Residential refrigerator regrets??

[Gray01]

Originally Posted by mobilemike

It is possible to remove the OE trailer charging wire from the coach and remove the Ford breaker. Then wire a larger wire set and a larger fuse to the trailer to get much more amps from your truck to the trailer.
80 amps with #2 wire set and a 90 amp breaker.

We do not doing any boondocking; we go from shore power to shore power 99% of the time. The ROI on hiring a vehicle electrician to do that (I do not do hillbilly)
would not be worth it for how we use the RV.

[Sbrownstein]

Originally Posted by Gray01

What exactly do you mean by that, 100 watts an hour, 100 watts while its operating (duty cycle), etc.
Also, what would you estimate the wattage consumption of the F&P (as opposed to your reefer? Thank you.

That would be 100 watts...all the time...as an average power consumption or 8.3 amps of 12 volt, including the Xantrex Prowatt 2000 efficiency. While I don't trust Energy Star numbers for absolute predictions, they are OK for relative numbers. So, your F&P has an Energy Star Rating of 464 KWh/year and my Frigidaire is 564 KWh/year. As a result if everything is roughly the same, your F&P will take about 80 to 85 watts or around 7 amps of DC. In 24 hours that would be 168 amp hours from your house bank.

Don't know about the F&P, but mine has a digital temperature display on the front panel and it never, ever changes. It does go through some defrost gymnastics and other things so the consumption varies at about:

Duty Factor/Watts
3%/600 watts
12%/155 watts
85%/65 watts

Of course, there is always a difference between accuracy and precision. These are measured numbers of long periods. Basic cycle for my reefer is about 7 hours.

[ScoobyDoo]

First, 2 points;
1 I'm just a dumb truck drive, don't much understand electric theory.
2 I have no dog in this fight, will stay with what I got the rest of my life.
From what little I know every time you change the form of energy, like 12V DC to 115V AC you lose some. What I don't understand is why people that do mostly boondocking do not use 12V DC compressor fridge?

[Sbrownstein]

Originally Posted by ScoobyDoo

What I don't understand is why people that do mostly boondocking do not use 12V DC compressor fridge?

The original reason that refrigerators do not use DC motors is that DC motors draw current at pretty much full amperage regardless of instantaneous load but AC motors draw based on the load at any given time.

However, modern refrigerators (and split air conditioners) now use built in inverters to run their AC compressors. This is done so that by varying the frequency of the inverter AC output (staying at the same voltage) they can vary the speed and throughput of the compressor. That is why new reefers are so efficient but that is what makes it hard to specify that actual amperage used. There are a variety of amperages used, depending on what part of the cooling cycle that they are currently operating.

They could make a modern reefer that exposed the DC input of the inverter but I have no idea what the DC voltage would be and there really isn't enough demand for it. I would suspect that they run on 120 volts DC, so a battery wouldn't be of much use.

[Gray01]

Originally Posted by Sbrownstein

In 24 hours that would be 168 amp hours from your house bank.

The 168 amp hour is a telling number. Our house bank is 2 each of the DP24MFS which are rated (each) at 60AH at 20 hours.

The fact that after 8 - 10 hours of battery/inverter usage for the reefer (while driving) and the existing voltage is at 12.7 vDC at the end of the drive, tells me that the truck charging circuit is doing a fair job.

[Sbrownstein]

Absolutely...driving is free. You can easily get 8 amps from your TV through a reasonable gauge connection.

[ScoobyDoo]

Originally Posted by Sbrownstein

The original reason that refrigerators do not use DC motors is that DC motors draw current at pretty much full amperage regardless of instantaneous load but AC motors draw based on the load at any given time.

I have no idea what this says...

However, modern refrigerators (and split air conditioners) now use built in inverters to run their AC compressors. This is done so that by varying the frequency of the inverter AC output (staying at the same voltage) they can vary the speed and throughput of the compressor. That is why new reefers are so efficient but that is what makes it hard to specify that actual amperage used. There are a variety of amperages used, depending on what part of the cooling cycle that they are currently operating.

Still more Greek to me. Likely I'm to dumb to understand.

