Proposal for contractor review · 120 V, 20 A branch circuits

Garage Circuits Proposal

Three new, independent 20 A circuits from the existing panel, each about 100 ft. Two feed locking ceiling outlets for desks in the garage. One feeds an exterior outlet for occasional outdoor use.

The plan

Circuit	Breaker	Wire	Run	Ends at
1 · Desk 1	20 A single-pole, GFCI; AFCI per local code	12/2 copper NM-B with ground	~100 ft	Garage ceiling, NEMA L5-20R locking receptacle
2 · Desk 2	20 A single-pole, GFCI; AFCI per local code	12/2 copper NM-B with ground	~100 ft	Garage ceiling, NEMA L5-20R locking receptacle
3 · Outdoor outlet	20 A single-pole, GFCI	12/2 copper NM-B with ground	~100 ft	Exterior 20 A tamper- and weather-resistant duplex, in-use cover

Panel: GE PowerMark Gold, 200 A main, 120/240 V single phase. Its label lists the THQL and THQLGF breaker families. Three full-size spaces appear to be free.

Wiring

New 12/2 NM-B run Removable cord, already purchased 1Contractor to verify (see list below)

Each circuit has its own breaker and its own run; nothing is shared between the two desks or the outdoor outlet. Numbered flags mark the four places the contractor needs to check.

For the contractor to check

1Panel. Exact breaker models for GFCI and any required AFCI protection; usable spaces; service load with three added circuits; available fault current and series rating.
2Runs. Voltage drop on 100 ft of 12 AWG (numbers below). Cable support and protection through the attic.
3Ceiling outlets and cords. Box support and sizing for the L5-20R; an independent strain-relief grip for each cord anchored to framing; clearance from the door and its travel; whether a cord drop to a desk is acceptable to the inspector under NEC 400.10 and 400.12.
4Brick entry. How the cable passes through the brick into the back of the box, protected from abrasion and water; whether it must change to wet-rated wiring there.
?Permit. Whether a permit is needed, whether a homeowner can pull it, and which inspections apply.

Voltage drop at 100 ft

12 AWG copper, 100 ft each way, 120 V, using NEC Chapter 9 Table 8 resistance at 75 °C. The usual target is about 3% for a branch circuit.

Load	Amps	Drop
Desk, typical computer and monitors	5	1.9 V · 1.6%
Desk, busy	8	3.1 V · 2.6%

At desk loads, 12 AWG stays under 3% on these runs. Actual run lengths decide.

Planned and already decided

Item	Status
Three independent 120 V, 20 A circuits	Planned
12/2 copper NM-B with ground, routed through the accessible attic	Planned
Two NEMA L5-20R locking receptacles in the garage ceiling (8.25 ft)	Planned Box and support
Two Conntek 8FL520520 cords: 8 ft, 12/3, L5-20P to 5-15/20R	Purchased
Desks away from the walls; no cord reels or recessed cabinets	Decided
Exterior 20 A TR/WR duplex in a weatherproof metal box, extra-duty in-use cover	Planned Brick entry detail
No living space above the garage; spray foam at the roof deck	Existing
Breaker models and AFCI requirement	Contractor

Materials

Prices and stock were read from each store’s website on Oct 10, 2026, for The Home Depot SE Austin (78704) and Lowe’s S.E. Austin (E. Stassney Ln.). Items in italics are only needed if the contractor calls for them.

