Why not simply a one-way 110V fridge?

[avanti]

Originally Posted by cruising7388

You're certainly correct, it can be done manually. But is this the way it's done in an RV application? To light off the boiler with manual piezo stimulation wouldn't you have to remove the outside ventilation cover of the reefer to do this? Isn't this done conventionally by remotely by pushing an "LP" or "Automatic" button on the fridge control panel and isn't the piezo lighter at the boiler going to require some battery source?

Well, it was done that way in the 2-way (120VAC & propane) Dometic in my old rig. There was no "Automatic" (that would certainly require electricity). You manually turned a switch to "propane". There were two pushbuttons. You held the first one in (which caused propane to flow) and you repeatedly pushed the other one (the piezo one) until it lit. You knew that because there was a little meter that had a needle that moved if it was lit. The meter didn't need power, either, since it was driven by a thermocouple.

Now that I think of it, I guess the piezo actually lit a pilot light that then stayed on until you turned the switch (which was really a valve) to "off". I am 99% sure there was no 12VDC connection to this unit.

[GeorgeRa]

From the get go in the design phase I picked a compressor marine fridge, ended up with Webasto Isotherm 85l / 3Cu.Ft. unit. 2 key reasons drove this decision:

- No need to level, absorption fridges will be exposed to slow death if operated in insufficiently levelled positions, it is accumulative disease. Often the definition what is leveled is – if you feel it is levelled. So, no more ambiguous levelling.
- Robust performance. In my recent trip on 235Ah batteries were about 90% SOC in the morning and full by noon time on cloudy/foggy Oregon Coast with 300W solar panels, Tillicum Beach Campground is gorgeous.

I have my unit wired for 12VDC and 120VAC and use both sources. Normally it is running on DC but when we comeback from a trip or before a trip the fridge is on AC, everything else is turned off, so just the fridge is powered by AC.

Back to OP’s question, can he use small house fridge, I would not recommend for the following reasons:

- They tend to by louder then Danfoss units. For me the clicking sound of the Isotherm relay was annoying, so I replaced the control with the electronic control module (Smart Controller by Isotherm).
- High power consumption as compared to Danfoss or equivalent.
- Will it survive bouncing.

[eric1514]

In a B the biggest electrical draw for an absorption fridge is the propane solenoid on the tank. Mine draws .7 amps. That’s almost 17 amps/day. That kind of usage makes a compressor fridge look a lot less power hungry.

[avanti]

Originally Posted by eric1514

In a B the biggest electrical draw for an absorption fridge is the propane solenoid on the tank. Mine draws .7 amps. That’s almost 17 amps/day. That kind of usage makes a compressor fridge look a lot less power hungry.

Very good point. If I still had an absorption fridge, I would lose the solenoid. I have ours on a convenient toggle switch so that I can conveniently turn it on only on the rare occasion that we need to use propane.

[eric1514]

Originally Posted by avanti

Very good point. If I still had an absorption fridge, I would lose the solenoid. I have ours on a convenient toggle switch so that I can conveniently turn it on only on the rare occasion that we need to use propane.

What is the valve that you control with a toggle?

[avanti]

Originally Posted by eric1514

What is the valve that you control with a toggle?

I was talking about the electric solenoid valve at the tank, same one you referenced.

[tex4judy]

We converted (are almost finished converting) a Sprinter with the secondary alternator, Lithium Phosphate batteries, and inverter. After listening to the guys on this forum, we invested in the Novakool. Last summer we traveled from NM to WA to TX and home and that frig was bulletproof. Everything was cool in the frig and cold in the freezer. I did add an extra vent pipe to the roof and we pumped air past the inverter and the frig and that might have helped. Many thanks to Avanti and the other guys for their help.

[TC8]

The best investment I made was to buy a Norcold/ARB 48 qt chest unit. In the many years of real world camping it is highly efficient. I can camp for 10 days in 90 degree plus temperatures. I use 2 agm batteries and solar panels. My beers are ice cold without ice. I was luck to find a used unit for $300. Now with my new RT 190p I have both refers going.

[john.orourke]

In our 92 GMC Rally STX conversion we use an Edgestar FP-430 12/110 fridge set at 36 degrees. Runs maybe 5 min per hour with minimal drain on the 105 amp hr battery at night and roof mounted 100 watt solar panel takes care of it in daytime. We like that the cold stays in the chest when you open it instead of falling out on the floor.

[InterBlog]

Originally Posted by Bud

I believe you, me too with a new or different B.

Bud

Why would it have to be new or different?

