whole house generac generator issues

bama_dudeApril 9, 2006

I am licensed HVAC biz owner.I installed a generac 12kw generator for my wifes aunt today.I have been staying away from generators although they are getting more popular here in my area due to hurricanes.I have enough to do already but I broke down and installed this one anyway.I spoke with my electrican before the install to get his opion on the proper wiring setup.We ended up with a auto outdoor switch panel.We wired the 40 amp a/c breaker and the 60amp sub panel breaker in.On startup we checked the volts and hertz.We had 247v and 61hertz.To make a long story short we fried 3 power strips,one tv and a microwave along with several light bulbs.I went through the wiring and everything looks fine.I am at a loss here as to what to do next.Any help would be great.Oh and some happy person removed to install manuals from the box.

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You must have it wired wrong. I bet anything you have a hot and neutral crossed and are feeding 240v to the 120v receptacles.
I've seen it happen when a fellow electrician, who said he knew what he was doing, wired up a power inlet box for a manual transfer panel and crossed a hot and the neutral.

247v and 61hertz is fine.

If you were unsure you should have sought out the instructions before going at it. A whole house standby generator is nothing anyone without substantial experience should be doing.

    Bookmark   April 9, 2006 at 11:06PM
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Sounds like a disaster to me, got current flowing out of the generator along with the incoming service or something mixing together. You're probably going to have to tell us more about what kind of transfer switch system it has with wiring details. Usually these have a flex line with 2 hots, a neutral, and a groung along with signal wires. The transfer panel has the hots from the generator on one side of the transfer, 2 hots to a 60 amp breaker in the service panel to give power to the emergency circuits under regular conditions, and different colored wires to remove branch circuits from breakers in the service panel and wire nut them to be fed from the generator panel. Some transfer panels just have an in and a out for each branch circuit and there is no master 60 amp breaker. Are you saying the A/C is now on the emergency panel? If it is it needs to be a breaker in the emergency panel and its 40 amp load will be part of the 60 amps. What you don't want here is crossing the utility power to generator power.

    Bookmark   April 9, 2006 at 11:06PM
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247 volts and 61 Hz is fine if it is between the 2 hot phases, of course.


Exactly where did you measure this 247 volts? If it was at a 120 volt outlet, then this certainly sounds like a swapped phase wire and neutral wire from the generator, most likely in the transfer switch.

What color of insulation is on the wires in the transfer switch?

    Bookmark   April 9, 2006 at 11:49PM
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Generac does or used to require that you pass their generator certification course or have factory startup to have a valid warrantee on an automatic system. Cumins/Onan too and I assume others. You need to have a certified pro inspect the installation. Check your warrantee fine print.

    Bookmark   April 10, 2006 at 1:13AM
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Generac does lots of things a little different than other gen-set makers. If you don't have a hot/neutral reversed, look for a "floating" or loose neutral someplace. More information would be helpful;

Was the house on gen-set or commercial power when everything "fried"?

At what point did you measure V and Hz?

Is the sub-panel new or pre-existing? (3 or 4 wire feed to sub?)

Do you have ground and neutral bonded at the gen-set? (a fairly common issue)

Was the gen-set install inspected by AHJ or not?

    Bookmark   April 10, 2006 at 7:08AM
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Found the problem today.My tech hooked the neutral to the groung lug in the generator instead of the neutral lug.I should have looked closer.Generator creates its own neutral on power interuption.Thanks for the replys.

    Bookmark   April 10, 2006 at 5:02PM
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One point here as I am a certified dealer and a licensed electrician. You did have a problem but there are some adjustments in the electronice that should have been done to bring the voltage and frequency closer in line. These have a variation of +-.5%, very tight. I always recommend the units being started up initialy by a dealer even if the install you did yourself. Dont forget to change the break in oil. I would switch to synthetic for your aircolled unit after the breakin period. Did anybody talk to you about fuel pressures? You may have a problem there that hasnt shown up yet.

    Bookmark   December 31, 2006 at 6:27PM
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When I installed mine and did the initial testing, voltage came online at 126VAC unloaded and settled in at 122 with a slight load and stayed there with a fairly heavy load except for a momentary dip when the AC compressor started. Frequency was between 60.1 and 60Hz all the time. Was very close for a factory calibration and required no adjustment at site.

What is there to be aware of on fuel pressure that was not addressed in the installation instructions? I do not remember the exact pressures but we did check it an ours was about 1" above the ranage. Adjusted the regulator for the whole house down slightly and then did the startup and breaking testing. Pressure never dropped more than 1" during peak loads and generator recovered quickly. Guess its ok but wanted to know what you were referring to. Ours is the newer low pressure model that runs at the same pressure as the rest of the house, not the older high pressure model that required its own regulator.

Your suggestion on synthetic oil is a good one for the air cooled engine. We run Rotella Synthetic in ours like most of our vehicles. Oil was very clean at the 1 year point but changed it and the filter anyway.

Been a good unit so far and very reliable. Has carried the house through several short outages and 1 of several hours but was lightly loaded that time.

    Bookmark   January 2, 2007 at 1:13PM
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First let me explain that I am not an electrician, I am a homeowner that purchased and had a Generac Guardian 10K series air cooled generator that was professionally installed with all necessary permits etc by a licensed electrician in late November 2010.

I am using the generator to ensure that critical power is uninterrupted to keep and maintain critical temperatures in egg incubators.

During the past month and a half I have lost to sets of eggs and I could not figure out what the problem was except the min/max thermometor in the incubator indicated that the temp went dangerously low but it does not indicate the amount of time the temp was at that low level.

Also during that time there have been 2 power outages in my area. and I was under the impression that the generator was operating normally?

Upon inspection last Friday I found that the Generator was in off line mode with a hard stop diagnostic of a "Undervoltage" (Shutdown Alarm). See page #21 in the Generac Owners Manual. It tells you how to clear the alarm and cites the ranges under which it will occur but it does not provide any information regarding what variables or conditions would cause this type of failure, any ideas?

Also, Why would a generator be designed under a "Low Voltage" condition, not to reboot or recycle itself to be ready to re-start in the event of another power failure or when the condition that caused the low voltage condition returned to normal?

Any suggestions or guidance would be greatly appreciated.


    Bookmark   April 10, 2011 at 10:26AM
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