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Help on Onan OT Transfer Switch

hoghunter69

Registered
Received the manual for the ONAN OTS based on the nameplate-
OTCU 150c model # Spec 14g Serial # A930497579
The manual I received does not seem to match. I will be using this with a
ONAN 35EK. In the manual there are references to terminal block TB3 and I do not see a TB3 or any documentation that says TB3 is an optional install.

I'm including a couple of pictures to see if anyone can help figure out TB3's location if it even exists. Want to make use of the autostart of the genset when the xfer switch senses power loss. One manual says water cooled uses 2 wire start and 3 wire for air cooled. I assumed water cooled was city water air cooled was radiator. Another says radiator cooled uses 2 wire.

Any ideas?
 

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EricWood

Subscriber
Last Subscription Date
10/15/2019
Re: Help on OT XFR Switch

You don't have TB3.

It was an optional adder (option code M003).

Your switch is for two-wire start only as configured. The three-wire start module would have mounted on the larger stand-off pattern on the door, above the relay box.

Send me a PM w email address, and I can get the manual to you.

Eric
 

EricWood

Subscriber
Last Subscription Date
10/15/2019
Re: Help on OT XFR Switch

Forgot the picture....TB 3 (30-point terminal board) gets installed on the left side interior of the cabinet.
 

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Gunny

Subscriber
Last Subscription Date
gratis
Re: Help on OT XFR Switch

Your EK uses2 wire start.

Air cooled refers to an engine without a radiator such as a CCK, JB, DJC, etc. They use a 3 wire start.

A RJ series uses a 2 wire start.

Yes that transfer switch will work with your EK.

Where are the covers?
 

Billy J Shafer

Subscriber
Age
69
Last Subscription Date
09/03/2019
That is what is called the OT III. The last of the best. Much better than what is in production today. In my way of thinking. Works well with the EK.
 

EricWood

Subscriber
Last Subscription Date
10/15/2019
Hey Billy,

Just a FWIW comment (although you probably already know); The OTPC's [digital line] and the OTEC's [economy-commercial line] both still use the solid OT III switch mechanism. Just changed the controls for each.

In my opinion the digital controller holds its own in longevity--biggest enemy seems to be close-grounded lightning strikes. I've seen the old tough Power Sentry take lightning damage too, but not nearly as much. Needed to be a very close hit, usually with other periphial damage to other components in the facility as well.

(apologies for the side-bar)

eric
 

Gunny

Subscriber
Last Subscription Date
gratis
That is what is called the OT III. The last of the best. Much better than what is in production today. In my way of thinking. Works well with the EK.
Agree, probably the best ATS built. Solid, reliable, easy to work on, good documentation.
 

Billy J Shafer

Subscriber
Age
69
Last Subscription Date
09/03/2019
Eric The one thing I don't like about the OTPC switch. Is the display. Sometimes if it was outside in the sun. The display was hard to read. Other than that it was a good switch.

Gunny. Went to one of the local coal mines. To check on an OT III making a funny noise after a lightning strike. Open the door and just shut it. Told them just go buy another switch. Everything inside was burned.
 

hoghunter69

Registered
Terminal Block TB1 has 1 NO and 1 NC terminal for both normal power and emergency power rated at 10a @ 250v. Can an overhead light be wired to the emergency side so when the genset is running, there is light available at the set? Or are these just relay connections?
 
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