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Topic: residential fridge power source--- shore or inverter power (Read 969 times) previous topic - next topic

residential fridge power source--- shore or inverter power

I am  installing a Whirlpool WRT111SFDM residential fridge in my 1997 U295.  Do I need to install an additional  power wire from the fridge to plug into the inverter outlet or do I just install jumper wire and plug from the fridge main electrical wire so that I can have two plugs from the same wire to switch from shore to inverter power.
Terry and Cheryl Brown
1997 U295 36'
Build #5066
2006 Jeep TJ Rubicon
1993 BMW R100 GSPD

Re: residential fridge power source--- shore or inverter power

Reply #1 –
Another option would be to buy a smaller inverter that has a built-in transfer switch and use that for the fridge.
Forest & Cindy Olivier
1987 log cabin
2011 Roadtrek C210P
no longer 1999 36' U320 build #5522
2013 Rzr 570 & 2018 Ranger XP1000
2006 Lexus GX470
2011 Tahoe LT 4x4
Previous 1998 45' 2 slide Newell, 1993 39' Newell

Re: residential fridge power source--- shore or inverter power

Reply #2 –
You should have two 120v outlets behind your LP refrigerator is located. One is powered from the inverter panel and the icemaker plugs in there.  The other is powered by the main panel which gets power from the landline or generator.  The 120 v side of the refrigerator plugs in there.  When there was power there the refrigerator ran on 120v otherwise LP.

Your new refrigerator should plug into the inverter circuit.  This one gets power from the land line or the generator or when they are not available from the inverter.  This keeps your refrigerator on all the time.
Roger Engdahl and Susan Green
2001 U320 3610 #5879 (Home2) - 2014 Jeep Cherokee or 2018 F150
Hastings, MN

Re: residential fridge power source--- shore or inverter power

Reply #3 –
In a alternate mode or emergency  I suppose an absorption refers 110 volt power side could be plugged into the inverter plug.  If you had enough battery and solar and inverter maybe a way to reduce the propane consumption? Gang plug the ice maker and refer 110 cords both into the inverter.  Versus use propane....

Lots of power but with enough system should work ok.

Fun to test just for grins.

A inverter has a max efficiency output power spot.  Past that the efficiency drops.

A big inverter may  a bigger high efficiency output range. 

Based on the only full output 12v chart published the efficiency drops quite a bit as the percentage of its rated power increases.

Cooling fans come on.  Transformer heats up. 

I know of no rv with multiple sized inverters around the coach to power local loads.

All have a larger central unit running closer to its max efficiency point.

Higher power needs stack the inverters to increase the efficient power output.

A Magnum turns on its cooling fans based on transformer temp and/or power output.

At 25% it turns on both fans at low speed.  At 50% medium speed.

Both consume power.

Probably why their chart shows less efficiency at higher outputs as at 100%the fans go on high.

Or when the transformer temps trigger the fans to come on and as it's heat increases turn the fans up more.

All efficiency rating are at 77 degrees.  And a normally non specified amount of power output.

There is a voltage drop for any wiring run.  A 12 volt wire will soak up power.  A 4/0 cable uses power per foot.

No free lunch. I think 110 volt wiring probably uses less power per foot versus running battery cables through a coach.

Probably why rv's have one large inverter close to the batteries and short runs of thick cables then distribute the power via 110 volt wiring.




"Riding and rejoicing"
Bob
1997 U320 40' Mid entry, build 5132,  wtbi ce27, 4th owner
2007 Solara convertible
2 prodeco tech outlaw ss electric bikes

1095 watts solar
08 Ls 460 and a sc430
2000 Ford F-250 superduty 4x4

Re: residential fridge power source--- shore or inverter power

Reply #4 –
Quote from: CAPEHORN31 –
I am  installing a Whirlpool WRT111SFDM residential fridge in my 1997 U295.  Do I need to install an additional  power wire from the fridge to plug into the inverter outlet or do I just install jumper wire and plug from the fridge main electrical wire so that I can have two plugs from the same wire to switch from shore to inverter power.

If I understand you correctly, what you want to do will tie the shore power and the inverter output together. 

