Restaurant Kitchen GFCI and Panel Capacity
A 1,800 sq ft restaurant is served by a 208Y/120 V, 3-phase, 4-wire service. The kitchen contains a 50 A, 3-phase range; a 30 A, 208 V storage water heater; a 20 A, 120 V dishwasher receptacle under the counter; a 20 A, 120 V receptacle on the roof within 6 ft of a condensing unit; and a 20 A, 120 V receptacle 20 ft from the building for a pressure washer. None of the receptacles is GFCI protected. The owner wants to add a 30 A, 250 V receptacle for a commercial mixer and a 20 A, 120 V receptacle for a cash register. The panel has no spare spaces, and the electrician proposes using tandem breakers. The dishwasher is cord-and-plug connected; the water heater is hard-wired. The AHJ enforces the adopted NEC and Maine Chapter 120 without amendments.
1. Which existing receptacles require GFCI protection, and does the proposed 30 A mixer receptacle require it?
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GFCI is location-based, not appliance-based. Under 210.8(B), receptacles in commercial kitchens, on rooftops, and outdoors require GFCI protection where they are 125–250 V single-phase and 150 V or less to ground. That catches the 20 A dishwasher receptacle, the rooftop condensing-unit receptacle, the outdoor pressure-washer receptacle, and the proposed 20 A cash-register receptacle if it is in the kitchen. The proposed 30 A, 250 V mixer receptacle is a 125/250 V single-phase receptacle with 125 V to ground; it also requires GFCI protection, using a 2-pole GFCI breaker or a listed 30 A GFCI receptacle. The hard-wired water heater is not a receptacle, so 210.8(B) does not apply; it may still need other specific protection if the appliance listing requires it. Replace the existing non-GFCI receptacles or provide upstream GFCI breakers, and verify the GFCI is rated for the circuit and load.
2. Evaluate the tandem-breaker proposal and the branch-circuit requirements for the new mixer and cash register.
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Tandem breakers are not a load calculation. They are permitted only in panelboard spaces listed and marked for tandem or CTL use, and they do not increase the bus rating. A 30 A, 250 V mixer needs a 2-pole breaker; a tandem that shares one pole cannot supply 250 V. Before adding the mixer and cash register, perform an Article 220 load calculation for the existing restaurant and the new loads, check the service and feeder capacity, and verify the panel bus and main are not exceeded. The cash-register circuit must be GFCI if in the kitchen; the mixer circuit needs conductors and overcurrent sized to the nameplate and continuous/noncontinuous classification. If the panel has no listed spaces, add a subpanel or replace the panel; do not backfeed a tandem as a substitute.
3. The water heater nameplate says 30 A at 208 V. What minimum conductor and overcurrent protection are required?
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A storage-type water heater is a continuous load under 422.13. For a 30 A nameplate at 208 V, the branch-circuit conductors must have an ampacity of at least 30 × 1.25 = 37.5 A and the overcurrent device must be sized for the continuous load, generally 125% = 37.5 A, so a 40 A breaker is the next standard size. 8 AWG Cu with 75°C terminations has 50 A ampacity, so it satisfies the 37.5 A minimum; 10 AWG Cu at 75°C is 35 A and is not enough. Verify the actual nameplate and termination ratings; if the heater nameplate specifies a maximum overcurrent protective device, do not exceed it. The 40 A breaker and 8 AWG Cu are the minimum compliant set, assuming the calculated load and voltage drop are otherwise acceptable.