Nova Kool R3800 AC/DC Refrigerator

[RossWilliams]

"Sorry to break it to you but that is a pretty basic PWM controller IMO."

Which is probably totally appropriate in a pretty basic PV solar system to handle the pretty basic function of delivering power for lights and a refrigerator. He will likely lose some energy under some conditions but its doubtful it will have any significance.

It's similar to the type of controller I'd buy at around $20

Its also similar to $125 controllers which appears to be what this one is priced at. You probably wouldn't buy those either. You would buy an MPPT controller because those are the newest guys on the block. That would be better but in this context is probably overkill.

[markopolo]

Some more thoughts:

RA_RS1 uses the Title line often when posting and I suspect many of us don't notice that line.

One of his Title fields had this:

It would just be an overnight situation..

If his goal is only to get through a mild temperature overnight stop and then drive again the next day then his proposed setup should handle that without issue assuming typical use consisting of lights & pump etc.. Winter use could be a problem but I doubt that he camps in very low temperatures. I'm referring to when it is cold enough that the batteries lose significant capacity combined with a near continuous heating requirement.

IMO maybe he's being misled by some reps and suppliers. None seemed to have explained to him that choosing a PWM controller would lower the output of the solar setup. A 170W Zamp panel (9.2A at 18V) will probably end up actually only delivering around 7A to the batteries at peak with the PWM controller. If you think of it as now being or functioning as 130W panel you probably wouldn't be too far off in your calculations.

It would appear that none of the reps or suppliers explained that power usage by the Nova Kool R3800 will vary. Assuming it uses a Danfoss BD35F compressor then the current use can range from 1.5A to 6.5A.

He probably has one of those relatively high current use separators under the hood so it's unlikely, IMO, that the input from the solar setup will cover the power consumption of the fridge. I'd expect a minor net loss there even on the best performing days. That doesn't seem to be a primary concern for RA_RS1 though. It appears that he won't mind cycling the batteries continually and just replacing them when needed. It's not a bad plan - in return he'll get convenience and ease of use with the new fridge.

[RossWilliams]

It would appear that none of the reps or suppliers explained that power usage by the Nova Kool R3800 will vary.

What causes the variation in amps being drawn? I assumed the compressor is an on/off operation, either drawing full current or almost no current. At least, aside from a surge when kicking in.

Update: apparently the variable speed compressors save energy by adjusting to run at lower speeds to maintain temperature. So they run longer, but draw less current which makes them more efficient. If the Nova Kool does that then it will actually use less power than he is projecting. But its specs don't say anything about that.

[booster]

Originally Posted by RossWilliams

What causes the variation in amps being drawn? I assumed the compressor is an on/off operation, either drawing full current or almost no current. At least, aside from a surge when kicking in.

Evaporator and condenser temperatures both can affect the running amps the Danfoss.

I put that information in a thread somewhere with the compressor spec chart just a little while ago. I will try to find it. Efficiency will also change, and it is opposite of lower amps, surprise!

Other thread is here

http://www.classbforum.com/forums/f5...pecs-9459.html


This was also linked early in this thread.

[GeorgeRa]

My Isotherm 85 with a Danfoss BD35F compressor with an electronic thermostat, the Smart Energy Controller varies compressor speed.
https://www.indelwebastomarine.com/i...nergy-control/

[mikeehlert]

Data: Winnebago Paseo, 100 Watts solar, 2 @ 105 Amp hour AGM batteries. MaxxAir fan on thermostat, 86F turn on. Nova Kool RFU6200 refrigerator/ freezer on warmest setting. All windows covered, full sun, 70F to 90F clear SoCal weather.

Experiment: 12.7 volts at about noon. Four days later at 0600, down to 10.5 volts.

Conclusion: I’ll need more solar, or battery, or run generator if I want to boondock for more than a couple days.

Your Mileage Will Vary.