This is not a good idea.
1992 Foretravel Grand Villa
U225 SBID Build No. 4134
1986 Rockwood Driftwood
1968 S.I.A.T.A. Spring
1962 Studebaker Lark
1986 Honda VF700C
1983 Honda VF750C
Charlie, the Dog was broken out of jail 24 Oct 2023
N1RPN
AA1OH (H)e who must be obeyed.

Re: residential fridge power source--- shore or inverter power

Reply #5 –
Quote from: Old Toolmaker –
This is not a good idea.
The Master of Understatement.  8)
1993 U280 SE 40' WTBI, Build: 4359
C8.3 300hp, 6-Speed, Exhaust Brake
960 watts on the roof (6 x 160)
Sorento (or BOLT) on a Kar Kaddy SS
"Nature abhors a vacuum"

Re: residential fridge power source--- shore or inverter power

Reply #6 –
You also need to check how many watts the residential fridge uses and then multiply by 3 for the startup load.

Quote: "Before shopping for an inverter, you need to know the power draw of your refrigerator in watts. This information is found on the manufacturer nameplate, expressed as amps or watts. If the plate gives the watts, you are home free. If amps are given, convert amps to watts by multiplying the amps times the voltage. For instance, if your typical 16 cu. ft. fridge draws 6 amps, you multiply 6 by 120 volts to get 600 watts. That is your running wattage. A fridge motor also needs a jolt of about three times its running wattage to start up, but this surge is needed for only a fraction of a second. To run this refrigerator, you will need an inverter that can handle 600 watts for long periods and a surge of 1,800 watts for a split second."

Pierce
Pierce and Gaylie Stewart
'93 U300/36 WTBI
Detroit 6V-92TA Jake
1140 watts on the roof
SBFD (ret)

Re: residential fridge power source--- shore or inverter power

Reply #7 –
Quote from: Roger & Susan in Home2 –
You should have two 120v outlets behind your LP refrigerator is located. One is powered from the inverter panel and the icemaker plugs in there.  The other is powered by the main panel which gets power from the landline or generator.  The 120 v side of the refrigerator plugs in there.  When there was power there the refrigerator ran on 120v otherwise LP.

Your new refrigerator should plug into the inverter circuit.  This one gets power from the land line or the generator or when they are not available from the inverter.  This keeps your refrigerator on all the time.

To further flesh out what Roger says, the inverter-fed transfer switch does the switching for you.  The main transfer switch sends shore or generator power to it when one of those is available.  When it's not, the inverter transfer switch gets 120V from the inverter (provided you have it turned on).  All outlets that are run off the inverter run off shore/generator when you have that power source.  There are no outlets (unless something was modified by an owner) that run off inverter only.  There are just outlets which run off shore/generator only.
Learn every day, but especially from the experiences of others. It's cheaper!  - John C. Bogle

2000 U320 36' non-slide / WildEBeest Rescue
2003 U320

Re: residential fridge power source--- shore or inverter power

Reply #8 –
Thanks, Michelle.  always nice to hear your help.

Pierce, 6x120=720. I doubt there are any new residential refrigerators you can put in your coach that use 6 amps @120v in normal use. My full sized Samsung uses 135 watts running maybe 5 watts at idle, about a 50% duty cycle based on months of real world measurements.  And that is very close to the yellow energy sticker that came with the refrig.  The Samsung specs say 6 amps @120v maximum load.  I checked with them, they said that is a warm startup with ice maker and power cool and power freeze on.  My smaller Victron inverter has 1500 watt short term peak output, about 2.5 rated continuous output.  That is twice the Samsung short term warm start load..
Roger Engdahl and Susan Green
2001 U320 3610 #5879 (Home2) - 2014 Jeep Cherokee or 2018 F150
Hastings, MN

Re: residential fridge power source--- shore or inverter power

Reply #9 –
I second all that Roger said, he crisply describes the "worst case" start load for his residential unit.

Refrigerator compressors do have an "Inrush" (LRA = "Locked Rotor Amps"). Worst case is a hot day and a veryrecent start -

The start event on the compressor lasts approx 1/3 of a second (300 milliseconds) and generally is 3-5 times the running load (RLA = "Run Load Amps"). The newer the refrigerator and the higher efficiency of the unit as depicted on the industry sticker, the lower the inrush/LRA are likely to be, as engineers have been working to reduce overall load and start load for years.

most scroll compressors equalize the refrigerant pressure between starts so there is usually a 6-10 minute minimum delay between shut down and restart built into the control logic to allow for a cooling of the motor winding and allow the refrigerant to equalize pressures on the input/output of the compressor so that the motor is not starting against coolant "pressure" in the line during this start event. Even with all that magic, the LRA is indeed 3-5 times the RLA.

