central air / shade question

[ronin_01r1]

i need your advice if you know anything about central air units.

my dad says it's better to keep the central air unit in the shade, that it will work more efficiently, use less electricity. so his idea was to build basically a large 4 legged table over the central air unit. there's roughly 2 feet of clearance between the top of central air and the table top. i think this thing is blocking the hot air from venting freely up and away from the central air.

i'm thinking i should make an appointment with the ac guy to do an annual check over the system and let me know if this 'table shade' is good or bad idea.

what do you think?

[High_Revs_17]

Agreed, the fan unit outside is used to cool the compressor unit just like a radiator functions on a bike, I don't think covering the unit will do anything to conserve electricity, the only time I've seen those covered is during the winter months when they aren't functional.

A properly serviced unit will cool much better during the summer, and adequate wall insulation and double layered windows help keep energy costs down. If you're about to spend thousands of dollars servicing this unit for whatever reason you might as well look into getting the entire system replaced if it's very old, it'll pay for itself after a few years in climate conditioning costs.

i think this thing is blocking the hot air from venting freely up and away from the central air.

[RCM78]

I'm an HVAC tech. Been doing it for just under 20 years.

Placing anything over the condensing unit will cause the hot discharge air to recirculate back through the condenser causing the unit to run hot and use MORE electricity. It could also cause compressor damage from the excessive heat and freon pressure.(Think of it like how much harder the human heart has to work against high blood pressure.) The warmer the condenser the higher the freon pressure goes.

The best thing you can do is have the unit serviced and make sure the condenser coil and indoor air filter is clean. That is the best way to maintain unit capacity and efficiency.

[RCM78]

If you're about to spend thousands of dollars servicing this unit for whatever reason you might as well look into getting the entire system replaced if it's very old, it'll pay for itself after a few years in climate conditioning costs.

You were doing ok until this point.

It doesnt cost thousands of dollars to service an A/C unit. If the unit is working fine and doesnt require any parts or refrigerant it shouldn't cost more then $200 for a spring startup.

Also, in most cases it takes about the lifetime of the new unit to pay for itself. Not a couple of years. In most cases it's not cost effective to replace the unit unless it needs to be replaced.

I would only recomend a replacement if the unit was losing a large amount of refrigerant every year, if the compressor failed, if the evaporator coil drain pan rotted, or if the heat exchanger failed in the furnace(provided the heating system was forced warm air.)

[ronin_01r1]

I'm an HVAC tech. Been doing it for just under 20 years.

Placing anything over the condensing unit will cause the hot discharge air to recirculate back through the condenser causing the unit to run hot and use MORE electricity. It could also cause compressor damage from the excessive heat and freon pressure.(Think of it like how much harder the human heart has to work against high blood pressure.) The warmer the condenser the higher the freon pressure goes.

The best thing you can do is have the unit serviced and make sure the condenser coil and indoor air filter is clean. That is the best way to maintain unit capacity and efficiency.


thanks for the advice. i removed the shade cover. i didn't think all that deflected hot air was going to be good for the unit..

the unit is 2 years old. do you recommend an annual inspection/service/spring start up?

[RCM78]

No not anually. Every two to three years is fine.

Honestly the only thing that needs to be done to the outdoor unit is cleaning the condenser. The condensate line inside should be cleared too. Other then that they are pretty maintenance free.

[ronin_01r1]

Ok, thanks a lot!

[Islandmon]

You were doing ok until this point.

It doesnt cost thousands of dollars to service an A/C unit. If the unit is working fine and doesnt require any parts or refrigerant it shouldn't cost more then $200 for a spring startup.

Also, in most cases it takes about the lifetime of the new unit to pay for itself. Not a couple of years. In most cases it's not cost effective to replace the unit unless it needs to be replaced.

I would only recomend a replacement if the unit was losing a large amount of refrigerant every year, if the compressor failed, if the evaporator coil drain pan rotted, or if the heat exchanger failed in the furnace(provided the heating system was forced warm air.)


On this case and point how about a 38 yr old unit. Seems to be running OK. It kept the house at 76 degrees but couldn't get it to 74 during the afternoon. Should I call the home warranty and have their service come check it out? Or does that sound fairly normal for a 96 degree day?
Or.....hint hint how to make it explde so the the warranty will replace it...HEHE

[RCM78]

On this case and point how about a 38 yr old unit. Seems to be running OK. It kept the house at 76 degrees but couldn't get it to 74 during the afternoon. Should I call the home warranty and have their service come check it out? Or does that sound fairly normal for a 96 degree day?
Or.....hint hint how to make it explde so the the warranty will replace it...HEHE

A properly sized and designed central air conditioner should be able to maintain up to 20 deg F below the outdoor temp. So in your case I'd say the unit is working to it's full potential. These last few days have been rediculously hot.

The problem with home warranty co's is when they replace stuff like heating and A/C equipment they use the cheapest shit they can buy and slap it in. Usually five years down the road the new unit is having problems allready.

