My funky power system build

[Skyjim73]

We should take delivery of our new 3124KB in February, and I've begun acquiring the major hardware for the solar charging system. Since I'm going slightly against the grain with a few of my choices, I'll list what I'm using and then once we get some experience with the system next year, let any interested forum members know if my system is working for us or if my theories have crashed and burned...

We'll hopefully be all over North America, but we do a lot of dry camping in the desert southwest. I am a pretty serious amateur astronomer, so I like to go to fairly isolated places for dark skies. My wife enjoys many of the national park campgrounds when we do "normal' camping, and at least in the western states most campgrounds in the parks lack hookups. I have a Honda EU-2000 we've used with our old hard-side trailer, which had four 6V golf cart batteries and a 2KW Heart inverter-charger with a 100 amp four stage charger. I've gotten used to managing my battery bank, doing regular equalization charges, and so forth, and my last set of Trojan T-105s lasted 8 years. But one thing we learned was that we really did not use the AC power capability except for stuff like wall chargers that a tiny, cheap inverter could have handled. But having a good DC charging system is a must for me.

I'm not going to take my new lightweight TM and burden it with a huge battery bank - at least not right away. But I will need reliable 12 volt power since I'm committing to a 12VDC/115VAC compressor fridge rather than the 3-way. So my version 1.0 battery bank is going to be a pair of 6 volt Trojan T-145 "tall" golf cart batteries giving me a 260 amp/hr bank to draw from. Trail Manor has agreed to fab me a slightly lower slung set of battery rack rails to get me an inch lower so the T-145s in their boxes are out of the way of the forward bed section when it folds down.

At first I figured I'd buy a Magnum inverter/charger, but I really don't need most of it's capability - and it's a really pricey way to get a good charger into the system, and the only one they have with a 65 amp or under charger output (using the 25% rule of thumb for charging rate vs bank size) only has 20 amps of AC pass-through rating. That worried me when looking at air conditioner startup loads - wanted to allow at least 30 amps to match the AC service the system is designed for and the common low amperage hookup in most RV parks. So, I could spend a lot more money for a bigger inverter/charger than I needed, and deal with the complexity of an AC sub-panel for the fridge and air conditioning, which I would NOT want pulling power from the inverter. We would only use the air with AC hookups and the fridge will only switch from DC when AC power is present - no point in incurring conversion losses making AC power via an inverter. Anyway, I'm instead going to try another setup.

I also REALLY didn't want to completely redesign the DC setup, but wanted at least some control over the battery charging. The converters typically installed, including the WFCO TM uses, have three stage charging now incorporated, but they taper out of bulk charge stage VERY quickly - just the opposite of what you want for quick replenishment in a campground via small generator. I knew I'd want some solar charging capability to extend my dry camping endurance and offset the power the fridge consumes en route to a campsite, but there just isn't that much roof area available on a TM, and I didn't want to deal with portable arrays. So, I want a fixed set of panels, preferably with pretty high low-light/partial shade performance to better deal with the variety of sun exposures in typical campgrounds.

So, Version 1.0 of my system:

Batteries: 2 x Trojan T-145 (260 amp/hrs at 20 hr rate)

Custom battery rails, 2 Sea sense tall GC battery boxes.

Replace the charger module of the factory 12 volt converter with a 55 amp Progressive Dynamics 3 stage unit, with PD control pendant installed to allow me to manually control charge stages during short AC availabilities. Automated but very conservative charging option for longer term hookup situations.

TM is upgrading the DC charge cabling - still waiting to confirm whether we can go to my desired 2 gauge from the factory 10 gauge, but as Fun Pilot has found out, at least 4 gauge is definitely possible. Happy to pay for this type of upgrade at the factory!

2 x Unisolar 64 triple junction amorphous solar panels. Unisolar made these panels, as well as sheet-style flexible arrays with self-adhesive backing for metal roof setups, in Michigan before they went out of business after the 2008 economic meltdown and the flood of cheap Chinese panels. The design isn't as efficient in full sun as typical crystalline arrays, but they have really excellent shade-tolerance and low light performance. You can still find new in box US-64s on E-bay last time I checked.

Morningstar Sunsaver 15 Max Power Point Tracking charge controller. Went with the pricier MPPT controller to run the panels in series for higher voltage to minimize wiring losses to the controller, which can down-convert to the needed voltage while utilizing more of the panel output, since MPP for the Unisolars is 16.5V. Normally it's more cost-effective on small systems to buy more panels and use a cheaper controller, but I want the panels hard mounted to the roof and I've got mass and space constraints, so I'm going to try for max real-world efficiency in less than ideal light conditions. Theoretically ought to work, but we'll see how it goes in practice. I might be wrong on this choice but I want to test that.

Edit: Almost forgot:Morningstar battery temp monitor cable and remote monitor. May not give me as much information as I want, andI could wind up wanting a Trimetric monitor for comprehensive info, but this was a good deal and I'll see how it goes.

