Community Forums

Gmdjeb · 06-02-2021, 05:30 PM

Greetings all,

I am surely no HVAC guy, but I was wondering if this is a feasible way to supplement cooling in my 2015 Jayco Greyhawk … the rooftop AC doesn’t help much above about 85 degrees outside temp.

I have a portable AC unit that I used to use in my home. It has a flexible exhaust hose that would vent the hot air out a window. (It is 120 VAC that worked fine on a 15 amp house circuit)

I am wondering if it is worth putting the AC unit on the floor between the driver/passenger seats in the cab. I would vent the hose out the driver or passenger window and fill the air gap with foam or other insulation.

I would continue to use windshield covers and aluminized covers at the windows inside the coach.

Is something like this worth trying? Has anyone tried it? Are there any hazards this might cause?

(Or are any readers rolling on the floor laughing, helpless with mirth, at my hopeless naivety?)

Thanks!

Regards,

JB

Arch Hoagland · 06-02-2021, 07:01 PM

The only problem I see is the draining the water from the bottom as it removes the moisture from the air.

AnotherMike · 06-02-2021, 07:38 PM

Here's my cut-and-paste regarding portable air conditioners. Note that I have an older front engine gasser MH, with the engine between the driver and co-pilot seats.

= = =
An air conditioner cools by taking air from the room, cools it, and returns it back into the room. It does the cooling by extracting the heat from the air passed through it and sending that heat outside using a fan.

That said, there are single hose units and dual hose units.

The single hose units have 3 ports. They draw a quantity of air from the space being cooled (port 1), passes it through the cooling unit and returns most of it to the room through the 2nd port. The rest of the input air is blown across the heat exchanger and sends the heated air to the outside through the exhaust hose (port 3).

The problem is that that the portion of the input air that was sent outside reduces the air pressure in the room... it creates a slight vacuum in the room... what some call negative pressure.

That negative pressure inside the coach draws warm outside air inside from any outside-to-inside air leak (like the skylight, bathroom exhaust fan, propane fridge vent, clothes dryer vent, over-the-stove vent, hot water heater door, etc... ).

A dual hose unit has 4 ports and doesn’t have to work nearly as hard as the single hose version since it does not create negative pressure - it is much more efficient. It draws air from the room (port 1), cools the air, and returns it to the room (port 2). It simultaneously takes in outside air through the intake hose (port 3), dumps the heat removed from the room air into that outside air, and sends the heated outside air back outside through the exhaust hose (port 4).

One thing you can do to really help it cool well is to insulate the exhaust hose. Since it is transporting heated air it heats up quite a bit - some get too hot to touch. Some units draw the room air in from the back side of the unit (port 1), so those units draw in air that was heated by the non-insulated exhaust hose.

I borrowed and used a single hose unit the first summer after I got my MH. In my coach the negative pressure situation caused the outside warm air to come in mostly through the heater and dash air conditioning ducts, a little from the shower skylight / vent and some from around the air stack behind and around the propane refrigerator. After I replaced the vacuum hoses on the dash HVAC assembly the airflow through the heater and dash air conditioning ducts was blocked, and I discovered airflow around the water heater, and a can of spray-foam fixed that. The final fix was to purchase a slightly used dual hose unit on Craigslist.

Another thing that helps is to position the two hoses so that the intake hose does not collect any of the hot air being ejected from the exhaust hose. On my RV I made up wooden panels that clamp in the drivers side and passenger side windows using pool noodles that I slit with a bread knife and fitted over the top of the glass edges. The intake hose goes to the wood panel on one side of the RV, and the exhaust goes to the other side (if there is a breeze I position the exhaust hose downwind). The unit sits in between the front seats next to the engine cover.

More info: https: // learn.allergyandair.com/portable-air-single-hose-vs-dual-hose/

Note that any portable air conditioner is going to have a condensate (water) collection tank. Most have a full-tank shutoff switch. Some units can have a condensate hose connected, some can be modified to have a hose.... and it's best to not to have the hose dump the condensate into a sink as you can fill your grey tank remarkable quickly... best to run the condensate hose outside into a grassy area. I ran the dump hose through a crack around the engine cover and into the planter next to the RV concrete pad.
= = =

Mike

jjrbus · 06-03-2021, 05:17 AM

I have seen good roof air replaced because the coils were filthy. If not done yet a thorough cleaning of the evaporator and condenser coils should be done. Requires going on roof and disassembling unit. Go to you tube and look at cleaning roof air videos.

tap4154 · 06-06-2021, 10:27 AM

Not all portable air conditioners need to be drained. I've had a Hisense unit for about five years in my family room, and it has an evaporation system, and never needs to be drained.

By the way the point about insulating the hose is very important. The way mine is arranged the hose is behind the unit where it draws the air in, and it was drawing in hot air radiating off the thin exhaust hose. I bought an insulating sleeve from a company called Coolaide and it made a huge difference in how well it cools. And the point that they create a vacuum is true. It's not as noticeable in a home, but in a smaller enclosed unit like an RV it will try to draw in air from the outside. In fact it might be good just to crack open a roof vent a little bit. In fact your forward vent would probably be the best one to open if you're going to put the unit in your cab area. However I still think you're going to benefit greatly from it.

I have no experience with the two hose units, but assume they're more expensive. They also come with a window kit, that you probably could adapt to vent it out your side window.

Cat · 06-08-2021, 10:23 PM

Used a two hose portable in a 38' mh in Southern Az for several years worked great, it also did not need to be drained. I don't believe it was much more expensive than single hose. Consumer reports ran tests on single hose versus two hose. The two hose was much more efficient.

katanajo · 06-11-2021, 09:24 PM

I came to the blog tonight as we are camping and it is 95+, no breeze, all sun and no rain in sight. Our Class C is a 30amp. Went to find a portable air conditioner as our top unit cannot keep up. There is nothing wrong with our unit, we just got bad spot of full sun and an odd heat wave. Everything sold out. had to settle for one unit I could find. Honeywell 10k BTU. It is bad. BAD. It can't keep the living area cool in a 34ft coach. Have had it running 64 degrees full blast since 3pm, it is 10:30 and am turning it off to use the top unit (still 89 degrees out). Going to buy a cheap window unit and build a frame. For now, we'll be sitting outside with fans on us.