About to pull trigger on danfoss fridge

[CA_Tallguy]

I'm very seriously thinking about ordering a Vitrifrigo Danfoss fridge. That is, unless one of you can talk me out of it. I have read several threads where lewster raves about danfoss type refers so it may not be him.

The unit takes about 5.5 amps of DC when the compressor is running, which I understand to be about 1/3 of the time. So, say 2 amps average 24 hours a day or 48 amp hours a day. This is less draw than a fantastic fan per hour.

I have a bit of a surplus of DC power from solar, though not if I want to watch much satellite TV in winter. Right now I don't even have my tow vehicle charging the airstream batteries. When on he road, my vehicle alternator could effortlessly run the fridge, maybe even via the regular tow plug harness though I would likely put in beefier wiring and an anderson connector. Maybe just to run the fridge when the engine is on. I'd ideally like to be a bit careful if I try to charge the house batteries from the alternator, with some regulator/isolator action going on. (Marine folks have a lot of info and resources for charging house batteries from alternators.) And I may go for a high output alternator if I really want to charge from the tow vehicle.

I'm also very keen to install an onan LP 2500 gen in the trailer along with some crazy expensive equipment like a inverter/charger with boost functionality.

In the airstream I have 400 amp hours of battery.

The Vitrifrigo unit I am looking at is the dp2600i. It is gorgeous in stainless steel, however if the front is scratched there is no way to replace just the insert. They have a lower model with a black frame door that takes inserts, but it doesn't make my heart swoon like the stainless steel. Maybe I could get a clear wrap put over the stainless at a vehicle wrap place.

Service is one drawback as I don't think it would be as easy as norcold/dometic, which can be worked on almost anywhere you go.

Am I crazy or should I go for it?

[truckasaurus]

Not the same but I installed an Isotherm in my Overlander with the Danfoss compressor and it's one of the best decisions I made on the trailer. It's super energy efficient and quiet.

[CA_Tallguy]

Thanks - that's very reassuring. Have you been powering from tow vehicle and generator or solar? While in transit or mostly in shore power? Have you found your batteries depleted at inconvenient times?

[Jammer]

It sounds like you know the tradeoffs. If you have solar and 400 ah of batteries it will probably work out fine for you.

Duty cycle may exceed 1/3 on hot days, if the door is opened frequently, or if you add a large amount of warm stuff at once, as might happen when you buy groceries or whatever beverages or mixers you like to keep cold.

The situation that is toughest on these setups are late fall boondocking trips in higher latitudes where short days and cloudy weather prevent the PVs from doing much of anything. We've had about 5 hours of sunshine in the last week, and that's fairly typical this time of year. If you stay in California you won't have that problem.

Originally Posted by CA_Tallguy

I'm also very keen to install an onan LP 2500 gen in the trailer along with some crazy expensive equipment like a inverter/charger with boost functionality.

Remember that your charge rate is limited to 1/4 or 1/5 (depending on who you ask) of your installed battery ah, so anything over 80 amps (1000 watts) won't do you any good.

Generators pose a risk of fire and also of carbon monoxide poisioning. Consider a portable setup as an alternative. 1000 watts is plenty to charge batteries.

Service is one drawback as I don't think it would be as easy as norcold/dometic, which can be worked on almost anywhere you go.

I wouldn't be concerned. They rarely fail, and any appliance tech who can fix a household fridge should be able to fix one.

[wkerfoot]

CA_TallGuy,

We installed the 9.5 CF unit in our 1954 Liner with two Optima batteries and 160 amps of solar. Works fine, noiser than absorption type (which are dead quiet), but will run 30 degrees off level and no gas, so running while in motion does not create any fire hazard.

Bill

[DKB_SATX]

If I lived in the trailer I'd absolutely go the Danfoss route, they're just less finicky. Since I'm "blessed" with a complete absence of off-grid refrigeration in the 28' project trailer, I'm buying a Danfoss fridge instead of an absorption unit. It would be hard to justify with a working absorption fridge, but the Norcold and Dometic Danfoss units are price-competitive with the absorption fridges.

