Minimum Circuit Ampacity

[lizzie14]

I'm working with an HVAC unit and the cutsheet lists RLA/FLA of the different motors and it also has a column for minimum circuit ampacity. Do I base the demand load for my panelboard on the MCA, or on 100% of the FLA plus 125% of the FLA of the largest motor? I understand that MOCP should be what's recommended but I'm a little confused on the MCA.

 

[sceepe]

Re: Minimum Circuit Ampacity

I use MCA but I'll be curious to see what other folks are doing. MCA will usually give you a little larger than you need.

Also don't forget the strip heaters they may or may not be listed in the info for the unit as they can be installed in the field. Makes it easier if the unit has factory installed heater and a single point power feed.

I also have had a problem with the strip heat kw ratings being at 240V but the unit voltage is 208V. Sometimes manufacturer will give you the "standard" heater that will operate at 85% of its rated kw on 208V or sometimes you will get a "custom" heater that will operate at 100% rated kw on 208V.

 

[lizzie14]

Re: Minimum Circuit Ampacity

Yeah I've normally used MCA but in this case it bumps us over to the next panel size and I wanted to save money if at all possible. Thanks for the insight.

 

[infinity]

Re: Minimum Circuit Ampacity

Use the MCA. The equipment manufacturer has already done the calculation for you as required by Article 440.

 

[lady sparks lover]

Re: Minimum Circuit Ampacity

I go for MCA they've done the work, just use what they give ya, then if it's undersized you will not be at fault.


Lady