new HVAC not cooling

[thewifeunit]

We recently had a contractor install a new unit (a Bryant Puron 2.5 ton in a 1500sq/ft 3br/2ba home) a couple of months ago. This week we've had some really warm weather with temperatures in the 90s nearing 100 degrees. The problem is the unit is not cooling the house. The unit runs all day and doesn't drop the temperature below 78 degrees. Our older unit never had this problem.

We called the contractor that installed the unit out and he said that was normal. He told us that these units won't cool more than 20 degrees below the ambient air temperature. He also said that the fact that our ducts are in the celing makes this problem worse. Something doesn't sound right here. I mean, our old unit cooled the house fine and that unit was smaller (2 ton).

What's going on here? Is he correct, ignorant or simply lying? Can you guys educate me on this? Should this unit be capable of cooling the house better than it's doing now?

[usethisone2007]

Not expert here, but it sounds like the guy is trying to swat you away, at least for awhile. Exactly how 'cool' does the new unit actually get the house now, vs what your old one got it to?

I would wait for some good feedback here and get your ducks in a row before you pressure the AC guy too much more. That way you'll maybe be able see through some of the smoke screen excuses he might be giving you.

Good luck. Post how it all gets resolved.

Brian

[CJT]

I'm in Texas. It's hot here. My house is bigger than yours, and 3 tons will cool it as low as I want to go.

The "20 degree" rule of thumb is across the A/C. So if your house is at 100 degrees, the A/C should be able to blow (more or less -- it's just a rule of thumb, not Gospel) 80 degrees. Then, once the house is cooled down to 80 degrees, it should be able to blow 60 degrees. Etc.

[amdx]

I&#39;d run this question over on >alt.hvac< Lots of professionals on there, I think you&#39;ll get good answer. Mike

[dm440c]

">alt.hvac

[HeyBub]

Got a thermometer? Put it in front of the AC air intake. Record the number.

Now put the thermometer in an outlet vent. Record the number.

That&#39;s the 20 degrees difference he&#39;s talking about. Outside temperature is irrelevant.

Even if it&#39;s 100° outside, you should be able to cool your inside to astonishingly low temperatures (given suitable insulation, leakproofing, etc.). I&#39;ve seen ice storage sheds keep blocks frozen with a piddly 1/4 ton window unit (and two feet of cork on the walls, ceiling, and floor).

Now *IF* you get a 20° differential AND you still can&#39;t cool below 76°, then the heat&#39;s getting IN faster than the AC can pump it OUT (insulation, open doors, etc.).

[Red Green]

"dm440c" wrote in news:857011a62794a@uwe:

[S. Barker]

2.5 ton is not big enough for 1500 sq. ft. Unless you have very high dollar windows and are super insulated with 6" walls. Should have been 3 or even 3.5 ton. s

[Cheri]

[Cheri]

[Erma1ina]

Don&#39;t waste your time with alt.hvac; it&#39;s a newsgroup filled with also-rans who take out their frustrations on "homemoaners" ;)

I haven&#39;t visited hvac-talk.com in quite a while but the following forum there, frequented by HVAC pros helpful to homeowners, likely would be a good source of info:

[Red Green]

"Cheri" wrote in news:x7WdnYSruLiDI9DVnZ2dnUVZ [e-mail]:

[Edwin Pawlowski]

Btu is Btu. If the new unit is larger, it should cool to a lower temperature than the old one. Proper sizing aside, the higher capacity can remove more heat. Proper sizing gets into things like humidity control where to big is no good. If the 2 ton unit was good, the 2.5 ton should be at least as good at reducing the temperature.

I&#39;d do a quick check of the basics first. Are the duct leaking? Was something left undone or is airflow blocked? Check the temperature of the air entering and leaving the AC. It should have about a 20 degree drop across the coil. Cooler at night with no sun load? By cooler, I mean the differential between outside and inside temperature. Personally, I think there is a problem and since it is new, get him back to check things, such as the pressures in the unit. There may have been a leak.

There is a lower limit, of course. At 100 degrees, a properly sized unit won&#39;t get it much more than 20 to 25 degrees cooler than outside, but if the old one did, the new one should.

[Edwin Pawlowski]

I mean, our old unit cooled the house fine

But a 2 ton did the job before. I do my 2000 sq. ft. house with 2 1/2 ton no problem.

[S. Barker]

I totally missed that input point. Strike my reply as non-valid.

steve

[Wayne Boatwright]

On Mon 09 Jun 2008 06:52:50p, Edwin Pawlowski told us...

The design and sizing of a system is also somewhat dependent on where you live. We live in the Phoenix area. Few people here would be happy with 95 degrees inside on a 120 degree day, a 25 degree differential. We can easily cool our house down to 70 degrees on a 120 degree day, although we usually keep it at 75 degrees.

[ransley]

If you had 2 ton and it cooled you fine before why did he want to put in a more expensive 2.5 ton and why did you agree to it, a larger unit will run less, but remove less humidity and that you didnt want, but to the point of cooling something must be wrong on the install if you are sure you had 2 ton before and it cooled better. The new larger unit wont remove as much humidity since it will run less, if it was put in right.

[amdx]

[amdx]

[ransley]

we have 3 ton and space pack cooling a 3500 sq ft 90 yr old original window, poorly to non insulated all original leaker. It was even guarnteed in writing by the installer to give a 30f drop which it exceeded when it reached 113f here in chgo after it was installed 20 years ago. I dont know where you get your numbers.