Do ALL Onans run at 1800?

[harwill]

This may be a stupid question ( maybe a not-so-FAQ), but do all ONAN sets run at 1800 RPM? I see the benefits of slow speed and the engine derating at that RPM.
There are a lot of RV units out there and I was wondering if it was safe to assume they were 1800s without doing the research. Often, a buy opportunity comes/goes quickly without time to get up to speed and I don't need another Gen-a-junk!

What say?

[Wayne 440]

No. Most older RV sets are 1800, but certainly not all. And the new belt drive stuff, well who knows what speed they run.

[richard.bessey]

Negatory

Not all Onans are 1800 RPM
In fact, I think alot of the newer models are the 3600 RPM models.
Most (Not all) of the older Onans are 1800 RPM

Always check the nameplate! Never assume!

[Isaac-1]

No, there are even some members of the same general engine family that have models that run at both 1800 and 3600 rpms (this is true of both large and small units), such as the 1800 rpm CCK vs the 3600 rpm CCKB, or the 1980's 3600 rpm Techstar series of larger generators, an example being the 20 kw 20DL4 at 1800 rpms or the Techstar version at 35 kw 35DL4B at 3600 rpms. I think there are even a couple of models where only the output in the model name differ between the 1800 and 3600 rpm units.

Ike

[Dave Edmonds]

The Onan Quiet Diesels drive a DC generator which in turn operates an alternator. They run at whatever speed they need to run in order to generate the proper amount of power. The nameplate on them states engine RPM as "variable".
Dave Edmonds

[harwill]

Glad I didn't bet money on that question! Thanks to all for the answers; guess the devil is still in the details! What I'm hearing is the oldies are the goodies. But the DC generator-to-alternator is intriguing. Sounds like a complicated solution. I wonder how efficient that can be? Maybe its a good solution to widely varying loads...

[Dave Edmonds]

'scuse me. I meant to say "inverter" instead of "alternator".
Dave Edmonds