Refer/Inverter Question

[ixtlan22]

So, we have two refer units on board, one older than the other, both are 110VAC and 12VDC capable...evidently the PO wanted two refrigerators for live-aboard....

Anyway...

During checkout I discovered that although both refer units worked fine on 110VAC, only one unit worked on 12VDC. Not thinking anything of it, I switched on the Inverter and HO-LA! the second refer tried to come on...but when it did it made a "things-arn't-sounding-too-good" operational noise (I suspect, from the compressor). Of course I immediately shut it, and the inverter, off. Checking further, I found that the PO had disconnected the 12VDC side of the unit making all the noise. On a whim, I hooked up the 12VDC side and WA-LA! it started right up and ran smoothly (Insert happy face here).

Now I have both refer units running well on either 110VAC shore power or 12VDC boat battery power....and I have plenty of power on the boat to run both if need be...but...and this brings for me the questions of the decade...when I turn on the inverter the older unit switches over and tries to run off the 110VAC inverter which has a modified sine wave. I'm not sure whether the new unit tries to run off the inverter because it's so quiet.

1st question is about running compressors on a modified sine wave inverter...is this a good thing, bad thing, or doesn't make any difference thing? Both compressors seem to run fine off the boat banks (although they do tend to dim the lights downtown...

2nd question is about the default relays in the refer units. My experience so far says that when plugged into shore power (or the inverter) the relays are set up so that they will default to 110VAC. My units seem to run fine as long as I manually turn off their connection to the 110VAC line when I turn on the inverter. Does anyone know if this is true (default to 110VAC) for all dual voltage refer units or just some?

Thanks to all who've read this far...inquiring mind just wants to know.

Ray on S/V Pure Joy

[sailvayu]

You don't mention brand but most these units are 12 vdc with a built in converter to run on 110 vac. It would be silly to use the inverter to covert 12 volt to 110 and then back to 12 volt. I would just unplug both units from 110 volt and run off 12 volt. You could wire them to the shore panel so that the 110 volt would only be supplied when on shore power but i would think you would have the charger on anyway so may not be worth that effort.

Fair Finds

[ixtlan22]

The "old" one is a Norcold 6800 "bin type" and I don't have the manual for it. The newer one is a Vitifrigo over/under cabinet type. Both are great running, very quiet machines (no affiliation).

Not sure how the voltatge coversions work, just that when I switched over to 110VAC on the inverter, the Norcold tried to run on it. Not sure what the Vitifrigo did...except it didn't make any noise.

Ray

[sailvayu]

I'm not sure how the transfer switches work as i have never been into one but un-plugging would be the simplest solution. If you have a quite Norcold you are lucky it can be a crap shoot with them some are quiet others are noisy as hell. i think they all use the same DanFoss compressors but with the NorCold they tend to rattle, it is fixable in most cases

Fair winds