Calling all A/C Guru's............

[CumminsPuller]

In the house we are renting we have three window A/C units. One in each bedroom 115v and one 220v in the main part of the house. During the day we shut the hallway door thus closing off the two bedrroms and the bathroom, in an effort to conserve energy in the part of the house not being used during the day. So with that being said the area that the 220v A/C unit is trying to cool is about 800-900 sq. ft... . The unit is a 15 year old Friedrich and if I am reading the tag correctly on it, it says that it is a 21,000 BTU unit. So I found a BTU calculator to figure what size of unit that is needed to cool a particular square footage. And the results state that a 18,000 BTU unit should cool our area sufficiently. This tells me that our current unit is not doing its job. Am I thinking correctly? The temp coming out of the vents varies 50-55 degrees yet in the living room where I have a thermometer that is 15' from the unit it will read 85 degrees in the middle of the day on a 90-95 degree day. All window blinds are kept closed all day to block the sunlight coming in and lights are kept off during the day in an effort not to produce any extra heat.





Any ideas or help would be greatly appreciated.



Jason

 

[EMD Diesel Power]

The thing that strikes my mind is that the unit is oversized for the area to be cooled. When the unit is oversized, it will cycle more and wont dehumidfy as much as it should, the temperatures will fluctuate more, and it just wont seem like its doing the job.



I cant really say if this is the problem though... . way too many variables that I dont know (such as house design--walls-corridors-rooms, type of insulations used and where, climate for the region, etc. etc. )



Another possibility is the age of the unit and has the maintenance been kept up on it? Even with a well-maintained unit, age will get to the point where its just not as efficient as it was before.



Also your vent outlet temperatures sound high to me. They should be around 40degrees. 10-15 degree difference doesnt sound like much... but it is. Check the condensors and evaporators for plugging. Also check filters. Pressures and freon may be getting low too but you need a manifold gauge set to check those.



You may be better off just running the 220 unit and having all the doors open for efficiency and better cooling (unit wont cycle as much). And use the 115s as needed.



Just my opinion. kinda hard to tell whats going on through a computer screen and not seeing the house and setup with my own eyes.



Im also not stationary (house-hotel) qualified... . but I am certified for mobile (truck, trailer, railcar) stuff. But the basics are pretty much the same. Hope this helps... and others can chime in on this too!

 

[CumminsPuller]

EMD,



Thanks for chiming in here. I understand where your coming from, to many variables. But the unit does not cycle at all. Compressor runs constantly. But we have an A/C guy coming this morning. I will get back and let you know what the verdict is.



Jason

 

[daytripper63]

the air coming out should be 20 degrees cooler than the air going in and the sizing of the unit to sq. footage depends on r-values of walls windows etc. if you temps are anything like ours here in Roseville Ca. right now 100 to 105 degrees you dont want to go over 500 sq. ft. per ton (1 ton of cooling is 12000 BTUs ) if you want comfortable cooling, if you oversize the unit you will not get proper dehumidification which can lead to other issues, easiest way to understand the benefits of dehumidification, ever notice how sometimes 72 degrees is comfortable and sometimes it is not? Depends on the humidity

If you want to get the most of your a/c rinse the outside Condenser coil the beginning of every summer with straight on water spray but not to much pressure cause if you bend the aluminum fins the unit can not dissapate heat properly so make sure you spray straight on to avoid coil fins bending and for you window air remove the grill on inside and you will see indoor evap coil and there should be a foam filter, make sure filter is cleaned regularly and make sure there is no dirt build up on coil surface

One thing to remember about all A/Cs Air flow is the Blood of the system if you restrict air flow in any way the unit will not perform