Can't wait to get things assembled after delivery and see how it all works!

Jim

[scrubjaysnest]

We have gotten on well with two 80 watt poly crystalline panels which in low light conditions preform better then the amorphous solar panels. I wouldn't try to keep the batts up with 128 watts because there is no way to reach C/20. C= batt aH capacity. We can't do it with 180 watts. We also would never try running the refrig on DC and charge only with the solar. But all that said it is refreshing to see a different approach and we will have to compare notes as we will be spending a good part of the winter in the AZ/NM/NV area.

[Padgett]

Don't forget that a compresser fridge uses about half the DC power of a gas absorption.

Only disconnect (and may be me) is the "desert southwest" with no mention of AC. My sister lives outside of Bisbee, AZ and it tends to get a tad warm there. but does cool down at night. Is probably easier to sleep than with the 90/90 we get in the summer.

In any event I founf the EU2000 (2000/1600) to be marginal and grunted starting the roof AC which is hard on everything while my Pred (2500/2200) handled it a lot better/faster.

[scrubjaysnest]

A look at the numbers is the concern. If the compressor frig draws half, say 6 amps@ 12 volts that is 72 watts times 24 hours that is 1728 watts. The panels at best will produce 128 watts times 6 hours = 768 watts. There for the batteries have to make up the difference of 1728 - 768 = 960 watts.
If the batteries are 225 aH @ 12 that is 2700 watts. Since we really don't want to go below 50% soc that is 2700 times .5 = 1350 watts. 1350 watts minus the 960, which is a deficit is 390 watts for lights and pumps and the heater maybe. This is why we prefer the three way absorption refrig. That 960 watt deficit per day is hard to make up.
The above example is best case. Throw is cloudy or rainy days and it gets worse. One has to be very conservative to get by on solar alone. We are right at the ragged edge with 180 watts. This means we don't use the fresh water tank and pump, a couple of 2 1/2 gal jugs for water. Use the furnace to take the chill in the morning, not run all night. All LED lighting. Also careful position of the solar panels. Out west in the dessert its not so bad but on the east coast or in WA or OR one will have to really look at it closely.

[tentcamper]

Is that the power rating for the compressor frig? It sounds like that little eu-2000 will be running most of the day.

Scrubjaysneste you may know the answer? If you are running the generator and recharging through the converter and the solar is charging the battery at the same time. Will either one, the converter or the solar control go into bulk charge? I would think they will trick each other with the 13.x float mode applied to the battery and just sit in float mode? I would think they would never go into bulk charge if both are producing 13.x???

[LoveToCamp]

Seeing all the concern over solar charging from those of you who camp with clouds or tree canopy, it makes me a bit happier that I don't have as much shade to camp in!

I have gone 7 nights at a time in the summer with mostly-shade, and my battery seems to top-off daily (my original TM had a lights-only controller, so I never really knew the state of charge). I got my new 2417 this spring, and that controller showed me I was up to at least 13.1 every day.

A few weekends ago, I took our TM out with 4 guys (yes, it was tight, but 3 of us had comfortable beds). Kept the heater at 65° in the evening, then 45° overnight each night. Through the evening, the heater was on about half the time. Overnight, it ran about 25% of the time, with outdoor temps of 30°. Each day, we were back up to 13.1, even with the sun low on the southern sky.

This weekend, I put a second 12v battery in, so I should have even more capacity going-forward. One of these years, I will be camping in New England, or Oregon, and will get to see if I get close to a full re-charge daily. But, for now, my 100w panel seems to keep me fully-charged daily.

[tentcamper]

Seeing all the concern over solar charging from those of you who camp with clouds or tree canopy, it makes me a bit happier that I don't have as much shade to camp in!

I have gone 7 nights at a time in the summer with mostly-shade, and my battery seems to top-off daily (my original TM had a lights-only controller, so I never really knew the state of charge). I got my new 2417 this spring, and that controller showed me I was up to at least 13.1 every day.

A few weekends ago, I took our TM out with 4 guys (yes, it was tight, but 3 of us had comfortable beds). Kept the heater at 65° in the evening, then 45° overnight each night. Through the evening, the heater was on about half the time. Overnight, it ran about 25% of the time, with outdoor temps of 30°. Each day, we were back up to 13.1, even with the sun low on the southern sky.

This weekend, I put a second 12v battery in, so I should have even more capacity going-forward. One of these years, I will be camping in New England, or Oregon, and will get to see if I get close to a full re-charge daily. But, for now, my 100w panel seems to keep me fully-charged daily.

I would try the norther camping before I bought an additional battery. I know we would all like a fully charged battery every day; But what we have found is we need enough battery to get us through our camping. So each day the battery is a little lower but we are still in the safe zone.

For many years we would go 7+ days warm weather without heat and be OK and that was without any solar or recharging. Now when we left CG the battery was near 50% and it would recharge from the TV when traveling. If I had solar I could have gone maybe 14 days.

In cold weather we need to recharge after 2 nights with the auto jumper cables We just got solar for our cold weather camping. Our belief is with solar we can push it to 4 nights in cold weather, which we never say anywhere in cold weather more then 3 nights. The battery is fine to discharge to slightly above 50%. Since we live in the north every automobile we have has a set of jumper cables. Only twice in 25+ years of having a camper in warm weather, have I had to recharge the battery with the jumper cables.

[Bill]

I have a 10-year-old Engel 43-qt frig/freezer with the Sawafuji compressor. This is a single-compartment unit, so it is a refrig OR a freezer, unlike your Dometic frig/freezer, which has a separate freezer compartment. Currently we are using our Engel as a home freezer.

It has an uncalibrated thermostat. Since we use it as a freezer, I simply set it to MAX COLD and let it run. It has settled at a temp of about -5 degrees F. This is in an ambient of 75 degrees, with no direct sunlight on the unit, and good ventilation for the cooling mechanism.

When the compressor is on, it draws about 2.3 amps on DC power. In the conditions outlined above, the compressor seems to run about 60% of the time.

So what does all this mean to you? My intent is to highlight the things that will have an effect on your unit’s energy consumption.

The factor that influences energy consumption the most is the thermostat setting. In other words, how cold do you want the unit to be inside? In my example above, I just set it to MAX and let it run. You can’t be nearly as cavalier about the setting.

If you demand a refrig temp of 35 degrees (in other words, a 40 degree drop from a 75 degree ambient), you will use a certain amount of energy. If you are willing to raise the thermostat to 45 degrees (a 30 degree drop from a 75 degree ambient), then you will cut the unit’s energy consumption by 25%. And similarly in between. This decision is complicated by the fact that although your unit has both a refrigerator and a freezer, it has only one thermostat. This means that you set the thermostat to the temp you want in the refrig, and take what you get in the freezer. If the freezer is too warm, you have to juggle. Get a good refrigerator thermometer.

The next major element in calculating energy use is what percent of the time the compressor actually runs (called duty cycle). It certainly will not run 100% of the time. If the compressor draws 6 amps when running, but runs only half the time, the equivalent current for calculation purposes is 3 amps. And if it runs only 1/3 of the time, then the equivalent is 2 amps. These are the numbers you would use in the battery-life calculations. As you would expect, compressor run time is determined by thermostat setting, as well as by ambient conditions.

Among the other factors that affect energy consumption are ambient temperature - how warm is it in the room? If you park your TM in the shade and open the windows for a good cross breeze, the ambient in the TM will be about as low as you can get it. If you go away for the day and close all the doors and windows to deter thieves, the temp inside the trailer will rise, and so will the energy consumption of the refrig.

Next is venting the refrigerator’s cooling mechanism. The TM’s 3-way refrig generates a lot of heat, so TM uses a relatively big fan to suck the heat out of the refrig mounting compartment. The Dometic 2-way will generate a lot less heat, but it is still important not to let it build up. Otherwise the refrigerator is fighting an uphill battle. Especially on a hot day, it might be wise to have a low power fan built into the compartment.

Along a similar line is sun loading. If you park the TM so that the refrig is in the sun, you are pumping heat into the compartment. You should either park the TM in a different direction, or at very least rig up a sunshade over that area of the wall.

So my refrig draws 2.3 amps DC, while yours draws 6 amps DC. Mine is set for really cold, so the duty cycle is high, while yours will be set warmer, so the duty cycle will be less. Since you are looking at solar as your exclusive source of power, you'll need to be aware of, and manage, the other items carefully.

My apologies for the length of this post. I hope it helps clarify some of the issues under discussion.

Bill

[Padgett]

About post #4. That might be true if the compressor ran continuously but just taint so.

Part of the reason the stock gas absorption fridge requires such a large energy budget is that it is really very inefficient in many ways. So on electric it pulls 150-180W almost continuously to cool not very much, even more than a Peltier plate.

OTOH a modern compressor fridge is very efficient, pulling 60-70W but with a 30-50% duty cycle. Once it is cold and the door stays shut it really does not use much power. With a top freezer, circulation does not need much help.

As a rule of thumb I'd figure 30W continuous or 60-70AH/day at 12v. Meanwhile a 200W array providing 140W @ 13v for 6 hours is about 65 AH so close to a wash.

Now that is just a SWAG so I'd be interested in hearing real world numbers but personally think a GA fridge is really a poor choice unless always on LP.

[tentcamper]

If bills numbers are in the ball park? And the fridge compressor runs 1/2 the time, it sounds like the compressor fridge could be in the 50-60+ amps per day load.

