When the building has to stay open, call the one who shows up.
I service commercial rooftop units, walk-in refrigeration, geothermal and standard split systems across seven central Oklahoma counties: Kingfisher, Canadian, Oklahoma, Garfield, Major, Logan and Blaine. HVAC/R since 1980.
4.8 stars · 300+ Google reviews · Master HVAC License · Licensed Oklahoma Mechanical Contractor · BBB A+ for 11 years
A grand opening with no cooling
On Friday, September 4, 2026, a newly built restaurant in Guthrie called at 1:00 pm on its grand opening day with no cooling. I had a technician on the roof at 3:00 pm, the same hour the ribbon was cut, and we came back Saturday to finish getting it cooling. Rooftop temperature that weekend was 105 degrees. The full story.
- The equipment was newInstalled by a different company, still under manufacturer warranty, and it would not run.
- The failure chainA burnt control transformer, a phase monitor fault and a failed machine control board.
- What the meter saidVoltage balance measured good, which pointed away from incoming power and toward the control side.
- What the manual confirmedThe transformer lands on the same connection as the phase monitor.
- Parts a week outSo we ran a documented temporary workaround and said plainly that it was temporary.
What commercial work I do
- Rooftop package unitsControl transformers, contactors, condenser fan motors, capacitors, phase monitors.
- Split systems and heat pumpsCommercial splits and heat pumps across restaurants, retail and clinics.
- GeothermalWater-source heat pumps and ground loops on commercial buildings.
- RefrigerationWalk-ins and restaurant refrigeration, quoted after I see the equipment.
- Controls and drivesControl boards, phase monitor faults, variable frequency drives on indoor blowers.
- RefrigerantRecovery under EPA rules, through the R-502, R-410A and R-454B transitions.
Commercial pages by job
Restaurant HVAC
Makeup air, grease on condenser coils, and the walk-in behind the kitchen.
$389 diagnosticRestaurant HVACRTU repair
Phase monitor faults, control transformers, boards and motors.
$389 diagnosticRooftop unit repairSecond opinion
Equipment that still is not running right after another company installed it.
Straight readCommercial second opinionAlso: the City of Watonga rooftop replacement, emergency commercial HVAC, Logan County commercial, strip center and retail HVAC, and commercial geothermal, where the loop field goes under your parking lot.
Who owns Hartzell’s Heat & Air
I do, Dave Hartzell. I have worked in HVAC/R since 1980, starting at sixteen and a half working for my dad doing electrical and HVAC/R, and I have owned the company for 15+ years. Master HVAC License, licensed Oklahoma mechanical contractor, chiller-class commercial work in the Dallas Fort Worth market.
Straight answers
How much does a commercial HVAC diagnostic cost in Oklahoma?
A commercial HVAC diagnostic from Hartzell’s Heat & Air is $389 flat for light commercial equipment up to 15 tons, the same day or night, with no after-hours surcharge and no weekend uplift. It can be booked online. Larger equipment is sized and quoted by the technician on site.
Does Hartzell’s do emergency commercial HVAC calls on weekends?
Yes. Commercial calls are taken on weekends and after hours, and the diagnostic stays $389 flat, day or night.
Will an HVAC contractor work on equipment installed by another company?
Hartzell’s regularly services commercial equipment installed by other contractors, including brand new equipment still under manufacturer warranty.
What happens if replacement parts are not available?
A commercial system can sometimes run temporarily on a documented workaround, and a contractor should tell you plainly that it is temporary.
What counties does Hartzell’s serve?
Seven Oklahoma counties daily: Kingfisher, Canadian, Oklahoma, Garfield, Major, Logan and Blaine. 602 S Main St, Kingfisher, Oklahoma 73750, 405-375-4822.
How fast can you respond?
Most commercial calls inside the seven counties are same day. The documented Guthrie response was two hours from phone call to technician on the roof, on a Friday afternoon.
I will tell you what is wrong before I fix it
Commercial diagnostic $389 flat, day or night, up to 15 tons.
Call 405-375-4822Hartzell’s Heat & Air · 602 S Main St, Kingfisher OK 73750 · Light commercial in Kingfisher
