Home AC question

[Patman]

The air conditioner in my house has never been all that effective at cooling down my house quickly even when it was brand new and I'm wondering how cold should the air out of the vents be? I measured the air coming out of one of the vents on the main level (which is fairly close to the unit, but not as close as one of the basement vents though) and the temperature was 59.6F. Outside temperature at the time was 70F this morning. I keep my thermostat set to 76 degrees when we're home and on warm days it pretty much runs the entire day just to keep it at that temperature.

We live in an end unit townhouse which is 1800sq feet and the AC that came with the house is a 1 1/2 ton unit. Is that big enough or should they have given us a 2 ton unit with this place?

FWIW, in summer 2006 we had to replace one of the valves on the outside unit as it leaked out all of the freon. Then in summer 2007 the freon was empty again for some reason so we got it recharged again. But even before that, this air conditioner has always struggled to keep this house cool. There is no way I could ever get this house down as low as 72 degrees on a hot summer day for instance, like my parent's house is (and their house is more than twice the size of mine)

Also, what temperature do most of you keep your thermostat set to in the summer?

 

[Barkleymut]

I keep mine at 75; i have a 2 story 2400sq ft home with dual zone heat/AC when it is over 95 F it runs non stop until 10 or 11 at night. When the high is only in the mid 80s both units probably run 45 mins out of each hour. I've had a couple of repairs done to mine I would say $1500 worth in 7 years.

 

[rshaw125]

Remember when you first run it it is taking the humidity out of the air. The vent temp should be in the 50's F.There should be a drop of about 20 degrees from the air going into the return and coming out of the vent. Some systems are much better designed than others. It may have been a poorly designed system from the start. With barely adequate equipment installed.

 

[hemitom]

1.5 ton unit should cool sufficently, but its borderline for your size of home. Insulation and sun exposure play a big part in sizing a A.C unit. You probably already do this ,close all blinds during the day,close all your vents in the basement, check your condenser {outside unit} for dead grass dirt etc in the fins, if its dirty try cleaning it with your garden hose.

 

[Bill in Utah]

3 ton unit for a 2300 sq foot 4 level house here.

We keep the house around 77 degrees on the level where the thermostat is at and upstairs it is around 79-80.

When it is hot (high 90s-low 100s) it runs for 20-30 mins at a time every 1.5 hours. Costs about an extra $25-$30 per month when in use.

House does have R23 walls and R40 in the attics.

59-55f is the temp of the outlet air.

Bill

 

[Chris Meutsch]

A properly sized unit shouldn't cool all that quickly anyways. You don't want short-cycling of the compressor (which happens when oversized units cool small spaces).

 

[Mr Nice]

Approx 75 degrees year round, even in winter time.

 

[XS650]

We keep ours at 80F (that wouldn't be as comfy in a humid climate)and use ceiling fans. When we got our 1` year home inspection (to be sure I took full advantage of the builders warranty), the inspector I hired told me that the air temp out of the ducts should be about 20F below the inlet temperature. If it isn't you don't have enough airflow to get good efficiency out of the system. Sounds like yours isn't dropping the temperature as much as it should.

I think mines a 3 ton. It's in a 1900 sq ft single dwelling with good insulation, good orientation, 90% sun block screens on the east and west windows during the cooling season and most of the south windows are shaded from the sun.

The AC usually doesn't run at all until the afternoon of days over 92-93 degrees. On the occasional 107-109F day, it only runs about 65% of the time during the hottest part of the day. If I ever have to replace it I will get a smaller one.

It helps that the climate here is dry and every night except for maybe 2 to 5 nights a year is cool enough to open windows until morning.

 

[Patman]

I think a big part of the problem is the fact that our house retains a lot of heat for some wierd reason. For example, in the late fall when the daytime temps don't go above 40F too often, our house will still be 70 degrees inside, even without the furnace on, and even on days when it's cloudy! So the air conditioner has to fight against that as well.

On the plus side, our basement is always nice and cool, which is where our TV is, and if we keep our bedroom door closed, it will cool off the room pretty fast too. It's just frustrating that the main level and other parts of the house aren't always as comfortable.

 

[Al]

Originally Posted By: Chris Meutsch
A properly sized unit shouldn't cool all that quickly anyways. You don't want short-cycling of the compressor (which happens when oversized units cool small spaces).

Exactly. A smaller unit is better than a larger unit bc it will run more and dehumidify more.

As mentioned, once the humidity is down (get your-self a decent humidity gauge), you should have say 20 degrees (minimum) from where the air goes into a return to where it comes out the supply. Check your filter to make sure its not dirty. Maybe the coils are iced up.