Qty	Item	The Home Depot	Lowe’s alternative
2	12/2 solid Romex NM-B with ground, 250 ftAll three runs	Southwire 28828269$155.00 · 35 in stock · aisle 45, bay 17	Southwire Romex SIMpull$155.00 · 56 in stock
2	NEMA L5-20R locking receptacle, 20 A 125 VCeiling outlets	ELEGRP L0520RL$19.99 · Ship to store, Oct 16–19	Hubbell Kellems L5-20R$54.81 · Online seller, ships Oct 19
1	Single locking-receptacle plate, 1.60 in. hole, stainless (2-pack)Ceiling outlets	ELEGRP 88SBS-SS2$10.00 · Ship to store, Oct 16–19	Same ELEGRP plate$26.99 · Online seller, ships Oct 19
2	1-gang 18 cu. in. PVC new-work boxCeiling outlets	Carlon B118A$0.92 · 905 in stock	Cantex 18 cu. in.$0.92 · 1,228 in stock
1	1-gang metal weatherproof box, three ½ in. holesExterior outlet	Commercial Electric WSB350G$5.95 · 170 in stock · aisle 45, bay 6	Sigma metal box$5.98 · Pickup Wed, Oct 14
1	20 A tamper- and weather-resistant duplex receptacleExterior outlet	Leviton TWR20-Y$19.54 · Ship to store, Oct 16–19	Eaton TR/WR commercial$9.08 · 17 in stock
1	Extra-duty in-use cover, 1-gangExterior outlet	Commercial Electric WCWR1PG$9.98 · 83 in stock · aisle 45, bay 6	TayMac Extra Duty, clear$11.28 · 44 in stock
3	20 A single-pole GFCI breaker, self-test, THQLPanel, one per circuit	ABB (GE) THQL1120GFTA$72.77 · 14 in stock	ABB (GE) 20 A GFCI$72.98 · Pickup Thu, Oct 15
1	½ in. insulated staples for 12/2, 100-packSecuring the runs	Gardner Bender MDI-150Y$5.21 · 7 in stock	Gardner Bender plastic insulated$5.48 · 7 in stock
1	⅜ in. NM snap-in connectorsPanel knockouts (3)	Commercial Electric, 5-pack$3.58 · 68 in stock · aisle 45, bay 14	Sigma ProConnex, 10-pack$5.78 · 23 in stock
1	⅜ in. NM clamp connector with locknutExterior box entry	Halex 20511, 5-pack$4.62 · Ship to store, Oct 13–16	Sigma die-cast clamp, 10-pack$5.68 · 5 in stock
2	Woven cord support grip with eye, fits ~0.45 in. cordCord support at each ceiling outlet	Flexcor FCSD40, 0.40–0.56 in.$17.49 · Ship to store, Oct 16–19	Hubbell Kellems, 0.41–0.50 in.$34.95 · Online seller, ships Oct 19
2	Heavy screw hook into a joistHanging the grips	Ceiling hook, 110 lb, 10-pack (buy 1)$11.66 · Ship to store, Oct 15–16	Hillman 4.94 in. hook$1.98 · 12 in stock
1	Duct seal compoundSealing the brick penetration	IDEAL 31-601, 1 lb$5.97 · 23 in stock · aisle 44, bay 14	Gardner Bender 16 oz$5.48 · 9 in stock
3	If AFCI is required, instead of the GFCI breakers: 20 A dual-function AFCI/GFCI breakerPanel	GE THQL1120DFP$59.99 · Not at SE Austin; limited at Austin Mueller	ABB (GE) dual function$74.98 · 5 in stock
2	If the ceiling is drywalled, instead of the new-work boxes: 1-gang PVC old-work boxCeiling outlets	Carlon B120R, 20 cu. in.$3.98 · 251 in stock · aisle 45, bay 11	Cantex old-work$1.98 · 472 in stock
1	If the exterior end must be wet-rated: 12/2 UF-B with ground, 25 ftExterior entry	Southwire 13055921$59.00 · 2 in stock · aisle 45, bay 15	Southwire 25 ft UF-B$60.98 · 5 in stock
1	If a sleeve through the brick is wanted: ½ in. × 10 ft Schedule 40 PVC conduitExterior entry	JM Eagle 67447$5.97 · 253 in stock · aisle 45, bay 2	Cantex ½ in. Sch 40$5.97 · 230 in stock · aisle 12, bay 8
1	For that sleeve: ⅞ in. SDS-Plus masonry bit (needs a rotary hammer)Exterior entry	Milwaukee 48-20-8328$39.87 · Ship to store, Oct 13–16	Bosch Bulldog Tough$39.98 · 1 in stock

Everything except the italic items: about $682 at The Home Depot or $790 at Lowe’s, before tax. Wire and breakers are $528 of it at either store. Measure the cord’s outside diameter before buying grips.

Where to shop

Totals for everything except the italic items, with 5% off at Lowe’s, before tax.

Option	Total	vs. cheapest
Split between both stores (below)	$635.86	—
All at The Home Depot	$681.62	+$45.76
All at Lowe’s ($790.01 less 5%)	$750.51	+$114.65

Lowe’s · $532.73

Wire, GFCI breakers, outdoor duplex, screw hooks, both box types, staples, duct seal. All in stock at E. Stassney Ln. except the breakers (ready Oct 15).

The Home Depot · $103.14

L5-20R receptacles, locking plates, in-use cover, snap-in and clamp connectors, cord grips. Most ship to the SE Austin store by Oct 16–19.

Most of the saving is the wire and breakers ($25.82 together). If one trip matters more than $46, buy everything at The Home Depot.

Before opening the garage door

Shut down the desk equipment.
Unplug each cord at the ceiling outlet.
Release the cord from its ceiling grip.
Coil the cords and stow them off the door path.
Check the full door travel is clear, then open.

This is a homeowner’s proposal for review, not an approved design. Code requirements depend on the adopted code edition and the local inspector.