How can I help my AC unit?

[ItBurnsWhenIPee]

Okay...I've got a (roughly) 30x30 insulated steel building/shop. The center of the ceiling is around 13' high, and it's about 9-10 feet tall on the sides. I don't know the r-value of the insulation, but I'm sure it's not all that high. Both the man door and the overhead door are insulated as well. Other than that...It's just a concrete cave with tools and benches and whatnot. Oh...And a car that resides there

It's been over 100 degrees outside lately, with some fairly impressive humidity to boot...So I hopped on the old Craigslist and got myself a used but in good condition 20k BTU window unit and stabbed it into the one window I've got. I'd have gone bigger, but no decent ones popped up while I was looking. Ah well...When this one dies I'll get a bigger one.

Now, it works...But it's working HARD to get the temps down to 80 in there. So here's my question: Aside from buying more BTU's of cooling power, is there any way to help this thing out to cool it down?

Additional insulation is pretty much out of the question, as is relocating the unit to a higher location for the time being (I'm still planning/installing all the equipment in the shop and I don't know what walls are going to have shelves up high yet).

An exhaust vent up top for the hot air to get pushed out maybe? Wouldn't I need an inlet fan as well for that to work at all?

Lemme have it

 

[ItBurnsWhenIPee]

I just went out and measured. It's 26' x 30' and the ceiling (in the center) is 12' 6".

 

[ddrewyor]

I have read that if you mist the condensor with cool water the heat transfer is better and the unit runs more efficiently and cooler. Never tried it but the actually make kits to do this for central air. Might be worth a shot to mist the condensor on the unit and see what you get. Take care

Dave

Here is a link to a site for a mister:
http://www.coolnsave.com/index.php/How-Does-it-Work.html
________
Honda XLV750R

 

[Jaguar Fan]

maybe add a stand-alone dehumidifier?

 

[rinny_tin_tin]

Okay...I've got a (roughly) 30x30 insulated steel building/shop. The center of the ceiling is around 13' high, and it's about 9-10 feet tall on the sides. I don't know the r-value of the insulation, but I'm sure it's not all that high. Both the man door and the overhead door are insulated as well. Other than that...It's just a concrete cave with tools and benches and whatnot. Oh...And a car that resides there

It's been over 100 degrees outside lately, with some fairly impressive humidity to boot...So I hopped on the old Craigslist and got myself a used but in good condition 20k BTU window unit and stabbed it into the one window I've got. I'd have gone bigger, but no decent ones popped up while I was looking. Ah well...When this one dies I'll get a bigger one.

Now, it works...But it's working HARD to get the temps down to 80 in there. So here's my question: Aside from buying more BTU's of cooling power, is there any way to help this thing out to cool it down?

Additional insulation is pretty much out of the question, as is relocating the unit to a higher location for the time being (I'm still planning/installing all the equipment in the shop and I don't know what walls are going to have shelves up high yet).

An exhaust vent up top for the hot air to get pushed out maybe? Wouldn't I need an inlet fan as well for that to work at all?

Lemme have it

Minimize effects of IR from directed Sun using insulation & trees
Use polarizing film on glass
Use heavy blockinn shades on windows
Seal holes, Wrap, Insulate
Use ceiling fans in conjunction with AC
Use rafter exhaust fan to dump hot air
Move to Duluth........

Even with all above (cept maybe moving to Duluth) you are still looking at a min of a 3 ton unit versus the 1-2/3 ton unit you have now.

 

[ItBurnsWhenIPee]

maybe add a stand-alone dehumidifier?

It seems to be taking care of the humidity fairly well. But that's just evaporating sweat talking.

As for the misting system...That would require running water lines 75'. lol...I'd rather not.

 

[ItBurnsWhenIPee]

Minimize effects of IR from directed Sun using insulation & trees see picture
Use polarizing film on glass Already done.
Use heavy blockinn shades on windows Only one window, and it's blacked out (and has the AC unit in it).
Seal holes, Wrap, Insulate done
Use ceiling fans in conjunction with AC I'm using a couple of box fans right now, but this is something I'll likely do.
Use rafter exhaust fan to dump hot air do I need an inlet fan to keep the pressure constant for this?
Move to Duluth........Wife said "no" :'(

Even with all above (cept maybe moving to Duluth) you are still looking at a min of a 3 ton unit versus the 1-2/3 ton unit you have now.

