Where to put the outside A/C unit: S, W, E, or N?

[Dick in Wisconsin]

Our outside A/C unit (the condenser?) sits on the west side of our house; which gets wonderful direct sunlight in the warm afternoons. Would it work more efficiently if it was on the north side of the house in the shade?

Intuitively I would say "YES". Anyone aware of any analysis or studies done? Any science or engineering behind this?

 

[PelicanPines]

Mine (two)... are on the east... If I were to do it again... I would go west.

Two zones... I have air handlers on the east side of the house... and in the attic on the west side of the house.

I have a third zone but that's a split in my office.

FWIW... my house faces due South...

 

[dave89iroc]

if practical, I'd say yes, shade would be better than direct sunlight

 

[Biomed]

From the installers standpoint I'm sure it is purely economics - put it as close to the furnace to reduce the length of the line and reduce installation difficulty. It would also be much easier to run the line the same direction (parallel to) floor joists.

From a homeowner perspective you would not want it next to or below a bedroom window (although the newer units are much quieter.)

From an operational perspective it has to be better in a cooler location, generally on the north or east side. Mine's on the east and I would do it there again.

It will be interesting to see if anyone is aware of studies about this.

 

[nsula_country]

Both of ours is on the West side. Direct afternoon sun. I'm sure it increases the load some.

CT

 

[isb cornbinder]

When I went to HVAC trade school in the early 1960s, we were told that the north shade side is the best option. So, unless the sun comes up and sets differently in your neighborhood, than the rest of the northern hemisphere, north is the best option.
So, you might ask where our HVAC pump is located. It is in the shade on the north side of the house.

 

[Gila Monster]

I don't think there's really any question that all things being equal, a condenser in the shade is better than one that gets direct sunlight. How much so is probably harder to answer.

But for the sake of an anecdote, I have a unit on each side of my house, and the shaded one seems to really pull the temperature down faster.

 

[dogdog]

I don't think it is north east west or south thing.... Shade area is the best. The condenser might work better if no additional heat is shinning on it... There is a condenser fan so , It wouldn't matter... This is not like you are building a building where you can choose the windows and entrance facing directions.... that you can google passive cooling.

https://en.wikipedia.org/wiki/Passive_cooling

 

[Jinks]

North will be cooler. If it must stay on the west side plant a tree/shrub to shade it &/or put a fence & cover over it. Just leave room for ample air movement.

 

[zmaxmotorsports]

Roof top units sit in the sun for years.

 

[Zeke]

Roof top units sit in the sun for years.

True enough as mine does too. But I think the breeze up there helps a lot. Where would I place a condenser? Maybe study the breezes around the house before automatically placing it on the north side.

 

[Milton Shaw]

Is it a heat pump not just an air conditioner. In the case of a heat pump it would work better in the sun in winter. In Wisconsin you have more heat needs than air conditioning.

 

[bushmechanic]

You can build shade around the things. I'd just put it where it's least likely to get grimy.

In all the developments I've seen laid out, nobody has paid the first ounce of attention to where those units are positioned, beyond hiding them from view when driving by or just keeping them as close to associated equipment as possible.

It doesn't really matter as much as people would love to think, from a physics perspective; but "professionals" who've been to "read some science Cliff's Notes and then screw it together" school will try to beat it into your head that they can't have any grass in the fins, they must be placed in the shade, it's cheaper to buy a new one than repair a leak, and so on...

Nonsense.

The radiator itself is largely shielded from solar loading by that thin, louvered sheet metal cover, and that's more than enough. You're evacuating heat energy; not trying to freeze a beer under that fan.

You can't get it away from ambient temperature no matter how much shade you find; the ambient temperature under the shadow of your house is the same as the lawn beside it...

If you want it to work more efficiently, why not put it in an air conditioned room?

 

[yeldogt]

The unit is moving air -- I bet you will find that the air temp is very similar.

The molecules in air are not like a wall taking in the heat of the sun.

 

[JakeKohl]

while there is probably a little heat induction from the sun's rays into a condenser coil, the amount of heat gain into the cooling fins from the sunshine, when compared to the amount of heat they are actively transferring to the moving air, is very very little. The sun is hardly worth considering with regards to placement of the condenser. If it's easy to put it in the shade, choose shade...otherwise, it is not a big consideration. MUCH more important is clear and free airflow in and out of the unit.

 

[Denwood]

The ambient temp on the south side of a house, (including radiant heat from structure long after the sun has set) will affect the air temp differential across the coils. I would think higher temp differential correlates to efficiency.

