Hello, I'm Jake. This is my first post. I'm here to ask for a sanity check on a portion of our service panel load calculation.
I'm 51, retired (military) and getting into the trades. I'm currently in trade school (RSI) with my wife for HVAC/Electrician and we're having a blast (3 months in).
We're renovating our house and applying what we've learned as we go. Now it's time to run a service panel load calculation and apply for permits. Full disclosure, I'm about 60hrs into this self-inflicted exercise and it's finally starting to make sense. But I'd appreciate a third set of eyes.
I typed up my steps for future reference. This portion is specifically for just our HVAC and mini-split system. Does anybody see any glaring errors?
Step 1: Add compressor RLA and fan FLA to get total amps
25.6 + 1.2 = 26.8A
Step 2: Add 125% to get conductor size (ampacity) requirement
26.8 x 125% = 33.5A (note: this about matches the MCA on the nameplate)
Step 3: Multiply compressor total amps by volts to get VA (watts)
26.8 x 240 = 6,432VA
Step 4: Multiply AHU FLA by volts to get VA (watts)
6 x 240 = 1,440VA
Step 5: Add compressor and AHU VA to get total VA
6,432+1,440 = 7,872VA
Step 6: Now do the same for the Mini-Split
Since RLA/FLA are not given, divide MCA by 1.25 to get total amps (this removes the added 25% safety margin to give us the FLA/RLA rating)
25 / 1.25 = 20A
Note: the head units (AKA evaporators, AKA air handing units) get power from the condenser in this system. So the amps listed on the head units are already computed in the total amps, 20A in this case.
Multiply total amps by volts to get VA (watts)
20 x 240 = 4,800VA
Step 7: Add total VA of the Compressor/Air Handling Unit (AHU) and the Mini-split to find total service panel electrical load
7,872+4,800 = 12,672VA
Step 8: Enter 12,672VA at 100% into the service load calculation
This is all our data on the nameplates:
AC Condenser Unit (5-Ton)
Nameplate Data
208-230V (240V)
Max Fuse / Circuit Breaker: 50A
Compressor:
RLA 25.6 (running load amps)
LRA 150 (locked rotor amps)
Fan Motor:
1/4HP
FLA 1.2 (full load amps)
MCA 33.2 (minimum circuit ampacity)
*This is only used to spec wire size, and it includes an added safety margin (usually 25%)
Air Handler Unit (AHU)
Nameplate Data
208/230V (240V)
3/4HP
FLA 6
Mini-Split Condenser
Nameplate Data
208/230V (240V)
Rated input 20.5A
MCA 25A
Max Fuse 40A
One last question... The name plate on our AHU doesn't list any heating elements. Does that mean our system is a heat pump?
I'm 51, retired (military) and getting into the trades. I'm currently in trade school (RSI) with my wife for HVAC/Electrician and we're having a blast (3 months in).
We're renovating our house and applying what we've learned as we go. Now it's time to run a service panel load calculation and apply for permits. Full disclosure, I'm about 60hrs into this self-inflicted exercise and it's finally starting to make sense. But I'd appreciate a third set of eyes.
I typed up my steps for future reference. This portion is specifically for just our HVAC and mini-split system. Does anybody see any glaring errors?
Step 1: Add compressor RLA and fan FLA to get total amps
25.6 + 1.2 = 26.8A
Step 2: Add 125% to get conductor size (ampacity) requirement
26.8 x 125% = 33.5A (note: this about matches the MCA on the nameplate)
Step 3: Multiply compressor total amps by volts to get VA (watts)
26.8 x 240 = 6,432VA
Step 4: Multiply AHU FLA by volts to get VA (watts)
6 x 240 = 1,440VA
Step 5: Add compressor and AHU VA to get total VA
6,432+1,440 = 7,872VA
Step 6: Now do the same for the Mini-Split
Since RLA/FLA are not given, divide MCA by 1.25 to get total amps (this removes the added 25% safety margin to give us the FLA/RLA rating)
25 / 1.25 = 20A
Note: the head units (AKA evaporators, AKA air handing units) get power from the condenser in this system. So the amps listed on the head units are already computed in the total amps, 20A in this case.
Multiply total amps by volts to get VA (watts)
20 x 240 = 4,800VA
Step 7: Add total VA of the Compressor/Air Handling Unit (AHU) and the Mini-split to find total service panel electrical load
7,872+4,800 = 12,672VA
Step 8: Enter 12,672VA at 100% into the service load calculation
This is all our data on the nameplates:
AC Condenser Unit (5-Ton)
Nameplate Data
208-230V (240V)
Max Fuse / Circuit Breaker: 50A
Compressor:
RLA 25.6 (running load amps)
LRA 150 (locked rotor amps)
Fan Motor:
1/4HP
FLA 1.2 (full load amps)
MCA 33.2 (minimum circuit ampacity)
*This is only used to spec wire size, and it includes an added safety margin (usually 25%)
Air Handler Unit (AHU)
Nameplate Data
208/230V (240V)
3/4HP
FLA 6
Mini-Split Condenser
Nameplate Data
208/230V (240V)
Rated input 20.5A
MCA 25A
Max Fuse 40A
One last question... The name plate on our AHU doesn't list any heating elements. Does that mean our system is a heat pump?