Now you've gone and shown me a sexy Italian model... I'll just have to keep telling myself it's too fancy for my Argosy and see if I eventually believe it. I'm afraid to ask, but how much more is it than a Dometic of similar size?

[lewster]

Only comment:

As I sell all of them (and this IS NOT a commercial plug), I would also look at the units from Indel Webasto Marine. Very nice units and a bit more efficient. Some even have dual compressors for added versatility.

Just for the record, I will NEVER install another LP gas/absorption fridge again! PM me if you want the reasons.

About to put a Cruise 195 in stainless in a 30 Classic next week.

[FC7039]

I bought mine from www.truckfridge.com. I am pretty sure they buy the base fridge from Italy as does Webasto. Compare the Truckfridge TF130 to the Webasto Cruise 130.
110 AC/12DC. No need to cut a vent or two which my trailer did not have. Runs off TV as you head down the road. It is very quiet. Much more so than a home fridge.
The door can be mounted on either side.
The front panel can be replaced with veneer.
My thread on my fridge.

[CA_Tallguy]

Originally Posted by Jammer

Remember that your charge rate is limited to 1/4 or 1/5 (depending on who you ask) of your installed battery ah, so anything over 80 amps (1000 watts) won't do you any good.

Thanks for all your comments. Regarding the limit in how much a bank can take in charging, I hadn't thought of this too much but it's an excellent point. I'm looking at trying to get a decent amount of amps from my tow vehicle alternator using some heavy wiring and I'm trying to find a smart-ish device, perhaps something like a Balmer Duo Charge, to deliver it.

The Balmer device explains itself as sort of a DC to DC charger. It has a limit on draw of 30A though, and I think it will cut out after that. I'm trying to get my head around how this device may or may not be different than a 30 amp charger.

I also need to get my head around how different charging sources will play together. For example, will my outback solar controller still deliver the full available output from the solar array even if I'm sending some charge amps via my tow vehicle?

Lots to learn.

[CA_Tallguy]

Originally Posted by DKB_SATX

...but the Norcold and Dometic Danfoss units are price-competitive with the absorption fridges. Now you've gone and shown me a sexy Italian model... I'll just have to keep telling myself it's too fancy for my Argosy and see if I eventually believe it. I'm afraid to ask, but how much more is it than a Dometic of similar size?

The norcold is indeed cheaper than the others but I don't think by much. And from what I gather, the others are much better rated than the norcold. I think it was in the west marine site where the reviews were not very good at all for the norcold danfoss type fridge. It didn't appeal to me because of capacity and design, from what I recall.

The Vitrifrigo with the black bezels where you can use an insert, maybe even stainless you pick up somewhere, is probably just a few hundred more than the norcold. There are a lot of advantages to that insert type (replacing for scratches or to update) but I will probably spend the extra $300 for the impractical full stainless that I think is just so gorgeous.

Novakool also looks nice and isn't terribly more expensive than absorption. The units that lewster posted also look wonderful, and I think the model he mentioned is as appealing to me as the Vitrifrigo. I am sensing they may be more expensive though. They also have dual compressors in that size and I don't know about pros/cons of that. I might like the interior layout better.

[CA_Tallguy]

Bottom line, I don't think the danfoss type units are priced in another league vs the rv types. I think the rv types are expensive themselves --- $1000 to $3000. And there are a variety of options in danfoss type units in about the same range, with I think the norcold at the low end.

[Wabbiteer]

I own a Vitrifugo, one of the small height stainless models. I paid $400 plus shipping sight unseen for it from a lost freight salvage outfit. I got a unit with the nylon door catch socket shattered and the mounting bezels warped from shipping damage but I'm happy with it, the interior fit and finish is utilitarian and plain but maybe sturdier than newer offerings from traditional US suppliers.

I've a bunch of hours mining forums and repair sites on Danfoss BD compressors and here's my take on them...

