Fred B
Senior Member
- Location
- Upstate, NY
- Occupation
- Electrician
New experience that hopefully can get a little guidance. Have to size a service loads that will be entirely related to 4 - five ton Geothermal heatpump and associated pumps and controls. The new service will be entire dedicated to these pumps and controls. Cant just add to existing house panel as it is currently 158A on a 200A service calculated load, 106A by turning on everything that was controllable.
The environmental company doing the install has given me numbers that add up to 214A for the pumps and all associated components. I also have the cut sheets for the motors that are showing all the questioned data. Now if I eliminate out of the count the motors that will never operate at the same time by only counting 1 of them, the real issue will be the 4 compressor motors and which numbers to use.
Now the question is for service sizing for the compressor motor loads given no two pump will ever start at same time how would you size the combined loads, by the RLA, FLA, MCA, OR LRA? Or would you use max fusing size for all 4 units? I am leaning to a blend of the RLA for 3 and LRA for just 1 as only one unit will ever start at any one time but all four could be running together at any given time? Using max fusing would push load to 280A on just those units. The environmental company numbers only used the RLA in the numbers they provided to total the 214A. Using the method that I am leaning to gives me 185A, and eliminating out of count redundant motors loads (some motors are set up as back up and only operate when the other matching one is not).
The environmental company doing the install has given me numbers that add up to 214A for the pumps and all associated components. I also have the cut sheets for the motors that are showing all the questioned data. Now if I eliminate out of the count the motors that will never operate at the same time by only counting 1 of them, the real issue will be the 4 compressor motors and which numbers to use.
Now the question is for service sizing for the compressor motor loads given no two pump will ever start at same time how would you size the combined loads, by the RLA, FLA, MCA, OR LRA? Or would you use max fusing size for all 4 units? I am leaning to a blend of the RLA for 3 and LRA for just 1 as only one unit will ever start at any one time but all four could be running together at any given time? Using max fusing would push load to 280A on just those units. The environmental company numbers only used the RLA in the numbers they provided to total the 214A. Using the method that I am leaning to gives me 185A, and eliminating out of count redundant motors loads (some motors are set up as back up and only operate when the other matching one is not).
