Bohn Evaporator Nomenclature and Walk In Cooler Fan FAQ: What a Purchasing Admin Learned

I handle purchasing for a small cold-storage company. We run three sites, and I process maybe 60-80 orders a year for evaporator coils, condenser fan motors, and replacement blades. A lot of those orders are Bohn parts. I am not a refrigeration engineer, but I have learned how to read Bohn evaporator nomenclature the hard way: by ordering the wrong model once and eating a restocking fee.

Here are the fan and evaporator questions I get from our maintenance crew, plus one or two I wish they asked before buying.

What is a Bohn walk in cooler, exactly?

A Bohn walk in cooler usually means a walk-in box cooled by a Bohn evaporator and a Bohn condensing unit. The box itself may be fabricated by someone else. Bohn is a commercial refrigeration brand; the important part is the mechanical system inside and outside the room.

What most people don't realize is that the brand on the door doesn't tell you much. The evaporator model number is what matters when you need parts. When a customer calls us and says they have a Bohn walk in cooler, the first thing I ask for is the evaporator rating plate, not the room dimensions.

How do I read Bohn evaporator nomenclature?

Bohn evaporator nomenclature is a compressed spec sheet. A typical model number contains the unit family, airflow arrangement, capacity, voltage and phase, and defrost type. The exact placement of letters and digits changes by product line, but the logic is similar. Air defrost models often have AD somewhere in the suffix, electric defrost often uses ED, and water defrost often uses WD. The number portion usually relates to capacity, often expressed as BTU/h at a given temperature difference.

Take this with a grain of salt: the exact pattern varies, so always check the rating plate. The surprise wasn't that the model code was long. It was that two similar-looking Bohn evaporators can have completely different defrost systems. One is air defrost for a cooler above 35°F; another is electric defrost for a freezer. If you swap them, you get ice buildup or a heater that never runs.

Don't order from memory. Find the rating plate on the actual unit, take a photo, and compare it to the current Bohn/Heatcraft data sheet. I'm not 100% sure every series follows the exact same pattern, and there are old labels that don't match the online catalog.

Where do I find the Bohn evaporator model number?

On most Bohn evaporators, the rating plate is on the side of the casing, usually near the electrical connections. On older units, paint might cover it. Use a flashlight and a phone camera instead of scraping with a screwdriver. If the plate is unreadable, measure the coil face area, fin spacing, and connection sizes, and note the defrost type. That is enough to narrow the options in the Bohn/Heatcraft catalog.

Keep photos of every unit plate in a folder. After the third time I climbed a ladder with a screwdriver to read a faded sticker, I started labeling the outside of each unit with the model number. As of March 2025, the Bohn/Heatcraft online catalog is the place to verify a current model.

Do I size a Bohn evaporator by box size or by BTU load?

By BTU load at a design temperature difference, not by square feet. The question everyone asks is how big is the room. The question they should ask is what temperature do you need to hold, and what is the heat load from product, doors, people, and lights. A 12-foot by 12-foot storage cooler carrying warm beverage kegs has a different load than one holding already-cold produce.

When a vendor quotes a Bohn walk in cooler package, I ask for the capacity table. If they say it will hold a room at 34°F, I want to know the conditions behind that number. Per FTC advertising guidelines (ftc.gov), product claims need to be truthful and substantiated. In practice, that means I want the engineering data sheet, not a rule of thumb.

What does outdoor fan mean in a Bohn system?

In commercial refrigeration, outdoor fan usually refers to the condenser fan on the outdoor condensing unit. That fan pulls air across the condenser coil to dump heat. If a walk in cooler has a remote Bohn condensing unit outside, the outdoor fan is part of that unit. It is not a portable fan or a house fan. Put another way, the outdoor fan is part of the condenser's heat rejection system.

When you search for a replacement outdoor fan, you need the motor plus the blade, and the motor must match the voltage and shaft diameter. A residential outdoor fan motor is not built for continuous operation in weather or for the higher static pressure of a refrigeration condenser. I learned this the frustrating way: we put in a fan motor that was close on physical size but wrong on RPM, and the condenser ran hot until we swapped it.

Can I use a Dewalt blower to clean a Bohn evaporator?

Yes, but use the low-speed setting. A cordless Dewalt blower is good for dry dust on evaporator fins, and it beats a broom because you don't touch the fins. Keep the nozzle a few inches away from the coil to avoid bending fins or driving dirt deeper into the core.

Our maintenance routine is simple: turn off power to the unit, use the blower to clear loose debris, then apply a no-rinse coil cleaner for any oil or grease film. Don't use a pressure washer near the fan motor, junction box, or defrost heaters. The most frustrating part of this job isn't the blower; it's reaching the coil. If the evaporator is wedged against a ceiling, expect a ladder and a sore neck.

How to replace a bathroom exhaust fan (and why it is not a refrigeration project)

If you are here because you want to know how to replace a bathroom exhaust fan, the short version is: turn off the breaker, remove the grille, disconnect the wiring and duct, unbolt the housing, install the new fan, and seal the duct connection. It takes around two hours for someone with basic wiring experience.

Do not let that knowledge transfer to a commercial walk in cooler. A bathroom exhaust fan is a residential 120V fan with low static pressure. A Bohn evaporator fan is a commercial-duty motor that runs at low temperature and pushes air across a coil. They are both fans, but they are not interchangeable. Our maintenance guy once tried to use a bathroom-style fan for a small evaporator because the blade size looked close. The motor burned out in two days.

For a bathroom fan, buy the replacement for the vent size and room CFM. For a Bohn evaporator, buy the exact model number from the rating plate.

What should I ask before buying a Bohn evaporator or replacement fan?

Ask what is not included before you ask the price. That one habit has saved me more than any discount. When I get a line-item quote for a Bohn evaporator, I check for these items:

• Condensing unit or evaporator only?
• Fan blades and motors included?
• Defrost type and controls?
• Line set, refrigerant, and electrical?
• Freight and old unit removal?

The vendor who lists every fee up front, even if the total looks higher, usually costs less in the end. Last year, one quote looked 12% higher than a competing quote, but the lower quote didn't include the line set or freight. The real difference was $1,400—no, maybe $1,600, I'm mixing it up with a freezer job. Either way, line-item now beats a change order later.