Generac 15KW rotor slip ring damage

Generac, Guardian, Honeywell, Siemens, Centurion, Watchdog, Bryant, & Carrier Air Cooled Home Standby generator troubleshooting and repair questions
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Orber
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I have a 17 year old Generac 15KW/13KW standby generator model #004390-1, serial # 3514453-3699533 (running on NG). It stopped working about 8 hours into a power outage. Initial evaluation revealed a damaged starter with damaged pinion teeth. After a replacement starter also got damaged, I decided to investigate further.

Generator AC voltage (power winding) output is zero, maybe residual voltage at best. There is no voltage from the stator excitation winding or the stator run winding. Rotor slip ring analysis reveals a missing brush on the negative side of the holder and a gouged/damaged slip ring ( so no DC excitation current). The engine also is leaking some oil (not sure from where yet, but not from crankcase breather).

Question: would replacing only the damaged rotor with a new voltage regulator be OK, or will I need to replace the stator as well? If the combo needs to be replaced, given the age of the unit, should I just consider a new unit?

Thanks in advance for any help, guidance, opinions or possible solutions.
Orber
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Clarification of post second paragraph: "there is no meter voltage measurement from stator excitation winding or the stator engine run winding...." Thanks for any assistance.
grsthegreat
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im not sure if you can find anyone out there that would press on a new set of rings. We had 2 shops here where i live, and both have closed up years ago.

that series of generators is known for busting brushes. ive replaced many over the years. i have had 2 that were major wrecks, but did not damage the rings (lucked out). they worked fine after rings cleaned and new brushes with bushings installed.

personally, id just replace it before i tried replacing rotor and stator. they will cost nearly 1/2 the price of a new unit, and take just about as long to install as removal and replacing generator. major thing is you will need to make sure you have a minimum of 5 control wires present from existing transfer switch. many old switches only have 4. if its in conduit not too big of an issue.
Orber
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Thanks for the response Jedi Master. New stator/rotor and AVR about $1800, plus time spent on installation (that's without looking at the cause of the oil leak). If a need a new PCB, that puts me over $2000.00. Local dealer wants a little over $6000.00 to install a new 14KW using the old transfer switch. I do have conduit to run a fifth wire. Should I still proceed with a new unit, in your opinion? Also, being in Michigan, would you add a winter kit to the unit if I go new? Thanks in advance.
grsthegreat
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Personally, id go for new. The new one has hydraulic valves, and it’s not 17 years old.

That being said, as long as pulling missing wire ( if even necessary) and depending on the distance gen is from transfer switch, I can usually swap out a generator for like sized one in 2-3 hours. Seems like a steep price to do job.

I just swapped one out last week. 3 hours total time. Only me… no help.
Orber
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Thanks for your input. That price was the least expensive of the estimates. Winter kit??
grsthegreat
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I personally really like the oil heater kit, and feel I can hear the difference in starting on cold unit. DONT get the battery or breather kits. Too much damaged units over the years caused by them. Especially the battery heaters. Everyone I service that has one, has a boiled off battery. I mean every one.

Another real benifit I love on newer units compaired to old ones are protection from failed voltage regulators. I just had another house that had 370 vac run thru their system due to failed voltage regulator on older 4000 series generator….one with the printed circuit board. The generator never shut down. Fries TVs, refrigerators, freezers, garage door openers, built in oven and one of those craft matic adjustable bed units. He said there multi $1000’s in damage. Just now messing with insurance company over it and their fighting him.

The newer unit would shut down and prevent this from happening.
Orber
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I appreciate the additional feedback. The distance from my unit to the transfer switch might be 20 feet max (to run the fifth wire). As an ordinary homeowner, I've never gone through the steps of breaking in a new generator. That's where the local guys want the hefty price markup (they want to run it in the shop supposedly for three hours, then change the oil to 5W-30 and swap out the filter, maybe something additional, then deliver it and install it

Would you or anyone else on the forum be able to comment on whether a pretty handy DIY'er may be able to tackle such a project without getting into too much trouble? You said you swapped one out yourself in 3 hours. Is the 2-3 thousand dollar savings worth it, or is it a foolish thought? (I'm comfortable with doing electrical work, plumbing and engine repair). Thanks in advance for any advice.
grsthegreat
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Well, I know guys that run the unit, prior to install, in shop.I never have except on units I’m repairing. I know of no requirement to do this. I never swap out oil to synthetic until it has 15-25 run hours…generac manual says 25. It usually takes a year use to reach this milestone on average. But could happen in a few days with an outage.

If you install the oil warming winter kit, the instructions say to change oil to synthetic at same time. I usually leave the winter kit unplugged until first oil change as I’m too paranoid of swapping to synthetic on engine not run in. But maybe that’s just me.

The hardest part on swapping out generator is moving a 500# generator. I have a transport cart that allows 1 man to move them. Might be hard for you to do it without help….like 4 guys and 2 pieces of 3/4” rigid pipe placed in lifting holes. This is when you find out who your friends are.

For a simple swap out , I would suggest a homeowner first shut off generator, then kill power to generator by pulling all fuses from transfer switch, unhooking battery in generator, and killing power to house as a safety precaution to untrained personnel. You unhook all wires inside generator control panel that feed from transfer switch, and remove conduit from generator . Shut off and unhook gas line. Remove unit

Install new unit. Pull 5th wire if necessary from transfer switch. You will need to add a T1 fuse block IF your existing transfer switch does not have 3 fuses already. Instructions for this are in fuse kit.

The new generator has 4 power leg wires just like old unit. You will need to make sure wires providing power from generator to house are sized properly to handle slightly larger generator. The 5 control wires needed are N1, N2, 194(15b), 23 and the new T1. The black 0 wire will not be used on older switches that don’t have load shedding capabilities.

The old rubber gas flex should be changed to the new stainless steel one supplied in generator. The generator has a built in sediment trap. You NEED to Buy some leak detector liquid from Home Depot and check all gas joints including the ones inside generator. You need to add a short 3/4” nipple from generator internal regulator to the outside of generator.

Most inspectors require generator to be bolted down if on concrete or light weight pad to prevent movement and straining of gas line.

It’s totally doable to someone with mechanical capabilities. Its not like someone trying to install a new transfer switch. That requires experience as far as I’m concerned. Ive seen so many botched jobs….including one I visited today.
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