• If you like antique engines, vintage tractors or old iron machinery, register and join us. When you register on Smokstak, please give complete answers and fill in all blanks. IF YOU ARE ON WIRELESS OR SATELLITE, GIVE YOUR CITY AND STATE! NO ZIPCODES! All registrations are manually approved.

Kohler 12 RES - Dead Leg

TNBob

Registered
Hi Folks,

I have a 12 RES I'm using for backup of my solar system. It is wired into my inverter along with the capability to 'by pass' the inverter/charger and send power from the generator straight to the house if want. I was doing that because of a particular situation I was testing with the solar controls and discovered the generator output to the house is only 120 VAC total with one of the 'hot legs' completely dead. I checked the voltage coming into the house main panel and also upstream at the generator input to the inverter enclosure with identical results as follows:

LEAD 1 to LEAD 2 = 120 VAC
LEAD 1 to NEUTRAL = 120 VAC
LEAD 2 to NEUTRAL = 2 VAC

Lead 2 appears to be absolutely dead.

Any suggestions. Any help appreciated

Thanks Bob
 

Zephyr7

Registered
If you’re showing 120v between hots (which should show 240v), then you have something other than an open going on. Lead 2 might be connected to neutral. Be careful making measurements with a DMM here since you might show “voltage” where there isn’t any due to the high input impedance of a typical DMM. A simple old-school pilot light tester won’t have this problem.

Check the voltage at the line breaker in the generator enclosure. See if you get 240v between the two hots and 120v from either hot to neutral (ground) at this location. If you do, then you have a wiring problem somewhere and I’d suspect something screwy with the way the inverter is wired into the setup. I’ve heard of solar “installers” doing weird things before.

Bill
 

dkamp

eMail NOT Working
Is there a windings connection point on the genhead somewhere OTHER than the leads you're measuring? If so, check the connections closely, perhaps someone reconfigured the winding connections to provide just 120... or there's a lead broken loose there...
 

Vanman

Subscriber
Last Subscription Date
07/10/2019
Alternatively, an open line on a three wire system will result in exactly these readings when there is a line to neutral load present on the dead line. The load makes the dead line have continuity to the neutral.

I’d check right at the generator terminals, and again on the generator side of the generator breaker, if so equipped.

If it’s dead there I’d start looking for a broken wire. Hopefully the winding itself has not failed.

Keith
 
Last edited:

Zephyr7

Registered
Alternatively, an open line on a three wire system will result in exactly these readings when there is a line to neutral load present on the dead line. The load makes the dead line have continuity to the neutral.
The 12RES is a single phase residential genset. No three phase option.

Bill
 

Mark Dieckmann

Registered
I believe that is a 4 lead alternator, capable of being reconnected for 120 volt only. You would get readings similar to what you have. Are you sure it ever produced 240 volt?
 

dkamp

eMail NOT Working
that's down the lines of what I was thinking, Mark-
if the genhead had four wires to two winding sets, you'd have 120 across each winding... connect them in-phase for 120v high current, and in series out-of-phase with a neutral connected to the centerpoint for 120/240 low current;.
 

TNBob

Registered
First, thanks to all concerned for the input. I'll start working through the suggestions in days ahead as time and weather allow. Fortunately the solar system is pretty capable so I have a bit of breathing room.

To answer some of the questions:

I bought the 12 RES as a 120/240 VAC system, and that's the rating given in the various tech documents (for example, Figure 1-1 of the Service Manual). Have I measured the actual output voltage before? No, not really. However it's been connected to the system/house for over a year, and I've run the house on 'by pass' (that is with the generator output not passing through the inverter but going directly to the house) several times during that period with no problem. What alerted me to the problem this last time was that a few of the 120 circuits in the house were without power, which I thought was strange. At first I thought it was nuisance tripping from the GFICs, but they wouldn't reset. I then put 2 and 2 together and checked the voltage coming into the house with the results I shared. It was apparent one 'hot' lead wasn't hot.

My next step was to check the voltage out at the power shed where the solar setup lives. To make sure it wasn't related to the solar set up, I measured the voltage right at the generator AC input to the solar system control center and got the same result as at the house. One leg is dead coming from the generator.

I don't know if that clarification suggests anything to anyone, but thought it might be helpful.

I'll be diving into the other suggestions as time allows.

Thanks,

Bob
 

Zephyr7

Registered
There is a double pole breaker in the generator housing, probably a 50A or maybe 60A breaker. Check the voltage at the output of that breaker.

I’d also check that the lugs on the breaker are tight. I’ve seen those vibrate loose before, which could have let one of the wires pop out. If that’s the case, I’d check all the other screw-type terminals too to make sure there are no other loose connections in there waiting to surprise you.

Bill
 

Zephyr7

Registered
Make sure to do a good visual inspection of the loose lug. Loose lugs can lead to excessive heating which sometimes damages the breaker contacts. Look for discoloration of the metal lug parts and the Bakelite housing of the breaker itself.

Bill
 
Top