I know that I don't have quite enough AC, and if this unit holds together for the year, I'll probably just buy another used unit (20k btu or better) this winter and install it as well.

Here's the entrance...I've got lots of trees

 

[rinny_tin_tin]

I know that I don't have quite enough AC, and if this unit holds together for the year, I'll probably just buy another used unit (20k btu or better) this winter and install it as well.

Here's the entrance...I've got lots of trees

Great work. Trees can make a big difference, and your unit, although undersized, can take the edge off the discomfort, inasmuch as you can't hang meat. Other things to consider is proper clothing--sandals allow you to cool off much much better than socks with shoes - however, if you are working with things that can drop on your feet....

Shut off heat producing equipment, unnecessary lights, computers, etc

Another item to consider is the supplemental use of a dehumidifier with your AC - as in general, although deH's do raise the temperature an average of 4 degrees F, they knock out the humidity and can make it more comfortable overall - however -- your electric bill is another matter!

But...good work ..it looks like you are at the reasonable edge of your maximum capability curve given your circumstance!

 

[ItBurnsWhenIPee]

I'm going to really test it this weekend. There will be 1/2 dozen guys in there, and we'll be installing all the lights, outlets, etc. If it can keep us from heatstroke for the entire day, I'll be happy with it not being a meat locker.

This year anyway. I'm constantly watching for a good deal on a full HVAC system to slap on there.

And I'm not really concerned with power consumption. I don't mind paying to play

 

[ItBurnsWhenIPee]

Thanks for the help, and if anybody has any ideas, feel free to post up.

I'll update this thread as I go along in the future to let everybody know how it works out.

 

[Kevin54]

Block any windows and let the air run on high all night when the temps drop and the sun is down. By morning it should be fairly cool in there. As long as the large doors is kept shut, and windows still blocked from sun coming in, it should be late afternoon before it really gets to heating up again where it is unbearable.

 

[rsanter]

you either need a bigger unit or to reduce your heat heat gain

if the sun hits the AC unit, you can shate it but dont restrict the airflow.

you can put more insulation in the atic
you can vent the atic space
you can put a coolroof coating on the roof
you can install a second small AC unit to act as a booster

bob

 

[Vicegrip]

Water spraying the condenser works. Put a set of gauges on and you can watch the head pressures drop like a rock when the spray is on.

Get 100 feet of 3/8 plastic tubing, a connector that lets you hook it up to your garden hose and a plug for the other end. Run the 75 feet to the condensing unit and wrap the rest around the condenser zip tying it to the metal cover. As you wrap the tubing poke it full of holes with a needle with the holes pointing inward towards the condenser.
Turn on hose and tweek for a spray that lets some but not tons of water run out the bottom while the unti is running. Add pin holes any whre the condenser is not getting spray

Fancy version... add a icemaker solenoid valve wired into the compressor contactor to turn the water off when the unit goes off.

Super lazy version to see if it works. Run a sprinkler at the condenser and check output air temps before and after 20 min or so.

 

[ItBurnsWhenIPee]

Water spraying the condenser works. Put a set of gauges on and you can watch the head pressures drop like a rock when the spray is on.

Get 100 feet of 3/8 plastic tubing, a connector that lets you hook it up to your garden hose and a plug for the other end. Run the 75 feet to the condensing unit and wrap the rest around the condenser zip tying it to the metal cover. As you wrap the tubing poke it full of holes with a needle with the holes pointing inward towards the condenser.
Turn on hose and tweek for a spray that lets some but not tons of water run out the bottom while the unti is running. Add pin holes any whre the condenser is not getting spray

Fancy version... add a icemaker solenoid valve wired into the compressor contactor to turn the water off when the unit goes off.

Super lazy version to see if it works. Run a sprinkler at the condenser and check output air temps before and after 20 min or so.

lol...I like the lazy version.