[booster]

Originally Posted by mikeehlert

Data: Winnebago Paseo, 100 Watts solar, 2 @ 105 Amp hour AGM batteries. MaxxAir fan on thermostat, 86F turn on. Nova Kool RFU6200 refrigerator/ freezer on warmest setting. All windows covered, full sun, 70F to 90F clear SoCal weather.

Experiment: 12.7 volts at about noon. Four days later at 0600, down to 10.5 volts.

Conclusion: I’ll need more solar, or battery, or run generator if I want to boondock for more than a couple days.

Your Mileage Will Vary.

Thanks, all information we see is good for the record. Those numbers do make sense, especially if the batteries are a bit old or weren't at an absolute 100% full. Solar would give maybe 120ah back, fan use maybe 80ah, frig use maybe 240ah. So net at 210 + 120ah available and 80+240ah used so within 10ah of each other.


This is the real world stuff we need in the record for folks to see.

[BillsPaseo]

Mike, running your batteries that low will reduce their life expectancy. 12.1V with no load is about as low as you want to take them.

[Knit]

My understanding is that the original poster has two 6v 224 amp-hour batteries in series. This results in having a battery system that is 224 amp-hours at 12v.

I have a 2013 RS that has similar batteries, 200W solar, and a Norcold model DE0788 AC/DC refrigerator installed as original equipment and find it to be a good combination of battery, solar and refrigeration for our needs. And one less vent to the side of the van.

Our Victron battery monitor rarely shown less than 80% SOC in the mornings when starting with a fully charged battery. This is over 60k miles all over the west. We do avoid super hot places during the summer, though.

Grew up in RVs that had 3 way refrigerators. Always found dealing with the propane refrigerator to be a PITA. Compressor refrigerators rock.

[booster]

Originally Posted by Knit

My understanding is that the original poster has two 6v 224 amp-hour batteries in series. This results in having a battery system that is 224 amp-hours at 12v.

I have a 2013 RS that has similar batteries, 200W solar, and a Norcold model DE0788 AC/DC refrigerator installed as original equipment and find it to be a good combination of battery, solar and refrigeration for our needs. And one less vent to the side of the van.

Our Victron battery monitor rarely shown less than 80% SOC in the mornings when starting with a fully charged battery. This is over 60k miles all over the west. We do avoid super hot places during the summer, though.

Grew up in RVs that had 3 way refrigerators. Always found dealing with the propane refrigerator to be a PITA. Compressor refrigerators rock.

More good information, and monitor confirmed . You must not use a lot of power beyond the frig and get pretty regular sun so matches your solar and battery bank well.



How much driving and/or shore power do you do? Stay in one place long?

[DWorrell3]

I switched out to a NovaCool 18 months ago and never looked back. I have a 2012 RoadTrek Popular and the OEM expansion fridge just didn't cool more than 40 degrees under ambient with DC power, either with the engine running or off the coach batteries. That meant if it was 104 degrees in Lubbock, TX, the fridge couldn't cool below 64. Shore power was marginal, but OK.

Now, I can maintain 36 degrees in any climate. The unit has internal inverter, so it will run off DC, either coach or engine power. Without shore power, no generator, I can get three full days with the fridge on coach batteries. I think the days of expansion refrigerators are limited. Dave W

[Tonycamco]

Have nova kool 5810
90 degree heat works great
Freezer 4 degree fridge 38 not cheap but fantastic

[mikeehlert]

Originally Posted by BillsPaseo

Mike, running your batteries that low will reduce their life expectancy. 12.1V with no load is about as low as you want to take them.

Yes I know. My return was delayed a day.