I think we all would like the faster cooling fridge like a 12v compressor fridge. But it all comes down to your style of camping and if it's a lot of dry camping or being connected to a shore power or a generator?

Plus's
- Gas absorption fridge runs on propane and use no 12V energy and does not do well holding temps in the 30's when outside temps are above 95 degrees.
- Compressor fridge cools faster and hold a cold temp better in hot weather.

[scrubjaysnest]

Is that the power rating for the compressor frig? It sounds like that little eu-2000 will be running most of the day.

Scrubjaysneste you may know the answer? If you are running the generator and recharging through the converter and the solar is charging the battery at the same time. Will either one, the converter or the solar control go into bulk charge? I would think they will trick each other with the 13.x float mode applied to the battery and just sit in float mode? I would think they would never go into bulk charge if both are producing 13.x???
Unless the folks living off grid disconnect the solar when running the ginny then it doesn't appear to be a conflict. They are mostly using some kind of inverter/charger also. Since we don't carry a ginny with us I really haven't looked into it.

[scrubjaysnest]

Bill's numbers look right and Padgett picked up on the fact my numbers didn't reflect the compressor cycling which will lower its consumption. The big thing to understand when setting up a solar system is how much power do you use in a 24 hour period. How much solar power is available in your area; this is measured in kwatts per square meter. Out of this how many hours of sun can you expect. From this you can ball park what you need in the way of solar panels. There are lot of variables that impact these things.
Tentcamper asked about using a charger along with the solar CC. When you place two or more voltage sources in parallel the resultant will be about the average of the sources. An example one charger at 14 volts, 1 solar cc at 13 volts that is 13.5 volts but what about the battery? It is also a voltage source. Yes it's one we are trying to charge back up to some where in the 13+ range. Eventually depending on the current supplied by the charger and solar cc the voltage will level out as the battery reaches full charge. At that point both the charger and the solar CC should be in float mode.

[Skyjim73]

I should point out that I have no expectation of the PV making up 100% of my daily power usage - it will, I think, simply offset most of the DC power consumed by the compressor fridge. My wife and I have been desert dry-campers for a long time, and we don't use the air conditioner unless we have hookups. We desert camp during the cooler months and head for the coast or the high mountains when it's hot. If I'm heading for the North Rim of the Grand Canyon like I normally do every June, I either drive straight through or stop at an RV park with hookups in Vegas or St. George. I we're on a long cross-country like the trip to Newfoundland I've been wanting to do for years, we'll probably go to campgrounds with hookups most nights while crossing the continent.

Absolutely correct that you can't depend on an EU-2000 to start our air conditioner! Not an issue for us, though. I expect to run the EU-2000 as needed to replenish the batteries, and I'll have to see what "as needed" turns out to be. Since we won't be hooked up with the converter supplying charge amps most of the time, I don't believe I'm going to have any problems with the solar controller prematurely jumping down to float voltage. And remember that I'll have the capability to tell the PD converter manually to remain in bulk charge mode as long as I am running the EU-2000, if needed. I realize I will need to monitor my battery bank voltage during these charges.

I'm getting the compressor fridge because I'm sick of absorption fridges that don't cool adequately while I'm driving through hot places on the way to the mountains, a pretty common trip profile for us. By using slightly larger batteries (260 AH vs a more typical 220AH dual setup) and having the solar array, I hope to arrive at a typical campsite with full or nearly full batteries for the first evening. We'll see how effective the charging is - like I said, this is version 1.0...

EDIT: Forgot to say - we are leaving the TM cooling fan setup untouched when they install the Dometic compressor fridge at the factory. Agree that ventilating that space it vital!

[Padgett]

Just a thought but can simulate a dry trip in the back yard fairly easily. Then you have a good idea what will happen.

Has anyone tried adding a "Hard Start" (http://www.amazon.com/SUPCO-SPP6-Start-Relay-Capacitor/dp/B0002YTLFE) cap to the roof AC ? Issue with EU2000 seems to be starting and not running.

[tentcamper]

skyjim73, the compressor fridges are some what new to RV'er. Most of us and it sounds like you are included, don't have any experience with them?

After you use it for a while, could you please share with us your experience. The pros/cons would be great along with any information on how the solar system does with keeping up with the fridge. I think most of us like the idea of a 12V compressor fridge, but have reservations about the power consumption.

[Bill]

Skyjim -

Just a thought ... Is there any reason to buy an EU2000, as opposed to an EU1000? I never found a reason. Since the EU2000 generally won't run the air conditioner, what loads are left? An EU1000 will charge the batteries with plenty of capacity left over. It will run a TV, run a microwave or a coffeemaker if you check the nameplate before you buy. It will not run a common 1500-watt hair dryer or a 1500-watt space heater, of course, but is it critically important to have the 1500-watt versions of these?

The EU1000 is smaller, lighter, cheaper, quieter, burns less gas - you name it. Why go 2000?

