genme
While this question is basic, I am not sure of the answer.

I am reading roughly 25 amps on each 120vac phase of our generator feed. So, combined this is 50 amps. Our generator can produce 83 amps @ 240vac (and 166 amps @120vac.)

If I wanted to figure the percent capacity of the generator being used, would the answer be 50 divided by 83, or 50 divided by 166? Thank you!
Model 5875, Nexus controller, 999cc Engine, 20kW LP, 2011
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mastr
Using 50/166 gives the mathmatical answer. Be sure not to exceed 83A on either "phase", regardless of what that formula indicates.
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genme
Thanks mastr!

My sincere thanks to everyone who has helped this newbe get his generator running. It was finally wired up yesterday (Saturday.) I'm breaking it in now.

Believe it or not, we lost power from 7pm to 11pm Friday night! We didn't know whether to laugh or cry that the generator wasn't ready to run (so we laughed.) Being without power (hopefully for the last time) reinforced our decision to get a generator.

As a side note, our generator (5875 20kw and possibly the 17kW model) can have the start time adjusted from 10 to 30 seconds (in one second increments) after a power interruption. What setting would you recommend, and why?
Model 5875, Nexus controller, 999cc Engine, 20kW LP, 2011
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mastr
It depends on what settings your utility uses for some of their stuff. Notice during a thunderstorm you will often get brief power "blinks" - I get alot of them. But around here they are short- only 2 seconds or so. If my power is off for 10 seconds, it is probably going to be off much longer, so I would use "10" if I had your set.

If you want the set to operate at every opportunity, set it at 10. If you find it starting up and shutting off too much, and 30 second outage doesn't bother you, set it at 30 and the set won't start needlessly for every thunderstorm. Or anywhere in between -just observe things for a while and decide what suits you.
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Ira
Unless you have something that is more negatively affected by a 30 second power outage than by a 10 second outage, I would set it at 30 seconds. I guess the subjective part is, if the power goes out at night, are you okay with the lights being off for 30 seconds instead of 10 seconds?

I have all of my electronics on UPS's, so they will ride out the 30 seconds without interruption. Other than the lights being out at night, the longer delay has no effect on me.
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Skip Douglas SkipD
I have no problem with the roughly 30-second delay that's programmed into our generator. After that delay, there's still the additional time for the generator's engine to start and for the generator's output to get up to the proper level before the transfer switch is commanded to switch to generator power. The typical total delay for us is about 40 to 45 seconds. Other than one or two clocks (on the stove and microwave) needing to be reset, we've had not a single problem with the delay timing.
Skip Douglas
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genme
On the one hand, I am considering not having the generator unnecessarily start by setting a 30 second start delay.

On the other hand, I am considering having the generator start sooner with a 10 second delay in the hope of avoiding the nasty utility power fluctuations that often occur immediately prior to a power outage. I'm not sure if 10 seconds would avoid this situation or not.

Sanity checks welcome.
Model 5875, Nexus controller, 999cc Engine, 20kW LP, 2011
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rico567
genme;10654 wrote:
On the one hand, I am considering not having the generator unnecessarily start by setting a 30 second start delay.

On the other hand, I am considering having the generator start sooner with a 10 second delay in the hope of avoiding the nasty utility power fluctuations that often occur immediately prior to a power outage. I'm not sure if 10 seconds would avoid this situation or not.

Sanity checks welcome.


Well....just going by what you've said, unless the fluctuations that occur prior to a power outage were sufficient to initiate the generator start sequence, I can't see how either 10 or 30 seconds would do any good. I read somewhere that the threshold is 60% for Generac, and that would presumably not be fluctuating higher, but would have to be sustained at 60% or lower.
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techntrek
The sequence and thresholds are below, copied from my manual. From what I've seen the timer is immediately reset if the power returns before the unit starts up, I'm not sure if it is after it starts but before the transfer. After the transfer it will stay on the genset if the utility power keeps fluctuating.

A. Utility Voltage Dropout Sensor
• This sensor monitors utility source voltage.
• If utility source voltage drops below about 60
percent of the nominal supply voltage, the sensor
energizes a 15-second timer.
• Once the timer has expired, the engine will crank
and start.
B. Engine Warm-up Time Delay
• This mechanism lets the engine warm up for
about 10 seconds before the load is transferred
to the standby source.
C. Standby Voltage Sensor
• This sensor monitors generator AC output voltage.
When the voltage has reached 50 percent of
the nominal rated voltage, transfer to standby
can occur.
D. Utility Voltage Pickup Sensor
• This sensor monitors utility power supply voltage.
When that voltage is restored above 70 percent
of the nominal source voltage, a retransfer
time delay starts timing.
E. Retransfer Time Delay
• This timer runs for about 15 seconds.
• At end of a 15-second delay, circuit board
action de-energizes transfer relay in the transfer
switch.
• Retransfer to utility power source then occurs.
F. Engine Cool-down Timer
• When the load is transferred back to utility power
source, the engine cool-down timer starts timing.
• The timer will run for about one minute, and the
generator will then shut down.
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