[ripaco]

I have a NovaKool 4500 in my 2004 Leisure Travel. Two lifeline 6V 220AH in series for a total of 220AH at 12V. 200 watts of Renogy solar panels on the roof with Bogart Engineering SC2030 solar controller and BE TM2030 Trimetric monitor so I can view exact amperage going in or out of the battery. It also uses a very accurate algorithm to show the exact percentage of charge in the battery (look it up on the Bogart engineering website if you are curious). NovaKool states that the running amps are 4.4 but I see around 3.4. The compressor refrigerator is not designed to use outside air to reject the heat from the condenser coil. It should have inside air with adequate ventilation as stated in the installation instructions. When I replaced the gas absorption refrigerator, I sealed up and insulated the outside vents but left them removable for access to the compressor and controls. I also insulated the van interior outside wall where the refrigerator is installed. two weeks ago I was dry camping 4 nights at 9100 feet elevation. It was overcast over half of the day every day. Ambient temperature was mid 50s by morning and low 80s in the afternoon. During the whole trip, I ran the generator around 20 minutes total. The battery never got below 87%.

[avanti]

Originally Posted by ripaco

The compressor refrigerator is not designed to use outside air to reject the heat from the condenser coil. It should have inside air with adequate ventilation as stated in the installation instructions. When I replaced the gas absorption refrigerator, I sealed up and insulated the outside vents but left them removable for access to the compressor and controls.

This does not sound optimal to me. I agree that these units don't require outside venting (because there is no combustion). But that doesn't mean that they wouldn't benefit from it. The heat has to get out of the van somehow. Better to use the existing vents if you have them (although I certainly wouldn't install them if you don't). Otherwise, you are just heating up the van interior needlessly. I guess that could be an advantage in the winter, but when the A/C is running, you are just pumping the "same" heat twice.

[mikeehlert]

Originally Posted by avanti

This does not sound optimal to me. I agree that these units don't require outside venting (because there is no combustion). But that doesn't mean that they wouldn't benefit from it. The heat has to get out of the van somehow. Better to use the existing vents if you have them (although I certainly wouldn't install them if you don't). Otherwise, you are just heating up the van interior needlessly. I guess that could be an advantage in the winter, but when the A/C is running, you are just pumping the "same" heat twice.

Good observation. I would preserve the air intake and exhaust using outside air in summer and inside in winter.

[Davydd]

Compressor refrigerators are designed for a controlled environment which outside air is not. If you winter camp you may have a difficult time keeping contents from freezing drawing in outside air. On the flip side, if you leave your air conditioner off as we many times do and endure close to 90 deg. weather, you stand a chance of not keeping your refrigerator under 41 degrees.

You still have to have a controlled environment in back of the refrigerator so adequate air movement and insulation from radiant heat build up in the outer van wall is still critical. In fall, winter, and spring if heat is on the inside recirculation of venting is a bonus and you don't have a cold leak to heat. In the summer, or air conditioning need, I don't think it makes much of a difference in pumping the heat twice. It is still better than leaving vents to the outside in an uncontrolled environment where your refrigerator has to work harder in hot weather. So, you pay for it with air conditioning or refrigerator running more. I will leave that for some other person to work out.

Another advantage to compressor refrigerators when designed originally, is you don't have to deal with the two vents on the outside in regard to maintenance and appearance.

[RossWilliams]

David - I think you are spot on. The heat taken out of the refrigerator is coming from somewhere in the coach. So trying to vent it to the outside is essentially trying to use your refrigerator to remove heat from the coach aka air conditioning. You are better off letting your air conditioner do the job it is optimized for. As soon as the compressor shuts off, the "vent" is going to leak your air conditioned air out and let heat back in.

[GallenH]

So from this discussion about venting: What do the current mfgs of RVs that have compressor fridges as stock do with regard to venting? Are there no exterior vents to the fridge compartment? I believe I read somewhere on this forum that space on the inside beneath the fridge is vented on some but honestly can't remember.

[Davydd]

Originally Posted by GallenH

So from this discussion about venting: What do the current mfgs of RVs that have compressor fridges as stock do with regard to venting? Are there no exterior vents to the fridge compartment? I believe I read somewhere on this forum that space on the inside beneath the fridge is vented on some but honestly can't remember.

Advanced RV has always installed compressor refrigerators. Air intake is at the base and exhausted at venting at the top. ARV installed two small computer fans to boost air out which also cooled the microwave sitting above the refrigerator. It did not have vent openings to the exterior.