Bill

[tentcamper]

I have a old honda EX800 800 watt from many years a go. Played with it a bunch in the drive and took it out once camping. We decided we don't like generators and camping. Long story about generators and camping.

It did a fine job. We only charged up to about 90-95% in an hour and stopped. I figures the last 5-10% takes 4+ hours on any charger and just decided to skipped it. It never came close to maxing out the generator. At the peek it was pulling 300-400 watts.

[Padgett]

Started with an $80 HF 900/800 two stroke. Main issue was noise. Then got a deal on a new EU2000. Quiet and still portable but had trouble starting the AC. Did not want a companion since did not want to carry two. Bought the Predator and everything is happy.

BTW my 1986 Vixen had a 12v/120v 4 cu. ft. Norcold so nothing new. Had about a 50% duty cycle at 4A. Are more efficient now.

[Skyjim73]

Tentcamper, I'll be sure to relate how it works - I had decided to go with a Dometic CR-1110 before getting on the forum here and finding out that Rickst29 had already swapped one into his TM!

At that point I'd been talking to my dealer and was able to talk to TM owner Mr. Eickoff at a local RV show and we confirmed that the dimensions work fine so TM agreed to install the compressor fridge at the factory. Funpilot is already having that done as well. I'm also planning to install a National Luna Portable power pack in my new truck next year under the shell, with a 105 amp/hr AGM deep cycle, and carry a fridge/freezer in the truck for truck-only trips into the boonies. Not sure if I will go with an Engel, ARB, or National Luna fridge freezer, but one of those in the 50 qt range will do the job for me.

Bill, I bought the EU-2000 because I had an EU-3000 to run the AC, but the way I camp I just don't use the AC much and the EU-3000 was just overkill (REALLY a nice unit if you need 3kw, though - electric start spoils you quickly!). I could just barely move it around myself, but I'm not getting any younger. Sold it and got the 2000. The EU-2000 rather than a 1000 was a choice made when I had my 2KW inverter/charger and I wanted to be able to use all of the 100 amps of battery charger on my big battery bank. With the 55 amp charger on the TM, you are right - the EU-1000 would be fine.

Can't wait to start fiddling around with this setup. C'mon, February!

Jim

[funpilot]

Todd told me that they were doing the same thing with my refrigerator (leaving the cooling fan in place).

[tentcamper]

I think you have to leave the fan in place to cool the compartment when the camper is closed???

[Skyjim73]

Tentcamper - That's right! Only question going in was whether there was anything about the back side contours on the CR-1110 that might preclude the use of the stock fan setup.

I wouldn't want to lose the ability to exchange air in that space while folded!

Jim

[rickst29]

Instead, I added an "exhaust" fan to the upper ventilation panel (12V computer fan, 140mm diameter, running at low speed). "Push" ventilation from the stock TM setup doesn't remove warm air from the heat exchanger, and the 80mm fan on the Dometic only works if the warm air at the Dometic rear ("aft" side) is being moved _out_, through the upper ventilation panel, with a bigger fan.

The Dometic leaves a couple inches of space between it's back insulation and the TM lower shell "body panel". If you leave the forced air tubing in place for the TM fan to blow upwards, it will have a lot of resistance, and very low volume (because it's squashed to 1/2 it's original diameter in one direction.) I removed that tubing, and glued a tiny panel from "front(hitch)-side bottom" over to "aft side top", where the heat exchanger is located. That little panel blocks intake air from going directly to the 140mm exhaust fan; instead, it feeds into the Dometic 80mm fan and surrounding exchanger, collecting heat. And then it's free to be sucked out by the big fan.

In optimal sun conditions and 90-95 degree highs, 100W of panel (about 70 watts after PWM Controller and wiring losses) is about a tie for Dometic 1110 power requirements. Shade, hotter weather, and any other significant use of electricity would call for more power.

[funpilot]

[QUOTE=Skyjim73; EDIT: Forgot to say - we are leaving the TM cooling fan setup untouched when they install the Dometic compressor fridge at the factory. Agree that ventilating that space it vital![/QUOTE]

My compressor fridge from TM was installed with the TM cooling fan. I have not been in any warm areas yet so cannot comment about its cooling capacity. What I can tell you is that I hardly here it when it is on. Skyjim, they did have to modify the cabinet slightly to get it in. When I was leaving, the cabinet guy came back out to measure what he had done for your trailer. He also said that the Nebraska plant wanted to know how this was done, so I presume that means they are considering offering it as a future option.

[tentcamper]

Instead, I added an "exhaust" fan to the upper ventilation panel (12V computer fan, 140mm diameter, running at low speed). "Push" ventilation from the stock TM setup doesn't remove warm air from the heat exchanger, and the 80mm fan on the Dometic only works if the warm air at the Dometic rear ("aft" side) is being moved _out_, through the upper ventilation panel, with a bigger fan.

