need to ask a question about amps

[george warner]

i've got 300 watts of solar, 4 6volt batteries at 230 ah each, hooked up in series and parallel which gives me 12volts and 460 ah, and a norcold refrigerator it says 4.6 amps , the question is is it pulling 4.6 amps per minute, 4.6 amps an hour or 4.6 amps continuously..

 

[Willy]

It's pulling 4.6A whenever the compressor is running, unless it's a solid state Peltier unit.. and then that would generally be continuous. ..Willy

 

[george warner]

thanks willy, i doesn't have a compresser, has a ac and dc heater that makes it work..

 

[Willy]

Sounds like a Peltier junction unit and.. it'll eat power like there's no tomorrow. The 'kinda' exception to this is the odd unit that has a thermostat, and even they are kinda half-assed cuz. ..Willy.

 

[Zil]

George, is your fridge made to run on propane?

 

[Willy]

Sorry, I misread. It sounds like an ammonia absorption fridge.. but still an energy hog. ..Willy.

 

[TucsonAZ]

Those suck A LOT of juice! Mine was using 2.5 times what my large home unit was using, 15 times what my normal 5cuft chest freezer was using and 25 times as much power as my chest freezer converted to an extremely cold fridge/warm freezer. Propane was just as bad but on propane.

I would dump it if you possible can and go for something else that uses less power.

To answer your question, that's when the compressor is running though the surge will be about 3-4x that amount and your inverter surge should be sized to handle that amount.

 

[george warner]

yep, its made to run on propane also, but i don't have propane in my cargo trailer conversion and didn't really want it. I found the manual online for it at norcold 4.5 amps is for the ac. 9amps for dc. yuk..... now i got to do something different.... thank all for the information.

 

[akrvbob]

I'll answer your question more generally. Appliances are based on the concept of amp hours. How many amps does a device use in an hour? So your fridge draws 4.6 amps an hour. That's actually pretty typical my Dometic/Waeco 12 volt compressor fridge draws 3 amps.

But that's only part of the problem. Next you need to know how many hours it runs per day. If it runs 20 hours a day then it uses nearly 100 amps a day that's a lot. But, if it runs 5 hours a day it's using about 25 amps which on your 230 ah bank is nothing (you can only use half of your battery bank, 230ah). If it runs 10 hours a day then it's using 50 amps, again, with a 230 ah bank you should be able to handle that fine.

The only problem will be if you are a heavy power user and you are drawing it down for other things. Or, and this is the BIG one, you get a week of rain and clouds. Then you are at real risk of running out.

However, rain and clouds also mean cooler so the fridge will run less. Whenever I know bad weather is coming I go into emergency rations on my solar so it will last and if you do that you should be fine.

A clarification on batteries. You may think since you have 4, 230 ah battteries you have 920 ah. However, that is at 6 volt and when you double the voltage, according to ohms law you cut the amps in half, so you have a 460 ah bank at 12 volt. But you can only use half of that so it fact you only have 230 available on a daily basis.
Bob

 

[Zil]

That fridge should only run on propane unless very short times on electric. It uses a heater element that will quickly kill your battery.

 

[Willy]

I'll answer your question more generally. Appliances are based on the concept of amp hours. How many amps does a device use in an hour? So your fridge draws 4.6 amps an hour. That's actually pretty typical my Dometic/Waeco 12 volt compressor fridge draws 3 amps.

It would be 4.5A AC.. 9A DC. That's a whole lotta juice and, I believe, it would probably have a considerably longer duty cycle. ..Willy.

 

[akrvbob]

Isn't the Norcold a native 12 volt fridge? I've never owned an RV or a RV fridge so I don't really know anything about them. I just thought they were 12volt. If it is AC then it isn't possible.

Longer than 10 hours a day? Again, I've never owned an RV but that seems like a lot.
Bob

 

[SternWake]

3 way absorption fridges are designed to be used primarily on Propane. The AC heating coil is for when grid power is available, and since grid power is inexpensive it is not much of a factor that it is an energy hog.

The 12 volt DC heating coil is designed to be used only when the vehicle is in motion, and it is designed to only help keep things that are cool, already cool. The alternator can supply the energy required.

These 12v heating elements in absorption fridges, despite drawing 9+ amps, are not really strong enough to circulate the refrigerant properly. They will have a 100% duty cycle on 12 volts dc in ambient temps above say 55f. If one were to power one exclusively on 12 volts, one would find it could not maintain safe food temps inside.

The 12 volt feature is there, because in many states it is illegal to drive through tunnels with a propane flame running, and refilling at gas stations one can see how having an open flame would be unwise.

The pre 90's absorption fridges are actually made better than post 90. Newer absorption fridges still require 12v to power the circuit board. One guy on another forum measured this 12 volt circuit board consumption at 17 amp hours per 24 hours. This seems excessive to me, if true. My 1.8 cubic foot fridge 12 volt compressor fridge averages about 18 amp hours per 24 hours.

Absorption fridges do not like to be run out of level doing so can cause crystallization of the Ammonia which clogs the lines. This is permanent, and cumulative.


