Advancing Alvar

[pattonsr]

David,

How is the NovaKool 6800 compressor fridge working out? I believe it has one thermostat and I remember one user saying that trying to get the freezer below 8 degrees would make the refrigerator too cold. You have probably the most time spent in an Advanced RV. I would hope that the Danfoss compressor fridge would work as well as a home unit.

You said earlier that you drove back to Willoughby, OH for a tuneup, checkover and some warranty fixes. Could you elaborate further especially the tuneup comment.

[booster]

Originally Posted by pattonsr

David,

How is the NovaKool 6800 compressor fridge working out? I believe it has one thermostat and I remember one user saying that trying to get the freezer below 8 degrees would make the refrigerator too cold. You have probably the most time spent in an Advanced RV. I would hope that the Danfoss compressor fridge would work as well as a home unit.

You said earlier that you drove back to Willoughby, OH for a tuneup, checkover and some warranty fixes. Could you elaborate further especially the tuneup comment.

I can't speak for the NovaKool, but but we have had an Isotherm Danfoss compressor frig in our Roadtrek 190 for about 4 years. All in all there have been very few issues once we go the original install venting properly.

There are a few things different in an RV, than at home, though. The RV units are not frost free, so you will probably find that as frost builds up you will need to adjust the thermostat setting a bit. Ours changes the most in the first 3-5 days and then settles down for about 3-4 weeks, at which time it needs defrosting.

Another difference that we have, that Davydd may not have, is that the home frig sees very consistent ambient temps and humidity, and the RV one doesn't. Ours vents to the outside, so it sees air from 25 to 100 degrees over time, and it can easily be 40 degree variation in a day. We see 2-3 degrees inside variation due to the temp swings, which is way, way better than the 3 way was.

The only downside of the compressor frig that I can see is you have to have more battery to power them.

[pattonsr]

The NovaKool 6800 that Advanced RV uses does not vent to the outside. Davvydd has been on the road for some time so it should be interesting to hear about defrosting, etc. as well as temperature control between the refrigerator and freezer.

[avanti]

Our 6800 is vented inside as well. Our only criteria are (a) ice cream not melting and (b) beer not freezing. I can report that meeting both of these goals has been no problem at all, summer or winter. It is a great fridge. Haven't used it continuously for more than about a week at a time, so I can't speak to the effects of significant frost.`

[booster]

The inside, outside venting is an interesting thing, and I think there are advantages to both.

Inside--more consistent temperature control because the ambient doesn't change as much, especially in cold weather because you heat the inside or the van.

Outside--less heat into the van in hot weather--less energy use when it is cold--maybe a bit more energy used if parked with sun right on the vent side.

Ours is outside by default because it replaced a 3 way. I am not sure which I would do if I was starting from scratch.

[avanti]

The other advantage of "inside", of course, is getting rid of those hideous vents. That was kind of a big deal for us. Also, the "less inside heat in summer/less energy in winter" equation reverses with the seasons, so I think it is more or less a wash. Some people add a small floor vent under the fridge that you can open or close as conditions suggest. Probably worthwhile if you can deal with the dust-intake issue.

[booster]

Originally Posted by avanti

The other advantage of "inside", of course, is getting rid of those hideous vents. That was kind of a big deal for us. Also, the "less inside heat in summer/less energy in winter" equation reverses with the seasons, so I think it is more or less a wash. Some people add a small floor vent under the fridge that you can open or close as conditions suggest. Probably worthwhile if you can deal with the dust-intake issue.

I think the heat reversal in the cold really wouldn't do anything for us, as we heat with propane. I think the frig would put in 125 btu or so, compared with 16,000 btu from the furnace. Of course same is true for the hot times when the air conditioner is running, not much heat compared to the AC capacity. With the AC running you need shore power, or tons of batteries so energy of the frig isn't an issue. I think the only time the heat would do much would be in warm weather, when you can't run the AC, and it still isn't huge. The air coming out of our outside vent with the frig running is warm to the feel, so it probably at about 100 degrees F.

I think if I were starting clean with an outdoor vent, there would be none visible. It would be a floor vent, like you describe but fixed, and a roof vent. They don't need to be as large as the 3 way vents, I think.

[Davydd]

Our refrigerator has been on since January 26 when we took possession. I just took a picture of the current condition and as you can see there is little frost and not enough to worry about defrosting. Those are homemade pizza dough balls I made and they are not frozen solid as there is a little give to them. The temperature was 16 degrees and the refrigerator was just above 32 degrees. I have it on the lowest setting. My understanding is you cannot control the freezer separately so you are at the mercy of how you control the refrigerator. The outside temperature is in the mid 60s. The inside van temperature was 72.



Here is how venting works. There is an intake at the baseboard and fans exhaust on both sides of the microwave/convection oven. You can barely hear them and you can feel a gentle exhaust if you hold up your hand to the vents.

[pattonsr]

avanti,

How cold can you get the freezer with your Novacool 6800?

How does your venting differ from what Davydd described?

[booster]

That is a very interesting freezer/cooling coil section in Davydd's frig. No door on the freezer.

I can see how it would develop less frost that way. I can also see how it might be tough to keep the freezer cold enough, especially the front where it is open.