The Dometic leaves a couple inches of space between it's back insulation and the TM lower shell "body panel". If you leave the forced air tubing in place for the TM fan to blow upwards, it will have a lot of resistance, and very low volume (because it's squashed to 1/2 it's original diameter in one direction.) I removed that tubing, and glued a tiny panel from "front(hitch)-side bottom" over to "aft side top", where the heat exchanger is located. That little panel blocks intake air from going directly to the 140mm exhaust fan; instead, it feeds into the Dometic 80mm fan and surrounding exchanger, collecting heat. And then it's free to be sucked out by the big fan.

In optimal sun conditions and 90-95 degree highs, 100W of panel (about 70 watts after PWM Controller and wiring losses) is about a tie for Dometic 1110 power requirements. Shade, hotter weather, and any other significant use of electricity would call for more power.

I had added 2 - 2 inch fans to my previous campers fridge compartment with 2 inch square ducts back to the upper coil. I would switch them on when the outside temps hit low to mid 90's. It did seem to allow the fridge temp to be 5 - 10 degrees cooler in 100+ temp.

But I have not added the fans for the TM. We did turn on the stock TM factory fridge fan in the mid 90's and it seem to do the same job as the 2 small fans in my previous camper.

[Padgett]

My experience is that any air flow over the cooling fins helps significantly.

Most refrigerators rely on convection for the heat exchange and that hot air rises for movement. Some (particularly bottom freezer models) add their own fans. In a closed TM with no natural circulation this becomes critical particularly in a gas absorption unit (compressors are much more efficient) but the important thing is that while more circulation is better particularly in hot weather, having some is critical.

[Bill]

"Push" ventilation from the stock TM setup doesn't remove warm air from the heat exchanger... If you leave the forced air tubing in place for the TM fan to blow upwards, it will have a lot of resistance, and very low volume (because it's squashed to 1/2 it's original diameter in one direction.) While I agree that a second fan may help with cooling the refrig mechanism, I'm sure you realize that the stock fan, mounted on the floor of the refrig compartment, is supposed to "pull" the heated air downward through the dryer hose and expel it out through the floor. It actually works pretty well, and a lot better than trying to cram air upwards through the tube, into the top of the compartment.

Bill

[rickst29]

While I agree that a second fan may help with cooling the refrig mechanism, I'm sure you realize that the stock fan, mounted on the floor of the refrig compartment, is supposed to "pull" the heated air downward through the dryer hose and expel it out through the floor. It actually works pretty well, and a lot better than trying to cram air upwards through the tube, into the top of the compartment.

Bill
Fascinating - my fan must have been mis-wired at the factory, because it always blew upwards. I thought it's #1 job was to bring fresh air for the propane burner, and #2 was to create some flow at the radiator. But the way you describe would blow road gunk down and away, rather than sucking it up. ;)

And (secondary topic), as Padjet noted: some fridge/freezer units have a fan to blow air through the radiator, and the Dometic 1110 inlcudes one. The big, slow fans which I chose runs with vastly less noise than the TM original (which I removed), and provides enormous airflow. (I just remembered, while writing this and looking at one package - with a fan INSIDE, that I removed one of them and sealed that side of the upper panel shut. I'm using one fan at, at roughly 50 CFM. Two tiny fans can't move that much air, even if they are "screaming" at 6-7000 RPMs.

My exhaust fan model, incidentally, is "AXP-GF140_WT" by "ZION".

[LoveToCamp]

rist29, I can't find anything using your manufacturer and model number for exhaust fans. I can't even find Zion exhaust fans. Are they computer fans?

I would love to have a quieter fan for the fridge cooling. Summers don't allow my fridge to get very cool, and using the fan should help.

[rickst29]

I mislead you by spelling it wrong, here's a link:
http://www.newegg.com/Product/Product.aspx?Item=N82E16835264008
it's also available at Amazon.

[tentcamper]

When I bought my last fans, for the previous camper. I was looking at power consumption to CFM. I figured if I need them when dry camping, I wanted to conserve the battery. That is why I ended up with the two small fans.

[Skyjim73]

Good info, guys - much appreciated at this end as i fidget, awaiting my TM from Nebraska! Can't wait to have a look at my fridge installation details once I have the trailer!

I'll be in some pretty warm places at times so intrigued by adding more airflow around the back of the fridge...if I can reduce the compressor run time by improving the heat rejection rate, I'm on board!

Looking forward to a short weekend shakedown cruise as soon as we take delivery, hopefully some time in March.

[tentcamper]

Good info, guys - much appreciated at this end as i fidget, awaiting my TM from Nebraska! Can't wait to have a look at my fridge installation details once I have the trailer!

I'll be in some pretty warm places at times so intrigued by adding more airflow around the back of the fridge...if I can reduce the compressor run time by improving the heat rejection rate, I'm on board!