 

[malodin]

we have an even smaller one in our house window and sometimes it does only heat our living room bout 12x12 or so, if i hook up a small fan under it or infront of it it heats up our tipout as well, so maybe just a smaller circulating fan to help "push" the cold air away from the a/c unit. it works for us it might help a little, i would think you dont want to put to big of a fan infront of it other wise you will just push more hot air rather than the cool air.

 

[ironman2424]

have you checked to see how many amps it's pulling? it may be low on freon or may have to much in it and the only real way to tell it by the amps it draws. high ampreage = high freon and low amps = low freon. this can really make a unit overwork itself in a hurry. and cooling effeicincy will suffer. also try putting a box fan or fan with a stand in front of it, this will help some. just don't block the hot air being sucked in the front to much. i have a small box fan in front of mine and it helps force the cold air out further into my shop. seems to do a better job of cooling with the fan in front.

 

[Bailey]

have you checked to see how many amps it's pulling? it may be low on freon or may have to much in it and the only real way to tell it by the amps it draws. high ampreage = high freon and low amps = low freon. this can really make a unit overwork itself in a hurry. and cooling effeicincy will suffer.

You bought it used. High amps is high pressure.High pressure is overcharge or much more common dirty condenser.Small units are usually sealed and are low on charge if anything.

 

[ItBurnsWhenIPee]

have you checked to see how many amps it's pulling? it may be low on freon or may have to much in it and the only real way to tell it by the amps it draws. high ampreage = high freon and low amps = low freon. this can really make a unit overwork itself in a hurry. and cooling effeicincy will suffer. also try putting a box fan or fan with a stand in front of it, this will help some. just don't block the hot air being sucked in the front to much. i have a small box fan in front of mine and it helps force the cold air out further into my shop. seems to do a better job of cooling with the fan in front.

I've not checked the amps. I probably never will either. It pumps out super cold air, so it's in good working condition as far as I'm concerned. It's simply a bit too small for the cubic feet I'm cooling. I knew that going in. It was cheap and 3 miles away from me...No brainer.

This past weekend, I had 3 guys in there messing around working on stuff and drinking a few brews...It was 105 outside with pretty high humidity to boot. It kept the place well under 80 the whole time (got as low as 72 for a while there!). That's good enough for me! I guess that I just needed to move stuff out of it's way for it to work properly (I'd had many large stacks of stuff stored in there that were probably slowing the cooling process).

I put a box fan blowing perpendicular to the output to help move the air around the shop better and got the whole place organized...Worked great.


I may install a second one later...or just a bigger one. But for now...I'm a happy and cool camper!

My only questions at this point is really whether or not an exhaust fan up high will help and whether or not I'd need an inlet fan elsewhere to make that work properly.

Thanks for all the input and advice folks. This place is great

 

[woodyJ]

You may be losing your cool air somewhere and the building may be absorbing the sun heat due to it's color. Something to think about. Get a Raytek infrared temperature detector gun $45-80 and use it to locate hot spots in your building. I thought about draping a canvas screen down from the eaves of my house to block the summer sun from heating up the walls. I already have a white roofing. I am also considering painting the southside of my house flat black to absorbe the sun's heat in the winter.

 

[Jaguar Fan]

I don't know anyone who has put a mister on the condenser, but I have a concern. If you have very hard water, my concern is you could end up with quite a bit of mineral build-up in a short time which in turn could reduce the effectiveness of the A/C.

Just a concern -- I don't have any practical experience with this -- perhaps someone else has real-world experience & can say my concern isn't a real-world problem.

 

[ItBurnsWhenIPee]

You may be losing your cool air somewhere and the building may be absorbing the sun heat due to it's color. Something to think about. Get a Raytek infrared temperature detector gun $45-80 and use it to locate hot spots in your building. I thought about draping a canvas screen down from the eaves of my house to block the summer sun from heating up the walls. I already have a white roofing. I am also considering painting the southside of my house flat black to absorbe the sun's heat in the winter.

I've got a temp-gun, and there aren't many "hot" spots. It's a pretty tight building. It's also already pretty light colored. I'm not painting it, and I'm not hanging stuff. I'll buy more AC power though

I don't know anyone who has put a mister on the condenser, but I have a concern. If you have very hard water, my concern is you could end up with quite a bit of mineral build-up in a short time which in turn could reduce the effectiveness of the A/C.

