If you've ever stared at a Bohn evaporator model number and thought, "I'll just grab the one that looks close enough," you're not alone. I made that mistake my first year (2017) — ordered a dozen MCHA units for a walk-in cooler retrofit because the specs on the datasheet looked similar. Didn't check the voltage suffix. Didn't confirm the defrost type. Cost me a $3,200 reorder plus a week of downtime. The client wasn't thrilled.
Here's the thing: Bohn evaporator nomenclature isn't designed to be confusing — it's designed to prevent exactly the kind of error I made. Once you know what each section means, matching the right unit to your application becomes straightforward. But there's no single "best" model for everyone. Your decision depends on your specific setup, and this guide breaks it down by situation.
How Bohn Evaporator Nomenclature Actually Works
Before we get into scenarios, here's the basic structure. A typical Bohn evaporator model looks something like this: MCHA 024 H 1 1. Bohn uses a consistent format: product line + capacity (in thousands of BTUH) + voltage/family code + motor type + defrost type. The exact number of digits varies, but the logic holds. Most people focus on capacity — "I need 2 tons" — and miss the coil coating code or the fan configuration. That's where mistakes happen. The question everyone asks is: "What's the capacity?" The question they should ask is: "Does this unit match my refrigerant, voltage, and environmental conditions?"
Here's a quick reference (based on Bohn's published engineering manuals; verify current specs on their official site):
- Product line: MCH = Medium profile, centered hub; MCE = Medium profile, end-mounted; LCL = Low profile
- Capacity: 024 = 24,000 BTUH (2 tons)
- Voltage/family: H = 460V/3/60 (common for industrial); F = 208-230/1/60; G = 208-230/3/60
- Motor type: 1 = single-speed; 2 = two-speed (energy-save)
- Defrost type: 1 = electric; 2 = hot gas; 3 = off-cycle (for medium temp)
One nuance I wish I'd known earlier: coil coating matters more than most buyers realize. A standard aluminum coil works fine in dry storage, but in a high-humidity seafood cooler? You'll want the copper/aluminum hybrid or a corrosion-resistant coating. That info is buried in the spec sheet — not the model number — so you have to check it separately. People think the model number tells you everything. Actually, the model number gets you 80% of the way; the full spec sheet covers the rest.
Now, let's apply this to real-world choices.
Scenario A: You're Replacing an Existing Unit in a Commercial Kitchen
If you're swapping out a failing evaporator in a restaurant or prep room, your constraints are tight: existing mounting points, existing refrigerant piping, existing electrical supply. This isn't the place to experiment. You need a direct physical replacement — same profile, same footprint, same voltage.
What to check:
- The model number of the old unit (if you can read it). Look for the product line — if the old unit is an MCH, stick with MCH. Changing profile means reworking the hangers and possibly the duct.
- The voltage code. This is non-negotiable. If the existing supply is 460V (code H), ordering a 208V (code F) unit means an electrician and a transformer.
- The defrost type. If your existing defrosst timer and heaters are set up for electric, hot gas conversion requires additional plumbing. In 2022, I saw someone order an off-cycle defrost unit for a freezer. It iced up in two days — messy and unnecessary.
Pro tip from my mistakes: Once, I ordered an MCE (end-mounted) unit to replace an MCH (centered hub). Same capacity, same voltage, but the drain pan orientation was different. The entire condensate line needed rerouting — a $300 plumber visit. Don't assume "close enough."
Scenario B: You're Engineering a New Cold Storage Warehouse
New construction gives you more freedom, but also more decisions. In this scenario, you're optimizing for total cost of ownership, not just unit cost.
If your warehouse needs 48,000 BTUH of cooling, you could spec one large unit (e.g., MCH 048) or two MCH 024s. Which one wins? Depends on redundancy requirements and defrost cycle timing. Two smaller units mean you can keep one running while the other defrosts — better for stable temperatures — but higher upfront cost. One large unit is cheaper per BTU but a single point of failure. People think larger capacity is always better efficiency. Actually, Bohn's part-load efficiency curves (see their published technical docs) show twin small units often outperform a single large unit in real-world duty cycles — especially in spaces with varying door activity.
Voltage planning matters more than you think. In a warehouse with multiple units, standardizing on one voltage (e.g., all 460V) saves on electrical distribution costs. Mixing voltages means separate transformers and panels. According to Bohn's spec sheets, most MCH units in 3-phase are available in 208-230V (code G) or 460V (code H). For a new build, pick one and stick with it.
Scenario C: You're a Distributor Stocking for Walk-In Cooler Kits
If you're a Bohn distributor or supply house, you probably keep a handful of evaporator SKUs that cover 80% of your walk-in jobs. The temptation is to stock only the most popular models — maybe the MCHA 013 and MCHA 024 in 208V with electric defrost. But here's where I've seen inventory headaches: a customer walks in with a small cooler build for a microbrewery (20' × 10' walk-in, medium temp, but they want hot gas defrost because they have a heat recovery system). You don't stock it. They order offline. You lose the additive sale of the condensing unit and coils.
On the other hand, stocking too many variants ties up cash. In 2023, our branch had six pallets of slow-moving 460V units that sat for months. The trick: know your local market. In our region, most walk-ins are 208V single-phase (code F) for smaller businesses, and 460V three-phase (code H) for larger industrial. We shifted inventory to 80% 208V, 20% 460V. Turnover improved.
For small customers — the guy buying a single evaporator for his butcher shop — treat them seriously. I learned this one the hard way. In my early ordering days, I'd rush through small orders. Then I missed a voltage suffix on a $350 unit for a new restaurant owner. By the time he found out, his crew was on site, his walk-in was half-built, and our error cost him a day of labor. He didn't order from us again. Small doesn't mean unimportant. It means potential. Today's $350 order becomes a $3,500 system order when he builds his next location — but only if you get it right the first time.
How to Know Which Scenario You're In
If you're not sure which situation applies, ask yourself three questions:
- Is there existing equipment in place? If yes, you're in Scenario A — match the existing model and voltage exactly.
- Can you choose the voltage and refrigerant freely? If yes, you're in Scenario B — optimize for the system, not just the evaporator.
- Are you buying for inventory or for a single known build? If inventory, Scenario C — focus on your region's voltage and defrost frequency. If a single build, start with the customer's existing constraints.
One more thing: Bohn evaporators are reliable, but they're not magic. The nomanclature won't prevent installation errors. I've seen units installed with insufficient clearance for airflow (Bohn manuals recommend 18 inches minimum on the return air side). The model number can't fix that. But if you take the time to decode it — and check the full spec sheet — you'll avoid the kind of avoidable mistake that cost me $3,200 and a week of credibility.
Prices as of March 2025; verify current pricing with your Bohn distributor. Always confirm voltage, defrost type, and coil coating before ordering.
