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thestealth
Premium
join:2009-11-10
Lasalle, QC

Room AC Unit Faulty?

I have a Danby DAC12344DE 12600 BTU room air conditioner installed in my living room window (~200 sq ft) . As many of you know there is a nice heat wave here in Montreal (32°C with a humidex of 40°C). I don’t think it is working as well as it should be since it is having trouble keeping the room at 24°C when set to 18°C. Even at night when the outdoor temperature drops to 22-24°C, the AC keeps running nonstop all night and the room temp may finally reach 22-23°C or so. I measured the temperature of the air coming from the unit at 16°C.

My question is this type of performance normal? If not, what can I check inside the unit, dust on the coils? If everything looks good on the inside, is it worth bringing this unit in for a checkup/repair?

Thanks




Msradell
P.E.
Premium
join:2008-12-25
Louisville, KY
From the information you provided it's hard to tell if the unit is working correctly or not. Is the room it's trying to cool open to the rest of the house or closed off? How much insulation is in your home? How much window area and is it thermal pane? How effective has the unit been at cooling this room in the past?

My gut feel says the unit is probably working okay and that the conditions just exceed what is capable of doing. Window units normally either work or fail, very seldom do they just become less efficient. When they do have problems, most times it's more cost-effective to replace them that is to try to get them repaired!

zach3
Zach
Premium
join:2000-05-04
Saint Louis, MO
reply to thestealth
A couple of things to check:

1. Is the filter generally under the cover on the inside of A/C unit clean???
2. Also when checking the filter look at the coils and see if they are clean.
3. Go outside and check the coils and see if they are also clean without any buildup of dirt or debris.

garys_2k
Premium
join:2004-05-07
Farmington, MI
reply to thestealth
You have a temperature drop of 8 C across the evaporator coil, about 14.4 F, which seems borderline but not too bad. I'd say it just can't keep up with too high a heat load.


leibold
Premium,MVM
join:2002-07-09
Sunnyvale, CA
kudos:10
Reviews:
·SONIC.NET
reply to thestealth
Exit temperature of the air coming from the AC is 16°C but room temperature only reaches 22-23°C (about the same as outside temperature of 22-24°C) after running all night long ?

Based on this description I would suggest you close the doors and windows and try again

Seriously, it does sound like the unit is working but there is too much heat entering the room. There can be many reasons for this and typically it is a combination of things:

- poor insulation of outside walls
- single pane windows
- air leaks to/from exterior
(those first three you don't normally expect in a Montreal home but who knows)
- open interior doors (a room air conditioner will not be able cool your entire house!)
- air flow through heating ducts
- room below too hot (heat rises and even with ceiling insulation you will get nice warm floor)
- forget to turn off heaters (forced air heating would be obvious but baseboard electric heaters can be easily missed)

To keep the performance of the room AC at maximum ensure that the filters are clean and replace them frequently (since the unit is running non-stop they may need replacement more often) and that the coils are dust free.
--
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StillLearn
Premium
join:2002-03-21
Streamwood, IL
Reviews:
·AT&T Midwest
I agree with what has been posted. A few thoughts... Temperature drop would normally be measured with a probe that fits into the exhaust vent. If you are using a thermometer totally outside of the AC exhaust, that would increase the measured temperature.

You could close doors to the living room. If there is no door, consider that the AC is trying to cool the rest of the house too. If you are sleeping in the living room during the heat wave, maybe rig some plastic sheets over the openings to the other rooms during the heat emergency.

Look to add insulation and air blocking to your AC install window. If the glass of the window is hot, that is a source of heat ingress. You probably removed the storm window to install that AC. You could cut some foam insulation board for use during the heat emergency. »www.homedepot.com/p/Owens-Cornin···00320352

I would look to add a second AC unit if you have a suitable power circuit and window.

Keep your refrigerator door closed as much as practical. Opening the door makes more heat into the living space. Reduce the temperature of your hot water heater temporarily.

lutful
... of ideas
Premium
join:2005-06-16
Ottawa, ON
kudos:1
reply to thestealth
said by thestealth:

it is having trouble keeping the room at 24°C when set to 18°C. ... AC keeps running nonstop all night and the room temp may finally reach 22-23°C or so.

AC keeps running because you asked it to lower the temp to 18C which probably can't be done under the current environmental conditions. Remember that the A/C itself is burning 1170W which is subtracting 4000 BTU/hr equivalent from the 12000 BTU/hr cooling capabilty.

FYi I turned on the A/C for the first time this year yesterday when Ottawa hit 34C with 41C humidex. I set for 26.5C. I am sure you could set for 25C or even 24C, and open the windows for an hour during the early morning. At least you will sleep without the noise.

thestealth
Premium
join:2009-11-10
Lasalle, QC
reply to thestealth
Thanks for all the replies.

