AC Disconnect Size, 30 Amp or 60 Amp for a Condenser

A 30 A pullout disconnect is big enough for a condensing unit when it passes the two checks in NEC 440.12: an ampere rating of at least 115% of the compressor's rated-load current and the fan amps added together, and a horsepower rating that covers the unit's equivalent horsepower. Across Goodman's GSX16 line the first check stays under 29 A, but the 3.5-, 4- and 5-ton models work out to 5 hp, more than the 3 hp Bussmann's B221-30F pullout is rated for at 240 V, so they take a 60 A switch.

This guide works both 440.12 checks, amps and horsepower, from the NEC tables for all nine GSX16 models, then reads a Mitsubishi rating label from a thread on r/AskElectricians, where the replies split between 40 A and 60 A. Our free AC breaker size calculator gives the overcurrent range from a plate that prints RLA, fan FLA, MCA and MOCP, like the GSX16's, and the steps at the end add the switch check it leaves out.

What does NEC 440.12 ask of an AC disconnect?

Two ratings. The switch needs an ampere rating of at least 115% of the sum of the compressor's rated-load current, or branch-circuit selection current if that's greater, and the other loads it carries, such as the condenser fan. It also needs a horsepower rating at least equal to an equivalent horsepower you look up from the unit's running and locked-rotor currents in two NEC tables.

NEC 2008 § 440.12(A)(1)

"The ampere rating shall be at least 115 percent of the nameplate rated-load current or branch-circuit selection current, whichever is greater." - NFPA 70, as reproduced by Solar365, solar365.com

A condensing unit has a compressor and a fan on the same switch, so 440.12(B) for combination loads applies. You add the currents at the rated-load condition and take 115% of the sum. A permanent split-capacitor or shaded-pole fan counts at the full-load amps marked on the equipment (440.6(B)). The rule says "at least," so a switch rated higher than the minimum always passes this check. A listed non-fused motor-circuit switch without fuseholders is exempt from the ampere check if its horsepower rating covers the unit (Exceptions to 440.12(A)(1) and (B)(2)), and the horsepower check still applies.

The horsepower side comes from 440.12(A)(2) and (B)(1). You treat the combined running current and the combined locked-rotor current as one motor, find the horsepower each one matches in Table 430.248 and Table 430.251(A), and take the larger. That number has to be met "in complying with the requirements of 430.109," whose first listed type is "a listed motor-circuit switch rated in horsepower." The Bussmann B22 catalog lists that horsepower rating next to the amps. Section 430.109 also lists a molded case circuit breaker and a molded case switch, with no horsepower in their entries, so this guide sticks to pullout switches.

The quotes come from the 2008 NEC, since NFPA's free view of later editions needs an account. EC&M's December 2022 walkthrough of Article 440 by Mark Lamendola describes the same two checks, the 115% ampere rating and the equivalent horsepower under 430.109. Where a jurisdiction enforces the IRC electrical chapters, the 2021 and 2024 Table E4101.5 row for condensing units and heat pumps sets the within-sight location and gives no ampere or horsepower rating for the switch. Check the edition and amendments your inspector enforces.

How do you turn a nameplate into horsepower?

Look up the running current in Table 430.248 and the locked-rotor current in Table 430.251(A), take the next higher value in each, and use the larger horsepower. At 230 V single phase, a running current over 17 A or a locked-rotor current over 102 A puts the unit past 3 hp and into the 5 hp row, which allows up to 28 A running and 168 A locked rotor.

Here are the 230 V single-phase rows that matter for residential condensers. The 230 V column covers systems from 220 to 240 V, per the note on Table 430.248.

Then compare with the switch. Cooper Bussmann's B22 catalog page, a 2011 edition, rates the 30 A fusible B221-30F at 1.5 hp at 120 V and 3 hp at 240 V. The 60 A fusible B222-60F and the 60 A non-fusible B222-60NF are rated 3 hp at 120 V and 10 hp at 240 V. That catalog lists no 30 A non-fusible pullout. Other brands publish their own ratings, so read the label on the switch you're buying.

Which GSX16 sizes fit a 30 A switch?

Models up to the 0361F do, with the fan at its marked FLA and our assumed six times FLA as its locked-rotor current. Amps never rule out 30 A, since every model stays under 28 A. The 3.5-, 4- and 5-ton models come out at 5 hp, over the 3 hp, and the 3-ton 0371A passes both 440.12 checks but carries a 35 A maximum overcurrent device, more than a 30 A fusible switch holds.

The figures below come from Goodman's SS-GSX16 spec sheet, worked at 230 V. We count the fan at its marked FLA, which 440.6(B) allows for a permanent split-capacitor or shaded-pole fan, and Goodman's sheet doesn't name the fan type. If you count it at the Table 430.248 current for its horsepower instead, the 5-ton's ampere figure rises to 28.75 A, still under 30, but the 0371A's running current becomes 15.4 + 2.2 = 17.6 A, over the 17 A of the 3 hp row, so it lands on 5 hp and needs the 60 A switch.

