Powering a residential fridge

[catonine]

I have searched threads and found several that just about answered my following question, but not quite. I am not well versed in electric matters so need help from those that are. My question: I am looking at removing my Norcold 1210 and installing a residential model. My choices of replacement is limited due to fact that my 2011 Southwind 32V has the fridge mounted so that half of it is in the hallway, therefore opening doors very wide is problem. I have found a few that I can use where this will be no problem. I have plenty of room in old cutout to mount a residential unit. Now, when driving will my alternator keep the house batteries charged up enough to operate fridge? I only have 2 house batteries and since we don't dry camp, this should be enough IF alternator can do the job. I also have a 1200watt Magnum inverter. This power thing is only concern when driving as we always use shore power. I can, if needed, run the generator as I drive. Help would be appreciated very much. Thanks

[boyland]

If possible i would add another battery.

I run with 3 batteries and have had no issues powering the unit.

It likely will be fine with 2 batteries but 3 would be better.

[Mr_D]

What output does your alternator have? Probably doesn't matter though as most residential refers don't take much power.

[ralphie]

Two good 12v hybrid or better batteries should work. Two 6v batteries would be better for the fridge and everything else, but I would first try the 12v route without expending additional funds.

[nothermark]

FWIW Try it before spending any more money on batteries. There are too many variables to say for sure but there are a lot of folks out there now with two batteries and a residential fridge. The issue might be getting to camp with a low battery. IF that is the case then look at increasing capacity or charging. If all you are running is the refrigerator while driving there should be ample capacity.

[38Chevy454]

Your alternator *should* be enough. I have no idea on your alternator capacity, but let's just assume 100 amps for sake of example:

Using the formula that Watts = Volts x Amps = 100 amps x 13 volts (your alternator puts out probably 13.5 +/- technically) provides 1300 watts of power. Of course you need some for the electrical needs of the chassis, so let's take 50% off the top for other chassis needs and some resistance losses and that the alternator is not running at 100% capacity. That leaves you with 650 watts available, but most residential frig only need 300-500 watts. So you have enough capacity with alternator and do not need the generator to run.

[catonine]

Thanks for reply. According to brochure the alternator is 130Amp but I have not looked to verify that. But it is the original alternator so that should be right. It has two 12 volt house batteries, they are Interstate but cant recall which ones.

[catonine]

Thanks for the information. I have a friend that installed a residential and did nothing but plug and play. He has it good and cold before leaving on trip and if needed, about every 4-5 hours on the road he runs genny.

[catonine]

Ralphie thanks. I currently hav 2 12 volt Interstate batteries, don't remember which ones right off hand though.

[catonine]

Mr D, book says 130 Amp. Thanks

[catonine]

Boyland, I would like to add a couple more but have no room and cant find a place to put them within reasonable distance. Thanks

[catonine]

I appreciate all the information you folks furnished to me. Like I said, electricity is not my thing, at least not when it comes to these fridges. My Norcold works as well as any I guess, but that is not bragging on it. I have found a residential that will fit the cutout with minimal cabinet work, (mostly just a little bigger trim), and the price is good as well. It is a Whirlpool, cant remember model number, but it is being put in a lot of MH nowdays. Ad it is about the same capacity as the 1210 and much lighter and cheaper. As a matter of fact I if I put it in and it fails, I can buy 41/2 more if needed, for the price of a new Norcold 1210. Again , thanks for all your help, I really appreciate it. John

[noflyboy]

Our Southwind has a residential fridge and 4 batteries. Here's some math I did on the power consumption of the fridge and it seems to match what I find in reality. So I guess here's some math:

The spec sheet on our fridge says 630kWh/year.
8,760 hrs / year, so 630000Wh / 8760 = 71.9W/hr on avg.

The fridge is 120V so 72W / 120V = 0.6A annual avg

But the converter draws from a 12V source, so the actual draw on the battery system is (not including converter efficiency waste):
72W / 12V = 6A avg

Now I have 4 6V batteries that have 208 amp hour capacity (20 hr rate, due to how battery capacity is measured this is of course hand-wavy) in the standard config of Series->Parallel so my battery bank ends up at 12V and about 400AH.

Just dividing 400AH/6H = 66H = 2.75 days. That's just for the fridge and of course it isn't the only power draw. So since I want to keep my battery charge from dropping much below 40% I end up only being able to run on battery for about 1 day. Something to keep in mind if you wanted to run with less battery capacity.

[catonine]

Nofly, thank you. I am just interested in running off house batteries as I go down the road. If needed I can run genny, but I believe that from what I have learned here, I can travel on batteries as the alternator keeps charging them. Thanks