Looking forward to a short weekend shakedown cruise as soon as we take delivery, hopefully some time in March.

I think with the compressor fridge, TM also installs the fridge vent fan for when the camper is closed. Our experience is the TM stock fridge vent fan does real good job if you turn it on when it's 90+ outside. It does as good of job as the fans I added in my previous campers. But you have a compressor fridge, so it may not be an issue in the warmer weather??

Let us know how the compressor fridge does. I think many of us would like to get some reviews. My assumption is it does a much better job of cooling. But my biggest concern is power consumption when dry camping?

[Skyjim73]

Tentcamper, I will share experiences as soon as i have some! ;-)

I think we may be able to get some test field info on the factory installation sooner from Funpilot, since he has his unit in hand already. Per his posts, TM did include the factory fan setup in his installation; I am curious if a multiple fan setup as described by rickst29 can improve the efficiency over the factory setup.

I'm concerned about dry camping as well, which is why I'm going with the solar setup right away and installing some Trojan T-145s on the tongue rather than T-105s, and going with a Progressive Dynamics charger board with a manual control pendant - that will allow me to keep the charge in bulk mode as needed while running my EU-2000.

With a 260 amp/hr battery bank fully charged to start a trip, and lower drain en route since the compressor fridge is much more efficient on DC than the standard units (about half the amperage with compressor running - don't know what the duty cycle is going to look like during a typical trip but that is one situation where there might be benefits to better fan ventilation...), even my 128 watt panel setup ought to be able to more than offset the fridge draw en route during daylight tows.

How close I come to providing all my power needs while dry camping is the big question for me. The relatively low wattage amorphous panels are an attempt to improve partial shade/mild overcast power output over crystalline panels which might or might not work well in the real world. Scrubjaynest thinks I'm probably not going to be putting out enough solar power most days and he may be right. I'm going MPPT on the charge controller and wiring the panels in series in an effort to harvest as much power as possible. Will see if it is enough to get me through most weekend trips without running the generator - that's a fairly low bar I've set for being satisfied with the performance. If I only have to run the gen every 3rd day or so while dry camping that would be nice, but I won't want to cycle the batteries too deeply to get there...

So right now I'm long on theoreticals and looking forward to finding out how it works for real. I expect much better cooling performance from the compressor fridge than I've seen from the Dometic absorption fridges I've owned in previous rigs. I generally drive through very warm places en route to cooler places where the absorption fridges run cooler. Would like to be able to store meat safely in the main fridge rather than feeling the need for ice coolers to do that job en route!

[rickst29]

Tentcamper, I will share experiences as soon as i have some! ;-) I think we may be able to get some test field info on the factory installation sooner from Funpilot, since he has his unit in hand already. Per his posts, TM did include the factory fan setup in his installation; I am curious if a multiple fan setup as described by rickst29 can improve the efficiency over the factory setup.I am not using the original TM fan at all- just the empty 4" diameter hole, now functioning as "intake", where the fan was originally installed by TM. There's a small fan built into the heat exchanger of the Fridge, but it's pointed at a section of the upper vent which I sealed. The effective airflow is all created by one fan, the 140mm 'Xion' which I described in that earlier post.

But the TM guys are pretty smart, I'm sure that they've got an effective scheme. The limiting factor is: The 4-inch "flex duct", used for pulling air down from the Norcold fins, would get squashed in the much more narrow space behind the CR-1110 insulation.

....With a 260 amp/hr battery bank fully charged to start a trip, and lower drain en route since the compressor fridge is much more efficient on DC than the standard units (about half the amperage with compressor running - don't know what the duty cycle is going to look like during a typical trip but that is one situation where there might be benefits to better fan ventilation...), even my 128 watt panel setup ought to be able to more than offset the fridge draw en route during daylight tows.

How close I come to providing all my power needs while dry camping is the big question for me. The relatively low wattage amorphous panels are an attempt to improve partial shade/mild overcast power output over crystalline panels which might or might not work well in the real world. Scrubjaynest thinks I'm probably not going to be putting out enough solar power most days and he may be right. I'm going MPPT on the charge controller and wiring the panels in series in an effort to harvest as much power as possible. Will see if it is enough to get me through most weekend trips without running the generator - that's a fairly low bar I've set for being satisfied with the performance. If I only have to run the gen every 3rd day or so while dry camping that would be nice, but I won't want to cycle the batteries too deeply to get there....
From my experience, I'm with Scrubjaynest on that question, when daytime temps exceed about 90F. MPPT certainly helps, but even if Solar nets 110 Watts for several hours on a nearly perfect (but too-hot) day, the fridge "average" consumption might be nearly 50 Watts during the hot afternoon. If your day is Solar-productive for 7-8 hours, you've generated (at best) about 1/2 KWH into the batteries. The fridge "average" consumption during the hot evening, cooler night and, and non-productive morning hours might end up around 25 Watts. 25W * 16 hours = 400 Watt-Hours, so I SWAG that you've got just a bit more than 100 WH "extra" (barely 8 AH @ 12V) into the batteries to run everything else.

