Cargo trailer ventilation?

[JRH]

Just curious, why was it a waste? Because you rarely use it or it did not perform? With my fan, unless I have the window open a crack, it's not really going to do anything since the trailer is sealed up pretty well. But I had nearly a 10 degree difference between running the fan and just leaving the vent cap open.

As for more insulation, that is no longer an option. I do have the ceiling done, but I am not ripping the walls down. Too much already in place to start over. I do have a large sun screen on one side (sort of a lean-to) that shades the west side in the afternoon.

10 degrees below ambient with full humidity is still tough unless it’s 75 outside and 50% humidity……I have 2 max-air fans in mr RV ( they are great fans too.) unless the AC is on all they really do in the daytime heat is suck cooking orders out and chop up the bees and flys that get in their cowl.
I have been up in the mountains so long , I heat stress over about 75- 78….
have to go find a cool place to be…
J.

 

[JRH]

What type of AC?

The one at Walmart for 148.00$ … midea…400 running watts ..3.3 amps…

 

[JRH]

If I fire up the AC before it gets above about 85 inside, it will cool it down to 75 and keep it there provided I am not going in and out a lot. But if it is already 110 inside, it takes a couple of hours to get it comfortable. Hence the problem. I randomly use the trailer, so if it's already blazingly hot, I have to suck it up for a while. I can turn the AC on remotely from my phone, so that helps a bit if I know I will be going out there later.

Prior to putting the solar panels up, I was using a generator for the AC so it's not like I could run it when I was not using it. But now I have 800W of panels on the roof, a Rover 40 and 300Ah of 12V Lifepo4. The AC draws 45 amps (@12V). So I don't have enough solar to run it all day if the compressor needs to run non-stop. But I can put it on a timer to run for a few hours every day if I want to try and keep it from getting too hot.

BTW, I had put up these "freezer strips" on the inside of the door, which help a lot with the opening and closing of the door.

The key I think is insulation…with enough insulation if you get it 70 at night it will stay 70 ..insulate it and get it cool early to have momentum…I do my rv that way and it works great… if you start at 85 damn degrees it will struggle to ever get cool with a small unit..it may never do it..

try this , get it cold early in the morn , then it will be easy to roll into the day…

ALSO try this…

if its really 110+ degrees out side , have you considered you’ve already gone to hell,for some reason…..?… goodness man, ..what did you do wrong.?

jus kiddin, but that is exceptional heat where I’m from..Yeow.
J

 

[Texas-Mark]

if its really 110+ degrees out side , have you considered you’ve already gone to hell,for some reason…..?… goodness man, ..what did you do wrong.?

It gets up to 110+ inside. Outside has been 102-104 for the last few weeks. Yes, it has been hell.

 

[JRH]

It gets up to 110+ inside. Outside has been 102-104 for the last few weeks. Yes, it has been hell.

Yep. Yep…. You musta did somthing wrong in your youth…so did I … so I won’t point .
fingers…
get your batteries out that heat…everything else will be ok…bring em inside …
give ‘em some ice cream … don’t leave them charged up in hell….they didn’t sin.. they are just passengers in the car ur drivin…?

 

[OffGridInTheCity]

Just curious, why was it a waste? Because you rarely use it or it did not perform? With my fan, unless I have the window open a crack, it's not really going to do anything since the trailer is sealed up pretty well. But I had nearly a 10 degree difference between running the fan and just leaving the vent cap open.

Trailer is sealed (except the fan openings and a small window in a back door) and we use the mini-split most of the time. In fact we cut a 1" piece of foam board to stuff in the opening to keep heat going out in winter. We did try the 'keep 75F' feature a couple of times when it was 90F outside but it wasn't that effective and at a 15deg difference the mini-split only needs <5 kwhs / 24hrs and we have a 13.5kwh lithium-ion battery on board.


MaxxFan fan failed to work properly after a couple of months. Would not respond properly to the remote control / ignored settings. Had to wire in an on/off switch to 'reset it' each day. Not sure what caused this. Not anti MaxxFan, just didn't live up to the $377 price in our situation. This is the one we installed - https://www.amazon.com/gp/product/B002OW5JG2/ref=ppx_od_dt_b_asin_title_s00


Bathroom wall fan - https://www.amazon.com/gp/product/B00407CK5W/ref=as_li_tl saw it in this youtube at 4:14... and followed their concept.

