Run Norcold off inverter long-term?

[phemens]

Hi,

I've got 4 x T125's in a balanced wiring setup with 300 watts of solar. I'm looking to pick up a Xantrex prosine 1000 W inverter, and I was wondering about the viability of running the fridge (a Norcold, not sure what model, don't have the manual in front of me, but it's pretty standard, fridge on bottom, freezer on top, 2 way) off the inverter. We have the trailer parked on a site for May, it gets pretty good sun, and I'd like to set the fridge to auto during the week when we are not there. Any issue with that? I'm guessing it probably draws 10-15 amps per day?
On a side not, what is the optimal wiring for the inverter? I'll have it set up about 4 feet from the batteries on 4 gauge cables, does it matter to which set of terminals I should hook it up to? I was thinking the same ones as the converter.

Thanks!

[Canadian_Rainbi]

I've seen our Norcold 1201LRIM draw 40 Amps from the batteries.

[sh410]

The refrigerater burns 1500 Btu/hr or 36000 Btu every 24 hrs if the burner runs continuous. It would burn thru a 30# bottle in 18 days burning 24 hours a day.

On our trip to Alaska we used 60# of propane with the frig on for 80 days plus the water heater and cooking.

[valhalla360]

It adds complication but if your fridge will switch energy sources automatically, you could put the inverter on a low voltage cut off switch.

When the panels are putting out enough juice, the fridge would run on electric. When the batteries drop below a predetermined level, the switch would cut power to the inverter. You would have to maintain the 12v connection to the fridge so that the igniter would still fire up the propane burner.

This would be a partial solution, when you have enough battery/solar power, it would save propane but once the batteries wear down, it would switch over. I would guess a 50-60% reduction in propane usage but probably a lot of complication and I'm not sure if the standard battery cut off switches would work well since they may not let your battery ever reach full charge. As soon as the solar comes on the voltage goes up and they reconnect the battery (not sure on this as I don't have one).

The fact you are asking this question suggests you would need a professional set this up for you.

Probably cheaper in the long run just to burn thru and extra tank or two of propane over the course of a summer.

[pianotuna]

Hi,

Assuming sunny perfect conditions over two days the solar harvest would be about 3 kwh. The fridge uses about 4.8 kwh. The battery bank (600/2) is 300 amp-hours @ 12 volts.

300 x 12 = 3.6 kwh.

So there are 6.6 kwh under perfect solar conditions but a demand of 9.6 kwh over 48 hours.

Another way to look at this is hourly. The fridge may use 200 watt-hours for each hour it runs. 6600 / 200 = 33 hours of run time for the fridge, before hitting 50% state of charge on the battery bank.

If you arrive on a Friday, move the fridge to 120 volts on Saturday morning and switch it back to propane on Sunday before you leave.

The savings will be about one pound of propane per week.

[phemens]

I'm going to give it a try only when we are there, I'll post back. I have no issue running off propane, which is what we normally do, I was just thinking that I could leverage a free resource (solar). I figure that if I run the fridge off the inverter for the weekend, the solar can more than catch up during the week while the fridge is on LP.
Thanks for all the input.
I made myself a sticky to remind myself to ask the question again next year 😉

[Krusty]

I think it would work fine to try it the odd day while you are present, but I think it would be far too taxing on the batteries to run for several days while you are not there. The batteries would become quite run down overnight, and if you had a cloudy day they would not recover.

[time2roll]

Will run fine on propane. No inverter needed.

Otherwise your solar collection is way short on power to provide ~300w around the clock even with moderate duty cycle of the fridge. Even the battery will be a bit stressed to keep above 50% charge overnight.

The answer will be the same next year too 😉

[pianotuna]

Hi,

The fridge may consume 4.8 kwh per day. Harvest from solar is about 1.5 kwh per day.

