Generator AC Qualification

[Tombman]

Hi,

I have a Xantrex 4548 system that has been working flawlessly for about a year. Today the power went out and it switched over to the batteries perfectly. Power has been out for about 10 hrs now and I decided to start up the generator to help out with the battery charging, since it is raining and cloudy out and the panels are only putting out about 400 watts.
After starting the generator (5k lister diesel @ 1800rpm) I waited for the led light to stop flashing, meaning the AC2 input has been qualified, but it never went solid. The control panel says AC1 input is zero, and AC2 input is steady at 119 volts on each leg at 61 hz. The hz limits are set to 55 to 65. The generator is running very smoothly with no surging. I have used this generator for many years without an inverter with sensitive electronic equipment with no issues.

Are there any reasons why the generator won't sync with the inverter? I must be missing something.

Regards, Tom

[Mike90250]

Wow, has the inverter ever successfully synced to a generator of any kind before now ?

I'll assume you have the XW in 240V mode. So you will need a 240V generator.

I have a lister 6/1 with a chinese ST-5kw head. Even with my power stroke flicker, it syncs right up. 59 - 63 Hz
I did have an issue with a bad breaker, it had high resistance when on, and would allow the inverter to sync, but when loaded, it lost voltage across the resistor, and would drop off after 10 seconds of the most awful groaning from the generator windings being unbalanced,

How do you control and monitor the XW, with a Gateway, SCP, or ComBox ?

[Tombman]

Hey Mike,

Thanks for your reply. My generator is a Winco 5kw, 1800 rpm head driven by an original English, Lister CS1-6 engine. It is the only generator I have tried to sync with the XW 4548. I am using it in 240 volt mode and my readings of 119 volts are per leg, as the SCP monitor only reads leg voltage and not combined volts. Both volts and frequency are spot on, but the light will not stop flashing.

[sensij]

never mind. I'll go back to lurking.

[Tombman]

More Info from Xantrex

Hi All,

I talked with a couple of techs at Xantrex today and they had me do some measurements and testing, and tweak some settings on my XW 4548 inverter. I even switched the AC2 wires to the AC1 breaker. Same thing, the generator input will just not qualify. He asked me to take the covers off the generator and see if the ground and neutral were bonded together. He said they could not be and said it had to have 4 wires coming out of the generator and not 3 for the inverter to have a ground signal to work with. I asked him if I could just run a seperate ground wire from the generator chassis to the inverter ground. He said try it and see. I did and it didn't work. I looked up the wiring diagram on Winpowers web site and it indeed shows the ground and neutral bonded.
So my question now is: Can this good old generator be modified to work, or do I need to buy one of those China units? Yuck.

Tom

[Mike90250]

You need to measure L1 vs L2, at the generator, no loads, and see if you get 119V or 240V. I never get 119 & 119. That would mean the 2 sides of the winding are identically perfect. does not happen often. I get 118V and 121V.

I wonder if someone modified the generator wire panel to get 2x the amps @ 120V ? Ir if you need to move a jumper to get 240V

[Tombman]

Hey Mike,

I have used this generator for years, hooked up to my house 240v panel via a transfer switch. I know it puts out near equal voltage on each leg. There is no panel on this generator, just a 4" handi box welded to the outside shell with neutral and the two legs in it. There is no seperate voltage regulator, just a diode bridge trio and the shunt field. It is really simple.
I will take take some voltage measurements at the generator tomorrow and report back.

[Mike90250]

The chinese ST heads have a simple harmonic winding & diode bridge. It does have redundant brushes on the slip rings. It's not known for a true sinewave output, the way the harmonic winding works, there's sort of a pointy peak on the sinewave, and I was prepared to have to clean it up some, maybe with filter caps and an AVR, but the XW qualifies it OK, on AC2 input. You are going to the AC2 input, and not AC1 ?


Do you have gen support & gen support + enabled ?
These are the settings I use for my 6/1 @ 1400' elevation - it pulls about 2700 watts with the following:
AC2 Breaker Size 19.5A
Generator Support Amps 13.1

from one of my other posts:

But you should be able to enable Gen Support + via the SCP or the Combox. Xantrex has some odd limitations/assumptions, to keep you from using all your generator power, eventually, reading through the appendix of the manual, you find the AC2 breaker setting limits power to 20% of what you put in, and then gen support adds another 20%. The way I was able to power and charge with my generator (3Kw antique diesel at 1400' elevation, wants to be loaded or it carbons up). I use the following settings to get a solid 2700w load on the genset. AC2 19.5A Gen support 13.1A Battery charge 40A Any power not going into loads, is used for charging, my normal base loads limit my charging to about 35A. any loads exceeding the capacity of the generator, get assisted by the inverter, inverting. When loads drop, charging resumes. To load your generator to it's continuous rating, you will have to fiddle around with things a bit. I did it by kicking the AC2 breaker setting to 40A, loading the charger up, and ratcheting down the AC2 setting till the charge dropped off. Then the same with Gen Support setting. Now that it's dialed in, and when the diesel is warm, the wife can put the toast in the toaster, reheat coffee in the microwave, and I just watch the meters swing around + or - on the Combox monitor.