A 1 1/2 unit is on the boarderline. But I would rather have the 1 1/2 Ton vs the 3 ton unit. And again if all the parameters are O.K. running more provides better de-humidification. AC companies usually oversize bc they don't want complaints...but that is so wrong.

In rare cases the fan may have one coil out and is running at too low a speed. It happens. Make sure your outdoor unit is clear and coils are clean.

But to repeat..you should have at least 20 degrees between the return to supply. Thats the first to check.

 

[Dantheman]

A 1.5 ton unit for 1800 sq. ft. ? Here in South Louisiana that same house would have 3 tons minimum . Seriously .

 

[Al]

Originally Posted By: Dantheman
A 1.5 ton unit for 1800 sq. ft. ? Here in South Louisiana that same house would have 3 tons minimum . Seriously .

Like I said..contractors size them so there are no complaints on cooling. They could care less if there is adequate dehumidification. They want zero callbacks.

 

[Chris Meutsch]

Yeah, check your coils for icing. If so, you most likely have a leak somewhere.

 

[alreadygone]

When wife was pregnant with youngest (he's 22 now) we had regualar AC (not heat pump) replaced with a "water source", also called "thermal linked" heat pump. With these systems water, instead of air is used to heat/cool freon. Much more efficient than outside air temp. Still well pleased with this system 22 years later. Have had total of 4 service calls to original manufacturer/seller less than $1,000. for all.

While some have buried heat sump lines with a recirculating pump, since we have a unlimited source of water from private well, we simply pump 3gpm out as waste while unit is running.

Bob

 

[Schmoe]

That 1.5 ton unit would really struggle here in Oklahoma, but, as they say, it's a dry heat....... Yours is running wayyyyyy too much. I thought all you Canadian guys didn't have AC? Keep the curtains closed as much as possible and run ceiling fans.

 

[oilyriser]

Originally Posted By: Patman
I think a big part of the problem is the fact that our house retains a lot of heat for some wierd reason. For example, in the late fall when the daytime temps don't go above 40F too often, our house will still be 70 degrees inside, even without the furnace on, and even on days when it's cloudy! So the air conditioner has to fight against that as well.


Have you measured your electricity and natural gas usage during this time? Add in heat from human bodies, too. The heat has to be coming from somewhere. Some places do a weird loop of water pipe on the water heater that circulates all the time by convection so there will be hot water at the furthest fixture without having to wait. This will waste energy and heat up the house.

Modern high efficiency ac systems don't cool the air as far. To get the high EER ratings, they try to avoid dehumidifying, and keep the temperature drop as low as possible. But then you need more air flow to take heat out of the house.

 

[Dantheman]

Originally Posted By: Al
Originally Posted By: Dantheman
A 1.5 ton unit for 1800 sq. ft. ? Here in South Louisiana that same house would have 3 tons minimum . Seriously .

Like I said..contractors size them so there are no complaints on cooling. They could care less if there is adequate dehumidification. They want zero callbacks.


Sorry , but that's what it takes to keep a home cool and dehumidified here . You won't see anybody replacing a 3 ton with a 1.5 ton when it's time to change one out . That 1.5 would run 24/7 until it burned up .

 

[Al]

My response was meant as a "General Response" . And we are talking Canada vs Louisiana. But my general statement still remains. A/C units are oversized bc contractors don't want call-backs.

1 1/2 tons should be adequate to do the job in his case if it is working properly (producing 20 to 25 degrees across the evap. coils) Would a 2 Ton unit be a better choice? Possibly. A 2 1/2 Ton would be good bc it would get the house cooled quickly assuming the temp is kept higher during the day. But again the dehumidification is lost.

 

[Schmoe]

I also got one of those programmed thermostats. That thing is worth its weight in plutonium. I keep ours at 74, then drop to 76 after 2300, then back to 74 at 0515, then to 78 at 0645 and then back to 74 at 1600. Your house could be insulated too well and being in Canada, it may have been designed to keep the heat in and not let the house "breath" any, meaning you not exchanging the hot air for the cold air fast enough, by design. A well insulated house should only keep a temperature drop of about 20 degrees F from the outside without any help. Your showing a 30 degree drop. Check you A coils and your evap. coils outside. Maybe due for a cleaning. I'm also concerned about your comment that you had a valve problem and all the freon leaked out. That freon, by EPA regulations, is not ever suppose to leak out unless there has been physical action that resulted in a leak, such a hole in the coil somewhere. I have trouble buying into a valve opened and it all leaked out, but you guys are in Canada. If a contractor told me that, I'd start looking for someone else.