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.
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
3. Generator control panel breaker: Should this breaker be included
in the system test sequence and if so how?
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: http://www.generac.com/PublicPDFs/0172890SBY.pdf
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
- Was the genset switch in the auto position when the power failure
- Did anyone check the genset during the power failure to ensure it was
in auto and no fault indications were present?
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.
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
2. 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 $1000.
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,
HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.