meets MCA requirements and the breaker does not exceed MOCP. If the AC requires a 40A breaker per MCA, install a 40A breaker, not a 35A breaker.