Does positioning of a portable A/C matter?

So, this is our first Summer in the new place.

The living area is basically one huge square, with an old back porch that has been closed off & glassed in... the house is oriented such that the back porch cops the brunt of the sun all day. While this does a wonderful job of pre-heating the place in Winter, it appears that no-one told the sun-room it could take the Summer months off. :rolleyes:

Sadly, the original back wall has been largely removed, which gives us a lovely view from the kitchen and lounge but... well... we can't close it off from the rest of the house.

It has just topped 40°C outside and in front of my 'puta it's currently sitting at 29, held there by an ooooold portable split A/C. The kind where the other half sits outside, with heavy gauge flexible piping connecting the two units through a window. Needless to say, this old gal is working hard.

Without the A/C running, measuring in the sun-room showed little difference to exterior temps, while measuring on the opposite, shaded side of the living area 'twas only 31°C

So... I'm curious... would positioning and orientation of the AC make any real difference - whether in efficiency, economy or practicality?

ie. At the moment it's positioned where the old back wall was, pulling in the 40°C air from the sun-room, dropping it a few degrees and pumping it into the living area.

Would there be any discernible difference if I turned it around, pulling in the cooler air from the living area and pumping that into the hot box?

Doing so would mean the A/C would not have to work so hard so help it to be more efficient

Yeah, that's sorta what I'm thinking.

I may try taking empirical measurements both ways over the rest of the week, which promises more of the same. It won't be a clinical study, but should give me a ballpark assessment.

Some shade over the windows on the outside of the sunroom will also assist. Canvas blinds, shade sails or shade cloth could all make a difference.

The only refrig portables I am familiar with are all in one type units with a large bore flex tube that is supposed to exhaust outside. These units have the condenser unit and evaporator unit in the same housing. Room air is drawn in by the fan and passed through the the condenser to cool the refrigerant, then passed through the discharge tube to the outside. However the air used in the condenser phase just described needs to be replaced with air that ultimately has to come from outside, normally at outside temperature, so these portables are not particularly efficient.

I am not sure whether the system you are describing, with an external condenser and internal unit runs refrigerant in flex tubes through the the flex hose to an evaporator in the internal unit, or is effectively an all in one unit outside (condenser and evaporator in a single unit) that then ducts the cooled air from the evaporator unit through the flex hose to the point of use. Either should be able to approach the efficiency of a wall mount unit of similar age, but a unit ducting the air through the flex tube would be at a disadvantage because of the difficulty of insulating the air passage in the tube, allowing a couple of degrees temp rise in the air on it's path to the outlet.

Either way, any particular design can produce a certain amount of chilled air at a certain difference between ambient and outlet temperature. If the unit operates at a lower ambient temperature, the achievable chilled outlet temp should be correspondingly lower. However, ultimately the chilled outlet air has to mix with the air in the room it is being fed into, and the proportions of room volume and chilled air being introduced will determine the temperature in the room. A suitably sized fixed split system won't chill a room immediately after being turned on, but will reduce the temperature progressively until it reaches the thermostat setting, and then runs intermittently rather than continuously to maintain that setting. In your case, I suspect that a portable probably won't have the capacity to overcome the solar gain of the sunroom, and a solution like external blinds and or insulation might be needed to control the solar gain.

I've bought some of this monster roll of shade cloth: https://www.kogan.com/au/buy/30m-sha...ome-furniture/

Using an ordinary sewing machine and UV thread https://www.ebay.com.au/itm/Bonded-P...s/151944145942

And used it to make covers for my walls, sides of the studio, the "greenhouse" and outside sitting areas.

It doesn't need to be the quality of a shade sail, but it sure does cut the heat from the direct sun! I was thinking of making it up into frames, or on rolls so it can be put up as a temporary solution while it's H.A.F.

Why aren't roofs covered with these kinds of monster shades?????

You should approach things logically. Refrigeration (Portable A/C) works by transferring the heat from one area to another. The cooler the environment where the heat exchanger coils are the more efficient the A/C will be. Shade and good air circulation around the heat exchanger coils is better that allowing the unit sit in direct sun light.

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Originally Posted by Skew ChiDAMN!!