As for power ratings listed for products, there is no set rule and generally the marketer will post information which makes the product look better than the competitor.

Even if they list what is an average power consumption, they do not state in what conditions that this consumption was measured, and with fridges there are a huge amount of variables which will affect how much energy the unit uses.

Generally absorption fridges need to be run on propane, or plugged into the grid. trying to run on on battery power alone is extremely unwise.

A lot of people whose absorption fridges are failing are going the residential fridge route as repair or replacement is a minimum of 1200$.

But a residential fridge might require a dedcated inverter, and an extra pair of GC batteries, and about 250 watts of solar, as a residential fridge is not nearly as efficient as a 12 volt compressor fridge, which will basically use half the electricity, or less of a residential fridge.

But the120v residential fridge might be 150$ where as a dedicated 12v fridge will be ~700$. And this leads too many down the inverter powering residential fridge route, then this person realizes they need more battery power and more recharging sources and often hears the low voltage shrill alarm on the inverter.

Then they wish that they had put the money they spent on a larger inverter, extra batteries and solar toward a 12 volt compressor fridge in the first place.

The people happiest with the residential fridge route, are those who go from campground to campground and plug in. Few boondockers use residential fridges successfully, and those that do have very large solar arrays and a large battery bank.

 

[stealthywon]

I was looking earlier today at these 2 fridges

Both had fairly good reviews on Amazon

micro size
Edgestar Compact Freezer Refrigerator with Lock - Stainless Steel

Power: 138 W/1.1 A $167.99

and small
Danby 2.5

1.5 amps 165 watts $119.99

 

[stealthywon]

I was looking earlier today at these 2 fridges

Both had fairly good reviews on Amazon

micro size
Edgestar Compact Freezer Refrigerator with Lock - Stainless Steel

Power: 138 W/1.1 A $167.99

and small
Danby 2.5

1.5 amps 165 watts $119.99

 

[akrvbob]

You can get a Whytner 45 qt 12 volt fridge for $500 today from Amazon. I love mine and consider it far superior to my Dometic/Waeco. I know numerous other people with them and they love them too.

My 190 watts of solar powers it without any problem year around. In the winter it runs less than 3 hours a day at 5 amps.

In the long run it's by far the cheapest way to have reliable refrigeration.
Bob

 

[Zil]

Get a 12 volt refrigerator. Bob has had good experience with whytner. there are other brands. Some better some not as good.

 

[Fearnoevil]

So I'm still trying to figure out the fridge thing, and have decided to scale back size-wise and power-wise. I was also looking at the Edgestar CRF150SS (has a full-range thermostat), which is available on e-Bay for $168 (free shipping). Its only 1.1 cu.ft, but at that cost I was considering getting 2 for 2.2 cu.ft., stacking them, and using one as a fridge and one as a freezer. So by the specs, that would use 2 x 138 Watts/1.1 Amps or 276 watts/2.2 amp hours, and at a price of just $336.

Anything comparable in a DC version seem to run well over $700 so at least $400 more, although to their advantage the propane option is certainly a good thing to have. On the other hand the extra $$$ could be spend to buy another 200w panel and upgrade to larger capacity batteries/inverter. Don't know if it all works out in the wash, but the other cost mentioned of repairing those absorption fridges is quite high, so advantage AC fridge, and if one takes a dump on me there's redundancy, so one more advantage for AC.

In my situation though I'll most likely be hooked to shore power a lot more than I will be boondocking, so there's that to consider. However I'm thinking that if I'm going to boondock at all, then everything does need to fit within those constraints, so there's that, lol. So weighing the variables as much as I'm able, I still think that the dual AC fridge comes out on top, but please feel free to shoot that full of holes if I'm all wet, all input appreciated ;?D

---

Also planning build a compartment for the fridge(s) and add a lot of insulation plus a vent channel powered by a small fan which will be divertable. outside for summer and inside for winter to utilize the waste heat. Any thoughts as to the efficacy of this type of setup (I'm sure someone's done this before ;?).

 

[george warner]

Thanks Bob, i ordered 45qt like your from home depot today $479. and free shipping. hope it works as good as yours..

 

[RogueRV2]

Based upon the exterior appearances of the 43 quart Edgestar and 45 quart Wynter, and that they share the same 'flash freeze' to -8 function, these two friges may have the same manufacturer. The Wynter at $479 is a good price. For a tad more, $529 at Home Depot, one can get the 65 quart Wynter. Yet even if the power draw is the same, the larger one will of course run more often and consume more power per day.

BTW, a quick 'thank you' from an aspiring RV Tech, to those sharing in-depth technical knowledge.

---

Fearnoevil,

It's good to think outside the frig/freezer box, however, because the Edgestar CRF150SS (full retail price can be $300), has a door that opens from the side, the gasket can leak, and when one opens the door all of the cold air is dumped. A top opening frig will contain much more cold air when the door is open and the gasket will not leak as much because cold air is heavier than warmer air, and will tend to stay inside the frig even when the door is open. Shopping by price is good, however one may get what they paid for. The best high efficiency 12vdc frigs all have top opening doors for good reason. Likely, the side door friges will run more often and the cost savings now could quickly be lost in time.