We recently installed a Lennox 16 SEER (and quiet!) unit on our North exposure. The only downside I see to that so far is the slight extra work cleaning once a season. It's quiet at under 70 db.

 

[soob]

TLDR: http://fire.nist.gov/bfrlpubs/build00/PDF/b00051.pdf

I didn't actually read it closely but it seems to say that ambient temperature has a huge impact on the efficiency of the system -- an increase from 95 to 115 F costs you like 15% more electricity to get the same cooling in BTUs.

How much hotter is the air on the south side in the sun with that condenser fan blowing? I'm not sure.

 

[tyme2par4]

TLDR: http://fire.nist.gov/bfrlpubs/build00/PDF/b00051.pdf

I didn't actually read it closely but it seems to say that ambient temperature has a huge impact on the efficiency of the system -- an increase from 95 to 115 F costs you like 15% more electricity to get the same cooling in BTUs.

How much hotter is the air on the south side in the sun with that condenser fan blowing? I'm not sure.

It's basic thermodynamics. The efficiency is based off of the temperature difference between the hot refrigerant and the outside air. If the sun is heating up the outside unit, your temperature difference will decrease, and your efficiency follows.

 

[bushmechanic]

TLDR: http://fire.nist.gov/bfrlpubs/build00/PDF/b00051.pdf

I didn't actually read it closely but it seems to say that ambient temperature has a huge impact on the efficiency of the system -- an increase from 95 to 115 F costs you like 15% more electricity to get the same cooling in BTUs.

How much hotter is the air on the south side in the sun with that condenser fan blowing? I'm not sure.

That paper, while interesting and seemingly applicable, isn't aimed in this direction.

 

[slimcake]

Is it a heat pump not just an air conditioner. In the case of a heat pump it would work better in the sun in winter. In Wisconsin you have more heat needs than air conditioning.

This!! Just built a new house and put the unit on the west side. It is the greenspeed system from carrier and was thinking more about winter than summer.

 

[yeldogt]

Again -- it's air temp the unit is worried about. The human body senses radiant heat -- this heat can travel through the air and never heat said air. Like a burning fire in the evening outside. The air between you is not hot.

You can't take the temp of the air static -- you are taking a temp of the thermometer. When taking air temps you need a fan.

 

[Marctrees]

I Googled the importance of shade question quite a bit sometime ago.

Bottom line is, of course it helps, but apparently way less than one may guess.

I end up it's deciding worth doing, but no bigee if not.

Certainly also nice to keep drenching rain off, tree droppings, etc.

Just make sure you basically don't affect the airflow. Marc

 

[txst]

I design and test air conditioners for a living. The smallest amount of air stratification in a psychrometric room will affect the efficiency. If the sun is beating on your house, the sheet metal cabinet of the condenser, the concrete pad that the air conditioner sits on, any gravel around it, etc., the radiated heat will increase the ambient temperature around the unit and lower the efficiency. If you have a heat pump and live in an area where you have more heating hours, a good option is to put it on the South or West side with a large shade tree that drops it's leaves in the winter to allow the sun to hit it.

 

[Falcon67]

Same here - unit is on the west side, wall gets 130+ in the afternoon. AC use hasn't change since installing the new heat pump system, but heating has. But then, sometimes we're running the AC in January.

 

[DC73]

I design and test air conditioners for a living. The smallest amount of air stratification in a psychrometric room will affect the efficiency. If the sun is beating on your house, the sheet metal cabinet of the condenser, the concrete pad that the air conditioner sits on, any gravel around it, etc., the radiated heat will increase the ambient temperature around the unit and lower the efficiency.

This^^^.

Of course it helps to shade the condenser. As mentioned above, you can build shade but it's very important to not restrict free airflow. Build the shade at least 5 feet above the top of the unit. And keep at least 3' around the sides of the unit free and clear.

If you move the unit, make sure it will sit in the shade most of the day but especially in the mid to late afternoon. I'm in the northern part of Texas with a house that faces north. This time of year, the sun moves north and shines on the north side of my house. I would not want my unit on the north side. My unit is actually located in a corner and is both south and east of the house and is blocked from morning sun by the workshop. Perfect location for the most part.

It's also important to keep the outside unit clean. I hose mine down on a regular basis to get dust and grime off of the coils.

DC

 

[eddieK]

True enough as mine does too. But I think the breeze up there helps a lot. Where would I place a condenser? Maybe study the breezes around the house before automatically placing it on the north side.

