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tireman9

Power Refrigerator Via Inverter?

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In my previous coach I installed a 750W inverter to power the 110v side of my absorption RV refrigerator.

I power the inverter through a relay that only draws 12V DC from coach battery to the inverter when my engine alternator is running so I'm not going to kill the battery.  This system worked fine. Kept food cold for a trip from Ohio to Oregon and back while driving about 6 hrs a day,

Installing similar in current Class-C  and have a connection I am pretty confident in but wanted another person to look at.  In the attached simple schematic O1 is the outlet the fridge is plugged into and is located in the fridge "closet".  O2 is an outlet in the space where a outside TV would be installed but I don't have a TV so the outlet is not used. I am installing the inverter in this empty space.

According to schematic from Coachmen both these outlets O1 & O2 are on on same 110v circuit which is hot when shore power is connected to the coach. The 110v heating element in the Dometic fridge is rated 350 watts

The inverter 12V + is connected to the continuous duty relay which connects through a 30A fuse to the coach battery,  The relay is activated only when the ign switch is on.

My question is.. If I make a male to male extension cord and connect the inverter to the O2 outlet will it work?  Getting to the back of the outlets makes a lot more work, The extension cord seems too simple but I figure that as long as I wire the extension cord correctly to the 3 prong plugs it should work.

Not to "code" but I think it is electrically safe.

 

Comments?

Inverter power (Medium).JPG

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Roger,

Those male/male extensions are called "dead man's plugs".

And, you will be backfeeding all circuits on your 30 amp coach, including the converter.  BAD IDEA.

 

Better to either move the plug as you leave in the morning or wire through a switch so you can choose power source.

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Brett, Is the problem having 110V from shore power connected to the output side of the inverter? Is this a problem even with the inverter isolated from 12V?

 

If I isolate the Inverted form O2 by either unplugging the "extension" or installing a relay switch you are saying it would be OK?

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Roger,

Just use a double pole, double throw switch to switch the hot lead and neutral of the 120 VDC to the refrigerator between inverter and shore/generator to the refrigerator. Couple of bucks and a clean installation.

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Brett

Can do.  Didn't think about the 110V side as I had no problems with prior install but I would prefer to do things in a safer manner.

 

Off to Lowes electric dept.

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Yup, with double pole, double throw:

Side 1: terminal 1 hot from main breaker box (shore power or generator)

            terminal 2 neutral from same

OUT: terminal 1 hot to refrigerator

         terminal 2 neutral to refrigerator

 

Side 2: terminal 1 hot from inverter

            terminal 2 neutral from inverter

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Got DPST so end up with on/off of the output of the Inverter. This accomplishes same as just completely removing the extension cord between output of inverter and the outlet that connects to the Refrig.

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Roger,

Perhaps I am not picturing what you are doing.  But, with the switch on, are you plugging it into one of the outlets behind the refrigerator and the refrigerator is plugged into the other outlet? Both outlets in the same fixture and supplied by the same hot and neutral from the main breaker box?

If so, you will be "backfeeding" the whole coaches 30 amp breaker panel including the converter.  This will create a closed loop and eat a lot of power.

That is why I suggested a double throw.  It would absolutely guarantee that only one source at a time powers the refrigerator with no backfeeding.

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1 hour ago, desertdeals69 said:

Why don't you just put a outlet receptacle on the end off the inverter power cord and plug the fridge into it?

I would like to not have to plug & unplug the refrig every time I connect to shore power. That plug is only acessable through the outside refrig vent door.

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2 hours ago, jleamont said:

Roger, you still have an absorption refrigerator or was it removed for a compressor/residential type?

Still have absorption fridge.  I'm in a Class-C.  The OE fridge works fine. I would just like to shut off the propane when driving.

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Do you have an ice maker in your current refrigerator? If you do the cord from the icemaker is plugged into a circuit from your inverter. The icemaker must have 110 power to work when you are on propane and not hooked to shore power.

I ran my propane fridge on propane when driving never a problem. Never found conclusive evidence it was a problem. Don't have it any more as I just installed a residential refrigerator. By the way I am running it using the old outlet for the ice maker behind the refrigerator.;)

Bill

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I agree with Brett, DP/DT is the best option. Two in's and 1 out just as he described is the best option, backfeeding can become a nightmare. Only better souloution would be an automatic transfer switch that would activate when you power on the inverter, or an inverter that automatically switches on when shore, or generator power is off and supports pass through operation.

