Need suggestion on whole a/c replacement

[yelakanti]

I have 10SEER 3.5 ton R22 system and now I am trying to replace with 3.5ton 16SEER carrier system. When I told my sales rep to go for a 4ton he suggested based on my town house to go with 3.5ton. I complained him that the house was not getting cool because may be I have too many windows. Because of the end unit my town house has lot of windows. My rep suggested following equipment.

1. 16SEER 3.5ton Carrier system (model : 24ACC642 Performance)
2. Coil is 4Ton (model CNPUP)
3. Furnace (model 58PHA090) Performance 90000BTU 80% efficiency)

My question is can I have 16SEER 3.5 ton system and 4Ton Coil. Will that create any problems with humidity. Any suggestions are highly appretiated. I dont think its two stage. Its a single stage. No idea if the furnace is variable or not.
Please give some suggestions.
Thanks in advance.

[BaldLoonie]

First, a good dealer would do a heat gain calc to see just what size you need for your place. Going bigger isn't always the answer. Usually cooling problems come from a lousy duct system - poorly laid out or typically undersized. So going bigger without enlarging the duct system doesn't do much.

The 58PHA is a single stage 80 with fixed speed high efficiency motor to get you 16 SEER out of the A/C.

[skippedover]

I agree with Baldie. Furthermore, I would accept no bid that doesn't include a detailed load calculation done to ACCA standards.

You state the old system had trouble cooling the place. Have you owned it since it was new? If so, did it ever do a good job? Have you maintained it religiously since it was new? Can your service company document the refrigerant charge level of the system? It's awfully difficult for a layman to know the appropriate questions to ask a service tech to determine if he/she knows what he/she is really doing. But poor cooling, as BL said can be a function of poor airflow due to bad duct installation but it can also have to do with inappropriate blower speed, under or over charged refrigerant system, a poorly functioning TXV and in rare instances at the residential level, even a loss of compressor capacity. In addition, you say you've got a lot of windows. Okay, so do you have window shades, drapes, insect screens? Do you windows face onto grass, asphalt, concrete or crushed stone? Are your roof shingles dark or light colored? These and many more questions are those included in a detailed load analysis. Furthermore, once the total load is accurately determined, it forms the basis for evaluating the distribution system. Of course, using a company that does it correctly from the start will cost more than a company that cuts corners. In both those cases, you'll get for what you pay!

[yelakanti]

Let me rephrase it. Actually my old system was cooling well except in the month of JULY every year when the temperature is 100 outside and I put my thermostat to 75 and it never reaches 75. It will show as 80. But other months it cools well. if I set to 75 it will be at 75. So the rep suggested 4ton coil for 3.5 ton unit. Is that ok?

[54regcab]

Optimizing the duct system would probably get you the extra 5 degrees of cooling in July. Simply doing a good clean on the condenser coil will make a HUGE difference in efficiency. The a-coil could be plugged with dirt, in most homes it's a pain to get at and rarely cleaned. Tinting the windows or adding windows shades makes more sense than installing a larger A/C unit IMHO.

[udarrell]

Optimizing the duct system would probably get you the extra 5 degrees of cooling in July. Simply doing a good clean on the condenser coil will make a HUGE difference in efficiency. The a-coil could be plugged with dirt, in most homes it's a pain to get at and rarely cleaned. Tinting the windows or adding windows shades makes more sense than installing a larger A/C unit IMHO.

Amen to that post.

Everyone wanting help on this forum ought to be required to list their location so it shows in their profile.