[Tombman]

Hey Mike,

The Winpower unit only has single brushes on the slip rings, but they are hefty. I am using AC2 input with AC2 priority, as per the updated manual and the Xantrex tech's instruction. We did try gen input on AC1 just to see if there was a fault in the AC2 circuit. No difference.

Does the ST5 have a floating ground or a bonded ground to neutral?

I haven't seen a gen support+ option on the SCP. I will look again.
After things were working ok, my plan was to tweak the settings to get a good load as you describe.
Thanks for the info.

[Tombman]

Interesting read

Some generators use GFCI breakers to feed the AC outlets. When connected to a panel that does not switch neutral the GFCI breaker will trip immediately. The affected generators have the neutral conductor bonded to ground to pass OSHA job requirements. Home or building electrical panels also have the neutral bonded to ground. This dual bond supplies two paths for return current to flow. The GFCI breaker will detect a difference in neutral vs line current flow and open the circuit.
To remedy this problem, the generator must be changed to supply a floating neutral or the transfer panel rewired to switch neutral. If the generator neutral is changed, the "NEUTRAL BONDED TO FRAME" label must be replaced with a "NEUTRAL FLOATING" or "NEUTRAL NOT BONDED TO FRAME" label. The generator will no longer pass OSHA job requirements.

There are four possible ground / neutral bond and transfer panel configurations.
Neutral bonded at generator, neutral switched at transfer panel. This is a correct configuration. Neutral for backup circuits will be isolated at the transfer panel and bonded within the generator. There will be no ground conductor current. This requires a three pole transfer switch.
Neutral floating at generator, neutral not switched at transfer panel. This is a correct configuration. Neutral for the entire system is bonded at the main service panel. There will be no ground conductor current. Only live lines are switched with a two pole transfer switch.
Neutral bonded at generator, neutral not switched at transfer panel. This seems to be the most common connection technique based on my research. Unfortunately it is not correct. Neutral will be connected to ground at the main panel and at the generator. Neutral current flow will flow along the ground conductor and through the generator chassis. This creates a potential shock hazard as the chassis becomes part of the current carrying circuit. The easiest way to fix the problem is to use a floating neutral generator or make the required changes to the generator internal wiring.
Neutral floating at generator, neutral switched at transfer panel. The neutral conductor has no ground reference. The neutral should be bonded within the generator or the transfer switch rewired to not switch the neutral conductor.
The generator and transfer panel should be considered as a system, not two independant items. They work together and must be compatible. Most generators I've seen have neutral bonded to the chassis, and most transfer panels do not switch neutral. This combination is not correct and could lead to a potentially dangerous situation. Make sure the person doing your installation checks to ensure compatibility with the neutral bonding issue. If he does not consider this an issue worthy of the effort find another electrician.
The manner in which the generator's neutral and ground wires are connected will determine how the panel must be wired. If the neutral is bonded to ground in the generator, you must switch neutral in the transfer panel in order to avoid a double bonded situation. If the panel is not capable of switching neutral the generator neutral must be isolated, possibly requiring rewiring. Check with someone qualified to determine which way your generator is wired - and if it can be changed.
My preference is to have neutral floating within the generator, and not switch neutral in the electrical panel. I have changed the wiring in my generator for this purpose. It greatly simplifies wiring in the panel, and eliminates the problem of split circuits sharing a common neutral.
A generator with floating neutral presents another potential hazard. It should not be used anywhere except when connected to a transfer panel. If it were used in a stand alone configuration such as at a campsite or with extension cords the neutral / ground bond should be reconnected and a ground rod provided. Some generator suppliers provide a 120V plug with neutral and ground lines connected. For stand alone use, this plug will reestablish the neutral bond at the generator. Many Chinese made generators (sample pics below) supply a 120V/240V selector switch and should not use this jumper plug.
If you decide to make such a plug, remember that neutral is the wide blade on the connector, and will usually use a white or chrome colored screw to tighten the wire. Click for picture.
Generac supplies a model 1276 transfer panel for use with their generators. I was very disappointed after looking through the installation instructions to learn it is not capable of switching neutral. The majority of their generators have neutral bonded to the frame. As such the two should not be used together. Use of the panel will get your lights and other appliances working again, but safety will be jeopardized. Separately each item is perfectly safe, but should not be used in combination without changes to the generator. If you plan to use the 1276 transfer panel, ensure your generator has neutral floating. If using a Generac generator, you may have to make some minor changes inside the generator output panel to make the system work properly and safely. I have wiring instructions for the Generac 4000EXL, 5500XL, 7550EXL, Wheelhouse 5500 here.
Coleman-Powermate supplies a similar type transfer panel which does not switch neutral either. Their generators I've seen for sale lately have been labeled with floating neutral, making them safe to use with the panel. Do not use these generators in a stand alone configuration without reconnecting the neutral / ground bond however.
There are several other similar panels which do not switch neutral. Typically they have a three position switch and a push button circuit breaker for each circuit, and a flexible metal cable with numbered red and black wires. A quick check online found several brands including EmerGen Switch models 6-5000 and 10-7500, GEN-TRAN, PRO-TRAN and others. Other panels may have two interlocking circuit breakers to select either generator or main power. If there are three sections being switched the panel is likely capable of switching neutral (see closeup of my Siemens transfer panel picture below). Otherwise the generator should have neutral floating from ground.
To determine if your generator uses a floating or bonded neutral perform this simple test. With the engine off, use an ohm meter between the chassis and neutral conductors in the outlet. If it indicates open circuit, the neutral is floating. A short circuit will indicate neutral bonded to ground. I don't recommend doing this to household circuits due to the possibility of exposed AC and damage to the meter.
Plug in an electrical tester as shown and start the engine. If it indicatess open neutral, live/neutral reversed, or live/ground reversed do not use the generator and have someone qualified check the wiring and make the necessary repairs. Use the tester throughout your house to ensure it is wired correctly. This sort of tester is often inaccurate for determining whether the neutral is bonded or not. Even with a floating neutral, the second light will often be on. I suspect this is due to very low leakage currents and a high impedance bulb in the tester.