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4 hours ago, wolfe10 said:

Roger,

Perhaps I am not picturing what you are doing.  But, with the switch on, are you plugging it into one of the outlets behind the refrigerator and the refrigerator is plugged into the other outlet? Both outlets in the same fixture and supplied by the same hot and neutral from the main breaker box?

If so, you will be "backfeeding" the whole coaches 30 amp breaker panel including the converter.  This will create a closed loop and eat a lot of power.

That is why I suggested a double throw.  It would absolutely guarantee that only one source at a time powers the refrigerator with no backfeeding.

I understand the goal of having only one power source at a time. In My Class-C I only have 110V in the coach when plugged into shore power.

Not sure if I understand the "backfeed"  or "closed-Loop" unless I were to keep engine running (inverter active) and also plug in the shore power.

I am installing a double poll switch that will isolate the inverter from the 110v system. Switch is accessible near control panel right inside my entry door.

 

Ross and others, I will be at Indy. I should be in Governing Board / Committee 30 amp lot unless I burn to the ground on my drive from Akron to Indy :o Aim to arrive on 10th late afternoon. Can give "free tours" of my rv on 11th:D

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1 hour ago, WILDEBILL308 said:

Do you have an ice maker in your current refrigerator? If you do the cord from the icemaker is plugged into a circuit from your inverter. The icemaker must have 110 power to work when you are on propane and not hooked to shore power.

I ran my propane fridge on propane when driving never a problem. Never found conclusive evidence it was a problem. Don't have it any more as I just installed a residential refrigerator. By the way I am running it using the old outlet for the ice maker behind the refrigerator.;)

Bill

No ice maker.  I understand that it is possible to run on propane. Issue I have is that if there were an accident having the propane "on" can be a big problem. (See Mac the Fire Guy)

Now some / many might not feel this is a serious concern and I understand accept that position. I may even be irrational in this concern but feel it is possible to keep the food cold enough to keep the DW happy using the 12 v system from my engine.

Coach has no on-board inverter from Coachmen.

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57 minutes ago, kaypsmith said:

I agree with Brett, DP/DT is the best option. Two in's and 1 out just as he described is the best option, backfeeding can become a nightmare. Only better souloution would be an automatic transfer switch that would activate when you power on the inverter, or an inverter that automatically switches on when shore, or generator power is off and supports pass through operation.

Agree but didn't find any fully automatic system. Also didn't find DPDT switch but figure it should be OK as long as I disconnect the 110v system when the chassis engine is off.

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Roger,

Feedback:  when the inverter is powering the outlet, the line from breaker box to that outlet will be POWERED. That means that all breakers in the main breaker box will be powered (unless you also shut off the breaker to the circuit that powers the refrigerator circuit).  With the breaker box hot, the converter will be powered.  It will charge the batteries.  Because neither inverter nor converter area 100% efficient, this "closed loop" condition will deplete power.  Yes, the alternator MAY be able to keep up, but at the least, a large waste of power and overheated alternator.

Again use a double pole, double throw switch or an ATS. The second ATS would be a lot more expensive and basically the same wiring.

 

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11 hours ago, Tireman9 said:

I understand the goal of having only one power source at a time. In My Class-C I only have 110V in the coach when plugged into shore power.

Not sure if I understand the "backfeed"  or "closed-Loop" unless I were to keep engine running (inverter active) and also plug in the shore power.

I am installing a double poll switch that will isolate the inverter from the 110v system. Switch is accessible near control panel right inside my entry door.

 

Ross and others, I will be at Indy. I should be in Governing Board / Committee 30 amp lot unless I burn to the ground on my drive from Akron to Indy :o Aim to arrive on 10th late afternoon. Can give "free tours" of my rv on 11th:D

Roger,  I will be in the PNO/GB/Com lot with no elec.  I will look you up or you could look me up, F31175 Bruce Chong.  I have been wiring your type of situation for some 42 years with inverters, relays etc.  I will draw you a wiring diagram of what you need.

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11 hours ago, WILDEBILL308 said:

Do you have an inverter in your coach now? 

Bill

Coach did not come with an inverter.  Only a standard converter. I am in a small Class-C so don't have the bells & whistles all you big class-a folks have.:rolleyes:

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