For pedestrian viewers: Sorry about the details, it'd be great not to have to show my work. This write up is to help make a ten-plus year or better install with a DC powered Danfoss, plus making Solar assist a better option. There are DC Danfoss compressors running for 20 and thirty years, they rarely die of old age but are murdered, kinda like Airstreams.

The magic box that makes it happen is the power/control module, actually a high voltage converter & motor control, it pulses 300V+ DC to each of the three compressor windings sequentially to start and run it. Its happiest when the voltage differences are less so running it at 24V (if possible) makes sense.

Two major enemies of the control module are heat and lightning/surges/brown outs. When you upgrade or install a compressor refrigerator make sure there is a smokestack set of vents, high and low, so cool air will be drawn in to replace heated air. Keeping the control module surfaces free of dust and not in stagnant air will double or triple its life expectancy. Adding a decent DC filter module - lightning arrestor circuit to stop spikes is safe insurance, the compressor modules are $350 retail and about half that rebuilt.

Just as a curiosity - there is a jumped set of terminals on the module that controls the compressor RPMs using a resistor - shorted with plain wire is slowest, above 8000 ohms is fastest. Not that you'll ever have to change them but it is possible if you are in the desert summer and the unit refuses to keep up with your sun heated trailer, there is a way to make it run harder for each minute of run time. This is a feature deep water boats can use, if the water (thus the hull) is 50° or 80°degrees as a baseline, then add tropical sun they can up the volume of coolth produced.

Remember these are primarily meant to be run while the battery is being charged, the car, truck or boat motor running and the alternator handling loads at a higher voltage than a fully charged battery at rest. A Danfoss 35 compressor unit on 12 Volts takes 5.5 amps on start-up and 4~ amps running on a 12v system with batteries being charged, that is 13.5V to 14.7V being fed to refrigerator. Anyhow - when running off of a half-discharged battery (12.1V even) that 5.5A on start-up will jump to 6.5A or better, the ~4A run current will jump to 5A. With higher currents a device produces higher temperatures internally, so not only is the run time amperage demand 20% higher there will be more waste heat in the control module. So keep the compressor area clean & cool and try to take only the top 25% of your batteries charge for long life and best efficiency.

Factoid: Back to the compressor/condenser air vent smokestack effect: In general needed refrigerator power increases 4% for each degree of daily average temperature increase (higher ambient rewarming the cooled section and electrical demand increase from loss of coil-to-air heat transfer efficiency). Draw cool and lint-free air in from the floor level where naturally the coolest air pools. Shield any heat sources from reaching the back of the unit or its free air space (heating ducts, sun heated shell, etc.). If you can wrap the hidden exterior refrigerated section of the unit with prodex or more foam it will help keep power requirements down. It may seem smart to vent the unit above it, under the counter, or through louvers above it but that keeps the warmed air flowing over the cold box for a longer duration, shunting the warmed air up and away will pay returns on energy/performance every minute it runs throughout its lifetime.

All the above figures were quoted as if in a perfect electrical circuit, direct connections to battery blah blah - SO upgrade your wiring to provide less than a 2% voltage drop to the module itself. 14awg is never to be used. Wire size maximum length @12V operation: 12AWG 8-feet, 10AWG 20-feet, 8AWG 33-feet & that is measured to the battery itself, include the run length through the main fuse and any branch fuse circuit supply runs in your calculations. This is for minimizing wire losses, giving start-up plenty of current immediately, as well as giving the control module first dibs on cleanest power as other things switch in and out.

Someone may pick apart the minutia written above on a dozen perspectives but overall the bulk of it is true. I especially like the idea of a custom chest style freezer that is super-insulated enough that is able to run directly on solar for 90% of its energy, dipping into battery storage or generator/grid for no-sun periods.

