The switches that switch the switches — what contactors, relays, and motor starters do, NEMA sizes, and the used replacement market.
Contactors, relays, and motor starters are electrically-controlled switches: a small control signal closes big power contacts. They are the muscle of every motor control center, the click behind every industrial starter, and a constant replacement market — coils burn out, contacts pit, and plants buy used spares rather than wait.
Contactors, starters, overload relays, buckets, and MCC parts. MCC selling guide →
Heavy-duty electrically-controlled switches for power circuits — motors, lighting banks, heating loads. A small coil voltage (24V, 120V) pulls in contacts rated for tens or hundreds of amps. NEMA sizes 00 through 9 standardize the ratings. The workhorse of motor control.
The same idea at control-circuit scale: small relays (ice-cube style) switch logic signals, timing relays add delays, protective relays (the switchgear kind) guard whole systems. Control relays are consumables — cheap, constant turnover, sold by the box.
Contactor + overload relay in one device: the contactor switches the motor, the overload relay protects it from sustained overcurrent (heaters or electronic overloads sized to the motor’s full-load amps). Combination starters add the disconnect or breaker. A complete starter bucket is the unit MCCs are built from.
NEMA-size contactors and complete starters from major brands (Allen-Bradley, Square D, Siemens, Eaton) are the liquid market — plants buy exact replacements to match existing MCC buckets. Value factors: NEMA size (bigger = more), coil voltage (120V coils are the common ask), overload heater inclusion, and contact condition. Solid-state overloads and smart starters (with communication) premium over bimetallic heaters. Photograph the label (catalog number, NEMA size, coil voltage) and the contacts if accessible. Ice-cube relays sell by the box, sorted by part number — unsorted relay boxes are mystery pricing.
A motor starter’s label carries five facts that determine interchangeability: NEMA size (00–9 — the frame rating), catalog number (the exact model), coil voltage (24V, 120V, 208V, 480V — the control voltage that pulls it in; wrong coil voltage = wrong starter for the panel), overload range (the heater or electronic OL’s adjustable FLA range — must cover the motor’s full-load amps), and voltage/HP rating (max motor it can switch). The coil voltage is the most commonly missed: two identical-looking starters with 120V and 24V coils are not interchangeable. Photograph the full label — like breaker catalog numbers, the starter label is the entire specification.
The service-call greatest hits: no control voltage (blown control fuse, open interlock, tripped overload — check the circuit before the starter), wrong coil voltage (a 480V coil on 120V control just sits there; a 24V coil on 120V burns instantly), welded contacts (the starter hums but the motor single-phases — replace the contacts or the unit), tripped overload (the red reset button — find why it tripped before resetting), and mechanical binding (dust and age). For buyers of used starters: a unit that pulls in crisply on the bench with a test coil voltage and shows clean contacts is worth the premium — it is the difference between a spare and a project.
Scale: contactors switch power circuits (motors, tens to hundreds of amps); relays switch control circuits (signals, small currents). Same principle, different jobs.
A contactor plus an overload relay — switching plus motor protection in one device. Combination starters add a disconnect or circuit breaker.
Standardized contactor/starter ratings from size 00 (smallest) through size 9 — each size covers a horsepower range at standard voltages. The size is on the label and determines interchangeability.
Yes — NEMA-size starters from major brands are a liquid replacement market. Coil voltage, overload inclusion, and contact condition set the price.
Coil burnout, pitted/welded contacts from interrupting load, and dust. A contactor that pulls in cleanly with good contacts is a premium used unit.
Photograph the equipment, nameplates, and quantities in place, then send them through the contact form.
We review what the equipment is, its condition and quantity, and how it grades for resale versus recovery.
For qualifying material, we discuss a direct purchase offer and the next steps.
Manufacturer nameplates, breaker catalog numbers, panel schedules. Labels are the entire valuation.
Call or text 312-880-8174 or use the quote form.
A real offer based on your photos and today’s market — not a calculator, not a guess.
Breakers, panels, switchgear, transformers — send photos for today’s price.