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Discussion Starter #1
I'm getting a Maxxfan Deluxe 7500 and an A/C (make/model TBD but will likely be 13.5kBTU).

At a later date, I will be installing around 400W of PV panels on the roof.

To allow for efficient roof space and proper air flow, what do you think the recommended locations of the fan and A/C should be?
 

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Well, without knowing the measurements of the solar you "may" install in the future you are sorta of wasting your time no matter where you place them.

You didn't listen when we gave you insulation advice - have you learned anything from that?
 

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We are used to giving advice and it not resulting in any help but it does get you to wondering why you look up the information and go to much effort. Sometimes it pays off and we feel we have helped. I'll go once more. The makers and installers say put the AC in the middle as best you can. Draw out the roof and see what space you have left. When you find there is no room for it when the solar is drawn in you can leave the fan out. Or put the fan in and when there is not room for it and AC and 400 watts of solar, replace the fan with an AC unit. I have found and downloaded the diagrams for popular AC units. You can look that up.
 

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I've gotta think that's a no-brainer

...But maybe that's because I'm not thinking right. Whether or not you put them in the center may make a difference but,
I would put one as far up front as would fit good and the other as far back as would fit good. If you want them to work together for air flow, what better way is there? The solar panels can be bought to fit
 

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I put the Maxxair (4500) at the back end of my roof. I was able to install completely from the back with an adjustable leg ladder.

The back location allows for air to be drawn from the front windows all the way thru the van to the back. I think it's the best spot. In the back you do have to contend with the hill-and-valley roof, but it wasn't a big deal with extra layers of butyl and then Eternabond.
 

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Here are some of the things I thought about. Having vent and AC works for me. I missed the vent's use while off grid especially the passive venting and rain use.
1. The size of AC & vent are givens, the hole is the same, and one or the other will almost certainly be in the front raised spot. Roof ribs limit where holes can go but not for solar panels.
2. Solar panels can be sized to whatever space is left. 400+/-W should be easy with EXT length.
3. Coleman Mach 8s vent front & back plus 2 adjustable down vents. Decide if you want direct air to a certain area, like a bed. Center roof would be most efficient in extreme conditions but given the small area it's probably academic.
4. Decide if you want MaxxAire venting or blowing in a certain area like over galley or bed.
5. Make cardboard cutouts & overlay on your floor plan to help with options.
 

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Discussion Starter #7 (Edited)
...replace the fan with an AC unit....
Are you saying that it is best in terms of airflow to have just a fan or A/C, or are you saying that I might not have the room to fit all three (fan, A/C, solar)?


...I would put one as far up front as would fit good and the other as far back as would fit good... If you want them to work together for air flow, what better way is there? The solar panels can be bought to fit
That's what I was thinking...


I put the Maxxair (4500) at the back end of my roof... The back location allows for air to be drawn from the front windows all the way thru the van to the back...In the back you do have to contend with the hill-and-valley roof.
Thanks. You described my "phase 1" of HVAC: just get the air flowing. I bought the roof adapter that Hein sells so ridges won't be an issue. It'd probably be easy to install a screen on the front windows to keep the bugs out.
For phase 2, I'll be buying the A/C in the next couple months (or sooner if the heat gets me!).


...I missed the vent's use while off grid especially the passive venting and rain use...
1....Roof ribs limit where holes can go but not for solar panels.
2....Solar panels can be sized...should be easy with EXT length.
3.Coleman Mach 8s...
4. Decide if you want MaxxAire venting or blowing in a certain area like over galley or bed.
5. Make cardboard cutouts...
What do you mean that you "missed the vent's use"? You didn't have it and wanted it?
1. "Roof ribs limit..." good point!
2. Good to know on sizing the panels.
3. I'm looking hard at the Mach 8 and 10. RD recommends them.
4. So you're an advocate of having the fan and A/C?
5. Working on floorplan now. :)

Thanks for the help! Do you guys think it's a good idea to have the fan and A/C, or should I just get one or the other? My plan on getting both was because I assumed air had to be pulled out (fan) as well as air coming in (A/C). Is that correct?
 

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I meant you might not have enough room. Remember if you shade even a portion of a solar panel it’s production is reduced, a lot! Keep this in mind when planning. That Maxx-aire is tall too. Wire the solar panels in parallel to avoid the loss from all them. I think an AC AND fan is best too. I have a 136” and the roof real estate will JUST allow 200 watts (or 300) with vent and AC. I haven’t done the AC.
 

