The Brand Story
Supco: The Parts Company That Started With a Service Call
Picture the Bronx in 1945. The war is over, and two naval engineers open a small business servicing refrigeration systems. Back then a sealed refrigeration system was exactly what the name said: sealed. Getting into one to diagnose a problem or add refrigerant meant cutting and brazing, and every repair risked creating a new one. The company those two men started, Sealed Unit Parts Co., would spend the next eight decades making the technician's day a little easier, one small part at a time. Most people know it simply as Supco.
Chapter 1 · 1945
A service company in the Bronx
Supco did not begin as a manufacturer. It began as a refrigeration service company, which meant its founders spent their days working on the same compressors, relays and fittings that would later carry their name. That point of view shaped everything that followed. When a part kept failing, or a job took three steps when it should have taken one, the people at Supco were the ones on their knees in front of the unit.
That service-first origin is still how the company describes itself. Its catalog grew out of real calls rather than a marketing plan, and the products that made its reputation are the kind a technician reaches for without thinking about who made them.
Chapter 2 · The 1960s
A way into a sealed system
The invention that put Supco on the map solved the problem its founders knew best. Supco engineers developed the patented Bullet Line Tap valve, a piercing access valve that clamps onto a refrigerant line and gives the technician a service port without opening the system the hard way. For a refrigerator or freezer that was never designed to be serviced, it turned a messy job into a manageable one.
Industry trade press dates the Bullet valve to the 1960s, and versions of the idea are still on service trucks today. It established a pattern Supco would repeat for decades: find the step in a repair that wastes the most time, then build a part that removes it.
Chapter 3 · Hard starts and vacuum gauges
Small parts, big problems
Supco's next contribution came from inside the compressor circuit. The company is credited with discovering the PTC (positive temperature coefficient) approach behind its two-wire hard start kits for air conditioning and refrigeration. A two-wire kit connects across the run capacitor terminals, so a technician can help a struggling compressor start without rewiring the unit. It became one of the most familiar part numbers in the trade.
In the 1990s Supco introduced what it describes as the first electronic vacuum gauge, the VG60, replacing the guesswork of reading a deep vacuum on an analog dial. Around the same period the company signed master distributor agreements with established component makers, including Therm-O-Disc, and grew into a supplier that wholesale counters could rely on for both its own designs and the replacement parts they needed every day.
Chapter 4 · 2000s to 2019
From Allenwood, a wider catalog
By the twenty-first century Supco was headquartered in Allenwood, New Jersey, with manufacturing in New Jersey, the Midwest and overseas, and a worldwide network of sales representatives and distributors. It grew partly by acquisition. Climate Technology Corporation, A-1 Components and Cam-Stat joined the company over the following years, then Aquasolve Chemical Company.
In 2019 Supco agreed to acquire National Appliance Parts Co., a Southwest Michigan maker of aftermarket electric heating elements founded in 1986. That deal expanded Supco's American manufacturing and made it a major aftermarket source for replacement heaters in clothes dryers and electric furnaces. The company's appliance business grew alongside its HVACR line, covering parts for dishwashers, ranges, microwaves, washers, dryers and refrigerators.
Chapter 5 · 2022 to today
A new home inside NSI Industries
In August 2022 NSI Industries, a manufacturer of electrical, HVAC and building technology products based in Huntersville, North Carolina, acquired Supco. The brand kept its name, its catalog and its focus. Supco's chief executive at the time summed up what customers should expect from the brand.
"technician-focused innovation at value-driven prices"
That idea now has a formal program behind it. Supco's TradeFox line is built around tools invented by working technicians, who submit their ideas through an inventor program. It is a fitting turn for a company that began with two engineers working on the equipment themselves.
The Lineup
What Supco builds today
Supco makes replacement parts, components, test instruments, tools and chemicals for HVAC, commercial refrigeration and home appliances. The HVAC365 catalog leans on the parts a service technician uses most:
- Capacitors: round and oval run capacitors, including dual run capacitors such as the CD40+5X440R rated 40+5 MFD at 440 volts, the part most often replaced on a residential condenser.
- Electrical components and controls: hard start kits such as the SPP5 Super Boost, and the 9063 through 9068 potential relays used to drop a start capacitor out of the circuit once a compressor is running.
- Condensate removers: the Supco 31, 75 and 70 condensate products used to keep condensate handling on air conditioning and refrigeration equipment working as designed.
- Belts: replacement drive belts for blowers, air handlers and other belt-driven equipment.
- Testing instruments: handheld meters and testers, including Supco's megohmmeter and capacitor tester lines.
- Chart recorders and charts: temperature recorders and the replacement charts that go with them, used to document cooler, freezer and process temperatures over time.
- Installation supplies: Dynotie cable ties such as the 36-inch DN36N and 48-inch DN48N, sold in bulk packs for securing line sets, wiring and insulation.
Together these parts make up a large share of the HVAC parts and supplies on our shelves, which says something about how deeply Supco is woven into everyday service work.
On the Bench
How a hard start kit actually helps
A compressor needs the most torque in the first second of a start, especially when it is fighting high head pressure on a hot afternoon or low voltage at the end of a long run of wire. A hard start kit adds a start capacitor to give the motor that extra push, then takes it back out of the circuit before it can overheat. Supco makes kits both ways. A potential relay senses the voltage across the start winding and opens when the motor reaches speed. A PTC device heats up as current flows and its resistance climbs until the start capacitor is effectively out of the circuit. Either way, the goal is a cleaner start and less strain on the compressor, though a kit is never a cure for a compressor that is mechanically failing.
At a Glance
Supco by the numbers
- Full name
- Sealed Unit Parts Co., Inc.
- Founded
- 1945, the Bronx, New York
- Headquarters
- Allenwood, New Jersey
- Parent company
- NSI Industries, since 2022
- Known for
- Bullet Line Tap valve, two-wire hard start kits
- Manufacturing
- New Jersey, the Midwest and overseas
- Markets
- HVAC, refrigeration and appliance parts
Questions
Frequently asked questions about Supco
What does Supco stand for?
Supco is short for Sealed Unit Parts Co., Inc., a name that comes from the company's early work servicing sealed refrigeration systems.
Who owns Supco?
Supco has been part of NSI Industries, a Huntersville, North Carolina maker of electrical, HVAC and building technology products, since NSI acquired it in August 2022.
When and where was Supco founded?
Supco was founded in 1945 in the Bronx, New York, as a refrigeration service company. It is now headquartered in Allenwood, New Jersey.
What is Supco known for?
Supco is known for the patented Bullet Line Tap valve, its two-wire PTC hard start kits and a broad catalog of replacement capacitors, relays, test instruments and appliance parts.
What is the difference between a Supco potential relay and a PTC hard start kit?
Both remove a start capacitor from the circuit after the compressor starts. A potential relay does it by sensing start winding voltage, while a PTC device does it by heating up until its resistance rises.
