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Old 10-06-2019, 01:43 PM   #1
CADman_KS
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Full size fridge electric question...

I have a question about how the full size fridge electrical works.

My understanding is that there is an inverter in there that powers the fridge when you're not on shore power.

But, when you're on shore power is the electrical feed for the fridge coming thru the main panel (the converter/breaker panel) or still thru the inverter?

Just wondering about the longevity of the inverter if it's being used all the time. Maybe they are more robust than I think....
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Old 10-06-2019, 03:03 PM   #2
PNW Fireguy
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On SP the inverter passes through the grid power from your Progressive Dynamics distribution center to the outlet feeding the fridge.
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Old 10-06-2019, 03:12 PM   #3
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I believe you are asking about a Residential Fridge (electric only).

Shore power feeds the breaker panel. (the converter is on one of the breakers)
A breaker feeds a 120 volt line to the inverter.
The inverter has a transfer switch built in which by-passes the inverter.

I power off my inverter when I'm on shore power.

hope this helps,
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Old 10-06-2019, 03:22 PM   #4
CADman_KS
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Quote:
Originally Posted by Arkware View Post
I believe you are asking about a Residential Fridge (electric only).

Shore power feeds the breaker panel. (the converter is on one of the breakers)
A breaker feeds a 120 volt line to the inverter.
The inverter has a transfer switch built in which by-passes the inverter.

I power off my inverter when I'm on shore power.

hope this helps,
Thanks for the great responses!

Yes, I was referencing the Residential fridge. I didn't know for sure what to call it.

I didn't realize the inverter had a pass-thru.

Thanks for the clarification!!!
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Old 10-07-2019, 12:32 PM   #5
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There is a transfer switch that selects which source power the refrig. Me I leave mine on. I do check out the readout once SP has been disconnected, just to make sure it is drawing power.
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Old 10-07-2019, 04:05 PM   #6
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Originally Posted by jeffba View Post
There is a transfer switch that selects which source power the refrig. Me I leave mine on. I do check out the readout once SP has been disconnected, just to make sure it is drawing power.
Having never had an RV with an inverter, it looks like we have a lot to learn about how all of this works together!!

Looking forward to getting to know about all of the new things in our RV...
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Old 10-07-2019, 04:26 PM   #7
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Your inverter only powers the reefer when it is turned on and you aren't on SP. Your batter(s) supply 12 volts to the inverter which ups it to 120 volt to run reefer. When the batteries drop below a certain level no more power to reefer. Mine has run on inverter/batteries (2 Group 27 wet cells) for 13 hours without quitting but very little else was being fed by batteries.
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Old 10-07-2019, 04:40 PM   #8
CADman_KS
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Originally Posted by WeBeFulltime View Post
Your inverter only powers the reefer when it is turned on and you aren't on SP. Your batter(s) supply 12 volts to the inverter which ups it to 120 volt to run reefer. When the batteries drop below a certain level no more power to reefer. Mine has run on inverter/batteries (2 Group 27 wet cells) for 13 hours without quitting but very little else was being fed by batteries.
Thanks for the input!

I do understand how the inverter works, at least the 12V DC to 120V AC part. What I did not quite understand (or know about) is the auto-switching on the inverter when you're plugged into SP. That is something that's actually built into some inverters, but none that I've ever used.

I'm a recovering engineer by trade, I just have to know how things like this work.

As for the length of time that the fridge will run on the inverter, I would think that it only requires a "large" amount of power when it's actually running. The newer residential fridges are pretty energy efficient, so as long as you kept the doors closed, and it wasn't a 110deg inside the RV, it should be good for a while...
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Old 10-13-2019, 08:51 PM   #9
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When you're plugged into SP make sure the inverter is off! If you are plugged in with the inverter on they say it will fight how the power gets transferred. Before I hook up to SP, I make sure the inverter is off. When you unplug, turn it back on.
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Old 10-13-2019, 09:08 PM   #10
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Originally Posted by Track50 View Post
When you're plugged into SP make sure the inverter is off! If you are plugged in with the inverter on they say it will fight how the power gets transferred. Before I hook up to SP, I make sure the inverter is off. When you unplug, turn it back on.
I plan on testing this this weekend, but the swich in there is supposed to be automatic.