Ours is a 3.0cf, and has the conventional freezer door. The freezer gets to zero of colder in normal use. We usually leave the freezer door open as far as the big door will let it, as we rarely have anything critical in the freezer, and it lets the frig run less.

That venting setup is very typical of how they have done boats for years, so most of the frigs are very good at working that way.

[avanti]

Originally Posted by pattonsr

avanti,
How cold can you get the freezer with your Novacool 6800?

Never measured it, but it can easily keep ice cream hard, as I said. It really doesn't seem to behave much differently from our home fridge.

How does your venting differ from what Davydd described?

The black rectangle below the fridge is a vent that also doubles as plumbing access (The round vents are the Espar heat). The original plan was to have a similar vent in the vertical panel between the microwave and the counter above the closet. For aesthetic reasons, we decided to see how it behaved with a passive vent inside the closet instead. It ran a bit hot, so I recently added a pair of quiet computer fans that actively exhaust into the closet. There is enough leakage around the large closet doors that it will probably be ok. I need summer to know for sure. If it still runs hot, I will either add a vent on the side of the closet facing the driver's seat, or else go back to plan A and add a visible vent.

Note that the Espar burner itself is outside below the vehicle. Only the hydronic heat exchanger is under the fridge. Since this unit gets its air from behind the fridge, it also helps to vent the area when it is running, FWIW.

[Davydd]

Originally Posted by booster

That is a very interesting freezer/cooling coil section in Davydd's frig. No door on the freezer.

I can see how it would develop less frost that way. I can also see how it might be tough to keep the freezer cold enough, especially the front where it is open.

Ours is a 3.0cf, and has the conventional freezer door. The freezer gets to zero of colder in normal use. We usually leave the freezer door open as far as the big door will let it, as we rarely have anything critical in the freezer, and it lets the frig run less.

That venting setup is very typical of how they have done boats for years, so most of the frigs are very good at working that way.

Booster,

That whole compartment you see there is the freezer. The refrigerator is above it with a separate door. I forgot to mention we have the refrigerator set on the lowest setting this week because we took out all the perishables with the exception of beer and fizzy water. That would affect the numbers I reported as it has been that way since Sunday. The ice cubes in the trays are frozen solid. I need to buy a 2 qt. ice cream container and see how it works. We so far have only bought small pints to consume almost immediately.

[avanti]

DavyDD,
We find that the inside of the suspended box (where you have the ice cube trays) is the coldest, being surrounded by the cooling coils. We keep the ice cream there.

[Davydd]

We have had Bs so long where the freezers were next to worthless except for an ice cube tray that we still forget we have it.

[avanti]

It's worth noting that, even with the cabinet getting quite hot, the NovaKool had no difficulty staying cool inside. My concern was strictly about power efficiency. i am sure the fan will make a big difference.

BTW: The NovaKool as a built-in output designed to power an external fan, so the mod was trivial.

[booster]

It will be interesting to see how the extra fan works out power wise for you. I played around with a fan inside the frig, and one on the vent just to see how much they would help, together or individually, and found they did save some frig power, but used more than they saved, in our setup. The Isotherm already has a fan of its own blowing over the compressor and coils (they are in a cube, not vertical up the back like most. IIRC, the NovaKool fan mounted on the bottom of the rear, blowing over the compressor, if you got that option, but I would have been looking at the smaller versions than yours.

I wish they made a chest type, on slide out of the cabinet, that would work for us. From what I hear from the boat folks, they use about 60% of the power of the frigs with a regular door.

[Davydd]

The 2005 Airstream Westfalia Sprinter had a chest type refrigerator. No reason you could not adapt boating solutions. It seems Advanced RV looks a lot toward what boaters do.

[avanti]

Originally Posted by booster

I played around with a fan inside the frig, and one on the vent just to see how much they would help, together or individually, and found they did save some frig power, but used more than they saved, in our setup.

Are you sure about that? A typical computer fan takes just a few watts--almost too smelt measure. Plus, you can get very cheap controllers that modulate the fans wrt ambient heat, saving even more.

[booster]

I was very surprised at the fan test, also. The inside fan was a very small 2" computer fan, I think it was .03 amps, and it ran continuously for one test, and only when the frig ran on another. It didn't do anything much for the frig temp evenness when cycling, did help a small amount when on all the time, almost nothing in frig power use gain. The fan in the exhaust vent was a 5" IIRC, and was at .08amps full speed, it needed to be running at about .05 amps to do any good for the frig power. It is on a matching speed controller and still in place. We don't use it, but I left it in case we ever had trouble with frig cooling when we hit very hot weather. The tests were run in the shop at constant temperatures, so I am pretty confident of the results.

All that said, the changes were very small, and we could gain more power savings by removing the freezer door, and removing the drip tray, than the fans cut from the frig running used power.

If you have a cabinet that is running pretty hot around the compressor and coils, you may get much more improvement than we did.

[mojoman]

Any suggestions for those building their own? My system will not be automated as yours is and what I take away from reading your threads is the trade off of a bit of parasitic loss. I plan on wiring all individual dc circuits through a circuit breaker switch panels to give me the ability to turn off anything. I also picked up on the noise of the inverter which I'll try to engineer out of my installation. I am installing this cabinet fan behind my isotherm 7.0 fridge:
http://www.amazon.com/AC-Infinity-AIRPL ... abinet+fan