Generac Troubleshooting

[Dave]

Utility power outage and the Generac 04390-2 (13kW NG) did not start in 50F weather. Assuming for now the problem is not with the generator because when the 200-amp breaker installed between the utility meter and the automatic transfer switch was moved to the off position, the Generac started as expected. Does this description sound like a relay or other automatic transfer switch component waiting to fail more permanently? Replies appreciated.

[Stormin Mormon]

Mental note to Dave: Do not start generator while under load. Make a sign, and tape it to the generator.

[Tom Horne]

Anyone who tries to answer this question with the information given is bound to be wrong or really lucky. Is the installation equipped with an automatic transfer switch?

-- Tom Horne

[Pete C.]

The OP referenced an automatic transfer switch twice. While I didn't find the part number the OP listed, presumably he's referring to a package of the 005253 genset and an RTS transfer switch.

The transfer switch manual:

The genset manual:

The installation and owner's manual: The OP didn't provide a lot of details, but some items to review (besides the manuals) would be:

- Was the system tested after installation by simulating a power failure via the utility disconnect breaker feeding the transfer switch?

- Was the 7 day exerciser function operating properly prior to the power failure?

- Was the genset switch in the auto position when the power failure occurred?

- Did anyone check the genset during the power failure to ensure it was in auto and no fault indications were present?

[Dave]

Ah, I see, transfer switch allows the machine to start under no load, then subsequently transfers load...

[Dave]

Thanks for the replies - some comments will be answered next time when/ if this failure repeats itself.

Regarding feedback, is it possible to start the generator under load with an automatic transfer switch in the circuit - isn't this one of the preventative features of an automatic transfer switch?

Other thoughts/questions regarding the system test sequence:

1. 200-amp breaker upstream of the automatic transfer switch: Use to simulate loss of offsite power
2. Main house panel service disconnect breaker (downstream of the auto transfer switch): If the auto transfer switch is working properly is it necessary to exercise this breaker in testing the system?
3. Generator control panel breaker: Should this breaker be included in the system test sequence and if so how?

[Smarty]

Dave,

Since the generator starts as expected when the breaker is manually switched, but fails to start when a power outage occurs, I would suspect the transfer switch controller board is behaving intermittently. This board controls the automatic transfer using a very simple method based on the amount and duration of power outage to turn on / switch the generator, and does the same in the reverse sequence as well when utility power returns.

Two suggestions:

1. Download the extensive (several hundred page) repair guide available at the Generac / Guardian web site which has complete diagnostics, flow charts, schematics, parts listings, drawings, and narrative. It is truly excellent, and is offered in a pdf file at no charge. It explains all of the Generac in great detail.

1. If the unit is still under the 2 year manufacturer's warranty, contact your local dealer and document the problem, and have them look at it. Even if it is an intermittent problem, you definitely WANT GENERAC to replace the defective part if and when it fails completely. The board itself is probably a few hundred bucks if you had to buy one yourself, and a new transfer switch is well over 00.

You might also note that there are two cartridge fuses protecting the 24 volt relay on the transfer switch, and one or both of these can, if not snugly installed, cause switching problems. I suggest buying a couple spares just in case one or both blow in a true emergency.

Hope this helps,

Smarty

[Pete C.]

The installation and owners manual I referenced in my other post has the detailed procedures for all tests.