We shall see...
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Old 10-14-2019, 05:56 AM   #11
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I believe once you plug in the invertvertor will shut off so you are powered by whore power.
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Old 10-14-2019, 07:35 AM   #12
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I believe once you plug in the invertvertor will shut off so you are powered by whore power.
Yes, this is what it's supposed to do. I don't know if it actually turns it "off", or just doesn't output any power. It might run all the time, but if it's not putting any power out, it should be idle.

For the curious (like me), I'll report what I find out after this weekend...
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Old 10-14-2019, 07:46 AM   #13
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The inverter is on unless physically turned off and therefore always a parasitic loaf when on. When inverting there is some loss( maybe 2-3%) for the electrical “transformation” efficiency. The fridge duty cycle on the yellow energy sticker will give you the annual kw-hrs. Do the math to figure the amp hours needed at 12v.
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Old 10-14-2019, 07:59 AM   #14
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Not true

Quote:
Originally Posted by Track50 View Post
When you're plugged into SP make sure the inverter is off! If you are plugged in with the inverter on they say it will fight how the power gets transferred. Before I hook up to SP, I make sure the inverter is off. When you unplug, turn it back on.
The above statement is simply not true. The inverter sits there and does nothing when hooked to shore power. Thatís what the built in bypass is for. The only time I shut my inverter off is when I store it. It wonít hurt a thing to leave powered on while hooked to shore power. Itís ok either way but it wonít hurt a thing to leave it on while camping.
Personal preferences arenít necessarily facts.
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Old 10-14-2019, 09:09 AM   #15
CADman_KS
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Originally Posted by Wayner197 View Post
The above statement is simply not true. The inverter sits there and does nothing when hooked to shore power. Thatís what the built in bypass is for. The only time I shut my inverter off is when I store it. It wonít hurt a thing to leave powered on while hooked to shore power. Itís ok either way but it wonít hurt a thing to leave it on while camping.
Personal preferences arenít necessarily facts.
The real way to answer the question is to put my amp clamp on it. Not for sure I want to know that bad.

This is where being a recovering engineer is in direct conflict with things that need to get done.
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Old 10-14-2019, 11:33 AM   #16
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Well said cadman. The idle current on most inverters is very low, on the order of a few hundred milliamps. I just turn my on and off to minimize it's running hours and maximize it's lifespan. Personal choice as to what you wish to do. Transfer switches, whether built into or separate from the inverter just look for 120vac on the priority input which is usually the input connected to 120vac from your fuse/breaker panel. If no power on that input, the contactor flops over to the other input to get a source of 120vac. Good to see you educating yourself on the inverter install in your trailer!
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Old 10-14-2019, 02:39 PM   #17
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Originally Posted by jcurtis934 View Post
... Good to see you educating yourself on the inverter install in your trailer!
In starting this post, that was my intention, educating myself, since we've never had an inverter before. All new territory, and I just wanted to understand how this thing works.

Not this thread is the end-all-be-all, but it doesn't sound like people are having issues with lifespan when they leave it on. I wish that it was in an easier to get to location than it is, if I decide I'm in the on/off camp. Not impossible, but not the most convenient either. Like, just put the inverter closer to the door kind of thing, and that would make it easier...
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Old 10-14-2019, 03:24 PM   #18
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I guess we're lucky with ours. We have a remote display inside that controls the inverter. Giving me on/off control, battery status, and current draw when inverting.
It's been on 24/7 for 4 1/2 years, except for a short period while in for service and still going strong.
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Old 10-14-2019, 03:53 PM   #19
CADman_KS
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Originally Posted by mhs4771 View Post
I guess we're lucky with ours. We have a remote display inside that controls the inverter. Giving me on/off control, battery status, and current draw when inverting.
It's been on 24/7 for 4 1/2 years, except for a short period while in for service and still going strong.
I'm kind of surprised that the remote option is not the "norm". I do know that our inverter has a remote option. I wonder how much that thing costs? It would be super easy to wire that into the main "control" panel.

Hummm....
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Old 10-14-2019, 03:57 PM   #20
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Originally Posted by CADman_KS View Post
... It would be super easy to wire that into the main "control" panel. ...
Well, that sucks. The remote for the inverter used in our RV, only is a simple on/off. Doesn't do any monitoring at all...
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