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I do want both AC and fan. Had fan-only for 2 seasons mounted in front-loved it. Leave it open all the time when parked in hot weather. If it rains-no problem. Not the security risk of open windows. Great forced breeze while sleeping, great venting if cooking inside. Needed AC so replaced fan with Mach 8 Low profile 9.2K. Chose 9.2K to insure it runs on 15amp circuit and still allow fridge & electronics to run. 13.5K would be better at 95-110F and it runs well on 20amp circuit. AC does not vent (no outside air exchange through the unit) but it will move air but only on 120V. Immediately missed the fan. Will be replacing my fan behind C pillar. Not the most efficient use of roof space but I still have 5'+ if I ever want to replace/expand my 100Wx2 panels. If u put fan at rear you should have about 7' with ur EXT WB to install solar. I like AC in front because the area is raised and condensate and rain won't pool at gasket.
 

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Discussion Starter #10
I meant you might not have enough room. Remember if you shade even a portion of a solar panel it’s production is reduced, a lot!...
Good info. Ok, I'm rearranging priorities. Fan and A/C is a requirement. Whatever solar will fit after is what will fit (regardless of wattage).

I do want both AC and fan... Chose 9.2K to insure it runs on 15amp circuit and still allow fridge & electronics to run...If u put fan at rear you should have about 7' with ur EXT WB to install solar. I like AC in front because the area is raised and condensate and rain won't pool at gasket.
Interesting point on running A/C and other electronics on 15A. (rubs chin while thinking)
That's exactly what I did with the fan. It's in the rearmost roof section and the louvers don't stick out the back. See my latest build update.


Thanks for the input, everyone! I've got the fan in. The A/C will go in the middle-front roof section (in line with the rear part of the opening of the sliding door). Solar will go where it can in a later phase of my power build. Since I can't run A/C off of solar all day, I only need a solar plan that can sustain fridge, stove, laptop and lights.
 

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I have a maxx fan and 9200btu Coleman AC on top of my 136wb. AC is as far forward as possible. BTW, if your ac is like mine, it won't completely fit on the raised part of the roof in the front. A few inches will hang off the back. There are foam pieces that came with the gasket I bought to fill these. Installing the AC isn't as easy as the fan because you don't have an adapter for the hole and the shroud sticks out farther than the front of the hole so you have to make sure it isn't too far forward.

My Maxx fan isn't as far back as it could go. The cover that overhangs doesn't hang off the back of the van like I've seen some here. I think it's about even with the back edge of the van or a little forward. That gives me roughly 48 - 50 inches of space to put solar panels. I think it would be too tight to put two normal renogy 100W panels. They may just fit but my plan is to go with two renogy eclipse 100w panels.

Sent from my SM-P900 using Tapatalk
 

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Discussion Starter #13
Cooking with electric is another serious power hog.
True. Something to add into the calculations.

Installing the AC isn't as easy as the fan because you don't have an adapter for the hole and the shroud sticks out farther than the front of the hole so you have to make sure it isn't too far forward.
I can't use the roof adapter made by Impact 3d for the A/C? It needs a flat surface and a 14x14 hole. Sounds like the roof adapter would work fine.
 

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The electric cooking does use a lot of current but often is accomplished in a short time and at partial power. You care about POWER used for total solar needed not current used. It’s the current which determines how big (and what type) an inverter and battery is needed. Power determines how much solar to put on the roof. For example 400 watts of solar can produce 2000+- watt hours of power on a summer day with sun. An induction cooktop might use 1800+ watts but will probably be used for 10 minutes or so to cook. It needs a big expensive (2000+watt) sine wave inverter but in that 10 minutes even on constant high (which is unlikely) it uses maybe 300 watt hours. A compressor refrigerator uses about 300-400 W-H for the whole 24 hours and LED lights are so efficient they are negligible. To push that 1800 watts to the cooktop may require 300 amp-hr battery set as inverters are very sensitive to low voltage. Lithium batteries are better at sending huge loads out. All this turns a $600 electrical set up with solar into a $3000++ set up. I use a butane cooktop because I like gas to cook on, and I used the money saved to travel to Europe for a month. For me doing is always better than having. YMMV
Ask Hein about the adaptor.
 