Just a concern -- I don't have any practical experience with this -- perhaps someone else has real-world experience & can say my concern isn't a real-world problem.

Yeah...I've got a well, and I don't have a softener. I'll be putting new heating elements in my hot water tank every year or two...So yeah...I don't see me spraying it either.

 

[bgarrett]

consider using earth tubes modified to your likes

http://www.mb-soft.com/solar/saving.html

 

[ItBurnsWhenIPee]

consider using earth tubes modified to your likes

http://www.mb-soft.com/solar/saving.html

What a horrible, HORRIBLE web page.

Great little system/plan they've got going on there. But they really need a lesson or two in non-headache inducing web design.

 

[tcianci]

The exhaust venting or anything else you can do to get the attic temperature closer to the ambient will help a lot. The best answer as you know is to have a properly sized unit for the heat load of your building. As far as misting the condenser goes, this is commonly done in window units these days but the water source is the condensate itself, it's free, cold, and is distilled so there is no mineral content. The units that I am familiar with use a ring-shrouded condenser fan that dips into a tray in the bottom of the unit and flings the cold water onto the condenser coil, the excess runs out of a drain hole. I think that cooling the condenser will probably not hurt but it may not really change things either, the unit was designed to provide adequate condensation of the refrigerant already. You may make it slightly more energy efficient. Have you considered just hanging a sliding curtain across a section of the shop that you want to keep cool. you effectively drop the square footage you are trying to cool. Don't worry about the top, cold air falls. You don't really need an input fan to vent the attic, your attic should be passively vented, air introduced at the eaves through soffit vents and exhausted through the ridge or gables. The air moves by convection.

 

[Coach James]

consider using earth tubes modified to your likes

http://www.mb-soft.com/solar/saving.html

I went to the website but my eyes started to burn from the layout. I'll take another look later. Thanks for posting it. Looks like interesting material, just painful to read.

Coach

 

[Doug I]

Get a spray can of coil cleaner. The radiator may look clean - but I sprayed down a clean unit and the got gray/black water off it when I rinsed it. Worth a shot

We've been using a dehumidifier in the house. We get about a gallon a day of water in it. That's water the central unit hasn't had to cool. It really makes a difference. Right now it's 107 outside at 55%, inside it's 76 at 30% - and it feels goooooooood. Even 80 feels comfortable when the humidity is down in the 30's.

 

[ItBurnsWhenIPee]

The exhaust venting or anything else you can do to get the attic temperature closer to the ambient will help a lot. The best answer as you know is to have a properly sized unit for the heat load of your building. As far as misting the condenser goes, this is commonly done in window units these days but the water source is the condensate itself, it's free, cold, and is distilled so there is no mineral content. The units that I am familiar with use a ring-shrouded condenser fan that dips into a tray in the bottom of the unit and flings the cold water onto the condenser coil, the excess runs out of a drain hole. I think that cooling the condenser will probably not hurt but it may not really change things either, the unit was designed to provide adequate condensation of the refrigerant already. You may make it slightly more energy efficient. Have you considered just hanging a sliding curtain across a section of the shop that you want to keep cool. you effectively drop the square footage you are trying to cool. Don't worry about the top, cold air falls. You don't really need an input fan to vent the attic, your attic should be passively vented, air introduced at the eaves through soffit vents and exhausted through the ridge or gables. The air moves by convection.

No attic...Open rafter/joist/steel purlin/whatever they're called.

 

[tcianci]

OK open rafters/joist/steel purlin/ whatever is fine, just let the hot air out the top

 

[ni[x]it]

No attic...Open rafter/joist/steel purlin/whatever they're called.

I used some of that 4'x8'x1/2" blue construction foam with mylar backing tacked to the underside of my rafters in places, and it made a substantial difference in radiant temperatures. I also cut it up and used it on my metal stamped garage doors.
maybe add a ridge vent too?

If you'd be willing to do the foam board, even up high, you may find it to be of great benefit.

Otherwise, it sounds like you've got it fairly under control.

 

[ItBurnsWhenIPee]

I've thought about the foam boards, but they would interfere with my lighting. Maybe once I get all that up, I'll look at it again and see if I can make it work.