[lewster]

Originally Posted by Wabbiteer

I own a Vitrifugo, one of the small height stainless models. I paid $400 plus shipping sight unseen for it from a lost freight salvage outfit. I got a unit with the nylon door catch socket shattered and the mounting bezels warped from shipping damage but I'm happy with it, the interior fit and finish is utilitarian and plain but maybe sturdier than newer offerings from traditional US suppliers.

I've a bunch of hours mining forums and repair sites on Danfoss BD compressors and here's my take on them...

For pedestrian viewers: Sorry about the details, it'd be great not to have to show my work. This write up is to help make a ten-plus year or better install with a DC powered Danfoss, plus making Solar assist a better option. There are DC Danfoss compressors running for 20 and thirty years, they rarely die of old age but are murdered, kinda like Airstreams.

The magic box that makes it happen is the power/control module, actually a high voltage converter & motor control, it pulses 300V+ DC to each of the three compressor windings sequentially to start and run it. Its happiest when the voltage differences are less so running it at 24V (if possible) makes sense.

Two major enemies of the control module are heat and lightning/surges/brown outs. When you upgrade or install a compressor refrigerator make sure there is a smokestack set of vents, high and low, so cool air will be drawn in to replace heated air. Keeping the control module surfaces free of dust and not in stagnant air will double or triple its life expectancy. Adding a decent DC filter module - lightning arrestor circuit to stop spikes is safe insurance, the compressor modules are $350 retail and about half that rebuilt.

Just as a curiosity - there is a jumped set of terminals on the module that controls the compressor RPMs using a resistor - shorted with plain wire is slowest, above 8000 ohms is fastest. Not that you'll ever have to change them but it is possible if you are in the desert summer and the unit refuses to keep up with your sun heated trailer, there is a way to make it run harder for each minute of run time. This is a feature deep water boats can use, if the water (thus the hull) is 50° or 80°degrees as a baseline, then add tropical sun they can up the volume of coolth produced.

Remember these are primarily meant to be run while the battery is being charged, the car, truck or boat motor running and the alternator handling loads at a higher voltage than a fully charged battery at rest. A Danfoss 35 compressor unit on 12 Volts takes 5.5 amps on start-up and 4~ amps running on a 12v system with batteries being charged, that is 13.5V to 14.7V being fed to refrigerator. Anyhow - when running off of a half-discharged battery (12.1V even) that 5.5A on start-up will jump to 6.5A or better, the ~4A run current will jump to 5A. With higher currents a device produces higher temperatures internally, so not only is the run time amperage demand 20% higher there will be more waste heat in the control module. So keep the compressor area clean & cool and try to take only the top 25% of your batteries charge for long life and best efficiency.

Factoid: Back to the compressor/condenser air vent smokestack effect: In general needed refrigerator power increases 4% for each degree of daily average temperature increase (higher ambient rewarming the cooled section and electrical demand increase from loss of coil-to-air heat transfer efficiency). Draw cool and lint-free air in from the floor level where naturally the coolest air pools. Shield any heat sources from reaching the back of the unit or its free air space (heating ducts, sun heated shell, etc.). If you can wrap the hidden exterior refrigerated section of the unit with prodex or more foam it will help keep power requirements down. It may seem smart to vent the unit above it, under the counter, or through louvers above it but that keeps the warmed air flowing over the cold box for a longer duration, shunting the warmed air up and away will pay returns on energy/performance every minute it runs throughout its lifetime.

All the above figures were quoted as if in a perfect electrical circuit, direct connections to battery blah blah - SO upgrade your wiring to provide less than a 2% voltage drop to the module itself. 14awg is never to be used. Wire size maximum length @12V operation: 12AWG 8-feet, 10AWG 20-feet, 8AWG 33-feet & that is measured to the battery itself, include the run length through the main fuse and any branch fuse circuit supply runs in your calculations. This is for minimizing wire losses, giving start-up plenty of current immediately, as well as giving the control module first dibs on cleanest power as other things switch in and out.

