Alternator set up

bobsw · August 07, 2007, 08:21:22 PM

I have a MCI-7 with a 8v92 TA The 24 volt alt or Generator went out. I plan to install two alternators one 12 volt to charge the house batteries and a 24 volt to run the coach. The original was operated by four belts. My plan is to put both alternators with the pulleys facing each other. Each alternator would be would have one belt and run off of the four place pulley on the engine. Is their any drawbacks to this plan or problems that anyone can think of. I would rather solve the problems in the planing stage than have to correct it after it is built.

TomC · August 07, 2007, 09:00:12 PM

I would use two belts per alternator. I have yet to see a big rig truck that either has two V belts or one wide serpentine belt running the alternator. It is always good to have redundancy. Good Luck, TomC

Tony LEE · August 07, 2007, 10:28:24 PM

4 belts for 280 amps x 25v = 7000Watts and they are only skinny belts with limited power handling capability - say 2500W for one belt

What rating are the new alternators?

Also need to make sure that the alternators are good for either direction of rotation.

DrivingMissLazy · August 08, 2007, 05:52:51 AM

Alternators are not direction sensitive. They can be run either way. Also, I would think that much lower total alternator capacity could be utilized than the original unit. Two belts sure sounds like a good idea to me.
Richard

Sam 4106 · August 08, 2007, 07:21:04 AM

Hi Richard,
You are, of course, correct that "Alternators are not direction sensitive." BUT the cooling fans on alternators ARE.
Thanks, Sam 4106

DrivingMissLazy · August 08, 2007, 08:22:04 AM

Quote from: Sam 4106 on August 08, 2007, 07:21:04 AM
Hi Richard,
You are, of course, correct that "Alternators are not direction sensitive." BUT the cooling fans on alternators ARE.
Thanks, Sam 4106

Thanks Sam. I was under the impression that they were all of what I call the paddle wheel type which are non directional.

have personally never seen one of any other type. Most of my experience has been with the larger type industrial alternators and their fans are all non directional.
Richard

pvcces · August 08, 2007, 09:49:18 PM

Richard, the fans in small alternators are generally laid out like the pinwheel appearance of a hurricane. When they have straight radial fins, they carry the nondirectional spec. This problem crops up regularly with boat engines that have right hand rotation (called left hand when in automotive use).

This is why a right hand boat engine could be used for a left hand bus engine.

For what it's worth.

Tom Caffrey

NewbeeMC9 · August 09, 2007, 03:21:50 AM

In addition to fan rotation, make sure there is relatively cool air for the fans to circulate.

bobsw · August 09, 2007, 11:24:20 PM

The Detroit diesel shop told me that the alternators can turn either direction I will double check when they come in. They are a week late comming in. I will have to check to see if I can get pulleys for two belts for the alternators. If I use two belts each they will have to be mounted almost touching at the pulleys to line up with the pulley on the engine. It will be fun to see if I can build the brackets needed to get the adjustment right on the belts and get it all up and running. Thanks for the comments so far.

TomC · August 10, 2007, 04:14:39 PM

Yes the alternators can turn either way, but many times the fan is set up to only turn one way. I've seen the fan blades slanted so they are pulling the air away from the alternator. If the fan blades are not slanted, just straight, then it won't matter. Good Luck, TomC