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Author Topic: Kohler 7CM21-RV generator  (Read 5999 times)
Van
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« Reply #30 on: July 16, 2012, 08:57:42 AM »

Yup diesel is the way I would like to go, but this is a step closer in the mean time. I did notice this unit has been running a little rich, but until I get the exhaust dialed in not much use in trying to retune at this point. And speaking of points, the ones in the unit appear to have been replaced... just not gaped very correctly.
  I have been mulling over the schematics for the different models, there are 2 7000 units in the installation manual one rated for 120/240 and mine at just 120v. The only difference that I can see at the moment, is that mine has a jumper at the circuit breaker and the 120/240 unit does not, easy fix I thinks to my self right, well not so fast there buck-a-roo, with out a full understanding of this set up I'm not willing to venture into uncharted (for me) waters till I sort this out. My buddy Paul the elec contractor has offered to have a look see. More to come! Right now gonna make a template (courtesy of the manual) so's I can get this 350lb beast mounted in it's new home.
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« Reply #31 on: July 16, 2012, 09:00:13 AM »

I converted my Powertech generator from 240 volt to 120 volt.  One of the instructions as part of the conversion was to place a jumper between the two breakers on the output.  The jumper may be there for a very good reason.
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thomasinnv
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« Reply #32 on: July 16, 2012, 11:04:12 AM »

The purpose of the jumper is to balance the loads between the two legs. Mine is setup the same way. Matter of fact, the jumper between the two is the only difference between 120 and 240 setup on mine.
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Van
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« Reply #33 on: July 16, 2012, 11:04:29 AM »

My point exactly, that jumper may be there for a reason that I am unaware of at this moment. For those that might be following along, here is the install manual with the schematics for mine (7cm21) and just below it the 7cm61 which is pretty much the same that I can see, cept for the jumper going into the double circuit breaker. So if anyone wants to jump in and help it would sure be a help Wink. thanks Mucho bunches Grin Grin

Edit. Helps if I put a link up huh! dummy me, see I need all the help I can get Grin Grin Grin
http://campkahler.com/files/kohler-7cm21-rv-installation-manual-tp5005.pdf
Page 29 for mine and page 30 for the 120/240 model Smiley
« Last Edit: July 16, 2012, 11:08:57 AM by van » Logged

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« Reply #34 on: July 16, 2012, 11:10:35 AM »

IMHO, unless you are planning on running any 240 loads, leave the jumper and just run 120. I originally wired mine as 240, but later changed to 120. I have no 240 loads, and being wired as 120 with the jumper between the two legs, it will always be balanced across the two legs. There has been some speculation that running unbalanced for a prolonged period of time can damage the generator head. If it's true or not I don't know, but I'm not willing to be the Guinea pig with my money.
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« Reply #35 on: July 16, 2012, 11:32:26 AM »

Where are all the generator gurus when we need one you guys are confusing the hell out of me I thought a true 220v generator had 2 hot 110v legs a neutral and ground  

Matt's generator uses both 110 legs for balance nothing in his coach tied to just one 110v leg then he has a 240v cook top so I don't understand the jumper at the generator ?
« Last Edit: July 16, 2012, 11:41:48 AM by luvrbus » Logged

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Van
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« Reply #36 on: July 16, 2012, 12:03:00 PM »

Clifford, on mine there are 2 separate 120 legs feeding the double breaker on the generator (called circuit interrupter), but only to one side of the breaker with a jumper feed to the second breaker. On the other side of the breakers going out there are one seperate leg on each to feed the breaker box on the coach. What Thomas says makes a little sense about the load being balanced that way thru the jumper. No, I don't plan on having any 240v appliances, the biggest loads will be from my 2 1350 btu Colemans. I know this is probably simpler than meets the eye. The other 7000 kohler mentioned, the 7cm61 (120/240) is as Thomas mentioned is for 240 powered appliances, which makes it an even pull off each 120v leg. Where as if I pull the jumper off and connect the 2 legs feeding the generators double breakers separately would make it unbalanced because of no actual 240 draw. Clear as mud Huh!  Huh Huh
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« Reply #37 on: July 16, 2012, 12:53:52 PM »

They way I read this is you are saying the generator needs to be wired for 240 or 120 outside the head why ?
« Last Edit: July 16, 2012, 02:27:31 PM by luvrbus » Logged

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Len Silva
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« Reply #38 on: July 16, 2012, 01:46:57 PM »

There is obviously more to changing from 120 to 240 than just removing a jumper.  There has to be some internal rewiring as well.  Otherwise, the jumper would be a dead short across 240 volts (GO BOOM).

