Calculating subpanel capacity

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Old 08-18-19, 03:10 PM
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Calculating subpanel capacity

I have a 200A main panel on the house feeding a subpanel that currently powers pool equipment and some minimal exterior lighting. The subpanel is fed with a 70A dual pole breaker in the main panel.

I want to add a circuit for a minisplit air conditioner to the subpanel. There is physical space for a breaker. How can I determine the remaining capacity?

In the subpanel I have the following breakers/loads:

15A breaker - Variable speed main pool pump motor - 240V labeled at 16A max but max draw is set to only 1200 watts. The pool guy replaced a 1hp pump with this 3hp pump (what he had on the truck) but dialed the speed way down when he installed it to provide similar flow to the one it replaced. It doesn't exceed 1200W and even has a soft startup (Pentair Intelliflo VSF). Do I need to consider the label max or what it really uses?

15A breaker - Single speed spa pump motor - 240V labeled at 11A max

15A breaker - Single speed water feature pump - 240V labeled at 6A max

15A breaker - Flood lights - 120V and approx 300W

15A GFCI breaker - In water pool lights - 120V and approx 750W

20A breaker - GFCI outlet

I know the 70A breaker can be changed out along with the conductors feeding the panel but what is the remaining capacity of the subpanel as it is now in its inspected, signed off configuration?

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Old 08-18-19, 04:08 PM
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There would be plenty of reserve capacity for a mini split A/C as they usually run on a 20A 240v circuit.
 
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Old 08-18-19, 05:28 PM
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The unit I'm looking at requires a 30A breaker with a 20A MCA. Three zone, 2 1/2 ton. I'm more interested in knowing the actual capacity so I don't get hung up when the inspector shows up.

Here it is: https://resource.gemaire.com/is/cont...bs.pdf?fmt=pdf

I know it would function but want to be able to justify the load calculation when I get a permit. My neighbor is a real piece of work, let's leave it at that. I saw another unit that used a 40A breaker, 30A MCA. Still safe?
 
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Old 08-18-19, 05:48 PM
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A load calculation is add up all the loads.
You have a 70A sub panel and less than 30A of connected load.

That spec sheet leaves a little speculation. It shows what the outside unit draws but doesn't really address the inside units. I'm guessing that three 9k inside units along with the outside unit will require the 20A operating load and the 30A protection.
 
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Old 08-18-19, 06:38 PM
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The outdoor unit is the only component that's connected to the breaker. Like most other minisplits, the indoor units receive their power from the outdoor unit and draw around 1A each.
 
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Old 08-19-19, 10:04 AM
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load calc

do not forget to check the main panel for load calc's as well. Just because the 70 amp panel is ok does not mean the the main panel has the reserve available. Have you considered voltage drop? Turn on your pool equipment and measure the voltage. equal to or greater than 120, 240 is great. The code allows a 5% drop to the last device.
The inverter system in the ac will make up any differences, but why make it work harder?
 
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