IMO, your massive battery bank is totally underwhelmed by your 64W * 2 panel Solar configuration. Under perfect conditions, they're only putting out 8.2A @ 13.4 V. That's a charging ratio of about 1A per 30 AH of capacity - way slower than the 1/20 ratio which Trojan recommends as a "minimum rate" for batteries at less than 85% capacity. (Their maximum recommended rate at that SOC is 1/10.) Unless cool, clear conditions decrease your Fridge power cycles while optimizing Panel output, you're probably going to lose a significant amount of AH each day.

[Skyjim73]

Right - but like I said several posts above, I'm figuring on the solar as supplemental wattage to (I hope) roughly balance off the effects of having the compressor fridge - not as primary charging source. I muddied that idea in my previous post - my bad. I guess I should have characterized how close I come to balancing my needs as the "interesting" rather than "big" question.

I am sort of grinning at considering 260 amp/hrs as "massive" since I had four golf cart batts in my previous rig, wired up with 4/0 cabling as a single bank of about 450 amp/hrs supplying a 2kw inverter. You are obviously correct in the context of what folks typically run on a TM, but it's an adjustment for me!

We found out that we appreciated having the big energy storage for extended dry camping, but we never really used that 2000 watt inverter for serious AC loads. We don't need a microwave while camping. I got used to the good three stage charging it gave me, though it bulk charged at 100 amps, at the start of a charge cycle, about 22% of the 20 hr capacity, way above Trojan's recommendations - yet I got terrific service life from my golf cart batteries, around 6 or 7 years over the 18 years I ran that setup - which I thought was pretty good for flooded lead/acid batteries.

Since the solar gives me lower than recommended charge rates between AC power availability, do you think I'm going to be hurting the batteries in the long run, even if I regularly charge via hookups or generator? I'm hoping I won't typically discharge the bank very deeply, never wanting to pull them lower than around 60% SOC, which still gives me about 100 AH to play with from a fully charged bank. I'm just guessing at what my consumption is going to be in the TM. Based on your experiences, do you think my "generator run every 3rd day" bar is expecting too much?

[tentcamper]

I am not using the original TM fan at all- just the empty 4" diameter hole, now functioning as "intake", where the fan was originally installed by TM. There's a small fan built into the heat exchanger of the Fridge, but it's pointed at a section of the upper vent which I sealed. The effective airflow is all created by one fan, the 140mm 'Xion' which I described in that earlier post.

But the TM guys are pretty smart, I'm sure that they've got an effective scheme. The limiting factor is: The 4-inch "flex duct", used for pulling air down from the Norcold fins, would get squashed in the much more narrow space behind the CR-1110 insulation.


From my experience, I'm with Scrubjaynest on that question, when daytime temps exceed about 90F. MPPT certainly helps, but even if Solar nets 110 Watts for several hours on a nearly perfect (but too-hot) day, the fridge "average" consumption might be nearly 50 Watts during the hot afternoon. If your day is Solar-productive for 7-8 hours, you've generated (at best) about 1/2 KWH into the batteries. The fridge "average" consumption during the hot evening, cooler night and, and non-productive morning hours might end up around 25 Watts. 25W * 16 hours = 400 Watt-Hours, so I SWAG that you've got just a bit more than 100 WH "extra" (barely 8 AH @ 12V) into the batteries to run everything else.

IMO, your massive battery bank is totally underwhelmed by your 64W * 2 panel Solar configuration. Under perfect conditions, they're only putting out 8.2A @ 13.4 V. That's a charging ratio of about 1A per 30 AH of capacity - way slower than the 1/20 ratio which Trojan recommends as a "minimum rate" for batteries at less than 85% capacity. (Their maximum recommended rate at that SOC is 1/10.) Unless cool, clear conditions decrease your Fridge power cycles while optimizing Panel output, you're probably going to lose a significant amount of AH each day.

I don't think the fridge will draws near 50W. I would think for planning, I would use a 20 watt light on all the time. A 14 cu/ft compressor fridge runs on less than 60W on all the time. This is a 3-4 cu/ft, same technology different motor. But it would be nice to hear some real numbers.

I could see where with your system, you most likely will be okay? But the fridge is wildcard? Also, your electrical needs and my needs are most likely different? It sounds like you have a generator. Bring it and check you voltage a few times a day. Don't use the generator unless you need it. Build up you experience level with the system and it's capability. Please share your experience, i'm sure it will be uses full to other. FYI: the rule of thumb for panels is 1 - 100W for each battery, but that is based on that you are discharging the batteries down to 60% each day.

'I am not using the original TM fan at all- just the empty 4" diameter hole" How do you keep it cool when traveling and the shell is down??