Generators and Motors
[Home] - [HELP] - [Forums] - [Library] - [Photo Gallery] - [Groups] - [Classified Ads] - [Subscribe] - [Links] - [Books] - [Sponsors] -

Go Back   SmokStak > SmokStak® Vintage Electrical Equipment > Generators & Electric Motors General Discussion > Onan Generators
Forgot Password? Join Us!

Notices

Onan Generators Restoring, operating and maintaining vintage Onan generators.

Onan Generators

Onan 3.0DJA-3CE-2236T 240V 12.5A to 120V 30A


this thread has 9 replies and has been viewed 2529 times

Reply
 
Thread Tools Display Modes
  #1  
Old 01-30-2011, 06:38:20 PM
bee hennigar bee hennigar is offline
Registered
 
Join Date: Nov 2009
Location: penticton british columbia, canada
Posts: 4
Thanks: 0
Thanked 1 Time in 1 Post
Question Onan 3.0DJA-3CE-2236T 240V 12.5A to 120V 30A

Can I toggle between both amperages?
Reply With Quote
Sponsored Links
  #2  
Old 01-30-2011, 07:12:08 PM
Jim Rankin Jim Rankin is offline
Registered-III
 
Join Date: Nov 2004
Location: Faunsdale, Alabama USA
Posts: 4,436
Thanks: 71
Thanked 1,186 Times in 969 Posts
Default Re: 3.0dja-3ce-2236t 240v 12.5a>120v 30a

With a -3c voltage code, you should have a 120, 120/240, 240 reconnectable generator end with 4 wires coming out. Reconnection diagrams are usually silk screened onto the cover of the wiring box attached to the generator. If you want to avoid load balancing and do not need the 240 volt output, I believe your generator can be reconnected for 120 volt output only. Then you would get the 25A all on a single line and neutral. If you only need 240, no need to reconnect from the 120/240 connection, just use the two lines for your 240, you will not connect to the neutral. Or if you want 240 and one of the lines is to be your neutral (you are in europe or australia for instance), you can reconnect for that instead.

The amperage is expressed as amperage per line. If you are connected for 120/240 you can pull 12.5 amps on each line x 2 lines = 25Amps (not 30). The 12.5 can be any combination of 120 volt loads connected line to neutral and 240 volt loads connected between the two lines. You can pull the full 25amps at 120 volts only if you can divide it perfectly between the two lines.

It would be possible to switch between the reconnection schemes if you had a suitable heavy duty switch. However, you CAN NOT switch with the generator turning.
Reply With Quote
  #3  
Old 01-30-2011, 07:13:48 PM
bee hennigar bee hennigar is offline
Registered
 
Join Date: Nov 2009
Location: penticton british columbia, canada
Posts: 4
Thanks: 0
Thanked 1 Time in 1 Post
Question 3.0DJA-3CE-2236T 240V 12.5A to 120V 30A

Hi; I'm guy named Bee,a newbee who loves old iron.Backup for our hybrid solar system is an Onan 3.0DJA-3CE-2236T. It powers a 100 amp 12v multi stage Heart charger/2000 watt inverter when the sun don't shine,a 240v 8 amp deep well pump for about 30 min. every 10 days to fill a reservour and a 240v 10 amp tanning bed for 10 min. 3 times a week in the winter. On a thread posted by dr_fusion and replied to by BTPost Bruce from Alaska about wiring this gen from 240v 12.5 amp to 120v 25 amp. Is it possible to wire in a switch to toggle from one to another?


Thanks beehennigar@hotmail.com
Reply With Quote
The Following User Says Thank You to bee hennigar For This Post:
  #4  
Old 01-30-2011, 07:19:16 PM
Billy J Shafer's Avatar
Billy J Shafer Billy J Shafer is online now
Subscriber
 
Join Date: Nov 2004
Location: Centerville, Texas
Posts: 17,010
Thanks: 8,810
Thanked 14,370 Times in 6,781 Posts
Default Re: 3.0DJA-3CE-2236T 240V 12.5A to 120V 30A

They do make such a switch. But most end up being destroyed when people switch them under load. I like just one wiring set up. That way no way to change to another voltage by mistake.
Reply With Quote
  #5  
Old 01-30-2011, 07:35:51 PM
bobbyz72 bobbyz72 is offline
Registered-III
 
Join Date: Nov 2009
Location: Stafford TX
Posts: 1,281
Thanks: 199
Thanked 406 Times in 312 Posts
Default Re: 3.0DJA-3CE-2236T 240V 12.5A to 120V 30A

You can put a couple heavy duty 20 amp light switches together, and make your own, just dont switch them while running..
Reply With Quote
  #6  
Old 01-30-2011, 07:46:15 PM
Jim Rankin Jim Rankin is offline
Registered-III
 
Join Date: Nov 2004
Location: Faunsdale, Alabama USA
Posts: 4,436
Thanks: 71
Thanked 1,186 Times in 969 Posts
Default Re: 3.0DJA-3CE-2236T 240V 12.5A to 120V 30A

Since you have a 120V load that is larger than you can connect to the generator while it is connected as 120/240 3 wire. You could either get a 240 volt inverter/charger unit and connect the generator for 120/240 or 240 only. The 240 is always perfectly balanced, current flows between the two lines.

OR get a 240/120 transformer of at least 3kVA/3000VA and use it to either

go up to 240 volts for the pump when the generator is connected for 120 only

or
go from 240 down to 120 for the inverter/charger when the generator is connected for 120/240 or 240 only.

Either way you will have all the capacity of the generator balanced across the whole winding.

