Rant: A/C Install

We haven’t had A/C for about a month, since I found out it wasn’t working about 3 days before leaving on vacation. It was just blowing hot air. It was in the 90’s. It sucked. So I call up Cropp-Metcalfe, who installed our new furnace last winter, thinking they may have miswired something to make that would make the A/C not work.

BACKSTORY: At the time, I opted for the high end furnace, since our sun room, where we spend most of our time, has tons of windows, and therefore our house has quite unique heating needs. Basically, with our old furnace, since our thermostat is in an inside hallway, the sunroom would cycle between being either too cold or too hot. Usually on the too cold side, unless we crank up the therm and turn the rest of the house into a sauna. We opted for the two stage Carrier Infinity furnace, which has a variable fan speed, which is supposed to keep the temperature more constant throughout the house. Basically the Cadillac of furnaces. In order to maximize the performance though, you should get the matching thermostat/control unit (a “measly” $600) for it, even though it does the job quite well without it. I opted against it at the time, with the thought of upgrading in the future. The unit still worked great, and our max heating bill last winter was about $200 vs $400 for the year before, so no complaints there.

So back to the story. A/C not working. Even though we didn’t have a service contract, they still came out within two days to check everything. Diagnosis: No more refrigerant in the unit. I really wasn’t all that surprised. Cost to run a leak check: $300. Cost to refill refrigerant: $2000(it still uses freon which is about $120/pound). Nope, wasn’t going to sink the money into that. Time to replace the A/C. I knew it was only a matter of time, since our unit was 30+ years old, and most likely older than that, and possibly the original unit that came with the house(built in the 50’s).

So we finally get back from vacation, during which poor Sammy had to live with no A/C, and I get quotes on systems. This time I opt for the cheap, most inefficient unit, since our cooling requirements are quite different from our heating requirements. We barely run the A/C in the summer, so efficiency was not a concern for me. Turns out, A/C units are alot more expensive than furnaces though (about $4k for the low end unit). About twice the price. OUCH! I figure, I’m probably not going to need much HVAC work after that though, so at this time I say throw the Infinity Control Unit in there too (may as well get the best use out of our furnace, which also controls the A/C). Maybe I can get a slight discount for getting multiple things at once. And throw the humidifier in there too, since I tried to get our old one working, and failed. It would work for about a day and then quit. Then I’d have to disconnect it from the water lines, clear the lines, and have it fail again a day later. I was done dealing with that. They did give me a slight discount though. I also decided to get the service contract($300/5 years), since that’s actually alot cheaper than the average cost of $150/year to have someone come out and service your furnace/AC without one. I shopped around on that last year. The one place I found that would do it for less seemed pretty incompetent based on the questions I asked them. Anyways, I digress, this is where frustration sets in.

So yesterday they come by and install everything. About 2 hours after they leave, I notice a problem. Hmm, the temperature upstairs BARELY seems to be getting any colder. However, in the basement, I’ve got massive condensation dripping off the exposed ducts. The A/C is definitely working, cause these things are cold as shit, but why am I not getting cold air upstairs? I eventually came to the conclusion that I’m not getting enough airflow. Since the new thermostat controls EVERYTHING, I try changing the fan speed to high. Does nothing. Change dehumidification level. Does NOTHING! At this point I am NOT a happy camper. I just spent $6k on this shit, and it doesn’t even work?! Lots of internet searching ensued, and I found nothing to help me. Adjusted the dampers. Nope, water still dripping in the basement. Upstairs still not cooling well.

Today, more research. I finally found out the thermostat has alot more hidden settings. They’re found in the installation manual, not the user manual, which is what I had. Turns out it will tell you the fan speed, the CFM, …. basically everything about the furnace. It was only moving about about 700 CFM, which is a problem, since I knew the fan could move about 1000 CFM. I was getting close to the problem. Checked the specs on my A/C unit(Carrier 24ACA330, which took more internet research), and found out it’s a 2 1/2 ton unit which it was supposed to be since that’s what our old unit was, and the thermostat is supposed to control the fan move 400 CPM/ton. Something didn’t add up. More research into into A/C systems.

Then more screwing with the thermostat. I went into the hidden install menu, and hit install it it tries to detect shit. At this point I’m thinking maybe I shouldn’t have done that). It auto detects the furnace and humidifier. It can’t detect the AC, but I looked at what the AC settings were before I did that. With the A/C unit I got, it also shouldn’t be able to detect it. So I hit A/C installed:yes. Then it asks me for kBTU. The default is 24. Umm, I don’t know. More research. Turns out the standard is 12 kBTU/ton, so for a 2 1/2 ton unit that would be 30 kBTU. I change it to that.

Voila! Presto! It works! No more condensation on the ducts in the basement. Nice cooling upstairs. Airflow up to 1000 CFM. The tech who installed it simply left the A/C kBTU setting at the factory default, as opposed to setting it properly for our unit.

So to summarize, if anyone else out there is having problems with duct condensation and a Carrier Infinity system, check your thermostat.

To get to the install menus hold the advanced settings key down for 10 seconds.

Your A/C settings should be set to 12kBTU/ton


~ by chriggy on July 11, 2008.

7 Responses to “Rant: A/C Install”

  1. I will say that other than the Thermostat screw up, they did a very professional job on installing everything.

  2. Oh God. Who knows how mis-configured mine is (and it.s a 3.5 ton heat pump for both heat and a/c). I barely understood this post.

  3. (And it was installed by a tech who was there to do something else, took off the other one, and I was like “why not put this one back on instead?”, so i didn’t exactly pay for the job, and he didn’t really have incentive to actually configure it)

  4. You probably don’t need to worry about it unless your unit has a variable speed fan on it. And your thermostat probably doesn’t have any settings like that.

    Our thermostat is more like a mini computer/control center, and it is designed specifically for our furnace. The furnace has a smart/circuit board in it, and the thermostat talks directly with that board, and takes over the fan speed control of the furnace, along with other things. It even checks airflow and tells you when the filter needs replacing.

    Before the new thermostat, basically the fan ran at speeds. High when A/C or heat is on, and low when it’s off to keep the air circulaing to equalize temperature between rooms. The new thermostat now controls the fan speed when A/C or heat is on also, therefore taking full advantage of the variable speed fan.

    To summarize all the technical stuff in the post in layman’s terms, it was set for an AC unit that was too small(2 tons instead of 2 1/2), and was therefore running the fan too slow. I just put all the technical stuff in there so that if anyone else is having that problem, all the info is in one place. It took me forever to find and put together all the info to finally solve the problem, even though the solution was really simple.

    And in my search, of course I came across some red herrings along the way too, which didn’t help.

  5. […] in the 90??s. It sucked. So I call up Cropp-Metcalfe, who installed our new furnace last winter,https://chriggy.wordpress.com/2008/07/11/rant-ac-install/Do your part to lower demand for oil – SitNewsAnother thing that uses oil are the many oil furnaces […]

  6. I have been a heating and cooling professional for over 30 years and you are probably the biggest douche bag I have ever. If you hire a competent professional you let them worry
    About these things. You are not a licensed master and if you continue to dispense advice
    You may find yourself as you so eloquently put it ….in a world of shit

    • @Sadam:

      I don’t see where your anger is coming from? If the so called “competent professional” that installed my unit had done his job properly in the first place, this post would never have been made. I think you just may fear for your job security due to the info being out there. FYI, if you post threats, i.e :

      and if you continue to dispense advice
      You may find yourself as you so eloquently put it ….in a world of shit

      You should know that your IP adress gives away a lot more about you than you think. Louisville, Kentucky, huh? Your IP has been logged and will be reported to the authorities along with your email address.

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