Looking at the wiring for the 7CM21-RV, the 120 volt leads connect to terminals 2 and 4, and with the neutral on  goes to term 1, 3 and ground.

On the model 7CM61 which is the 120/240 model, L1 connects to term 4, L2 connects to term 1 and the neutral connects to term 2, 3 and ground.

All removing the jumper would do is remove power from one of the breakers.
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Van
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« Reply #39 on: July 16, 2012, 02:30:58 PM »

Clifford, this is where I fall off the edge with elec lol. I am gonna need to re-wire my bus to take advantage of the available 50 amp at the rv parks, I know... you told me early on to just go ahead and set up for 50A, in the beginning  ( I think that was the one and only time I had never taken you advice Embarrassed Grin). To set up for 50A I know I am gonna need two hots(120V ea.) one neutral, and a ground. Now wiring this stuff up in the coach I'll probably use an 8 or 10 gauge (what ever I can lay my hands on Roll Eyes Grin) wire. I got the pig tail, no biggy. Where I get lost is, I checked the schematic and am thrown off kilter when I saw the jumper wire in there feeding the two circuit breakers. Thomas posted something that kinda clicked, it was about "Balanced Load (s)" so I think I am starting to understand it now, the jumper keeps the load balanced when wired for 120V-50A only. Removing the jumper, allows for two separate 120V hots when using appliances requiring 240V to operate on. So how am I doing so far? I'm ready ta drop back three and punt  Grin Grin Grin Grin


    BZZZZZZZZ Shocked Shocked  
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Van
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« Reply #40 on: July 16, 2012, 02:35:42 PM »

Len there are two hots attached at the first breaker, the jumper goes across to the second breaker, thanks fer lookin at the schematic by the way Wink Smiley

   Some photos might help here, I'll go git em" Grin
« Last Edit: July 16, 2012, 02:37:22 PM by van » Logged

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« Reply #41 on: July 16, 2012, 02:47:20 PM »

Van we will be home for a couple of days this weekend I have a bunch of MC cable we removed from the building here come get it save your money it only will cost you a Burger King  I am not losing count of the burgers lol   

good luck
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Van
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« Reply #42 on: July 16, 2012, 03:20:25 PM »

OK Clifford, I might splurge and take ya up town to Carls lol!
 Here are a few photos, first one is the top view, Breakers, flex pigtail

Second shot, wires 4-2 along with jumper on a three way spade connector hooked to the first breaker w/jumper feeding the second breaker. The two leads on the other side are from the connection pig tail.

Here the pig tail (oink! Grin)comes in,top/left the grey LO and the green are grounded on the stud

Wire 1-3 coming from the wire tied bundle are grounded to the chasis via the green screw.

  Wink Wink
« Last Edit: July 16, 2012, 03:24:11 PM by van » Logged

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« Reply #43 on: July 16, 2012, 04:26:54 PM »

I would wire any motor home generator under about 8 KW for 120 volts.  It eliminates any concern about load balance and is just simpler to deal with.

The shore power, of course, would be wired for 120/240.
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« Reply #44 on: July 16, 2012, 05:29:03 PM »

To anyone else reading and following this thread...DO NOT simply "throw in a jumper" and think you are going to "balance" your generator. Most generators are reconfigured inside the head by moving jumper wires around INSIDE the head. If anyone is planning on changing anything about the way your generator is wired, you MUST get the manuals and do it the way YOUR generator is designed to be wired. My generator head is not reconfigurable, it is designed to be able to connect the two 120v leads for a load balanced operation. Yours may not be. You need to find out, don't just do it because "someone else did and it worked for them". IF YOU LET THE SMOKE OUT, DON'T BLAME ME! YOU HAVE BEEN WARNED!!!
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There are three kinds of people in this world....those that make things happen, those that watch things happen, and those that just wonder what the heck is happening. Which one are you?

1977 MCI Crusader MC-8
8V71N/740
95% converted (they're never really done, are they?)
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