They could make a modern reefer that exposed the DC input of the inverter but I have no idea what the DC voltage would be and there really isn't enough demand for it. I would suspect that they run on 120 volts DC, so a battery wouldn't be of much use.

Now I have to get argumentative. The fact is that in the trucking industry, compressor refrigerators that run on 12 volt DC have been around for decades. (And I have seen a few in campers) Now I can't tell you how much power they draw but can report my limited experience. A friend had one factory installed in his '97 Pete. He had a family emergency, left the rig, in August, Texas, truckstop. (Never seen shade in a truckstop). Truck sat for a week before I got there to recover it. I was worried, because of the 'fridge running on the starting batteries all that time. Once truck started, decided I should clean the garbage out of fridge before it got worse. Stole one of his ice cream bars, and headed for home.
Might want to look at https://www.truckfridge.com/
Not the only brand that uses the 12V compressor, but a place to prove the idea works...
Of course another thing the trucking industry know that RVers can't seam to get a handle on; A roof you don't need to dick with every year...

[twinboat]

Boats have been using 12 volt DC compressor refrigerators and cold plate systems for a very long time.

The rest of the stuff about inverter run household refrigerators is only relevant on some high end models. The typical Westinghouse 18 CF fridge still uses a standard 120 volt compressor.

[nothermark]

Originally Posted by Sbrownstein

The original reason that refrigerators do not use DC motors is that DC motors draw current at pretty much full amperage regardless of instantaneous load but AC motors draw based on the load at any given time.

>snip<

They could make a modern reefer that exposed the DC input of the inverter but I have no idea what the DC voltage would be and there really isn't enough demand for it. I would suspect that they run on 120 volts DC, so a battery wouldn't be of much use.

First statement is false. DC motors self regulate the current drawn the same way AC one's do. What you can do is wire a DC motor to blow itself up under no load but that is a different issue.

Most refrigerators are still simple motor driven compressors. A few rectify the AC going in and then use an Inverter to drive the AC motor at a different or variable frequency for better efficiency at more cost and complexity.

[FatChance]

How can one determine if a residential refrigerator has a simple motor driven compressor or a rectifier/inverter to drive the motor? I ask to know if it can be run with MSW or requires PSW inverted power? We have a Haier (GE) 15cf residential refrigerator and no one on their customer service line has a clue or can find anyone who can help.

[twinboat]

Originally Posted by FatChance

How can one determine if a residential refrigerator has a simple motor driven compressor or a rectifier/inverter to drive the motor? I ask to know if it can be run with MSW or requires PSW inverted power? We have a Haier (GE) 15cf residential refrigerator and no one on their customer service line has a clue or can find anyone who can help.

I'm pretty sure that if the compressor starts and stops, its not inverter driven. You hear it run for ten minutes or so every 45 minutes.

The inverter driven models varry the compressor speed as the cooling demand changes.

[Gray01]

Originally Posted by FatChance

How can one determine if a residential refrigerator has a simple motor driven compressor or a rectifier/inverter to drive the motor?

Most of the better quality modern residential reefers use inverter technology. If your reefer uses that the mfr will usually list that in the specs and/or documentation.

[Gray01]

Originally Posted by ScoobyDoo

Might want to look at https://www.truckfridge.com/

It is not an issue of 12 volt reefers.

What some (like us) want is the same comfort, convenience and technology on the road that we have at home. We have zero desire to live the "12 volt life". We use our RV as our hotel; we do not camp or boondock.

Thankfully, the newer residential reefers provide those attributes, and they work just fine with our model of RVing.

[CountryFit]

Originally Posted by FatChance

How can one determine if a residential refrigerator has a simple motor driven compressor or a rectifier/inverter to drive the motor? I ask to know if it can be run with MSW or requires PSW inverted power? We have a Haier (GE) 15cf residential refrigerator and no one on their customer service line has a clue or can find anyone who can help.

it's known that samsung rf18 is inverter driven, which accepts msw.
unlikely haier is using inverter.
my magic chef is not, so only psw is accepted. 6a draw from batts when compressor is running, else 0a. when defrost kicks in, it uses about 10a.