Distance from the evap AND high voltage source is much more important than sun / shade. A condensing unit in the shade verses one in the sun under idyllic absolutely identical circumstances will release heat better, but there are so many factors involved in lowering op costs and amperage draw.

The first and foremost is proper air delivery and clean filters so that the indoor cool stays clean.

 

[yeldogt]

I design and test air conditioners for a living. The smallest amount of air stratification in a psychrometric room will affect the efficiency. If the sun is beating on your house, the sheet metal cabinet of the condenser, the concrete pad that the air conditioner sits on, any gravel around it, etc., the radiated heat will increase the ambient temperature around the unit and lower the efficiency. If you have a heat pump and live in an area where you have more heating hours, a good option is to put it on the South or West side with a large shade tree that drops it's leaves in the winter to allow the sun to hit it.

I remember reading an energy department study .. and the difference was minimal when the unit was properly positioned and getting free air.

What's the worst case situation?

 

[txst]

I remember reading an energy department study .. and the difference was minimal when the unit was properly positioned and getting free air.

What's the worst case situation?

It depends on the system. Manufacturers usually list the expanded ratings tables in their product data. I just pulled up a 13 SEER system and at 95F, the capacity was 34,400 BTUH at 3.13Kw, for an EER of 11.0. That same system at 105F has a capacity of 31,000 BTUH at 3.32Kw for an EER of 9.33. You can see the trend based on ambient temperatures. If you are thinking about a location, you can place a thermometer in different areas to find how much the temperature varies due to the surroundings.
It' true an AC does not "feel" the sun load, but it does see the effects of the sun heating up the surroundings. My brick home in Texas would radiate a significant amount of heat well after the sun went down after it baked all day in the hot sun. This definitely influences the system performance.

 

[eddieK]

It depends on the system. Manufacturers usually list the expanded ratings tables in their product data. I just pulled up a 13 SEER system and at 95F, the capacity was 34,400 BTUH at 3.13Kw, for an EER of 11.0. That same system at 105F has a capacity of 31,000 BTUH at 3.32Kw for an EER of 9.33. You can see the trend based on ambient temperatures. If you are thinking about a location, you can place a thermometer in different areas to find how much the temperature varies due to the surroundings.
It' true an AC does not "feel" the sun load, but it does see the effects of the sun heating up the surroundings. My brick home in Texas would radiate a significant amount of heat well after the sun went down after it baked all day in the hot sun. This definitely influences the system performance.

Not enough factors are considered. If a condenser is set a considerable distance from the evap...with several fittings to accomplish...or if setting it in "the shade" is a considerable distance from the main panel...high amp draw could lower EER.

Then there is the metering device...cap tube or piston will lower the EER verses a properly sized TXV.

And we have not even factored in proper air static...

 

[txst]

Not enough factors are considered. If a condenser is set a considerable distance from the evap...with several fittings to accomplish...or if setting it in "the shade" is a considerable distance from the main panel...high amp draw could lower EER.

Then there is the metering device...cap tube or piston will lower the EER verses a properly sized TXV.

And we have not even factored in proper air static...

True - the affect on installed efficiency is with all other things being equal. But, I would sacrifice a bit of lineset length to keep the OD unit in a cooler location, with the possible exception if that lineset is run in an attic. The distance to a main panel has little to do with power consumption, as power=volts x amps. While the current may be higher due to the voltage drop, the overall power is similar (though the installation cost may be higher). The other factors (airflow, metering device, etc) apply regardless of where the outdoor unit is located (unless there is a really long lineset).

 

[James-W]

I have mine located on the north side of the house under a shade tree. The HVAC installer said it was a good idea to have it shaded if possible, so that is where I put it. I prepared the area, placed the concrete pad, ran the power, got everything ready for the HVAC guy.

 

[eddieK]

True - the affect on installed efficiency is with all other things being equal. But, I would sacrifice a bit of lineset length to keep the OD unit in a cooler location, with the possible exception if that lineset is run in an attic. The distance to a main panel has little to do with power consumption, as power=volts x amps. While the current may be higher due to the voltage drop, the overall power is similar (though the installation cost may be higher). The other factors (airflow, metering device, etc) apply regardless of where the outdoor unit is located (unless there is a really long lineset).

The point is this...an installer does not locate an outdoor unit in a location based upon shade...many other factors apply.

I have been setting units on roofs for over 40 years... Sun is the least of my concerns when locating a unit. If it can be in shade, why not...but if that shade is a type of tree that creates tiny particles, this will wreak havoc clogging the condenser.