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Old 07-20-2009, 06:02 AM   #1
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I am going to have to replace my A/C very soon I'm afraid. The condenser is approx. 8 to 9 years old, 3 1/2 ton, with the evaporator in the attic 20 years or better. They are not a matched pair. I've been told my duct work will support a 4 ton, which I will upgrade to. I have gas heat now and will probably stay with that instead of changing to a heat pump. I'm afraid since I've always had gas heat I could not get used to a heat pump. I would like to go with a 14 to 15 seer condenser and maybe 95% furnace. My home is very insulated and I continue to get huge power bills in the summer. We have ceiling fans and leave the thermostat on 78 degrees. I think it is a combination of old and mismatched units.

With all the brands on the market today, which is the best for the money. I'm in SE Georgia, and Nordyne is a big brand here. Also Comfortmaker and Trane.
Any input would help.

Thanks
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Old 07-20-2009, 06:55 AM   #2
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brand isn't a big deal.. Just get a good installer
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Old 07-20-2009, 08:56 AM   #3
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Why would you consider upsizing your unit to 4 tons? Was a heat caluculation done?

Unless you need 4 tons, you may wind up with a less efficient/comfortable system.

V
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Old 07-20-2009, 09:48 AM   #4
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DIY:Load Calculator
An oversized unit won't dehumidify your house properly and that is important in your area I believe.
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Old 07-20-2009, 10:21 AM   #5
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Originally Posted by archbarb View Post
I continue to get huge power bills in the summer. We have ceiling fans and leave the thermostat on 78 degrees. I think it is a combination of old and mismatched units.
How does your elec. bill compare to this table?

http://www.eia.doe.gov/emeu/consumpt...on_tables.html
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Old 07-20-2009, 01:38 PM   #6
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Load calc. first then check out the upgrades on heat pumps over the years. I had a gas only furnace until upgrading to a HP last year. For my elect./gas rates, the HP saves a ton of cash. Upfront cost is minimal. Have an 80% variable speed furnace as backup heat and it's locked out over 35*. Couldn't be more comfortable.

Research systems and installers and heat load calculations and worry less about brand names.
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Old 07-21-2009, 08:49 AM   #7
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As said get load calc done before increasing the size of your unit. You want the unit to run to remove humidity and it needs to run about 15 minutes before it reaches peak performance. If you get a larger unit it will short cycle and you will have more problems than you have now with higher electric bills.
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Old 07-21-2009, 07:35 PM   #8
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it will short cycle
More than 3 on-off cycles/hour?
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Old 07-22-2009, 07:48 AM   #9
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In order to get to the SEER rating on your equipment you need to have a 10 to 15 minute run time. I suppose it depends on the thermal envelope as to how many cycles per hour it will have. This is one reason why its so critical to have equipment sized properly. Bigger is not better.

If you install a larger high SEER unit the homeowner may have utility bills that are the same or more than they were with the old unit.
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Old 07-22-2009, 07:36 PM   #10
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So, less than 3 cycles/hour and minimum 10 minutes on-time for proper operation. . .?
I guess right-sizing would have the thing running 90% of the time on the hottest day.
I'm thinking now the thermal inertia/specific heat of the house air and furnishings determines the cycle length; a house in Europe with heat-storing masonry may possibly take many hours for one on-off cycle.

Last edited by Yoyizit; 07-22-2009 at 07:39 PM.
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Old 07-22-2009, 08:33 PM   #11
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I'm thinking now the thermal inertia/specific heat of the house air and furnishings determines the cycle length.
I am fascinated by your academic insanity. While the rest of us are out here thinking, you are out there THINKING!!!
__________________
Settle down! If you were that important, the city would give you lights and a siren for your car
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Old 07-22-2009, 09:02 PM   #12
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you are out there THINKING!!!
So that's what that burning smell is! A mental overload!
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