Old air handler / new compressor. Won't cool?

[jjgrosso]

Ok, Im a totaly newb here and know enough about HVAC to be dangerous. Anyways, back in August of '05 my exterior compressor unit was replaced with a new Goodman 1.5 ton unit. The old one was an approximately 15 yr old Carrier. It was covered under a home warranty I had at the time. Anyways, ever since when the summer arrives (I live in AZ) my AC just does not work worth a darn. Once it gets about 100 out I have difficulty keeping my house below 80. The air handler inside is still an old Carrier. I have had the system serviced and the techs find no coolant leaks, the coolant levels are fine and the system is functioning. Even the transfer coils are clean and I am using a higher flow fiberglas air filter. Yet the AC will run non-stop from about 11am - 8 or 9pm just to keep the place at 80. My condo is 1040 sq foot and both my indoor and outdoor units are 1.5 ton. My thought is a new air handler with a similar SEER rating and a variable speed fan will rectify this problem. However several techs from several companies all give me different answers. So really what I need to know is if it is even worth replacing or not and if in fact it will help at all. Any advice would be greatly appreciated.

[swnoel]

Sounds like your system is undersized... it probably was always a problem.

Have a heat gain done on your home to find out if it was sizes right from the beginning.

[firecontrol]

"The system is functioning" doesn't always mean that they did any checks to verify that it's functioning to it's full capacity.

If the old 1.5 ton unit did the job without any problems, and all that has changed is the new outdoor unit then you're dealing with possibly a missmatch of equipment that won't produce, when the old unit went bad it caused a problem with the indoor unit components or when they installed the new outdoor unit they let something loose in the system that has plugged up a circuit in the indoor coil. There are other possibilities, but most aren't found by a 10 minute service call only looking at the outdoor unit.

Give them a call back and see if they'll send someone out that can do a more complete evaluation of what's going on.

[beenthere]

Possible mismatch issue.
Or, its possible the newer nominal rated 1.5 ton condenser doesn't have the same true BTU rating of the old unit.

[bmathews]

It sounds a bit undersized. Can't tell from the armchair. But probably the culprit. Maybe poor insulation, crappy windows, weatherstripping, etc...

[udarrell]

If the old 1.5-ton handled the heatload okay, then the new condenser should probably do better than 80-F depending on actual load conditions.

You didn't state the SEER level of the new condenser. The new higher SEER units have a smaller compressor. Many of them use a 16,500-Btu/hr compressor in the 1.5-ton rated condenser.

There also could have been a problem with the quality of the install.
The are numerous things that could be causing a reduction in nominal tonnage capacity.

Hopefully, during peak load days it will be enabled to reach 76 or 77-F degrees.
If it gets the humidity low, & you use fans to create air movement, you should be very comfortable. Here is a linked "Human Comfort Zone Chart."
http://www.udarrell.com/air-conditio...tent-heat.html

[jjgrosso]

Thanks for the responses everyone. The exterior unit is a 10 or 12 SEER unit. THe air handler....god only knows. Its at least 15 years old. Im not sure exactly what the temp difference is from the air going in to the air coming out of the vents. I dont have the tool to measure that....though I could probably use a simple thermometer to get an idea.

In regard to wheter or not it was working well prior to the compressor unit being changed, Im not sure. I bought the condo in March of '05 and the compressor died in August of that year. And during that first summer (June-Aug) it was working but it started to fail.

[swnoel]

Who believes that 1.5 ton would be enough for 1040 sq. ft. condo?

I don't have to look at it... I know it didn't work well!

Before I would have sold you that outside unit I would of at least asked how the original worked... get the heat gain done.

[BigJon3475]

Could be a number of things. If it's mismatched already you could loose capacity. If it's overcharged you could loose capacity. If it's not moving the air needed you could be loosing capacity. Maybe any number or all of them together.

[BigJon3475]

...

[docholiday]

Why dont you call Goodman and ask them? No, you better call Carrier and ask them... No, ask the idiot that put it in, since he invented it. Maybe since he's such a genius, he can perform a capacity test. (I would seriously doubt he would have any clue how to do this)

[jjgrosso]

Well sounds like I have a list of potential problems that need to be addressed. Wonderful. Anyways, I appreciate your input guys. Ill have a head load test done and have a tech check the system for problems. I just wish I could find a reputable and skilled company to do this. Seems all that have come in the past screw up every time.

[BigJon3475]

Maybe if you list a location.......some suggestions could be thrown out.

[dac122]

It's been a while now since I had a heat load test done on my house and among other things they measured the living space volume (length, wide, height of each room), measured windows, took a stab at insulation values, estimated age of windows and doors and construction, ran it through some modelling software, and poof out came some heating and cooling capacity numbers.

Can anyone give this poster some idea what should be measured on a heat load test, so that if someone comes over to do it the poster will have some idea if its being done right?

[beenthere]

Pretty much what you just described.

And if you want it to be more aacurate yet, a blower door test to find out what your infiltration rate is. But you won't get that for free.

[jjgrosso]

Maybe if you list a location.......some suggestions could be thrown out.

Arizona. In Mesa, just outside of Phoenix.

[BigJon3475]

Againa thinking out loud.....


Any chance you upgraded from R-22 to R410A?


In MJ8 both Phoenixes have a cooling design temp of 107/108

Not sure since I never see those but are those close numbers to where R410 starts to fall off quicker the R-22 falls off to some of the members in that area?

[jjgrosso]

Againa thinking out loud.....


Any chance you upgraded from R-22 to R410A?


In MJ8 both Phoenixes have a cooling design temp of 107/108

Not sure since I never see those but are those close numbers to where R410 starts to fall off quicker the R-22 falls off to some of the members in that area?

I have no idea.

[Airmechanical]

you need to find a good HVAC contractor in your area

then be specific about how cool you want your house on the hottest day

your specific needs may require a 2 stage system that is oversized for "normal" conditions


.

[BigJon3475]

Find out what refrigerant the system uses.

Read this: http://www.eurocooling.com/articler410a.htm