A transformer can take voltage up and down, Once you get one big enough (3 kVA minimum), the ratio between high and low and the maximum voltage is what is important. Some transformers have multiple small % voltage trimming taps. If that is the case, when using a transformer in reverse, I have been told the taps won't work to adjust the voltage, though I don't know why.

My recommendation would be to use the transformer for the well pump. It could be smaller and the losses (only a small %) would not be as critical with the smaller load on the generator.
Reply With Quote
  #7  
Old 01-30-2011, 07:50:45 PM
Wayne 440 Wayne 440 is online now
Registered-III
 
Join Date: Nov 2004
Location: Kentucky
Posts: 5,963
Thanks: 363
Thanked 5,044 Times in 2,425 Posts
Default Re: 3.0DJA-3CE-2236T 240V 12.5A to 120V 30A

Quote:
Originally Posted by Jim Rankin View Post
...Some transformers have multiple small % voltage trimming taps. If that is the case, when using a transformer in reverse, I have been told the taps won't work to adjust the voltage, though I don't know why...
I have used tapped transformers "backwards" on several occasions, and the taps work as well one way as the other. YMMV.
Reply With Quote
  #8  
Old 01-30-2011, 08:43:47 PM
Dave Edmonds Dave Edmonds is offline
Registered-III
 
Join Date: Nov 2006
Location: Jackson, Mississippi, USA
Posts: 1,780
Thanks: 423
Thanked 679 Times in 495 Posts
Smile Re: 3.0DJA-3CE-2236T 240V 12.5A to 120V 30A

Jim's idea makes the most sense, and eliminates having to change any wiring to accommodate the various items. Have to ge a transformer, though.
Have you made sure that the charger can't be rewired for 240-volt operation? Some units have internal jumpers that allow them to be connected for 120 volts or 240 volts - if yours offers that option, all you have to do is change it over and go "totally 240"!!
Dave Edmonds
Reply With Quote
  #9  
Old 01-30-2011, 08:57:36 PM
Jim Rankin Jim Rankin is offline
Registered-III
 
Join Date: Nov 2004
Location: Faunsdale, Alabama USA
Posts: 4,436
Thanks: 71
Thanked 1,186 Times in 969 Posts
Default Re: 3.0DJA-3CE-2236T 240V 12.5A to 120V 30A

In my previous response, I assumed that the Heart charger/inverter was over 12.5 amps. Even with losses, 100 amps @ 12 volts (1200 VA) would most likely "fit" on one leg of a 120/240 generator. Still even if it is less than 12.5 amps, it would be better to balance it since your generator will have this load full time whenever the "sun don't shine".

So, find a 2.5 kVA or larger dry transformer(10 amps tanning bed x 240 volts = 2400 VA ) to go from 120 to 240 and supply your 240 volt system with it. When it's not needed, switch off the transformer and connected 240 volt wiring you won't have even the small loss associated with an unloaded transformer's magnetizing current.

Like Billy says, sooner or later the reconnection switch will get switched under load.
Reply With Quote
  #10  
Old 01-31-2011, 03:15:19 AM
Isaac-1 Isaac-1 is offline
Subscriber
 
Join Date: Aug 2008
Location: Leesville, Louisiana
Posts: 3,277
Thanks: 120
Thanked 1,153 Times in 914 Posts
Default Re: Onan 3.0DJA-3CE-2236T 240V 12.5A to 120V 30A

I agree with what the others have said, set the generator up for 120V only so you get the full output, and not have to worry about balancing between 2 1,500 watt legs. These generators are just too small to try to balance loads set up in 120/240 when you consider it can be overloaded by a single 15 amp household appliance when set up in split phase 120/240 mode. These relatively small dry type transformers can often be found at scrap prices (check out ebay in the $75 - $100 range, new they sell for around 10 times this much), but be aware they are very heavy, so if you can find one local it would be better.

Ike

p.s. many of these transformers are used in industrial areas for lighting and office equipment, most common ones take 240/480 on the primary side and drop it to 120/240 on the secondary, you would be running it in reverse only using one of the taps. Some may take 240V primary to 120V secondary only, but in my limited experience are less common. It does not hurt much if the transformer is slightly oversized, like others have said you will probably want to put a disconnect switch on it when not in use to prevent running losses. If you know an industrial electrician they might even be able to get you a scrap one for free.

Last edited by Isaac-1; 01-31-2011 at 03:22:17 AM.
Reply With Quote
Reply


Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

F o r u m Jump

Similar Threads Chosen at Random
Thread Thread Starter F o r u m Replies Last Post
Another stupid question about converting from single phase 120v to single phase 240v! Patrick Onan Generators 7 11-30-2011 02:08:16 PM
Which generator 120v or 240v? pnora Onan Generators 13 01-27-2011 10:07:26 PM
Kohler 5.5cm21 120v change to 240v marvink Kohler Generators 0 12-28-2007 11:26:19 PM
MDJE 7.5K reconnecting to 120V/240V LarryGlover Onan Generators 6 08-07-2007 10:01:40 PM
Onan DJC-3CE/2236T Lee Wise Onan Generators 10 03-13-2007 09:25:47 PM


Use "Ctrl" mouse wheel to change screen size.
All times are GMT -4. The time now is 09:52:08 PM.

Smokstak and Enginads site search!


All use is subject to our TERMS OF SERVICE
SMOKSTAK® is a Registered Trade Mark - A Community of Antique Engine Enthusiasts
Copyright © 2000 - 2016 by Harry Matthews P.O. Box 5612 - Sarasota, FL 34277