Air Conditioning - correct size for replacement?
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jimbodance
05-09-05, 08:38 AM
Hi!
I have a 1300 sq ft home in Dallas Tx. The old system was a 2.5 ton system. During the summer in the evening when I went to bed the old system would run for 5 minutes and off for 5 minutes. I kept the thermostat set for 78-80. In the afternoons it would run for a longer period of time but be off for about 5min. When I get home from work I would set it below 78 and let it run constantly for about an hour, and then return it to about 79.
Based on the above results would I be making a mistake of upgrading to a 3 ton unit. I have settled on a trane system of 12 SEER. The 2 contractors I have gotten quotes from seem to 2.5 or a 3 ton will work fine. I don't want to get a system bigger than I need.
Jimmy Boyer
I have a 1300 sq ft home in Dallas Tx. The old system was a 2.5 ton system. During the summer in the evening when I went to bed the old system would run for 5 minutes and off for 5 minutes. I kept the thermostat set for 78-80. In the afternoons it would run for a longer period of time but be off for about 5min. When I get home from work I would set it below 78 and let it run constantly for about an hour, and then return it to about 79.
Based on the above results would I be making a mistake of upgrading to a 3 ton unit. I have settled on a trane system of 12 SEER. The 2 contractors I have gotten quotes from seem to 2.5 or a 3 ton will work fine. I don't want to get a system bigger than I need.
Jimmy Boyer
TigerDunes
05-09-05, 08:56 AM
Do yourself a favor and insist upon a written Manual J heat/cool load calculation for properly sizing equipment. This gives both you and your dealer protection if there is ever an issue regarding size.
Is this a heat pump replacement or strictly an AC condenser? Are you also replacing air handler or possibly replacing evap coil on a furnace? A 2.5 ton sounds OK/possibly borderline high but your run times seem to raise questions. I don't see how you can properly dehumidify your home with these short run times and I see you live in the Dallas area. An oversized or undersized system is nothing but a problem! Check into the cost difference to upgrade to a minimum 14 SEER. In 2006, I believe 13 SEER will become the federal mandated minimum. I would recommend purchasing from authorized dealers and seeking a minimum 3 quotes. Good Luck!
Is this a heat pump replacement or strictly an AC condenser? Are you also replacing air handler or possibly replacing evap coil on a furnace? A 2.5 ton sounds OK/possibly borderline high but your run times seem to raise questions. I don't see how you can properly dehumidify your home with these short run times and I see you live in the Dallas area. An oversized or undersized system is nothing but a problem! Check into the cost difference to upgrade to a minimum 14 SEER. In 2006, I believe 13 SEER will become the federal mandated minimum. I would recommend purchasing from authorized dealers and seeking a minimum 3 quotes. Good Luck!
Ed Imeduc
05-09-05, 09:58 AM
Get 3 bid for the job here and have them run a heat load on the home. Now Dalles Tx If you are going to stay in this home for10 years or more Id go for a SEER of 16.
Now just out of the box here. But 2.5 or 3 ton for 1300sq ft sounds like a lot to me. But dont know the home. I have 3 ton here on 1900sq ft down in FL. The other thing is just that 5 minutes off time. How is the attic vents ????can you put a attic vent fan up there.How is the insulation in the home wall and attic? The main thing for the AC is to run so it gets the humidity out of the home . This way you will feel much cooler at that 78o
ED ;)
Now just out of the box here. But 2.5 or 3 ton for 1300sq ft sounds like a lot to me. But dont know the home. I have 3 ton here on 1900sq ft down in FL. The other thing is just that 5 minutes off time. How is the attic vents ????can you put a attic vent fan up there.How is the insulation in the home wall and attic? The main thing for the AC is to run so it gets the humidity out of the home . This way you will feel much cooler at that 78o
ED ;)
Grady
05-09-05, 09:25 PM
One big drawback to the high SEER equipment is, it does not dehumidify as well as the same sized lower SEER. From your run times, it sounds like you might be oversized already. Like Tiger Dunes said, be sure to get written Manual J.