The generator should be grounded properly. A house should have a single ground point. Once the generator is plugged in through the twistlock plug, its chassis is connected to the house ground. Driving another ground rod to connect the generator is incorrect when it is supplying backup power via a transfer panel. If you are using extension cords with the appliances being powered entirely isolated or away from other sources of power such as while camping a ground rod should be used.
Schneider Electric has an Application Note on Standby Generator Panels which has very good information about neutral bonding. It should clear up any misunderstanding about the importance and reasoning behind the issue of the neutral and ground connection. Nova Scotia Power has a bulletin detailing inspection requirements, and information regarding neutral bonding. Please read both.

[Mike90250]

I am using AC2 input with AC2 priority

I've never set priority

Gen Support + is in the Advanced and Extras settings. It helps balance the Loads on the 2 different power legs L1 & L2 Should not affect how the unit gets qualified. Still trying to think of something. Here's a scan of the ST head schematic
ST-n_schematic.jpg It has a GROUND terminal on the chassis, I don't think any internal wires are bonded.

[Tombman]

Still searching for an answer

Today I was able to analize the Winpower gen head more closely. While running without any load the voltage at the brushes measures 128.1 and 128.3, 256.2 across the legs. The hz are at 60 and steady.
I measured between the neutral leg and ground and it was open. (no bonding) This is contrary to what the wiring diagram from Winpower shows. So, I then installed a jumper to bond ground and neutral, just to see if that would let the XW4548 qualify on AC2, but no joy. I just can't figure this out. I have read numerous articles about bonding generators online, and triple checked all of my wiring I did a year ago when installing this system. I am stumped.
I did read a number of posts on the subject from a member, Chris Olsen. Is he still a member of this group? I would like to run this by him.

Tom

[Tombman]

Generator Support +

Hey Mike,

I think you have different firmware than I do. I see no generator support + in my SCP menu at all.

[Willy T]

Why don't you put some kind of a 240V load on the generator and pull the voltage down until it qualifies, then drop the load. A one shot timer can make it automatic once you find the size of the load you need.

[Mike90250]

128.1 and 128.3, 256.2 across the legs. The hz are at 60

That voltage is too high to qualify. If you load it with loads (2 toasters) to qualify, you have to get some battery charging happening first, to Load the genset down to keep it from disqualifying from overvoltage when you remove the "priming load".

ComBox_GenQualLister6-1.jpg