38yrs old is way past due. Id recomend an upgrade in your case.

[Islandmon]

We figured its overdue. We just bought the house this yr. I figure we're going to need 5 g for a new one.. Maybe next yr. My fear is what the electric bill will be due to the A/C :(

[John712]

I would only recomend a replacement if the unit was losing a large amount of refrigerant every year, if the compressor failed, if the evaporator coil drain pan rotted, or if the heat exchanger failed in the furnace(provided the heating system was forced warm air.)

FACK!!! I just found this out today with mine, I need an entire replacement.

[FigNewTon]

Thanks for all the info RCM. My unit has been working pretty well (knock on wood) but I had a few similar questions you have cleared up.

[JimRBlue]

What's the average cost in converting a forced hot air (gas) to central air / combination unit? I know that there is no exact formula, but in a few years time I would like to convert the present system which is pretty old and only has heat.

[Cakes206]

They got sprinklers sprayin water on the units here at work lol.

[IrocRob]

They got sprinklers sprayin water on the units here at work lol.

Ralph - do you know how much of an efficiency improvement you can get
out of a water cooled unit? And are they available at the household level
or is this idea still only used for commercial units?

I may just resort to a sprinkler that switches on with the outdoor unit.....:lol:

[RCM78]

Ralph - do you know how much of an efficiency improvement you can get
out of a water cooled unit? And are they available at the household level
or is this idea still only used for commercial units?

I may just resort to a sprinkler that switches on with the outdoor unit.....:lol:


Water cooled unit's or Chillers are strictly large industrial commercial units. They usually start around 100 tons and go way up from there.

If you have the land you can look into geothermal technology but the initial cost usually scares people away.

[RCM78]

They got sprinklers sprayin water on the units here at work lol.


Sometimes ya gotta do what ya gotta do!!! If the condenser is on the roof and the roof is black it doesnt have a shot in temps over 95 deg.

Water has much better heat transfer capability then air so spraying water on an air cooled condenser "effectively" makes the surface area of the condenser bigger. But there is a drawback. Your also cooling the refrigerant (and lowering the temperature) alot more then it should be and that can cause the evaporator to freeze.

[RCM78]

What's the average cost in converting a forced hot air (gas) to central air / combination unit? I know that there is no exact formula, but in a few years time I would like to convert the present system which is pretty old and only has heat.

Hard to say Jim. I just installed a complete system in my uncles house. The brand was Trane (my favorite) and all the material cost him $3500. If a trane dealer did the job it would've been $7000 easy.

I installed a two stage 80% efficient gas furnace with a variable speed blower and a 15 seer 3-ton Air Conditioner.

This is the setup I would recomend for an older home that wasnt built with A/C in mind. The variable speed blower will regulate itself to compensate for the undersized ductwork you find in heating only applications.

[Marker54]

my dad says it's better to keep the central air unit in the shade,

So now we know that building a table or something to block the sun isn't a good idea...but was his thought process accurate?

Lets just say you were putting in a new system...would it be smarter to put it on the side of the house that gets the most shade...or the side that's easiest for installation? Or does it really not matter?

[High_Revs_17]

Engine Ice or Water Wetter?

They got sprinklers sprayin water on the units here at work lol.

[RCM78]

So now we know that building a table or something to block the sun isn't a good idea...but was his thought process accurate?

Lets just say you were putting in a new system...would it be smarter to put it on the side of the house that gets the most shade...or the side that's easiest for installation? Or does it really not matter?

If the choice was practical I would locate the outdoor unit where it would be in the shade the longest.

[JimRBlue]

Thanks sir.. Perhaps down the road I will have to give you a ring.

[ronin_01r1]

So now we know that building a table or something to block the sun isn't a good idea...but was his thought process accurate?

Lets just say you were putting in a new system...would it be smarter to put it on the side of the house that gets the most shade...or the side that's easiest for installation? Or does it really not matter?

so i got a call back from my ac/heat guy. he said any cover should be at least 5-6 feet above the fan.

i've read that planting trees for shade is effective also.

[CBRBob]

But you don't want leaves to get sucked onto the unit, that will keep airflow down. Simple house shad works best.

[RCM78]

so i got a call back from my ac/heat guy. he said any cover should be at least 5-6 feet above the fan.

i've read that planting trees for shade is effective also.

Most manufacturers recomend 8'. But I dont like to see anything above the condensing unit.

[John712]

I got mine in the open sun and still works fine, well although it was just filled, But PS came today and need a new 2 1/2 ton 150,000 BTU. and you do not want to know the price for a york!!!

[JimRBlue]

It ain't cheap staying cool in the heat..

[RCM78]

I got mine in the open sun and still works fine, well although it was just filled, But PS came today and need a new 2 1/2 ton 150,000 BTU. and you do not want to know the price for a york!!!

Sent you a PM...