For now I will open it up and look for dust. If there is none, then I suspect I am expecting too much from this unit considering the current circumstances.


Jackorama

join:2008-05-23
Kingston, ON

1 edit
I have the portable Danby DPAC120068, 12000 Btu and this is normal for this type of heat.

Today I have mine set at 77F and the lowest it is getting is 80F. I am using it in a small apt. living room and it is comfortable. Use a couple of fans to direct it to the back bedroom and it is slightly a little warmer, but still comfortable. A few days before this heat wave the ac was performing well cycling on and off at the desired temp. In past years had the same thing happen when the heat and humidity got too high. I did remove the back and vacuumed it before using it this year.

I think this is just normal for a portable/window unit during a heat wave. And it is normal to have to empty the 15L external water tank twice a day during a heat wave on my unit.
--
"Whenever they invent something that's moron proof, someone comes by and invents a better moron."

"Ever stop to think, and forget to start again?"

"Those of you who think you know everything are annoying those of us who do."


54067323

join:2012-09-25
Tuscaloosa, AL
reply to lutful
said by lutful:

Remember that the A/C itself is burning 1170W which is subtracting 4000 BTU/hr equivalent from the 12000 BTU/hr cooling capabilty.

That is not true, the amount of power an A/C consumes does not subtract in that manner from it's BTU rating.


leibold
Premium,MVM
join:2002-07-09
Sunnyvale, CA
kudos:10
Reviews:
·SONIC.NET
reply to thestealth
I'm not sure what other heat-mitigation you are already doing but if your living room window is facing the sun consider closing blinds/curtains to reflect much of the radiant heat instead of letting it into the room.

That doesn't work with black blinds/curtains as those will turn your windows into very efficient solar collectors!
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54067323

join:2012-09-25
Tuscaloosa, AL

1 edit
reply to thestealth
Do you see any icing up on the evaporator coil?

Is the coil wet top to bottom?

Also is the unit level front to back, many times when people install window units they tip them toward the outside for drainage which can reduce the capacity as there is no condensation for the slinger ring on the condenser fan to pickup and blow through the condenser coil.


Jackorama

join:2008-05-23
Kingston, ON
said by 54067323:

Do you see any icing up on the evaporator coil? Is the coil wet top to bottom?

^ This.

This would happen a lot during this type of high humidity conditions when I had a window unit. Would have to run just the fan until the ice melted and the coils dried up a bit.


54067323

join:2012-09-25
Tuscaloosa, AL
said by Jackorama:

This would happen a lot during this type of high humidity conditions when I had a window unit. Would have to run just the fan until the ice melted and the coils dried up a bit.

If an A/C is icing up it either has a restricted air flow or more commonly it is low on refrigerant.


Jackorama

join:2008-05-23
Kingston, ON
Most likely something like that. It was only a cheap 6000 BTU small window unit and only would do it when the humidity was 90% + with high heat.


Brrrrrr

@151.190.40.x
reply to thestealth
At night, put the fan on low to increase the amount of humidity removed from the room. Make sure the coils don't ice up. (If they do, just set it to 'fan only' until the ice melts.)


Brrrr

@151.190.40.x
reply to leibold
said by leibold:

- poor insulation of outside walls
- single pane windows
- air leaks to/from exterior
(those first three you don't normally expect in a Montreal home but who knows)

Montreal houses have really crappy aluminum windows. Their electricity is so cheap, they don't care much about energy conservation. (Most houses have electric heat.)


alkizmo

join:2007-06-25
Pierrefonds, QC
kudos:1
reply to thestealth
When I had a window AC unit, I had to hose it down every year.
I first realized that when it was 3 years old and not performing well. I had never cleaned it at that time. When I did, the performance raised by quite a lot.

That being said, 12600 BTU for a living room isn't enough in this heat. Living rooms are open spaces connect to corridors and the kitchen and no way to isolate it from said areas.

For this heat wave, I recommend you shelter yourself in a small bedroom with that window unit.

older dog
Premium
join:2005-06-09
reply to thestealth
Click for full size
Click for full size
You can compare my results to your situation to make a determination if your unit is defective. Assuming you don't have a lot of heat gain from open halls, oven etc you AC is defective. The temperature of the air coming out of the unit should be around 50f 10c

These are the temperature readings I am getting in a 500 sf apartment, top floor, well insulated with a plasma TV and the computer on. The AC is 10,000 BTU, the 98 is the outside temperature.


54067323

join:2012-09-25
Tuscaloosa, AL
reply to alkizmo
said by alkizmo:

That being said, 12600 BTU for a living room isn't enough in this heat. Living rooms are open spaces connect to corridors and the kitchen and no way to isolate it from said areas.

Thats a whopper of an assumption.