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True. Something to add into the calculations.


I can't use the roof adapter made by Impact 3d for the A/C? It needs a flat surface and a 14x14 hole. Sounds like the roof adapter would work fine.
Maybe. It's a little different install because you have a very thick gasket to install and if I remember correctly it isn't exactly 14x14. Maybe off a quarter. If you put the AC at the front you can't because of the raised roof.

Sent from my SM-P900 using Tapatalk
 

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The electric cooking does use a lot of current but often is accomplished in a short time and at partial power. You care about POWER used for total solar needed not current used. It’s the current which determines how big (and what type) an inverter and battery is needed. Power determines how much solar to put on the roof. For example 400 watts of solar can produce 2000+- watt hours of power on a summer day with sun. An induction cooktop might use 1800+ watts but will probably be used for 10 minutes or so to cook. It needs a big expensive (2000+watt) sine wave inverter but in that 10 minutes even on constant high (which is unlikely) it uses maybe 300 watt hours. A compressor refrigerator uses about 300-400 W-H for the whole 24 hours and LED lights are so efficient they are negligible. To push that 1800 watts to the cooktop may require 300 amp-hr battery set as inverters are very sensitive to low voltage. Lithium batteries are better at sending huge loads out. All this turns a $600 electrical set up with solar into a $3000++ set up. I use a butane cooktop because I like gas to cook on, and I used the money saved to travel to Europe for a month. For me doing is always better than having. YMMV
Ask Hein about the adaptor.
I can't see how you guys are spending less than $1,000 on your solar. For the main components I'm somewhere around $1600 for 250ah and 200 watts using the same charger and inverter the Gary has. That doesn't even include anything to hook the batteries to the van battery or wire and fuses.

Sent from my SM-P900 using Tapatalk
 

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See attached picture for a part of my current spreadsheet detailing my build cost in the third column.
A full detail of my budget although an earlier version is here:
http://www.promasterforum.com/forum/showpost.php?p=130033&postcount=2
If you haven’t bought the stuff yet and want to do 200 watts and 230 amp-hr batteries, interconnect, and wiring for less than $1000 I can make you a list of products and suppliers.
 

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Maybe. It's a little different install because you have a very thick gasket to install and if I remember correctly it isn't exactly 14x14. Maybe off a quarter. If you put the AC at the front you can't because of the raised roof.

Sent from my SM-P900 using Tapatalk
We do make adapters for the AC. The hole is the same but the outside is 18.25 square to accommodate the seal.
 

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Discussion Starter #20
...Lithium batteries are better at sending huge loads out. All this turns a $600 electrical set up with solar into a $3000++ set up. I use a butane cooktop because I like gas to cook on...
I would LOVE to do lithium, but do you want to give me your beer money to help pay for those crazy expensive batteries? You can drink Natty Light for a few months, right? ;-)
Butane/propane was suggested to me by someone else AFK. It's definitely an option I'm considering.

See attached picture for a part of my current spreadsheet detailing my build cost in the third column.
A full detail of my budget although an earlier version is here:
http://www.promasterforum.com/forum/showpost.php?p=130033&postcount=2
If you haven’t bought the stuff yet and want to do 200 watts and 230 amp-hr batteries, interconnect, and wiring for less than $1000 I can make you a list of products and suppliers.
I 'm still in the planning phase of my power plan... haven't bought anything yet.

The future build of mine places the AC at the rear over the bed, then the fan near the bath, next the solar panels. I think that layout optimizes their function.
https://centrelab.smugmug.com/PERSO-GL/XLFLEXsafaricondocom/n-MNSpq/i-Mb4Xzkm/A
https://centrelab.smugmug.com/PERSO-GL/XLFLEXsafaricondocom/n-MNSpq/i-MHVK2J2/A
Whoa. You just made me jealous. haha! Those Safari Condos look pretty nice. I've already got the fan in the most rear roof section, so my A/C will have to be in the middle. It looks like there will but "just enough" room on either side of it for narrow panels and then three up front.

We do make adapters for the AC. The hole is the same but the outside is 18.25 square to accommodate the seal.
Oh, cool! Do you have a link for the Promaster A/C adapter? On eBay, I only see the fan adapter.

This is all good info, everyone. Thanks!
 
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