Undervoltage fault during exercise cycle

Generac, Guardian, Honeywell, Siemens, Centurion, Watchdog, Bryant, & Carrier Air Cooled Home Standby generator troubleshooting and repair questions
nrp3
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Mon Feb 11, 2019 6:34 am

The relay alone is pretty reasonable and those instructions are pretty decent with wiring diagrams. I might try that out now that I've installed the board and the conversion harness.
Chris
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Mon Feb 11, 2019 8:47 am

You should be able to go in and view the hardware/software in the Nexus and see of it will have the newer version with the timer programmed in.
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Weserb
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Thu May 30, 2019 1:43 pm

Hello,

I’m having same issue (random Undervoltage shutdowns during exercise cycle). Happens in summer and winter. Engine fires up perfectly, but shuts down after 10 seconds. Will start and run normally if manually selected on.
2010 10KW Guardian +50
Serial 0059180
Model 0059180
Software OH6711 RevE

How can I determine my firmware version to see if it would be helpful to purchase a new Nexus board with the increased hold off time? Or alternately, is it possible to purchase new slip ring and brushes and install myself as it’s a very remote location?

Many thanks!

Wes Erb
Alaska
Chris
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Thu May 30, 2019 4:46 pm

How many hours are on the generator?

It might need a slip ring cleaning and brush pack. The slip rings aren't replaceable.
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Weserb
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Sun Jun 02, 2019 11:08 pm

Thanks Chris, the unit has 115 hrs total. Actually, in reading a tech manual I found, it claims the 8 and 10 kw units don’t have brushes or slip rings. The manual says the voltage is controlled by a capacitor that regulates the output. That being said, I can’t find this capacitor, so maybe that info is wrong.
Chris
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Mon Jun 03, 2019 9:23 am

Yes, that's the wrong manual for that unit. Nexus units used voltage regulators built into the controllers. The models before Nexus (most refer to them as 'Pre-Nexus') did use a voltage regulator capacitor system on the 8kW and 10kW, but it was ditched...

A resistance reading from the 0 to 4 wires that go down to the brushes will give you an idea if they are the trouble, but the connectors require special meter probes to test them as a normal size meter probe will damage them!
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Weserb
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Tue Jun 04, 2019 2:16 pm

Thanks Chris, I think you’re right, slip ring tarnish would explain intermittent problem, will polish and see. It might also explain the unit surges sometimes at idle, which could be from inconsistent voltage being transferred across brushes and causing regulator to act up. Thank you for clearing up capacitor question. If cleaning slip ring doesn’t solve issue, is it possible to switch out Nexus controller for newer Evolution controller that allows longer hold off time?
Chris
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Tue Jun 04, 2019 4:13 pm

Unfortunately no. Those controllers are totally different along with the connectors, where the wires are located in the connectors, and even the stepper motors and new intake system. It would be a tremendous undertaking and be more money than it's worth... :cry:
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Weserb
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Tue Jun 04, 2019 4:27 pm

Thanks Chris, I’ll hope the slip ring/brush cleaning will do the trick. Really appreciate your help! Cheers...
Chris
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Tue Jun 04, 2019 4:43 pm

No problem! Let me know if you need any parts along the way. :cool:
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