[MrWizard]

phemens wrote:
Hi,

I've got 4 x T125's in a balanced wiring setup with 300 watts of solar. I'm looking to pick up a Xantrex prosine 1000 W inverter, and I was wondering about the viability of running the fridge (a Norcold, not sure what model, don't have the manual in front of me, but it's pretty standard, fridge on bottom, freezer on top, 2 way) off the inverter. We have the trailer parked on a site for May, it gets pretty good sun, and I'd like to set the fridge to auto during the week when we are not there. Any issue with that? I'm guessing it probably draws 10-15 amps per day?
On a side not, what is the optimal wiring for the inverter? I'll have it set up about 4 feet from the batteries on 4 gauge cables, does it matter to which set of terminals I should hook it up to? I was thinking the same ones as the converter.

Thanks!

Won't work
That electric heating element uses 300+ watts, about 25 amps at 13v when cooling
The cooling cycle is almost continuous, you would need solar supplying 50 amps charge all day every day,
25 amps to power the fridge, plus 25 amps to replaced what was used from the batteries during the night

[mlts22]

I feel dumb by asking... is the fridge going to be on propane or on the 120VAC inverter? If on the inverter, it has a substational current draw, a draw large enough that it will require far more than 300 watts.

If it is using propane (I've found a 20# bottle lasts about 20-30 days in warm weather), then the control board will need battery voltage, but it will be far less, and a 300 watt panel would be good enough to counteract what electricity the board uses.

I also second leaving it on gas. I tend to leave mine on propane all the time except when on the road.

[AH64ID]

I draw ~25A of DC running my Norcold off the Inverter, and the Fridge run's a LOT of the time.

I will only do it when driving a long distance, if at all.






What is the peak power draw of your Inverter? My Xantrex 1500w continuous 3000w Peak has 2 Ga running to it, and will peak at ~150A.

[BFL13]

I just tried out the Norcold 821 on electric from the Xantrex PSW 1000w inverter (Can Tire version) It showed approx 30a DC draw on the Trimetric.

AFAIK the fridge is on about 2/3 the time based on how it works on propane.

Leaving the fridge on propane comes to about 17AH a day battery draw. No idea how much propane that is but a bottle should last a couple weeks ???

I have the inverter on the battery bank using store-bought #4 "starter cables" 18" long and it handles 100a loads without fuss which is max for the 1000w inverter (divide by 10 rule)

FWIW, we are using the trailer as a summer cottage off grid and when we go home for a couple days we take the food and leave the fridge off. I got the 17AH figure from when we left the fridge on propane for three days and we were down 51AH on return according to the Trimetric. The solar can do that easily, but it seems silly for the little food involved in our case.

[jhilley]

300 watts is more like 18 amps in full sun. The heater in the refrigerator is probably 300 watts, that would be 25 to 30 amps while running. If you aren't opening the doors, it shouldn't run often. I think you should be fine.

I think I would use 2 gauge cable as long as you have to run new cable any way. Connecting to the same terminals as the converter should be fine. I would install two Power Posts and terminate all cables on them and then run a single cable from each terminal to each power post.

Blue Sea Power Post

[valhalla360]

The inverter is probably fine.

The charging storage system is likely the downfall.

300watts of solar translates to around 25 amps. BUT that assumes the panels are at peak output. Assuming a clear sunny day, you may get close to that for 3-5hrs when the sun is at the right angle. You may get another 4-6hrs with lower output maybe 10 amps. So total amp hours generated per day is probably on the order of 150 amp-hrs (optimisticly).

Assuming you get a warm day in a closed up trailer, the fridge may run pretty much continously. Based on your 10-15amp draw (which sounds right compared to ours), the fridge will draw 240-360 amp-hrs per day. But inverters aren't 100% efficent, so it's likely more like 250-400 amp-hrs per day.

Then you have the issue of cloudy days. If you get a cloudy day that is still warm, the fridge keeps pulling amps but the solar panels may produce only a small fraction of the rated power. That could easily leave you with dead batteries and a fridge that isn't running.

You can refine the numbers based on the actual draws and outputs but it's not a real promissing idea if you have a lot of stuff that will go bad if the fridge shuts down.

Solutions:
- More solar/Bigger Battery Bank
- Store someplace you can plug in (a small 10-15amp plug would handle this load)
- Convert to a more efficent compresser based fridge (not a household fridge)
- Run off propane when away