If you're staring at a Bohn condensing unit sitting on a pallet, and the pressure is on to get a walk-in cooler or stand up freezer running by Monday morning, you're in the right place. This checklist is for service techs, maintenance supervisors, and contractors who need to get it done right the first time. I've put together 7 steps based on hundreds of installations and a few painful mistakes I hope you won't repeat.
Step 1: Match the Model Number to the Spec Sheet (Don't Assume)
Check the unit's data plate against the order. I once had a job where the model number was off by one digit—the unit was for a low-temp stand up freezer, not a medium-temp cooler. Discovered this when the suction pressure wouldn't come down. The difference? About 4 hours of rework and a rushed exchange.
Here's your checklist at this stage:
- Confirm the unit model matches the evaporator type (e.g., Bohn's BA, BH, or BE series).
- Verify the voltage and phase are consistent with your site power supply (208V 1-phase vs. 460V 3-phase makes a huge difference).
- Check the BTU/hr rating against the load calculation (not just the box size).
I can only speak to Bohn units specifically. If you're working with KeepRite or Heatcraft, the nomenclature is different (your mileage may vary).
Step 2: Inspect for Shipping Damage (Before You Spend 30 Minutes Unboxing)
Walk around the crate. Look for any signs of a forklift meeting the side of the unit. I said 'looks fine from the outside.' My lead tech said 'we should open the access panel.' I was wrong.
Avoid my mistake:
- Check for oil stains on the packaging—that's a red flag for a cracked coil or loosened line fittings.
- Visually inspect the condenser coils for bent fins (anything beyond 10% is a performance hit).
- Rotate the fan blade by hand (with power off) to ensure it's not hitting the shroud.
Take pictures of any damage before touching the unit. This saves you a headache with the return process.
Step 3: Confirm Refrigerant Type and Charge (It's Not Always R404A)
This seems basic, but I've seen two jobs go sideways because the crew assumed the unit was charged with R404A when it was R448A. Bohn units are often pre-charged at the factory. The data plate will tell you what's inside. If you're retrofitting an old system, make sure the new unit's charge is compatible with your existing line set.
Industry standard: Per ASHRAE Standard 34, refrigerant designations are safety classified. R448A has a lower GWP than R404A, but it also runs different head pressures. Don't mix them.
Note to self: Always keep a copy of the unit's pressure-temperature chart at the job site. You will need it when the system acts weird at 5 PM on a Friday.
Step 4: Review the Line Set Requirements Before Running Piping
Bohn's installation manuals specify line set sizes for a reason. Using an oversized suction line on a condensing unit that's 100 feet from the evaporator? You'll get oil return issues. Using a line that's too small? You'll starve the compressor.
A quick check:
- Measure the actual distance (don't estimate). Add 10% for fittings.
- Check the manual for the recommended line sizes at that distance.
- Confirm you're using the correct insulation thickness (3/4 inch for suction lines is standard, but 1 inch is better for long runs).
I once had a client who insisted on using leftover 1/2 inch line from an AC job. Three months later, the compressor failed due to liquid slugging. The rework cost more than running the correct line the first time.
Step 5: Look at the Electrical Connections (Double-Check the Control Voltage)
Bohn condensing units often come with factory-installed controls, but not always. If you're wiring in a new thermostat or pressure control, confirm the control voltage (24V or 120V). A 120V control circuit hooked up to a 24V coil? You'll let the magic smoke out.
Safety note: Lockout/tagout before poking around terminals. I'm not a safety manual, but I've had enough close calls to check twice.
An overlooked step: Verify the minimum circuit ampacity (MCA) and maximum overcurrent protection (MOP) on the data plate match your breaker and wire sizing. This is a code requirement (NEC Article 440), not just a suggestion. If you're using a 20-amp breaker on a unit that requires 25 amps, your setup will nuisance-trip and your customer will be unhappy.
Step 6: Install with Service Access in Mind (You'll Thank Me Later)
Your back hurts now, but imagine having to replace a fan motor in a 24-inch gap between the unit and a wall. I've been there. Position the condensing unit with enough clearance for:
- Airflow across the condenser coil (Bohn recommends 36 inches minimum for top-discharge units).
- Access to the compressor compartment for oil changes or start-up checks.
- Replacing the filter drier without pulling the unit.
If the installation site is tight, consider using a concrete pad or curbs that elevate the unit for easier access to the bottom service panel.
Step 7: Perform a Pre-Start Check (The 10 Minutes That Save You 10 Hours)
Before you hit the disconnect switch, run down this list:
- Turn off all disconnect switches for both the condensing unit and evaporator.
- Check all high-pressure and low-pressure switch settings (make sure they're not bypassed from the factory—it happens more than you think).
- Verify the crankcase heater has been energized for at least 12 hours (compressor oil needs to be warm, especially in cold weather).
- Confirm all valves are open (sounds silly, but I've seen a king valve left closed and the unit short-cycled on start-up).
- Meter the control transformer output voltage before connecting the thermostat.
This worked for us on a recent install of a Bohn condensing unit for a stand-up freezer. Normal startup is straightforward, but our situation had a long line set (75 feet). If you're dealing with a short line set or a package unit, the calculus might be different.
Common Mistakes to Avoid
Here's what usually goes wrong when people rush through this checklist:
1. Assuming everything is compatible. Just because a dewalt fan moves air doesn't mean it's suitable for condenser cooling. Use the manufacturer's fan specifications, not a general-purpose fan from a hardware store.
2. Forgetting about the low ambient control. If your installation is in a climate that hits below 50°F, the condensing unit needs a fan cycle control or a flooded head pressure control valve. Bohn offers options for this—don't skip it unless you want flooded starts on cold mornings.
3. Misunderstanding 'pre-charged.' Most Bohn condensing units are shipped with a holding charge of nitrogen or a small refrigerant charge. This is not enough to run the system. You'll need to add refrigerant based on the system volume.
4. The mason jar myth. A quick aside: people sometimes ask about using mason jars in a commercial cooler, like 'are mason jars freezer safe.' Standard mason jars (without tempered glass) can crack in a stand up freezer below 0°F because of thermal shock. This has nothing to do with refrigerants, but I've had three conversations about it in the last year alone. If someone asks you, tell them to use labels instead of glass.
Wrapping Up
This checklist isn't exhaustive—I left out things like evacuation and leak testing because those should be standard practice. But these seven steps have saved me from at least three major rework events in the last 18 months.
Last bit of advice: Keep a copy of your Bohn installation manual (the one from the factory, not a summary) in the panel cover. If something goes wrong at 2 AM, whoever's on call will have the wiring diagram right there. I've been that person on call, and trust me, it's worth the two seconds it takes to tuck it inside.
