Electrical/Electronic Question

RFB · Jan 7, 2012

Sirs,

I have a standby (could be considered prime power) generator system.

It is a Kubota V3300T turbocharged coupled to a Marelli (USA) generator head, Maximum Output 45,000 watts; Continuous Output Power One-Phase 40,000 watts; Load Amperage at 240 volts, Maximum Load
188 Amps, Continuous Load 167 Amps.

It is sized to power 6500 (6 tons of heat pump HVAC) square feet of combined residence, shop and garage as well as deep well pump and everything that goes with a complete electric location. (No other power source beyond utility supplied electric.)

I have recently completed the installation, and run it with full load about one hour per month as a system check and to keep the fields in good shape.

My question:

I have to small uninterrupted power supplies (UPS) for my computer and router.

They refuse to function under generator power. They receive the power (the LED panel on the UPS shows input voltage and frequency.), but will not provide any output. Once back on line power (not generator) they work fine.

The generator has AVR of +/- 1%. I measured the input voltage to the UPS and it holds steady at 120 - 122 volts, and 62Hz.

Any ideas?

BobRip · Jan 7, 2012

If possible I would temporarily set the generator to 60 hz or as close as possible. Try to keep the load constant. The frequency will probably drop as the load increases. Then try to run the inverter. This would help isolate the problem. Utility power is very close to 60 hz.

RFB · Jan 7, 2012

Yes Sir, that is what we aimed for. Is 62Hz too much out? (It stays between 60 and 62Hz, and 120 to 122 volts)

glkingar · Jan 7, 2012

You might look into the type of sine wave the generator puts out and see if that is compatible with your UPS. I have seen that as an issue in the past.

yelbike · Jan 7, 2012

Three things that come to mind.

Check to ensure that the UPC is sensing the properly grounded/bonded system. You can eliminated this by putting a temporary jumper between the grnd and neutral terminals at the receptacle. If that solves the issue you'll have to ensure you're system bonding and ground is not compromised when you run your genset. Don't leave the jumper permenently.

The next is a little more difficult to check and to resolve. I you have a true RMS dvom check to see if you have a pure and clean sine wave. Check the peak to zero volts. If you get very lose to 167-172 volts then thats not your problem. If the voltage is out of that range then most likely thats your problem in which case you'll have to set up something different for that circuit. What comes to mind is a battery back with a true sine wave inverter or put up with the fact that a couple items will not work when your running on your genset.

Lastly it may be an interference issue where the genset is putting to much noise on the line and you'll need a chock coil to suppress the resonating frequencies. If this is the case its a pretty simple fix. Contact the generator manufacturer, they may have a kit or you can try a local electronics stores. The kit is pretty low tech and useally pretty cheap. The kits pretty involve a few coils of wire wrapped around an iron core. One chock coil per line including the grnd and neutral.

Confused yet, cause I am. and I need a beer:drink:

RFB · Jan 7, 2012

I am not an electrician, but the gentleman that performed the install is a very reputable one, and so I have at least a rational reason to believe that the system is properly grounded/bonded.

I watched when he made the connections and everything is well grounded and bonded at every conceivable location.

Nonetheless, you indicate a jumper from the ground to neutral at the outlet that the UPS is plugged into?

Are there any negatives or drawbacks from doing that? (Referencing your "Don't leave the jumper permanently" statement.)

I do not have a "true RMS dvom" (nor the knowledge to use one) so I may have to "put up with the fact that a couple items will not work when your running on your genset." I will not have the internet while on gen power anyway, because power failures around here also shut down the dsl systems. The point of the UPS is to buy time for a proper shutdown of the computer system.

I might even try plugging straight into the outlet instead through the UPS. Everything else works plugged in directly, so that might be the simplest solution.

Thanks for the feedback.

yelbike · Jan 7, 2012

Your neutral conductor gets grounded only once, at the service entrance and no where else. By putting the jumper your grounding the neutral a second time. Its okay to do it for a short (no pun intended) time but over time your running the chance of getting circulating (eddie) currents in the neutral "circuit" which could cause heating of the neutral conductor.

Some electronics electronics "search" for a voltage difference between neutral and grnd. If the voltage is out of range it shuts down to prevent damage.

k0ua · Jan 7, 2012

If you UPS is an APC brand you can set the sensitivity of the UPS "down" to work on not so clean power and they will then run. I had to do that with mine when running on the generator. Look online on the APC (American Power Conversion) website and download he manual for your UPS and reprogram it. It was an easy thing to do. I cannot speak for other brands.
Some of the real small UPS's made by APC do not have this setting but all of the 750 VA on up seem to unless they were very old.

James K0UA

B7510HSD · Jan 7, 2012

"I might even try plugging straight into the outlet instead through the UPS. Everything else works plugged in directly, so that might be the simplest solution.
" I would not recommend this if you value your PC !!

Tractor Seabee · Jan 7, 2012

RFB said:
I am not an electrician, but the gentleman that performed the install is a very reputable one, and so I have at least a rational reason to believe that the system is properly grounded/bonded.

I watched when he made the connections and everything is well grounded and bonded at every conceivable location.

Nonetheless, you indicate a jumper from the ground to neutral at the outlet that the UPS is plugged into?

Are there any negatives or drawbacks from doing that? (Referencing your "Don't leave the jumper permanently" statement.)

I do not have a "true RMS dvom" (nor the knowledge to use one) so I may have to "put up with the fact that a couple items will not work when your running on your genset." I will not have the internet while on gen power anyway, because power failures around here also shut down the dsl systems. The point of the UPS is to buy time for a proper shutdown of the computer system.

I might even try plugging straight into the outlet instead through the UPS. Everything else works plugged in directly, so that might be the simplest solution.

Thanks for the feedback.

RFB,

I have an APC 1000VA UPS and it works fine. On the back there are two outlets at the top and 6 outlets at the bottom. The top 2 are labeled surge protected only. Those two outets are not on the battery side. Make sure you are not plugged into those. Sometimes the simple stuff escapes us.

Ron