The Call at 4:57 PM
It was a Friday, 4:57 PM, and I was already mentally checking out. Then the phone rang. A client, a small manufacturing shop I’d worked with before, was in a panic. A new contract was starting on Monday morning, and their power utility had just notified them of planned maintenance outages for the next two weeks. They had a 70 kVA SDMO generator on order, but it was scheduled to arrive in four weeks.
“Can you get me a 70 kVA SDMO generator installed by Monday at 7 AM?” he asked. My gut instantly said “no.” A normal install for a unit that size—with the necessary pad, breaker, conduit, and connection to their main panel—takes two dedicated guys a full eight-hour day, not counting permit delays. But my gut also heard the desperation in his voice. The alternative was losing a contract worth $12,000 a month. (Note to self: stop answering the phone at 4:57 PM on a Friday.)
Why We Needed a 70 kVA SDMO Generator
When we first spec’d the job two weeks earlier, the client’s initial assumption (a pretty common one) was that they could get away with something smaller. He was looking at 50 kW SDMO generator models, thinking that would cover his lights, computers, and the main HVAC system. But this new contract was for a high-precision CNC milling job that required a constant, conditioned power supply for the machines. The 70 kVA model wasn’t just an upgrade; it was the minimum to handle the surge when those spindles kicked in.
The numbers confirmed it: a 50 kW unit would have under 20% buffer for startup loads. The 70 kVA model (which, for clarity, is roughly 56 kW of continuous power) gave them the safe headroom they needed for a 30% surge. We nearly went with the smaller unit simply because it was in stock. That would have been a $15,000 mistake in lost production.
The Race for a 50 kW SDMO Generator (And a Transfer Switch)
We found the 70 kVA SDMO generator from a distributor in a neighboring state. The rush fee was an extra $800 (on top of the $22,000 base cost), but it could be delivered by Saturday morning. That gave us Saturday and Sunday to install. Tight, but doable.
But the real problem wasn't the generator. It was the transfer switch. The client had a vague idea of how to install a generator transfer switch. He’d watched a few YouTube videos and wanted to “just have an electrician backfeed a 50-amp breaker,” which, per the National Electrical Code and basic common sense, is a fire hazard and a danger to lineworkers. I had to explain, very firmly, that if we were doing this, we were doing it right.
So there I was, Saturday afternoon, coordinating the installation of a 70 kVA SDMO generator (20' long, 7' wide, one-ton weight) while simultaneously sourcing a 200-amp automatic transfer switch. The local supply house had exactly one left in stock. (Finally!)
The Install (and the Mistake I Almost Made)
The unit itself is a workhorse. The SDMO’s Kohler-sourced engine is known for reliability, and this 70 kVA model was no exception. We had it craned into place on its concrete pad by 10 AM Sunday. The crew was efficient, running the conduit and pulling the heavy gauge wire. I was feeling pretty good about the timeline.
Then, the electrician stopped. “Where’s the neutral-ground bond for the transfer switch?” I froze. “What do you mean?” I asked. “I thought it was integral.” He pointed to the manual. For this specific setup, the bond jumper needed to be installed in the switch enclosure, not the generator. We had the wrong part.
My initial assumption was completely wrong. I thought all SDMO generators shipped with a bonded neutral for the switch. They don't. It depends on whether you're running a service-rated or non-service-rated transfer switch. We spent an extra three hours running to a wholesaler to get the correct bonding kit. That was the trigger event that changed how I think about every install, even for a simple 50 kW SDMO generator.
What I Learned: The ‘Honest Limitations’ of a Backup Plan
The system worked. By 6 PM Sunday, we had power tested and the system functioning. The client saved his contract.
Here’s what I took away from that weekend:
- Don’t undersize for the surge: A 50 kW SDMO generator is fantastic for a house or a small office. For a manufacturing startup, you need the 70 kVA for the headroom. The 70 kVA isn't the “best” generator—it's the right one for that specific load.
- A transfer switch isn't optional: The “how to install a generator transfer switch” search is the most common way people start their journey. My advice? Don't try to hack it. A proper automatic transfer switch costs $500-$1,200 but saves you from electrocuting a lineman or burning down your building.
“The alternative to a proper install wasn't saving money. It was losing a $150,000 contract or causing a safety incident. The cost of the transfer switch became a rounding error.”
This was true 10 years ago when the options were crude and manual. Today, automatic switches are safer and more affordable. It's a myth that they are only for high-end “largest quiet generator” setups. A 200-amp automatic switch for a 70 kVA unit is a standard, safe configuration.
Final Checklist Before You Buy
If you're looking at an SDMO generator, whether it's a 50 kW or 70 kVA model, ask yourself:
- What is my starting surge? (Add 30-50% to your running wattage).
- What is the code requirement in my area? (Get a permit! It protects you).
- Is my installation crew familiar with the specific bond requirements of the transfer switch?
I recommend the SDMO line for 70% of industrial and commercial backup needs because of its Kohler partnership and reliable build quality. But if you're just powering a few lights and a refrigerator at home, the 70 kVA is overkill (unfortunately). You might be better off looking at something like a Westinghouse 4500 watt inverter generator for portability or a smaller Kohler standby unit. For a home, a 10-20 kW unit is more appropriate.
That Friday call was a nightmare, but it taught me to always plan for the thing that can go wrong—even on a Saturday when you just want to go home.