So... I'm curious... would positioning and orientation of the AC make any real difference - whether in efficiency, economy or practicality?

ie. At the moment it's positioned where the old back wall was, pulling in the 40°C air from the sun-room, dropping it a few degrees and pumping it into the living area.

Would there be any discernible difference if I turned it around, pulling in the cooler air from the living area and pumping that into the hot box?

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I know it's somewhat counter intuitive, but air con works buy "burning" electricity to chill the air. The "burnt" electricity is waste heat and unless vented to the outside air will add to the hot air already inside the house.

Others have suggested shading the sun facing windows -- this is a must to my mind.
then you need to dump the waste heat from the unit outside. Best location would be on a south (or east) facing wall.

Another thing that can help is to replace the existing flex hose with insulated HVAC hose like this: https://www.ebay.com.au/itm/100MM-X-...4383.l4275.c10

I should've mentioned: this is a rental.

I looked into awnings and sail cloth early on, 'twas obvious this would be a problem and I couldn't see why it hadn't already been done given the age of the house. But after a few months it soon became apparent that they wouldn't last; we're on a mountain side and that side of the house also cops the occasional gale-force gusts. Many's the time Ma Nature has rearranged my firewood pile for me.

The unit is a true split system; the condensor hangs outside the window and is connected to the internal unit (evap) by flexible piping that carries the refrigerant. With it's age and the fact that it's "portable" (Heh. Strictly in the sense that it can be moved around, albeit with a bit more effort than I'd like.) I'm constantly surprised the piping hasn't suffered fatigue or leaks. They don't make 'em like this any more.

Stupidly, I hadn't given consideration to where the condensor is sitting though. Thanks for pointing it out, fellas!

It's actually hanging from a window in the sun-room... getting blasted by the sun. I'll have to look at moving the whole system to t'other side of the house, where it's better protected. That's going to mean a bit of cheating; I'm not allowed to modify the windows (rental) and they have permanently fixed flyscreens on that side, requiring the panes to be lifted out internally for cleaning. (I know, I know. Silly idea, but that's what's there. :oo:)

But I should be able to slice a flap in the flyscreen to fit the condenser body through, provided I either replace the screen or stitch it properly once the unit is removed.

Obviously I'd rather make sure that this is where I want to place it before I commit.

Thanks again, fellas. It's all food for thought. :think:

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Originally Posted by Skew ChiDAMN!!

I should've mentioned: this is a rental.

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Being a rental doesn't stop you from installing curtains.
While nowhere near as effective as external shading, heavy curtains will cut down on the thermal load inside the house.

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Originally Posted by ian

Being a rental doesn't stop you from installing curtains.
While nowhere near as effective as external shading, heavy curtains will cut down on the thermal load inside the house.

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:yes: Curtains are already in place. They were the first things we fitted, in Winter, to retain heat as we rely on wood heating and snow isn't an unusual sight here either; we get to experience the joys of both ends of the bell curve.

After a couple of hours in the sun, though, they quickly become radiators.

FWIW, the place is fully insulated; 'tis not a shonky build, in case I mistakenly gave that impression. :-

If I owned the place it'd be a toss-up between double-glazing or a sheltered deck on the North side, probably the latter.

You can, at some reasonable expense, do a quite good "temporary" double glazing solution. Glider put me on to this idea. The windows can be overlaid with sheets of perspex (actually acrylic), either inside or out, and screwed into place. Maybe individual sheets for each window or whatever works for the property and the widow configurations.

Acrylic ain't cheap, but neither is energy. I reckon 3mm would be sufficient because rather than the acrylic being an insulation as such, you are just trying to stop the modified temp air contacting the outer sheet.

Indeed you could have tinted acrylic on that window for summer and change to clear for winter.

Could you install a reflective foil onto the windows?

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Originally Posted by Skew ChiDAMN!!

FWIW, the place is fully insulated; 'tis not a shonky build, in case I mistakenly gave that impression. :-

If I owned the place it'd be a toss-up between double-glazing or a sheltered deck on the North side, probably the latter.

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must admit that when I coupled "rental" with "Oberon" and "large shed" plus the view I'd previously seen of your back (or was it front?) yard in winter, I assumed you lived in an older farmhouse