 

[Texas-Mark]

Today's test was starting the AC at 9:00am and running it until 2:00pm. It should be noted that I do have some 24/7 loads like a small 600W inverter that runs a wifi router, PTP access point to get internet out there, and a few other small items. So in the morning, I am already down a bit on the batteries. The inverter for the AC is dedicated for that, so it is only on when the AC is running. That said, at 2:00pm I was down to 72% on the batteries. There should be enough sun left to get them back to 100%.

The inside temp was at about 77 degrees when the AC shut down, but was slowing rising because it is another sunny 100+ degree day. Temps here usually peak around 5:00pm. So, if I do plan to run the AC on a daily timed scheduled, I have to be careful to take into account cloudy days so I don't run the batteries down. On the flip side, the AC would be cycling less on those days, so it's possible could be ok. All I can do is test and monitor.

This cargo trailer conversion is stationary, so I could add some more ground mounted panels or even mount some off the side in a lean-to fashion to harvest that afternoon sun and extend the AC run time. I'm not sure how much I can over-panel the Rover, but this string would be West facing, while the rest are flat on the roof.

 

[JRH]

Trailer is sealed (except the fan openings and a small window in a back door) and we use the mini-split most of the time. In fact we cut a 1" piece of foam board to stuff in the opening to keep heat going out in winter. We did try the 'keep 75F' feature a couple of times when it was 90F outside but it wasn't that effective and at a 15deg difference the mini-split only needs <5 kwhs / 24hrs and we have a 13.5kwh lithium-ion battery on board.
View attachment 158346View attachment 158348View attachment 158347

MaxxFan fan failed to work properly after a couple of months. Would not respond properly to the remote control / ignored settings. Had to wire in an on/off switch to 'reset it' each day. Not sure what caused this. Not anti MaxxFan, just didn't live up to the $377 price in our situation. This is the one we installed - https://www.amazon.com/gp/product/B002OW5JG2/ref=ppx_od_dt_b_asin_title_s00


Bathroom wall fan - https://www.amazon.com/gp/product/B00407CK5W/ref=as_li_tl saw it in this youtube at 4:14... and followed their concept.

Good lookin trailer…. Great job…!

 

[OffGridInTheCity]

Good lookin trailer…. Great job…!

Thank you for the kind words!

 

[Texas-Mark]

Not anti MaxxFan, just didn't live up to the $377 price in our situation.

Yes, for that price it should just work. I saw it had a lot of similar reviews about failures.

Your trailer conversion looks great. Unfortunately, I don't have room in mine for a bathroom/shower. Then again, mine is not really used for travel.

 

[wme]

The word from the RV guys is that Max-fan changed some voltage sensitive parts. The new stuff is unhappy with much over 12.5v.
I'm running LifePo4 batteries so l installed a DC to DC converter with 12v out, so far (2 years) my fan is still working
`

 

[OffGridInTheCity]

The word from the RV guys is that Max-fan changed some voltage sensitive parts. The new stuff is unhappy with much over 12.5v.
I'm running LifePo4 batteries so l installed a DC to DC converter with 12v out, so far (2 years) my fan is still working
`

I read this too. I use a 120v -> 12vdc converter and I can 'adjust' the 12vdc output. I tried lowering it to <12.5v and it didn't correct my situation. Installed a hard on/off switch, which may? reset things on power up (have no idea) but this made it responsive to the remote control again.

 

[JRH]

Yes, for that price it should just work. I saw it had a lot of similar reviews about failures.

Your trailer conversion looks great. Unfortunately, I don't have room in mine for a bathroom/shower. Then again, mine is not really used for travel.

When buying 3 of the max fans 3 years ago for the RV I read over and over about the ones they had most trouble with was the remote control and auto rain closing ones ..I chose to save a few hundred bucks..and buy the ones you have to stretch to reach and operate , and that don’t close when it rains… they have worked perfect ever since I got em. Great fans…
I need the exercise when reaching…… and I know how to tell when it’s raining… keeping things simple is best…
old school , ya know…!