My husband and I retrofitted a new electrical system that includes solar and lithium. For our needs, we've never run out of power, and I cannot foresee a situation in which we would (knock wood) - and I'm running a large computer out of the van (and a Danfoss compressor fridge). The retrofit was a tremendous amount of work, and one of the best decisions we've ever made. Life's hard enough without having a B van tell you where you can go or how long you can stay.

[bjarvis5620]

Having spent many years with a sailboat I moved to a powerboat. It had a Norcold fridge that was poor. I replaced it with a Vitrifrigio with a separate freezer draw and a fridge. I could not be happier.

On a boat the fridge is the biggest user of power and consumes around 80AH per day. To support that sort of drain a battery capacity of around 250AH hours is needed without any other loads. Typically sailors will use 2 4D size batteries for an installed capacity of a little over 400AH.

You would need at least that much if you were to try to dun a domestic 11V fridge off an inverter. I don't know of many RV's let alone Class B's that have that much.

Bill

[Bud]

Originally Posted by InterBlog

Why would it have to be new or different?

My husband and I retrofitted a new electrical system that includes solar and lithium. For our needs, we've never run out of power, and I cannot foresee a situation in which we would (knock wood) - and I'm running a large computer out of the van (and a Danfoss compressor fridge). The retrofit was a tremendous amount of work, and one of the best decisions we've ever made. Life's hard enough without having a B van tell you where you can go or how long you can stay.

InterBlog, you took this quote Out of Context, that simple.

Please go back and read What I responded to, Nothing like you .......

Thanks.

Bud

[hepcat]

So, for me, choice of refrigerator is more about how the van is equipped. If you're doing an electric-only buildout, or your van is equipped with huge batteries and solar, then a 12v compressor fridge is perfect.

If, OTOH, your van is like mine with a single small coach battery, but a large propane system, then the 3way makes a lot more sense. I have a propane stove, fridge, and furnace and I use them all regularly. My fridge is the old-style rotary switch kind with a piezo-electric lighter. I run mine on propane probably 90% of the time as I'm seldom on shore power.

[dicktill]

Does anyone have a Nova Kool R4500? How do you like it? Any problems or complaints?

Thanks, Dick

[gregmchugh]

Originally Posted by dicktill

Does anyone have a Nova Kool R4500? How do you like it? Any problems or complaints?

Thanks, Dick

We replaced the 3 way in our 08 Roadtrek RS Adventurous with the R4500 and never regretted it, actually kept things at a constant temperature in the summer...

[12gocamping]

We tried that on a previous camper and would not advise it. Worked fine when on electric but not on the battery. Though it does not take much power to run the fridge, it takes a lot each time it cycles and has to start again. The bar fridge we had cycled on and off a lot so, in no time, the battery did not have enough power to start it up on its next cycle. I know another person who had a similar experience and ended up ditching it and buying a propane fridge instead.

[Mtsailor]

The original question was asking about using a 110v dorm type vs the much more expensive 12v type. I have both, almost exactly the same size and have tested them with amp/hour meters. I was shocked to find that the cheap 110v Magic Chef (from Lowes) refrigerator running on a good sine-wave inverter actually used slightly less power than the expensive Nova-Kool R4500 with the Danfoss compressor. And that was measuring DC current into the inverter for the Magic Chef refrigerator. So, contrary to what most people including me assumed, there isn't an efficiency downside to the cheaper 110v assuming that it's powered from a good quality sine-wave inverter. Both have been reliable, but the 110v lives in the house and the Nova-Kool lives in our Roadtrek, so I can't compare reliability. One downside to most of the 110v dorm type is that the condenser coils are located inside the side panels of the refrigerator, so the sides must have air flow around them, whereas the 12v Nova-Kool has the typical condenser outside on the the back and therefore works better as a replacement for a propane refrigerator.

I'm among the group that changed from propane to compressor, and wouldn't consider going back. The compressor refrigerator just works well all the time regardless of ambient temperature and level. Our propane never did work well, but I suspect that it was abused by the previous owner by operating it off-level. I wouldn't be surprised if that's the case for many propane refrigerators. I know that it's possible to make propane refrigerators that work extremely well. I live off the grid and for 40 years used ancient Servel propane refrigerators manufactured 70 years ago. They worked so well, that you could turn down the thermostat and turn the entire refrigerator into a freezer.

We traveled once with friends with a roadtrek that had the propane solenoid valve, and they used about half the power just to keep that valve on as we used to run the refrigerator, and had more trouble keeping the battery up than we did. We have 150 AH battery capacity and a 100w solar panel on the roof. In sunny weather if we are parked in the sun and it isn't extremely hot, that panel keeps up with the refrigerator. In less optimal conditions, We have another portable 100w panel that we also deploy. We do find that it uses more power when the outside temperature is 90-plus. The only time we have had any issues with dry camping for a week or so has been during predominately cloudy weather.

