In my first year (2017), I thought I had it figured out. I'd ordered a 600 kVA Kohler SDMO generator for a commercial site, grabbed a Kohler 14RCA for an RV customer, and even threw in a 3000 watt RV generator as a backup. All looked good on paper. But the surprises came fast—and expensive.
Generator Sizing: Bigger Isn't Always Better (Or Is It?)
People think that oversizing a generator guarantees safety. Actually, undersizing kills reliability, but oversizing can also wreck fuel efficiency and startup surges. Let me explain with my two mistakes.
Mistake #1: The 600 kVA Monster
I spec'd a 600 kVA Kohler SDMO for a factory that only needed 400 kVA continuous. My logic: 'More headroom, no risk.' The result? The generator ran at 40% load most days, carbon buildup fouled the injectors, and after six months, we had a costly overhaul. That mistake cost $4,200 in rework plus a week of downtime.
What I should've done: Match the generator to the actual load profile. A 500 kVA unit would've run at 80% load—sweet spot for diesel efficiency. The industry rule of thumb (NEC 700.5) suggests sizing for 80-90% of nameplate capacity for standby applications. I ignored that.
Mistake #2: The 14RCA RV Generator
Kohler 14RCA is a 14 kW residential/light commercial standby generator. But I sold it to an RV owner who needed a mobile unit. The unit was installed on a trailer—great. But the RV's existing 3000 watt RV generator (a cheap portable) was still connected. The 14RCA's automatic transfer switch didn't like sharing a bus bar with the old gen. Result: Under-volt trips every time the A/C kicked on.
Never expected the portable to interfere. Turns out, the 3000-watt unit had a poor power factor that confused the ATS. The surprise wasn't the 14RCA—it was the cheap backup causing chaos. We disconnected the old generator, and the 14RCA ran flawlessly. Lesson: Don't mix generator types without verifying compatibility.
Battery Chargers: The Nikon D40 Case
Now, a weird one. A client brought a Nikon D40 battery charger to a job site, wanting to charge it off a Kohler generator outlet. I assumed 'any AC outlet works.' Wrong. The charger's switching power supply was sensitive to the generator's THD. The 14RCA's THD is around 5% (clean enough for most electronics), but a cheap portable might hit 20%. We fried two chargers before I checked the specs.
I have mixed feelings about this. On one hand, a dedicated inverter generator would've been safer. On the other, a simple voltage regulator filter costs $30. I now recommend customers use a pure sine wave inverter for any sensitive electronics. Kohler's own manual states: 'Devices with sensitive electronics may require additional filtering'—I should've read it.
Spark Plug Wire Crimping: A $450 Lesson
Finally, how to crimp spark plug wires—yes, that's related. I once replaced spark plug wires on a Kohler generator engine (same terminals as many automotive). I used a standard ratcheting crimper. The crimp looked fine. But the wire insulation was slightly damaged inside. After 50 hours of run time, the misfire started. We replaced the whole set—$450 parts and labor wasted.
The assumption is that all crimpers are the same. The reality is that resistor-type spark plug boots need a specific die profile. A proper crimping tool (around $60) has a stepped die that doesn't crush the conductor. People think the crimp is the hard part—actually, selecting the right tool is. Now I use a tool from Wire Care (part #WC-208) and test each connection with an ohmmeter.
“Switching from a generic crimper to a proper tool cut our rework rate from 12% to under 1%. That's efficiency saving real money.”
What I Learned: A Pre-Check Checklist
After those three fiascos (and a few more I don't have space for), I created a simple checklist for any generator-related job:
- Size against load profile — not nameplate max
- Verify voltage/waveform compatibility with attached devices
- Use proper crimp tools for spark plug wires
- Cross-check all grounding and neutral bonding per NEC 250
Since implementing this checklist 18 months ago, we've caught 47 potential errors. That's saved roughly $8,300 in rework and customer compensation.
So if you're choosing between a Kohler 14RCA and a 3000-watt portable, or wondering if your Nikon charger will survive—please, take the extra hour to verify. It's cheaper than fixing the mistake. (Trust me, I've got the invoices to prove it.)
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