Guides
Setting up an HVAC contractor business: parts to stock before instruments
A starting parts list for an HVAC contractor truck, a fetch log method for building your own, the paperwork that rides along, and when to add instruments.
What to take away
- A truck that carries instruments but no repair parts still books a second trip on most no-cool calls.
- Build the parts list from a two-month fetch log, not from a supplier's suggested stock package.
- Capacitors, contactors, fuses, filters and condensate pumps cover the largest share of repeat visits in most residential markets.
- Paperwork is part of the kitasset list, safety program, insurance certificate, and your own quote and handover templates.
- Buy instruments one at a time, each tied to a reading you can explain to a customer.
Start with the parts, not the instruments
Most new firms buy gauges first and capacitors last. That order costs money. A diagnostic call that ends with "I will come back with the part" bills one hour and burns two, and the customer remembers the second visit, not the first.
The parts that close calls are cheap and unglamorous. The instruments that prove the diagnosis are the ones you can add later, one at a time, as the work justifies them.
The repair-parts stock list
This is a starting list for a residential and light commercial truck. Adjust quantities to your call volume, and adjust the mix to the brands you actually service.
| Part group | Typical items | Why it earns truck space |
|---|---|---|
| Electrical | Run and start capacitors, contactors, relays, fuses, terminal blocks | The single most common no-cool and no-heat failure on residential equipment |
| Controls | Thermostats in the types you support, transformers, boards for the two or three models you see most | Turns a diagnostic into a repair on the same visit |
| Filtration | Pleated filters in the sizes your local housing stock uses | Sold on almost every maintenance call |
| Condensate | Pumps, tubing, fittings, pan treatment tablets | Cheap, light, and the cause of many water-damage callbacks |
| Refrigerant and fittings | The refrigerants your area uses, line set materials, brazing consumables | Only if you are certified to handle them |
| Sealing and insulation | Foil tape rated for the application, mastic, pipe insulation, fasteners, hangers | Finishes the job so it does not come back |
Refrigerant is the one line item with a legal precondition. Who may buy, handle and recover it is set by the federal program described at the EPA Section 608 technician certification pages, and the certification attaches to the person, not the company.
Build the list from a fetch log
A suggested stock list is somebody else's market. Yours is in your own call records.
For two months, write down every part a technician had to leave a job to collect. Note the part, the date, and the job type. At the end of the period, sort the list by how often each item appears.
Anything that shows up three times or more belongs on the truck. Anything that appears once stays at the shop or gets ordered. This is the whole method, and it costs nothing but a notebook and the discipline to fill it in.
The log also tells you what to stop carrying. Parts that sat untouched for a season are cash in a box, and that cash is better spent on the items the log keeps flagging.
Paperwork that has to travel with the tools
- An asset list with purchase dates and service intervals for every instrument
- The written safety program, not just the personal protective equipment
- Insurance certificate and trade registration accessible from the vehicle
- Manufacturer installation instructions for the equipment you install most
- Your own quote, scope-of-work and handover templates
- A place for site photos and readings to land the same day
The employer's obligation is to run a program, not to own gear. That distinction is set out in the OSHA guidance on safety and health programs.
Keep records that show income and expenses clearly, in the form described in the IRS guidance on records a small business should keep. A reading nobody wrote down did not happen, and a job nobody documented is a job you cannot defend.
What each registration has to show, and which ones must be in the vehicle, is covered in the licensing and compliance guide.
Instruments: buy them one at a time
Buy each instrument against a specific reading you intend to take and explain. A manifold set earns its place the first time you show a customer a suction pressure that does not match the outdoor temperature. A static pressure gauge earns its place the first time you prove a return duct is starving the coil.
Skip the pre-assembled kits. They are built to a price point and usually include one instrument nobody on the crew trusts. Buying individually costs a little more per item and leaves you with a set where every piece gets used.
Two habits keep the readings worth having. Compare a new instrument against one you already trust before it goes on the truck, and log the comparison. Then write down what each reading proved on the job, so the next technician can pick up the thread.
What not to buy yet
Three tests before anything outside the parts list and the paperwork. Has a customer asked for this work more than once? Can someone employed today do it competently? Would renting it for the next three jobs cost less than a year of ownership?
Specialty fabrication equipment, a second set of instruments before a second technician exists, and recovery gear for refrigerants you rarely meet all fail those tests. For the items that pass, the equipment and setup guide sets the order in which a firm equips itself.
What each instrument has to prove at handover, and who checks it, is in the service quality guide for owners.
How the stock list shows up in your price
Every part on the truck is capacity, and capacity shows in the price. A firm that closes on the first visit spends fewer hours per job and can quote a lower number for the same margin.
The arithmetic connecting hours, parts cost and price is in the pricing and profit guide. Run it once the fetch log has settled and the stock list has stopped changing.
Who is allowed to work unsupervised, and therefore which truck needs which parts, is set out in the hiring and training guide.
A part that shows up three times in two months of fetch logs has already told you it belongs on the truck. The log is the stock list.
Common questions
How much should be on the truck versus in a store?
For a single-vehicle firm, almost everything, because a trip to a store is a trip to a store. As you add vehicles, a small central stock of slow-moving items starts to pay for itself.
Should I buy instruments as a kit or individually?
Individually, guided by what each one proves. Kits are assembled to a price and usually include something nobody on the crew will read confidently.
What is most often missing from a new firm's truck?
Static pressure measurement, followed by a reliable way to record what was measured. Both are inexpensive relative to what they let you charge for.
Do I need combustion equipment if I only do cooling?
Not for cooling work. Decide in advance what you will do when a furnace customer calls in October, because that answer decides whether this becomes urgent in your first heating season.