 

[JRH]

Thank you for the kind words!

Watching your vid , I can tell you have a good woman to be onboard with all that stuff… treat her right.. she’s the exception nowdays… I’m Gona get one of those small exhaust fans… that’s cool.

 

[OM617YOTA]

Here are some pics of what I did, during construction. Two intake vents low, and two exhaust vents high and on the opposite end of the trailer. Two 12v fans in series to run off the 24v system, with a thermostat set at 95f. The cross flow and low/high mounting makes for decent natural ventilation via stack effect, which combined with the white trailer, and solar panels mounted on top creating shade, means the trailer basically stays at ambient temp unless I'm working the inverters hard and for a while. In the evenings, the sun can shine directly in the door, and the trailer actually stays cooler with the door closed rather than open.

 

[Texas-Mark]

Two intake vents low, and two exhaust vents high

I like the idea of powered intake vents. I may still try that at some point.

For now, I am trying another approach. I added another 400W string facing the West (had to borrow panels from another project). Today I started the AC at 8:30am. I am doing hourly monitoring of the solar and battery draw. With the Rover 40, I will be limited to 40A (@12V). At 10am I was at 33A solar and -7A on the battery pack. So at best, I will break even at noon and the afternoon (unless the AC cycles a bit). I will still have to shut down the AC at some point in the afternoon to allow the batteries to charge back up. With that West facing string, I am hoping maybe 4pm.

I suppose I can put that 400W string on a separate CC that I have on hand to get more than 40A total. Don't really want to buy a larger one since I just got the Rover 40 not that long ago. But maybe I will get that 60A HQST that has been in my Amazon cart ever since I read about it in another thread.

 

[OM617YOTA]

It's actually the exhaust vents that are powered. Don't know that it makes a difference, just the exhaust vents were closer to the wiring, so that's where I put the fans.

Different conditions as well, we just don't see the temps that Texas does, and what works for me may be laughably inadequate for you. I expect we'll get above 100F for a couple days(literally two) and that's it. I don't like the inverters getting that warm, but they are rated for it.

 

[Texas-Mark]

It's actually the exhaust vents that are powered.

Ahh.....I thought the fans were on those lower vents.

 

[Rocksnsalt]

I have a 12x6 cargo trailer conversion. It has powered roof vent and a side window. During the day when I am not using it, the powered roof vent runs when the internal temp reaches 95 degrees. Obviously it will never be cooler inside than the outside ambient temperature, but it is always 10-20 degrees hotter inside. With the window closed, it will be 20 degrees hotter even with the fan running since there is no fresh air intake. With the window open, it will still be 10 degrees hotter, but since the window is right next to the the ceiling vent, there is not really that much overall air flow other than in the window, and right out the vent,

I have a 5K BTU AC that i can remotely turn on, but the hotter it it is inside, the harder it is is to cool it down, and I have to fire it up a lot earlier if I plan to go out to it. Note: We have been having 100+ days for weeks now. I have panels on the roof that offer some shading and a sun screen shade on the West side that helps a little.

So my question is, has anyone installed a fresh air intake somewhere like in the floor, and did it help? I don't want to be making holes for just a degree or two difference.

Is the trailer white?
If not, PAINT IT WHITE.
THAT will do more than anything, and really help any insulation and mechanical systems out.


In the end nature will rule unless you mechanically condition the inside. Shade outside walls and insulation is pretty much all you can do. Putting an undermount vent has it’s own challenges. Ambient temp is ambient temp… but it may be slightly cooler especially if surrounded by shade. Critters of all types may like that as well. ?

 

[Texas-Mark]

Is the trailer white?

Yes, it is white.

So at noon, the Rover 40 was pushing 42A. That must be the limit, as I know I have more solar available. The Rover was angry though and throwing up a caution, but it did not shut down. I do have a cooling fan on it.

Because of that, I had to reposition those West facing panels so they are nearly horizontal. That dropped the Rover down to 39A which I am more comfortable with. This will hopefully work out ok as I have no shade from the West, and as the afternoon progresses, the West panels will pick up what the roof looses.

I do think I will need to go with either a larger SC or add a second one to that West facing string. I don't like pushing equipment to the limits.