How can you logically state the living room is too large for a 12K unit unless you know the size of the living room and what it connects to?


robbin
Premium,MVM
join:2000-09-21
Leander, TX
kudos:1
reply to older dog
said by older dog:

...you AC is defective. The temperature of the air coming out of the unit should be around 50f 10c

You have no basis to state that. Without knowing the temp of air going into the unit you can't make an assumption of the temp coming out.

lutful
... of ideas
Premium
join:2005-06-16
Ottawa, ON
kudos:1
said by robbin:

said by older dog:

...you AC is defective. The temperature of the air coming out of the unit should be around 50f 10c

You have no basis to state that. Without knowing the temp of air going into the unit you can't make an assumption of the temp coming out.

Temp difference = BTU rating / CFM rating ... is a good ball park estimate.

robbin
Premium,MVM
join:2000-09-21
Leander, TX
kudos:1
Point being is that the poster didn't state a temp difference but instead a set temp (unit should be around 50f 10c).


retired ac

@rr.com
current draw should be between 10.6 & 13.7 amps with an outside ambient temp 102-108 f
from the rating plate the unit. If you can test the current draw and its in those limits unit ok. The best temp btween inside & out is 20 degress f with a room window ac.


54067323

join:2012-09-25
Tuscaloosa, AL
reply to lutful
said by lutful:

Temp difference = BTU rating / CFM rating ... is a good ball park estimate.

And when working with a window unit where is the CFM listed??

older dog
Premium
join:2005-06-09
reply to robbin
said by robbin:

Point being is that the poster didn't state a temp difference but instead a set temp (unit should be around 50f 10c).

You are correct that I should have qualified my statement with "in my case", but I did say he should make his own determination and I gave my results for comparison. Going by what the OP stated with a room size at 200sq the room should be cooling off at the very least overnight.

I have done this simple check out of curiosity to see if my AC has lost cooling ability over the years on different units I have owned.

thestealth
Premium
join:2009-11-10
Lasalle, QC
reply to 54067323
said by 54067323:

Do you see any icing up on the evaporator coil?

None that I can see. I assume this is the room facing coil.

said by 54067323:

Is the coil wet top to bottom?

The bottom 1/2" or so has some dampness

said by 54067323:

Also is the unit level front to back, many times when people install window units they tip them toward the outside for drainage which can reduce the capacity as there is no condensation for the slinger ring on the condenser fan to pickup and blow through the condenser coil.

My unit does have a slight lean towards the outside. Does this really make that big of a difference? Should I get my level out and shim the unit?

said by leibold:

I'm not sure what other heat-mitigation you are already doing but if your living room window is facing the sun consider closing blinds/curtains to reflect much of the radiant heat instead of letting it into the room.

I have close off the room and closed all the blinds (old style vinyl type that no light passes thru).

said by alkizmo:

When I had a window AC unit, I had to hose it down every year.
I first realized that when it was 3 years old and not performing well. I had never cleaned it at that time. When I did, the performance raised by quite a lot.

I have never done this to this unit. I assume you hosed it out to clean both the inside and outside coils of the unit? When the heat breaks I may give this a try, though I may just go the compressed air/vacuum approach.

said by older dog:

You can compare my results to your situation to make a determination if your unit is defective. Assuming you don't have a lot of heat gain from open halls, oven etc you AC is defective. The temperature of the air coming out of the unit should be around 50f 10c.

I did the same setup as you to measure my output temp and only got 16C or so.

Thanks for all your help. Maybe I was expecting a bit much from this unit. Once the heat breaks I will give the unit's coils a good cleaning and shim it level. Just maybe this will solve my problems.

lutful
... of ideas
Premium
join:2005-06-16
Ottawa, ON
kudos:1
reply to 54067323
said by 54067323:

said by lutful:

Temp difference = BTU rating / CFM rating ... is a good ball park estimate.

And when working with a window unit where is the CFM listed??

One should not "trust" the CFM value even if was listed on the manual. Same goes for BTU value. Both of them are easy to measure on window or portable designs.

lutful
... of ideas
Premium
join:2005-06-16
Ottawa, ON
kudos:1

1 edit
reply to robbin
said by robbin:

Point being is that the poster didn't state a temp difference but instead a set temp (unit should be around 50f 10c).

Yes. I was actually supporting your comment. When an A/C is trying to reach an unrealistic low setting, the outlet temperature will be approx [Room temp - (BTU/hr) / CFM ].

I posted link for a simple flap type air flow sensor in the electronics forum. The CFM is easy to estimate by assuming uniform flow over whole area of the outlet and measuring it near the middle of the outlet.


54067323

join:2012-09-25
Tuscaloosa, AL
said by lutful:

I posted link for a simple flap type air flow sensor in the electronics forum. The CFM is easy to estimate by assuming uniform flow over whole area of the outlet and measuring it near the middle of the outlet.

And instead of rigging something up, why not just do it the way professional A/C techs do and use a thermometer and compare inlet temp to outlet temp and compare that to the service specs?