HVAC Calculations

[dadsterd]

I was always taught to size HVAC at 125%. Can you apply the largest motor rule to the feeder of a panel with multiple HVAC on it? Use the 125% of largest and 100% of the rest of the units? Any help will be greatly appreciated.
Thanks in advance.

 

[Dennis Alwon]

If I understand you correctly then you are on target.

 

[electrofelon]

I was always taught to size HVAC at 125%. Can you apply the largest motor rule to the feeder of a panel with multiple HVAC on it? Use the 125% of largest and 100% of the rest of the units? Any help will be greatly appreciated.
Thanks in advance.

You don't size HVAC at 125%. That is already build into the MCA on the data plate. If you have multiple HVAC on a feeder, you can deduct 25% of the largest compressor of each unit except the largest unit.

 

[Dennis Alwon]

You don't size HVAC at 125%. That is already build into the MCA on the data plate. If you have multiple HVAC on a feeder, you can deduct 25% of the largest compressor of each unit except the largest unit.

I think he is talking about the calculation for the feeder. You are correct you don't use the min cir. amp but if he is using the amp load then you do use 125%.

I have a feeling this is a test type question

 

[electrofelon]

I think he is talking about the calculation for the feeder. You are correct you don't use the min cir. amp but if he is using the amp load then you do use 125%.

I have a feeling this is a test type question

Yeah Dennis, a feeder. For multiple HVAC in a feeder, I add up the MCA, when deduct the extra 25% over count on all but the largest unit. Of course one could add up all the parts of each unit and count the largest motor out of the group at 125%, same thing.