Someone may pick apart the minutia written above on a dozen perspectives but overall the bulk of it is true. I especially like the idea of a custom chest style freezer that is super-insulated enough that is able to run directly on solar for 90% of its energy, dipping into battery storage or generator/grid for no-sun periods.

Very nice analysis of the operating system!

GOOD JOB!

[truckasaurus]

Originally Posted by CA_Tallguy

Thanks - that's very reassuring. Have you been powering from tow vehicle and generator or solar? While in transit or mostly in shore power? Have you found your batteries depleted at inconvenient times?

The trailer has 2 6V batteries and a nice monitoring system, after all the endless calculating and worrying about usability it turned out to be a non concern. The batteries get a charge whilst driving and or from my Honda EU3000 or shore power; I don't have any solar yet. I have not even come close to using 25% of the battery bank yet as my trailer is pretty efficient, even after several days boon docking. Next I'm adding LED flat panel lights which I haven't seen anyone else use on here yet so that will help too. On the Sovereign (33') I'm doing next I'll install a larger variant much like you are discussing no question. As an added bonus the Isotherm is a beautiful piece of kit unlike the RV appliances I checked out.

[CA_Tallguy]

Thanks to everyone for all the feedback. I feel very comfortable with the whole prospect now and have ordered the Vitrifrigo in stainless. Cost about $1600 plus shipping and should arrive late next week.

I am also doing a lot of research on battery to battery charging systems like the Xantrex Echocharge, Balmar Duo Charge, and the similar Sterling model.

These basically are multistage battery charging systems that run off 12 volts instead of shore power. They don't care what the incoming voltage is, as long as it is in range, and they put out a charge program for your specific battery type. The Xantrex is 15 amps, Balmar is 30 amps, and Sterling is 50 amps.

The Balmar has an issue where if your load pulled is over 30 amps, it will shout down. I've got to figure out of a severely drained battery bank can suck more than 30 amps via heavy cabling when it is connected. On the other hand, the actual LOAD from my trailer will likely never come close to 30 amps, so if they are not counting a drained battery bank as something that will pull amps, then it should be OK.

I need to get my tow vehicle setup to charge enough to at least run the fridge. If I don't install one of these systems right away, I will likely just setup some dedicated wiring and relays so the fridge runs off my tow vehicle when the engine is on. That will leave my solar alone to do its thing with charging the house batteries as it does now.

I think everyone should be using something like one of these rather than just straight up connecting the house batteries in parallel to the tow vehicle. The xantrex 15 amp unit might be able to be run via a tow connector, but a separate anderson style connector would be the safe way to go, not to mention more effective. I wouldn't run anything bigger than that via the tow connector, and probably wouldn't even do 15 amps either.

The marine market also has a ton of alternator controllers that they use on their boats. If I get greedy for power, I may try to go that route and also upgrade my alternator to high output.

These alternator controller systems seem like they could provide oodles of charging amps.

[lewster]

Originally Posted by CA_Tallguy

Thanks to everyone for all the feedback. I feel very comfortable with the whole prospect now and have ordered the Vitrifrigo in stainless. Cost about $1600 plus shipping and should arrive late next week.

I am also doing a lot of research on battery to battery charging systems like the Xantrex Echocharge, Balmar Duo Charge, and the similar Sterling model.

These basically are multistage battery charging systems that run off 12 volts instead of shore power. They don't care what the incoming voltage is, as long as it is in range, and they put out a charge program for your specific battery type. The Xantrex is 15 amps, Balmar is 30 amps, and Sterling is 50 amps.

The Balmar has an issue where if your load pulled is over 30 amps, it will shout down. I've got to figure out of a severely drained battery bank can suck more than 30 amps via heavy cabling when it is connected. On the other hand, the actual LOAD from my trailer will likely never come close to 30 amps, so if they are not counting a drained battery bank as something that will pull amps, then it should be OK.

I need to get my tow vehicle setup to charge enough to at least run the fridge. If I don't install one of these systems right away, I will likely just setup some dedicated wiring and relays so the fridge runs off my tow vehicle when the engine is on. That will leave my solar alone to do its thing with charging the house batteries as it does now.