Inverters all have a "surge" capability to accommodate very short term high transient load. It is pretty easy to calculate your needs for an inverter run and surge capacity (as Roger so well illustrated and has implemented).

One caveat, if you are marginal on inverter capacity or buy a really low cost cheap inverter (many of these cheap units shamelessly misrepresent actual running and surge capacities) you should confirm that the unit will start your refrigerator in hot weather "multiple start" scenarios. An overloaded inverter will "trip" off-line to save itself and the wiring of the coach or the motor it is trying to start, leaving you with no power going into your refrigerator/freezer. Left for too long, things will melt, food will spoil. Yuck.
Tim Fiedler    2025 LTV Unity MBL on Order
2000 Chevy Tracker 2 Door Convertible 4WD Now lifted 4.5"
1985 Citroen 2CV6 Charleston
Murphy Rebel on wheels with 175HP Titan
Cessna P337
1980 48' Westport MY (!/4 Share)

Re: residential fridge power source--- shore or inverter power

Reply #10 –
Thanks for your info.

My buddy rewires for heated floor and cooktop coaches for 240 volt as needed. 

He stores and oversees jimmy  buffets sports mobile 4x4 van and does the Ketel one prevost among many others.

We are going to install the autoformer in a bay and hardwire the progressive industries protector into the coach.

Having the gen checked and serviced next week.

May have a VR issue, 
"Riding and rejoicing"
Bob
1997 U320 40' Mid entry, build 5132,  wtbi ce27, 4th owner
2007 Solara convertible
2 prodeco tech outlaw ss electric bikes

1095 watts solar
08 Ls 460 and a sc430
2000 Ford F-250 superduty 4x4

Re: residential fridge power source--- shore or inverter power

Reply #11 –
Roger,

Think you are pretty close in your estimation. This is from a manufacturer. While they typically quote 2 or 3 times, to be safe 6X is possible. Quoted from their spec sheet:

Rated or Running Current / Power for CRF150SS-1

The calculation for the above example would be: 1.1A x 115V = 126.5 Watts

Model CRF150SS-1 has a rated current of 1.1A running on 115 Volts.  This will require 126.5 running watts for typical use.  As noted above, there are periods of startup or surge power that typically can be 2-3 times the amount of running watts.  As a rule of thumb and for precautionary reasons, you should consider that up to 6 times the amount of rated current may be required for initial startup of the appliance.

Startup or Surge Current / Power for CRF150SS-1
The startup amperage draw rating will be noted on the compressor itself by referring to the  Lock
ed Rotor Amp aka "LRA" value.  In the example below, the LRA is 5A (5 Amps) which would be equivalent to 575 watts for startup for a unit plugged into a 115V outlet.

Pierce
Pierce and Gaylie Stewart
'93 U300/36 WTBI
Detroit 6V-92TA Jake
1140 watts on the roof
SBFD (ret)

Re: residential fridge power source--- shore or inverter power

Reply #12 –
Thanks for all the help everyone.  I guess I  had a senior moment.  All I had to do was plug the fridge into the inverter outlet.  All is well works great.  I was trying to over engineer it.
Thanks again,
Terry
Terry and Cheryl Brown
1997 U295 36'
Build #5066
2006 Jeep TJ Rubicon
1993 BMW R100 GSPD
 

Re: residential fridge power source--- shore or inverter power

Reply #13 –
I finally called Frigidaire for the information on the 22.6 cu. ft. unit that cam in the coach when we bought it. 133 to 193 watts running and 1200 watts start up. Now I just have to figure out which small inverter I will buy and how to wire it.
1999 40 ft. U-320 wtfe build 5563 Chuck & Lynda's "Rollin' Inn"  2030 watts solar
prev. mh's 71 GMC 5 yrs. 73 Pace Setter 1 yr. 78 Vogue 5 yrs 81 FTX 40ft all electric 18 yrs. 1996 Monaco Signature 3 yrs.
2014 Grand Cherokee Overland
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