The sheet prints no locked-rotor current for the fan, and Table 430.251(A) has no row below 1/2 hp. We used six times the fan's FLA for its locked-rotor current, an assumption of ours, and no row changes if you leave it out. If an inspector takes the 1/2 hp figure of 29.4 A for the fan, the 0361F and 0371A also land on 5 hp.

Take the 0481F. Its 19.2 A running current is over the 17 A of the 3 hp row, and its 112 A compressor locked-rotor current is over 102 A, so both tables land on 5 hp. A 30 A switch passes the 22.1 A ampere check and still fails on horsepower. The 60 A pullout's 10 hp rating covers it.

The last column also matters when the pullout's cartridges are the unit's protection. Goodman's note says to use "time-delay fuses or HACR-type circuit breakers of the same size as noted," so the 0371A's 35 A rating already needs a 60 A fusible switch, even though it passes both 440.12 checks. On the 208 V columns of the same two tables every model lands on the same horsepower.

What about the thread's 40 A and 67 A labels?

The Mitsubishi label prints no rated-load current, and 440.6(A) then points to the compressor's own nameplate, which the thread doesn't show. Taking the 30 A inverter input as a stand-in, our estimate, 115% of it is 34.5 A, over 30 A, so a 30 A switch is out. In Table 430.248, 30 A is a 7.5 hp current, inside a 60 A pullout's 10 hp, and the label gives no locked-rotor current to check.

The unit is a Mitsubishi PUZ-AK60NL, 208/230 V single phase, approved for HACR-type devices or time-delay cartridges. Its label lists 40 A on the "BREAKER" line, 67 A as "MAX. FUSE", a minimum circuit ampacity of 38 A, an inverter input of 30 A and two fan motors of 0.2682 hp. The poster read it as "40 amp min with a 67 amp max" and asked whether a 60 A device and disconnect was right.

Several replies went straight to the panel side. One said "40 amps times 125% overload equals 50 amps. So you need 50 amps minimum to the disconnect." That isn't the test in 440.12, which multiplies the unit's own currents by 115% and never starts from the overcurrent device. The poster also asked why a disconnect would be rated higher than the device in the panel. Because 440.12 sets a floor, a plain 60 A pullout such as the B222-60NF on a 40 A circuit passes it, and the 40 A device still protects the circuit. Bussmann's 60 A whip kits are another matter, since the catalog caps their upstream device at 30 A for the B222-60NF12W and 50 A for the B222-60NF34W.

The poster settled on 40 A in the panel and a 60 A disconnect at the unit, which matches what the label supports. Whether that 40 A line is the only size allowed or a starting point was argued in the thread, and the switch question doesn't depend on it.

Checking a nameplate with BuildSolver

Enter the nameplate MCA and MOCP in the AC breaker size calculator with the compressor RLA and fan FLA. For the GSX160481F it returns a standard size from 25 A to 40 A, and Goodman's note then asks for the 40 A size. The page doesn't size the disconnect, so run the two 440.12 checks below by hand before you pick 30 A or 60 A.

1. Copy RLA, LRA, fan FLA and MOCP off the unit's rating label, or the spec sheet for that exact model. Goodman's sheet says to "always check the S&R plate" on the unit being installed.
2. Add RLA and fan FLA, or the Table 430.248 current for a fan that isn't split-capacitor or shaded-pole, multiply by 1.15 and compare with the switch's ampere rating.
3. Find the horsepower for the running current in Table 430.248 and for the locked-rotor current in Table 430.251(A), take the larger and compare with the switch's horsepower marking at your voltage.
4. If the pullout's cartridges are the unit's protection, check that the MOCP fits a fusible switch of that rating.
5. Size the wire to the MCA with the AC wire size calculator, and place the switch within sight of the unit as covered in our guide to disconnect types for AC units.

Put your own plate's RLA, fan FLA, MCA and MOCP into the AC breaker size calculator, then check the horsepower marking on the pullout you plan to buy before you order it.

Sources

• NFPA 70, National Electrical Code 2008, Article 440, Sections 440.6, 440.12 and 440.14, as reproduced by Solar365: 440.6, 440.12 and the following page
• NFPA 70, National Electrical Code 2008, Article 430, Section 430.109 and Tables 430.248 and 430.251(A), as reproduced by Solar365: 430.109, Table 430.248, continued, Table 430.251(A)
• Mark Lamendola, EC&M article on NEC Article 440 air-conditioning and refrigerating equipment, part 2, December 6, 2022: ecmweb.com
• International Code Council, 2021 and 2024 International Residential Code, Chapter 41, Table E4101.5: 2021 and 2024
• Cooper Bussmann, Quik-Spec A/C Disconnects, Series B22, catalog page with disconnect and horsepower ratings, 2011: catalog PDF
• Eaton, B221-30F air conditioning disconnect product page: eaton.com
• Goodman, GSX16 split system air conditioner product specifications SS-GSX16: goodmanmfg.com
• Source question and label photo, r/AskElectricians, "What's the right size disconnect?": reddit.com

For estimation purposes only. A licensed electrician sizes, installs and signs off the circuit and the disconnect under the code and amendments your jurisdiction has adopted.