Inverter Transfer Switch Issue

[Aeolus15]

I have a Sinewave Inverter with a built-in transfer switch. When shore power is connected, the transfer switch works fine and moves all equipment connected to the inverter back to shore power. However, with the generator on (same wiring as shore power) it appears the transfer switch does not sense it and equipment stays on the inverter. In short, the transfer switch works with shore power but not with the generator. Any idea why?

[Sailmonkey]

1. What type of generator do you have? Some high speed generators produce a distorted sine wave that some inverters/chargers are not happy with. Sometimes this can be alleviated by loading the generator, with a resistive load like a space heater.

2. Are you absolutely certain that the shore and generator both feed prior to the inverter? Stranger things have been done than separating them.

[Aeolus15]

The generator is an older Onan 8KW (MDKD).

Both the generator and shore power are input to the same rotary switch. There is only one output from that switch for the inverter to see. There is no other AC source.

[Sailmonkey]

Have you tried adding a resistive load to the generator?

Is the generator voltage correct?

[Aeolus15]

Only minor loads are on the inverter: a refrigerator, ice maker, and interior outlets. The boat is a power boat. The primary reason for the inverter is to keep a refrigerator and the ice maker on during all-day transits, without needing to run the generator.

All other AC loads are separate. The generator easily handles the other loads, including 3 air conditioners, all running at the same time. Typically, we only run the generator while at anchor, or when we need something that is not powered by the inverter.

[smac999]

check the voltage and freq entering the inverter from the gen. (unplug shore so you know for sure it's coming from the gen). if either are bad the inverter will stay on. just like a UPS does. a good inverter would have max / min settings for both to adjust.

[Jetx]

Also confirm that neutral and ground are connected at the generator (and nowhere else). The inverter typically expects/requires this, and the transfer switch won't stay connected if the inverter senses that they are not. At least that's the way my Victron Multiplus behaves.

More complete explanation here: https://community.victronenergy.com/...rent-devi.html

[Twilite]

Originally Posted by Aeolus15

I have a Sinewave Inverter with a built-in transfer switch. When shore power is connected, the transfer switch works fine and moves all equipment connected to the inverter back to shore power. However, with the generator on (same wiring as shore power) it appears the transfer switch does not sense it and equipment stays on the inverter. In short, the transfer switch works with shore power but not with the generator. Any idea why?

If your inverter is static, meaning if their are no adjustments available, your up the creek..The loads on shore power work because the incoming utility is infinite and the genset is not. The inverter should be replaced with one that does have adjustments and of the correct size for your loads..1/2 to no more than 3/4 capacity would be good when fully loaded. If it does have adjustments, open the input sync window on frequency to the max. Open the voltage tolerance window +/_ 15%. Turn off all loads, start gen set while monitoring the input from genset to see if it will sync then. If it does, then try loading one device at a time. If you have a Min/Max meter, set it to record minimum and maximum on each the freq. and voltage one at a time to determine which if any it kicks out from. There you can tell alot about whats happening by noting the fluctuations if any from the genset. Hope this helps.

[CatNewBee]

Read first the manual, there are inverter, that shut off by a frequency shift from 50 to 51Hz, especially solar grid inverter, it isa feature, not a bug, and usually configurable. I guess your generator does not provide steady 50Hz or the Voltage is out of the acceptable range on the inverter. .
Do you use power assist on the inverter?

[waterman46]

Originally Posted by Aeolus15

The generator is an older Onan 8KW (MDKD).

Both the generator and shore power are input to the same rotary switch. There is only one output from that switch for the inverter to see. There is no other AC source.

And I assume you checked the voltage on the AC line going from switch to invertor, with generator running and switch in GEN position? If 120V not present there, then check the generator side of the switch to see if it is getting AC from the generator.

The invertor usually would use a simple relay activated by a coil, to sense power on it's AC input line which switches the bypass relay to connect AC direct to it's AC output terminals. Should not need any great sine-wave AC to do this, but in fact your Onan does produce good sine wave power.

[CatNewBee]

Originally Posted by waterman46

And I assume you checked the voltage on the AC line going from switch to invertor, with generator running and switch in GEN position? If 120V not present there, then check the generator side of the switch to see if it is getting AC from the generator.

The invertor usually would use a simple relay activated by a coil, to sense power on it's AC input line which switches the bypass relay to connect AC direct to it's AC output terminals. Should not need any great sine-wave AC to do this, but in fact your Onan does produce good sine wave power.

It depends on the inverter. There are cheap bypass only inverter with a relay switching on input power, and inverter that have sophisticated electronics to check the input power quality, synch the sine waves and seamlessly switch to the source or even powerassist thesource with the inverter.

Because it does not switch simply when the power comes from a less stable source like the genny, I assume, the later is the case.