Understanding Continuous Loads

[ndan305]

Does the continuous load factor of 125% apply to motor loads and AC equipment?

For example:
I have a panel with:
1x AC unit, using MCA and MOP on nameplate
1x 2 hp motor, using 1.25*FLC
1x combination motor (2 hp and 1 hp motor), using 1.25*FLC largest motor + FLC smaller motor

The three loads are continuous loads that can operate more than 3 hours. Do I add up all the loads and add 25% on top of it to size my feeder conductors and panel breaker?

Then going on to service loads feeding the panel.. add another 25% on top of what we added up so far? It seems like safety factor on top of safety factor.

Panel load = total continuous load*1.25
Service load = panel load*1.25

 

[david luchini]

The three loads are continuous loads that can operate more than 3 hours. Do I add up all the loads and add 25% on top of it to size my feeder conductors and panel breaker?

Add the FLC of all the motors, and add 25% of the largest motor.

That is the load on the panel. No additional adjustments needed.

 

[Eddie702]

Any HVAC equipment is a continuous load as far as i am concerned

 

[Knightryder12]

Any HVAC equipment is a continuous load as far as i am concerned

I wouldn't think all HVAC equipment is continuous load. If it takes 3 hours for your mechanical HVAC equipment to get back to your set-point, then something is wrong with your HVAC equipment.

 

[petersonra]

Any HVAC equipment is a continuous load as far as i am concerned

The code tells you what a continuous load is. If it doesn't routinely run for 3 hours continuously it's not a continuous load. It would be very rare for any HVAC equipment to run continuously except in a case where somebody left the door open or something else unusual happened.

 

[electrofelon]

Any HVAC equipment is a continuous load as far as i am concerned

Long story short, motors and HVAC are not continuous loads and are calculated differently (but have a similar 25% factor). See 220.3

 

[LarryFine]

I wouldn't think all HVAC equipment is continuous load. If it takes 3 hours for your mechanical HVAC equipment to get back to your set-point, then something is wrong with your HVAC equipment.

I could see it if it's the first heating or cooling of the season of a vacant house.

 

[Knightryder12]

I could see it if it's the first heating or cooling of the season of a vacant house.

Wow, that's a real stretch.

 

[LarryFine]

Wow, that's a real stretch.

Some cheap frugal people wait until the heat or cold is unbearable to turn on the A/C or heat, respectively.

 

[Tulsa Electrician]

What does HVAC stand for?
Heating, ventilation, Air conditioning.
I would say it depends on each.
I know of ventilation that's runs non stop and some that runs as long as the business is open.
Now for a house I have wired air handlers that run 24/7 and the heat/ cool run so many cycles an hour.

My compressor on my AC unit had ran for more than three hours just before it Locke up. Then my wall unit ran untill it was fixed.

 

[electrofelon]

Other than a curiosity question, it makes no difference either way.