Added 12V Power/Inverter Power To Refrigerator

[tireman9]

After listening to Mac "The Fire Guy" at a couple of FMCA events I no longer run with the propane valve on when driving.

In the past most trips were relatively short so the temp of the fridge has not risen too much but since I am headed to Redmond, Oregon from Akron, Ohio I have a number of long days ahead of me so I decided to Mod the electrics.

Biggest problem is that the Coachmen wiring diagram is more of an estimate on what the staff did when they assembled my Freelander. No color coding, no wire sizing identified and numerous un-used wires and connectors along with some uninsulated wires just laying under the floor. Sooo after doing a lot of testing and creating my own wire diagram here is what I did.

Refrig needs 2.7A @120V or 324Watts.

Harbor Freight has a nice inverter rated at 400W continuous

I have space in my battery box to permanently mount the inverter.

There is an Ignition hot feed in the battery box area.

Ran wire from Ign Hot to a rocker switch in the control panel by the door. Then from this switch to a relay in the battery box.

The relay controls the power from the battery to the Inverter.

Eliminated the battery clamp connections off the inverter and using ring or spade terminals w/heat shrink tube on each end, made all the wiring permanent.

Battery to Inverter is 10Ga

120V Inverter to DPDT switch is 14Ga HD exterior rated extension cord.

10A fuse on the Ignition hot connection to the rocker switch

120V output from the inverter runs to a DPDT switch. This switch connects either the Inverter or shore power to the Refrig so isolates the two power sources.

Still to-do is label the switches

Now when driving down the road my engine alternator is providing ample power for the Refrig and if I shut off the engine there is no drain on the coach battery. The rocker switch and the DPDT switch are redundant in controlling when the refrig is running off the coach 12v system.

[obedb]

When we had a gasser, quality inverters either did not exist or were quite expensive. We now have a "new" 2003 Phaeton with a Freedom inverter/ charger that should be up to powering our Dometic. We cooled with propane in the gasser and it worked well. I will try the inverter on our big absorption frig. If it is hot on our trip west we will probably be running our Onan 7.5 Quiet Generator and that can power the frig.

So far, I am really impressed with the genset.

[huffypuff]

See you guys at Redmond

[desertdeals69]

T9 The key to how successful your refrigerator operation works depends on the efficiency of the inverter. To provide the 2.7 amps at 120 volt will take how many amps at 12 volt? Probably 30 or more amps. You should not mount the inverter in the battery box because of corrosion. Depending on the size of the alternator it may have to be larger. When an alternator is rated, the amp rating is the max it will put out which could be twice the continuous duty it will be able to do. Talk to me at Redmond, I will be there.

[kaypsmith]

I will always use an inverter which is rated at double the required load. 324 watts is much too close to the rated watts of the 400 watt inverter, heat that will be produced in this scenario will become an enemy, in addition to DD69's comments.

[tireman9]

Thanks for replies. I have received some feedback on other site so will be changing the system.

1. Increasing the Inverter to a 750W unit by Husky

2. Am moving the Inverter and relay out of the Battery box to area under counter. I will monitor the temperature of this area

to see if I need for the inverter fan to blow through opening in counter face into living quarters or if the air space under counter which runs around the water tank is large enough.

3. Will be connecting the inverter positive side using 10Ga wire 2' long directly off the Coach Battery relay that is already under the counter. This line will have 50A fuse in it and a 50A rated "trigger" relay. The Coach Battery relay is connected to the Deep Cycle coach battery w/2G wire provided by coach mfg..

4. Will run 6' of 6Ga directly from Battery ground to the Inverter.

5. The trigger relay will still be activated by combination of Ignition Hot plus a rocker switch. Will lower fuse on the trigger line to 2A

6. The 120V Inverter output will use 14G to the DPDT switch and 14G from DPDT to the refrig. The total length of the 14G from inverter to refrig through the DPDT switch is 12'

Not sure what to do about the battery disconnect switch, which is not part of this refrigerator / inverter system but just a disconnect on the ground side of the coach battery. Many of these switches are sold for various applications in car, truck, boat and RV application. Some concern was expressed about battery explosion with my components in the battery box but none of these would in my opinion be "sparking" under normal operation. The batter disconnect switch almost always emits a small "zap" whenever I connect the battery to the system. This to me would make this a more likely cause of battery explosion than having the inverter and relay in the battery box. This obviously is a separate question for those knowledgable in 12v system and battery safety.

Thanks again for the replies.

[kaypsmith]

"Not sure what to do about the battery disconnect switch"? This statement raises concerns for me, any camper style, "absorbtion fridge", will still need 12 volt supplied, even if it is being run on 110/120 ac.

The controls use 12 volts whether on gas or electric, if this is taken away, the fridge will not work.

Kay