I think everyone should be using something like one of these rather than just straight up connecting the house batteries in parallel to the tow vehicle. The xantrex 15 amp unit might be able to be run via a tow connector, but a separate anderson style connector would be the safe way to go, not to mention more effective. I wouldn't run anything bigger than that via the tow connector, and probably wouldn't even do 15 amps either.

The marine market also has a ton of alternator controllers that they use on their boats. If I get greedy for power, I may try to go that route and also upgrade my alternator to high output.

These alternator controller systems seem like they could provide oodles of charging amps.

Don't forget the Magnum ME-SBC, or Smart Battery Combiner. It will take incoming '12VDC' current from one battery bank or source and and properly charge the second battery bank. Easy to set in/off parameters too.

[CA_Tallguy]

I think that I did look at that one, lewster. As far as I can gather, it doesn't do any voltage/amperage conversion to put out its own multistage charging program. The reason I like the others is that they all do that, so for use with a dumb alternator, I feel they will treat my batteries better.

These others (and I'm mostly taking about Sterlimg, and maybe Balmar, as I have not examined Xantrex closely enough) also monkey around to try to convince your alternator to put out more juice than it otherwise would. The Sterling unit claims to charge house batteries up to 5 times faster than just combining, and it says it can make your alternator work at close to capacity.

They go to great lengths to explain how they are DC to DC battery chargers, and NOT combiners. To me, it sounds like the magnum unit just combines during a certain set voltage window. On the other hand, I feel like the three brands I mentioned will be like hanging a 15 to 50 amp device on your tow vehicle and sending those amps to the trailer after some conversion.

From what I've read, it sounds like simply combining has a lot of risk especially if you connect batteries at different charge levels. The boating folks talk on their forums about the house battery bank sucking down the starting bank at inopportune times. And with the tow wiring most of us use, I could see it being unsafe if you have a large battery bank in the trailer and two batteries in a tow vehicle that are trying to equalize over a 12 or 14 gauge wire in a basic harness.

I suspect the magnum unit might help buffer that flow but maybe not as I'm not sure it was designed for this specific, mobile purpose.

What I'm after is a device that will aid in getting the amps to cross the wire. That seems to be the biggest challenge in charging from a tow vehicle. If I can push 30 amps back to the trailer, it seems like that would be far more than most people will get by combining. And if I can generate that much or even 50 to 100 over what I am doing now with a high output alternator, I figure there has GOT to be a way I can get that back to my battery bank.

[CA_Tallguy]

Here's a pretty good video from Sterling showing some of the technology in action. The unit they show is a bit more complicated than what I previously posted about. This is an "alternator to battery charger" that sits between both house/tow vehicle batteries and alternator.

http://youtu.be/hKURbJOoICk

But as he points out in the video, raising the charging voltage a bit helps tremendously with transferring the amps down the wire, especially with voltage drop on the wire run. And I think this video also illustrates how the device pulls a load from the tow vehicle system and makes the alternator work harder.

[CA_Tallguy]

Just came across another unit a bit unexpectedly. It even has a built in MPPT solar charge controller, so it can optimize/synchronize charging voltage from solar AND your tow vehicle at the same time. When your hose batteries are full, it can pass through solar to the tow vehicle to top up batteries there. Also the same with shore battery charger.

It's the CTEK D250S along with the SmartPass add on unit to expand capacity, the base capacity is 20 amps.

Here's a video about it....

http://youtu.be/TjqcOAjT4W4

[CA_Tallguy]

Two more companies popped up that seem to be competing against CTEK - they are Redarc and Projecta. They are Australian and I don't see the products coming up with US retailers though.

I love how compact and multifunctional these units are and that they could include MPPT solar but I'm kind of addicted to complexity and lots of flashing lights and info displays. Hmmm.

If I didn't already have a fancy outback solar controller, I might just jump all over the CTEK to at least start out.