And if I could find a reasonably priced ridge vent, I'd be all over it.

 

[boiler7904]

First off, an AC compressor that runs constantly is more efficient than one that constantly cycles on and off. It will last longer too. In my area, AC systems are designed for a 30 degree temperature differential - meaning a properly sized system will cool your 105 outside air to 75 without any problems. You aren't likely to get beyond that unless special parameters are set at design / unit selection. In your case, I'd be happy with a 25 degree temp change on an admittedly undersized unit.

My home AC was having trouble doing a 15 degree change a couple of weeks ago when the temp and humidity were both right at 100 - not comfortable at all. Luckily it was an easy fix of having the unit recharged. Cleaning the **** out of the condensor seems to have helped too.

Have you thought about adding a couple of ceiling fans for circulation?

Install blinds or some sort of covering over any open windows to cut down on solar gain.

With a vaulted ceiling, any exhaust fans are going to be exhausting your cool air outside defeating the purpose of AC. Having an intake fan will make that effect worse.

Intake and exhaust need to be matched. Too much intake, you create a positively pressurized building and get a lot of door slamming. Too little intake, you create negative pressure (vacuum) and the building will be constantly sucking dirt in.

 

[ItBurnsWhenIPee]

First off, an AC compressor that runs constantly is more efficient than one that constantly cycles on and off. It will last longer too. In my area, AC systems are designed for a 30 degree temperature differential - meaning a properly sized system will cool your 105 outside air to 75 without any problems. You aren't likely to get beyond that unless special parameters are set at design / unit selection. In your case, I'd be happy with a 25 degree temp change on an admittedly undersized unit.

My home AC was having trouble doing a 15 degree change a couple of weeks ago when the temp and humidity were both right at 100 - not comfortable at all. Luckily it was an easy fix of having the unit recharged. Cleaning the **** out of the condensor seems to have helped too.

Have you thought about adding a couple of ceiling fans for circulation?

Install blinds or some sort of covering over any open windows to cut down on solar gain.

With a vaulted ceiling, any exhaust fans are going to be exhausting your cool air outside defeating the purpose of AC. Having an intake fan will make that effect worse.

Intake and exhaust need to be matched. Too much intake, you create a positively pressurized building and get a lot of door slamming. Too little intake, you create negative pressure (vacuum) and the building will be constantly sucking dirt in.

An exhaust fan in the ceiling (along with an intake "port" down low somewhere) would pull hot air out from up there, wouldn't it? Isn't that a good thing?

And yeah, I'm probably going to do a ceiling fan or two, I just need to get all my lights and outlets up there first in order to figure out where to put the fans

 

[boiler7904]

An exhaust fan in the ceiling (along with an intake "port" down low somewhere) would pull hot air out from up there, wouldn't it? Isn't that a good thing?

And yeah, I'm probably going to do a ceiling fan or two, I just need to get all my lights and outlets up there first in order to figure out where to put the fans

A low intake and high exhaust gives you a chimney effect so your cooled air is going to go straight up and out the exhaust fan.

 

[Vicegrip]

I don't know anyone who has put a mister on the condenser, but I have a concern. If you have very hard water, my concern is you could end up with quite a bit of mineral build-up in a short time which in turn could reduce the effectiveness of the A/C.

Just a concern -- I don't have any practical experience with this -- perhaps someone else has real-world experience & can say my concern isn't a real-world problem.

Yes it will crust up if you have hard water. One thing you can do to slow the problem is run more water and enough that it does not dry all up as it is sprayed on the coils. As the water runs off it takes suspended minerals with it. If it dries in place it leaves all behind. Open loop water cooling is a stop gap measure at best.

 

[tcianci]

Boiler,

I think you are overstating the amount of cooled air that will be lost to an attic vent. Remember that cooled air falls, and hot air rises. It is this fact that allows open freezer chests to work at your local super market. That being said, a reasonable solution would be to have vents to admit air placed at a level above that of where the cooled air is introduced into the building. The intake vents along with exhaust, either static or fan assisted will lower the temperature in the attic space of the building, thus limiting the volume of hot air that can "build down" and make the habitable area of the building less comfortable.