Bohn Evaporator Nomenclature: A Practical Guide (With Mistakes I've Made)

If you're looking at a Bohn evaporator, you know the part number isn't just a serial number. It's a code. It tells you the capacity, the coil type, the voltage, and a bunch of other details. But here's the thing I've learned the hard way: if you misread one letter, you can end up with a $3,200 paperweight.

There is no universal 'cheat sheet' for this. The nomenclature varies slightly by product series, and it’s changed over the years. The best approach depends on where you are in the process and what you’re trying to do. So, let's break it down by scenario, based on mistakes I've personally documented.

Scenario 1: You're on a Job Site and Need a Replacement ASAP

This is the most stressful scenario. A freezer goes down, the product is thawing, and the boss is calling every hour. You have the old evaporator in front of you, and the tag is (hopefully) still legible. In my first year (2017), I once pulled a tag that was almost worn off. I grabbed a cheap flashlight and still read the model number wrong. I saw 'G' but it was actually 'C'. The difference? One is for a medium-temp cooler, the other for a freezer. That mistake cost $890 in redo plus a one-week delay.

My advice for this scenario is simple: do not trust the tag alone if it's faded, but trust it completely if it's legible. What most people don't realize is that Bohn tags from the early 2000s used a different font style that can make '6' and 'G' look very similar. Here is my checklist that I keep in my truck:

• Clean the tag with a dry rag. Do NOT use water or solvent; it can smear the ink further.
• Take a photo with your phone, zoom in, and use the flash. The digital image is often clearer than your eyes.
• Match the physical dimensions (length, width, coil face area) against the model number's implied dimensions.

If you have the model number correct, ordering should be straightforward. The issue is accuracy. In this scenario, the 'prevention' is taking that two minutes to triple-check. As Bohn's own documentation implies, the model number is the single point of truth.

"5 minutes of verification beats 5 days of correction."

Let me rephrase that: a bad part will cost you time, money, and credibility. It's not worth the risk of a quick glance.

Scenario 2: You're Designing a System and Picking a New Unit

This is the 'ideal' scenario. You have time. You can choose the perfect unit. The problem here isn't reading the number; it's picking the wrong one for the application.

The fundamental question everyone asks is 'what's the BTUs?' The better question is: what's the fin spacing and the application? I get why people focus on capacity—it's the headline. But for a Bohn evaporator, the nomenclature for fin spacing (e.g., '4' for 4 fins per inch, '6' for 6, '8' for 8) is arguably the most critical.

I once designed a system for a cold storage warehouse. We installed a high-capacity unit with 4 fins per inch. It was for a room kept at 38°F. A few weeks later, we got a call. The coil was icing up. The problem? The high humidity in the room (from constant door openings) was freezing on the coil. We needed a unit with 6 fins per inch for better air circulation and defrost. The capacity was fine, but the coil geometry was all wrong. The replacement logic was: 'Wasted time, credibility damaged, lesson learned: always check the application against the fin spacing.'

Here’s my current design checklist:

1. Application: Cooler (34-45°F), Freezer (-10 to 34°F), or Blast Freezer (-20°F & below).
2. Fin spacing: Matches the application to prevent icing.
3. Defrost: Electric, hot gas, or off-cycle. This is often encoded in the model number.
4. Voltage: Single-phase (115/208-230) or three-phase (208-230/460). Make sure it matches your power supply.

Most buyers focus on the capacity code and completely miss the defrost type. The defrost is in the model number (e.g., 'E' for electric). If you pick an off-cycle defrost unit for a freezer, you will have a disaster. That $3,200 unit I mentioned? That was exactly that mistake.

Scenario 3: You're Training a New Hire or Need to Decode a Unit for Reference

This is the educational scenario. You’re looking at a unit’s tag and you need to explain it to a junior technician or you just want to understand the limitations of what you already have. The pressure is low, but the need for accuracy is high.

In this case, the best tool is Bohn's official product documentation (available as PDFs from their website or from a distributor). I should add that I keep a binder of the most common models.

The nomenclature tends to follow this pattern, though it varies by family:

• Product Line: e.g., 'B' for Bohn, sometimes omitted.
• Coil Type: e.g., 'H' for horizontal, 'V' for vertical.
• Nominal Capacity (in thousands of BTUH): e.g., '10' for 10,000 BTUH.
• Fin Spacing: '4', '6', '8'.
• Defrost: 'E' (Electric), 'G' (Hot Gas), 'A' (Off-cycle/Air).

A great training exercise is to grab an old, non-working unit or a photo of a tag and have your new hire decode it. Then, look up the actual specification on the Bohn site. It’s cheap training. We've caught 47 potential errors using this checklist in the past 18 months. That’s 47 issues we fixed before they could create problems in the field.

How to Tell Which Scenario You're In

• You are in Scenario 1 if the unit is already failed, the product is at risk, and you are in a time-critical replacement. Your job is to verify, not to learn.
• You are in Scenario 2 if you are specifying a new unit for a new project or a planned renovation. Your job is to design, not to react.
• You are in Scenario 3 if the unit is working fine, or if you have time to properly educate yourself or your team. Your job is to understand, not to purchase.

Stick to the relevant checklist for your scenario. The first two scenarios are high-stakes. The third is for building long-term competence. Don't mix them up. I’ve done it, and it doesn’t work.