[GeorgeRa]

Originally Posted by Mtsailor

The original question was asking about using a 110v dorm type vs the much more expensive 12v type. I have both, almost exactly the same size and have tested them with amp/hour meters. I was shocked to find that the cheap 110v Magic Chef (from Lowes) refrigerator running on a good sine-wave inverter actually used slightly less power than the expensive Nova-Kool R4500 with the Danfoss compressor. And that was measuring DC current into the inverter for the Magic Chef refrigerator. So, contrary to what most people including me assumed, there isn't an efficiency downside to the cheaper 110v assuming that it's powered from a good quality sine-wave inverter. Both have been reliable, but the 110v lives in the house and the Nova-Kool lives in our Roadtrek, so I can't compare reliability. One downside to most of the 110v dorm type is that the condenser coils are located inside the side panels of the refrigerator, so the sides must have air flow around them, whereas the 12v Nova-Kool has the typical condenser outside on the the back and therefore works better as a replacement for a propane refrigerator.

I'm among the group that changed from propane to compressor, and wouldn't consider going back. The compressor refrigerator just works well all the time regardless of ambient temperature and level. Our propane never did work well, but I suspect that it was abused by the previous owner by operating it off-level. I wouldn't be surprised if that's the case for many propane refrigerators. I know that it's possible to make propane refrigerators that work extremely well. I live off the grid and for 40 years used ancient Servel propane refrigerators manufactured 70 years ago. They worked so well, that you could turn down the thermostat and turn the entire refrigerator into a freezer.

We traveled once with friends with a roadtrek that had the propane solenoid valve, and they used about half the power just to keep that valve on as we used to run the refrigerator, and had more trouble keeping the battery up than we did. We have 150 AH battery capacity and a 100w solar panel on the roof. In sunny weather if we are parked in the sun and it isn't extremely hot, that panel keeps up with the refrigerator. In less optimal conditions, We have another portable 100w panel that we also deploy. We do find that it uses more power when the outside temperature is 90-plus. The only time we have had any issues with dry camping for a week or so has been during predominately cloudy weather.

This is a very interesting data; do you still have these results? Just the losses on inverter would be around 10% so Magic Chief would need to be quite more efficient.

[Mtsailor]

George,
Sorry, I didn't keep the raw data, just the notes I made of the end results. The test of the Nova-Kool was at an ambient temperature of 73 degrees ave, and the Magic Chef was at 70 degrees, so that would have favored the Magic Chef slightly, but I doubt that would have been significant. Bottom line is that for similar size refrigerators operating at the same internal temperature, with similar ambient temperatures, the DC refrigerator used 40 amps from the battery in 24 hours, while the AC refrigerator operating through an inverter used 34 amps from the battery.

I think that there may be several reasons for the surprising results. Many devices are inherently more efficient in higher voltage versions. Inverters for example are typically more efficient in 24 and 48 volt versions than 12 volt versions of the same inverter. I've noticed the same thing in some motors and fluorescent lights. I suspect that this is because resistance loses are less at higher voltage, not just in the wiring, but in the device itself.

Inverter efficiency can be very misleading. If an inverter were 100% efficient, you would expect that to get 1 amp at 120 volts (120 watts) out would require 10 amps of 12 volts in, or 11 amps with 90% efficiency (modern inverters are often more like 95%). Surprisingly, it's not unusual to get that 120 watts out with less that 10 amps in. That would appear to mean more than 100% efficiency which is, of course, impossible. What is going on is that what is important to inverters is watts, not amps. A fully charged battery is more than 12volts, so it takes fewer than 10 amps to get 120 watts. With solar panels charging, it could be 13 or 14volts or even higher. At a float voltage of 13.4 volts, the inverter would need to use just 9 amps for 120 watts in (if 100% efficient). With 95% efficiency, current in would still be less than 10 amps, making it look like more than 100% efficiency. In actual use, I've often found this effect to often be even more dramatic, particularly with inductive loads (like a refrigerator). Perhaps some inverters have circuitry to help them handle inductive loads better.

[Saldar]

The nova kool 4500 is the fridge that's always been on the Travato 59K. I like mine a lot. It's vast for 2 people. My only problem is that it's easy to knock the temp knob and turn it into a giant freezer. Yes, it can be a giant freezer. I put electrical tape lines on the knob so it's easier to monitor the setting.