Ducted AC

mikeypj · 08-19-2018, 03:47 PM

Would it be possible to run duct work in the ceiling of a skoolie? I want to go with just 1-AC unit if possible. Doing solar so need some room up there..Also, i think its possible to run a rooftop ac unit off a genny while driving..am i correct in this?

CaptSquid · 08-19-2018, 04:32 PM

I'd suggest running the ductwork above the windows. Overhead room is precious on these beasties and very few people walk along the edges.

Ronnie · 08-19-2018, 05:58 PM

On a full size bus one a/c unit is not going to be enough, not sure what size your bus is. Rv's can and do run the rooftop a/c off the genny while driving, so see no reason you can not do the same.

I have two 13,500 btu rooftop units on my 34ft bus. In the shade one will do just fine but out in the sun it needs both.

Stu & Filo. T · 08-19-2018, 07:28 PM

Thats what I'm doing, I installed 2 ac units & started building ducts down each side of the bus about 2 ft off center of the ceiling, My plan is while sleeping if I need ac run the fwd unit & if I'm up front say watching tv,reading, run the back unit.I'm also making the ducts deep enough to where i'll have 1 in wire chases inside the ducts. I'm also thinking of running the ducts to the drivers compartment & have a flapper valve where I can close the ducts off & pipe cool air to the drivers compartment from the fwd unit, my neighbor keeps telling me it would be cheaper to put in dash air but I'm not so sure.

mikeypj · 08-19-2018, 07:34 PM

Is the ductwork like dryer vent hose?

Stu & Filo. T · 08-19-2018, 07:59 PM

Quote:

Originally Posted by mikeypj

Is the ductwork like dryer vent hose?

No I'm making it out of wood

Ronnie · 08-19-2018, 09:04 PM

Although dryer vent hose might work, I think it will be more noise then something smooth .

JDOnTheGo · 08-20-2018, 06:07 AM

Quote:

Originally Posted by mikeypj

Would it be possible to run duct work in the ceiling of a skoolie? I want to go with just 1-AC unit if possible. Doing solar so need some room up there..Also, i think its possible to run a rooftop ac unit off a genny while driving..am i correct in this?

Yes and yes.

As noted, however; ceiling height is the issue. My A/C ducting is not complete so completely unproven. That said, I've constructed a 3/4" tall space between the 'top' of the ceiling panels and 'bottom' of the roof insulation. It is very wide with cold air using half of the ceiling width and return air the other half. My hope is that the cold and return air will flow sufficiently well thru this space. The duct 'volume' math works out ok but that is no guarantee. In all, it's cost me about 1" of headroom.

EastCoastCB · 08-20-2018, 06:34 AM

Quote:

Originally Posted by mikeypj

Would it be possible to run duct work in the ceiling of a skoolie? I want to go with just 1-AC unit if possible. Doing solar so need some room up there..Also, i think its possible to run a rooftop ac unit off a genny while driving..am i correct in this?

Rooftop units are pretty darn inefficient. With a generator they're fine but with solar you'll want something more efficient.

Ronnie · 08-20-2018, 08:17 AM

Not sure he meant running the a/c off solar, just wants room for solar. At least think that is what he means.

I would be curious if anyone has measured wattage on a rooftop and measured wattage on a mini split of the same btu rating to see how they compare?

EastCoastCB · 08-20-2018, 08:23 AM

Quote:

Originally Posted by Ronnie

Not sure he meant running the a/c off solar, just wants room for solar. At least think that is what he means.

I would be curious if anyone has measured wattage on a rooftop and measured wattage on a mini split of the same btu rating to see how they compare?

Yeah, mini splits use about 1/3-1/2 the power IIRC. Chris or someone else will know.

Mini Split A/C in an RV | Beginning from this Morning

https://www.youtube.com/watch?v=IHDT5ZEpKkw

Tango · 08-20-2018, 09:03 AM

I'm no A/C expert, but wood sounds like a poor choice for ducting air unless it is somehow absolutely sealed against moisture. Vents are subject to quite a bit of condensation. Even with thorough insulation, mine routinely condense and drip.

Just a thought.

Stu & Filo. T · 08-20-2018, 10:23 AM

Quote:

Originally Posted by Tango

I'm no A/C expert, but wood sounds like a poor choice for ducting air unless it is somehow absolutely sealed against moisture. Vents are subject to quite a bit of condensation. Even with thorough insulation, mine routinely condense and drip.

Just a thought.

My plan is to line it with 1/4 insulation,,,Should I rethink it??? S&S RV only use foam insulation

Tango · 08-20-2018, 11:10 AM

Insulation inside or out? Inside will collect moisture. But either way, wood will also collect moisture from the air and I would expect a lot of mold issues. Commercial & residential ducting is either metal inside with insulation outside or semi-soft insulation ducting that is foil faced (waterproof) both sides.

Getting metal ductwork fabbed is cheap and can be made to almost any size/configuration but proper insulation is a must.

Side note:
I have probably a half mile of ducting here at my studio and have noticed that our adjustable metal exhaust grates condense and drip but the plastic ones do not.

mikeypj · 08-20-2018, 08:12 PM

Quote:

Originally Posted by JDOnTheGo

Yes and yes.

As noted, however; ceiling height is the issue. My A/C ducting is not complete so completely unproven. That said, I've constructed a 3/4" tall space between the 'top' of the ceiling panels and 'bottom' of the roof insulation. It is very wide with cold air using half of the ceiling width and return air the other half. My hope is that the cold and return air will flow sufficiently well thru this space. The duct 'volume' math works out ok but that is no guarantee. In all, it's cost me about 1" of headroom.

Mine is 6'5". i could drop the ceiling 3" and still have plenty of room..lol..im 5'7

mikeypj · 08-20-2018, 08:16 PM

Quote:

Originally Posted by Ronnie

Not sure he meant running the a/c off solar, just wants room for solar. At least think that is what he means.

I would be curious if anyone has measured wattage on a rooftop and measured wattage on a mini split of the same btu rating to see how they compare?

Not even going to try AC of solar..Not with AGM batteries and 400W of panels. Strictly genney only..

Ronnie · 08-20-2018, 08:45 PM

That's what I have, 400 watts of solar, and AGM batteries.

My two rooftops are not ducted. I find that I can run one and close all the air flaps except the rear one, in order to push the air all the way to the back of the bus. Just a thought that might save ducting. I do not have anything that would obstruct the air movement. If you do well then back to ducting.

mikeypj · 08-21-2018, 02:05 PM

Is anything smaller than a 13500 made for a rooftop unit?

PNW_Steve · 08-21-2018, 02:16 PM

9200 BTU Coleman:

Coleman Mach - Mach 8 Cub Low Profile Rooftop RV AC | Airxcel

o1marc · 08-21-2018, 02:36 PM

Quote:

Originally Posted by mikeypj

Is anything smaller than a 13500 made for a rooftop unit?

Are you looking for smaller size or less BTU? There's not a whole lot of difference in price between a 9200 and a 15000 in the same size package,

You may also like: