A/C replacement

10 years ago

We live in Atlanta in a 3000 sf two story house built in 2001. We need to replace our units so we received four quotes and they are very different. The last quote we had was to replace the A/C units only (the rest were for A/C and heat at the same time). So that's my first question, (1) if the heat is working fine now but is 12 years old, should we wait to replace them when broken versus now to get economies of scale. (2) The second question is we currently have 3 ton down and 2.5 up. the cooling has been fine for the most part though lately those upstairs complain that it is too hot. Should we get 3 ton for both? (3) the last quote was for upstairs 2.5 ton 16 SEER system single stage and downstairs 3 ton 2-stage 16 SEER. It was for carrier infinity. Does that sound right?

Appreciate any advice I can get.

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Comments (4)

tigerdunes
10 years ago
Several questions.

What size living area for downstairs and upstairs?

How would you describe home's insulation and building qualities especially for upstairs? Attic insulation is good?

Tell me about your existing furnaces; age, brand, model, size, efficiency, var speed or not.

Post back.

IMO
jbw35
Original Author
10 years ago
The approx split must be about 1600/1400 because the den is open to the second floor and the foyer is open. The home was built new in 2001 so the furnace is that age. It's a basic Lennox system - builder minimum, but according to the guy who maintains it, it is in good shape. I never asked him how long he thinks it would last.

The insulation is good. The ductwork has some re-routing to do because airflow in a couple of rooms is not as good as it could be. As far as heating goes, the upstairs hardly ever comes on because the heat from below in the open den area heats the rooms well enough. The lower level gets chilly but that's also because of the open den area, and the fact that the den air vents are mid wall instead of at the bottom of the wall. Also the air vents themselves are split in three with the 1/3 pointing left, 1/3 right and 1/3 straight.

Does that help any?
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Holy cow! That's nuts. I've been quoted between $7,000-10,000 for this project. Here is the summary one company provided me on their quote: Remove old air handler in attic area and electronic air cleaner. Remove old drain pan and drain lines in attic. Properly dispose of old equipment and debris. Remove existing copper line from indoor unit to outdoor unit. Also dispose of outdoor condensing unit. Install new attic unit on vibration free pad and install emergency drain pan underneath. Unit will be of Rheem manufacturer, and be equipped with new R410A refrigerant. Reconnect all ductwork transitions necessary to existing trunk line. Wrap duct transition using R-8 value insulation. Install new PVC drain lines, a primary secondary and emergency to prevent any future water leaks. Install a new Spacegard media high efficiency filter on the return side of air handler. Central ac unit will be high efficiency and of seer rating chosen by homeowner. A new cooper line set will be installed from indoor to outdoor unit. A new outdoor high efficiency condensing unit will be installed and leveled on a condenser pad. All copper joints will be properly brazed assuring no leaks. A nitrogen leak test will also be included in installation to assure no future leaks. A deep vacuum will placed on unit after lines are brazed to remove any debris or moisture that may affect system. All permit costs to be paid by homeowner. ***** carries all insurance, and homeowner has no liability. All electrical connections to performed by licensed electrician. Also we will reroute thermostat wiring, so homeowner only utilizes one thermostat. Warranty: A 10 year manufacturer warranty is included on outdoor compressor and air handler. An additional 3 years on all workmanship provided by *****. A free service startup will be applied for the following summer season. Option 1: Rheem air handler 13 seer model# 13AJM36A01 Rheem condensing unit 13seer RHSLHM3617AA 3 ton capacity Unit 3 ton capacity R410a equipped. Total Investment: $5450.00 Option 2: Rheem air handler RHPNHM3624JC 3ton capacity Rheem condenser RARL036JEZ 16seer This unit is eligible for a rebate. Total Investment: $6995.00
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Thanks, for the replies. I specifically asked about the existing duct work, and all three said it's fine. Actually the noise is probably due to our trying to compensate for the temperature differences between upstairs and down... we have to mostly close the downstairs vents to push enough air upstairs to get the temperature half-way decent. Perhaps with the VS unit running longer, we could open the downstairs vents more and eliminate that problem. It sounds like 2-stage is out simply because it would be too big for our house. Regarding thermostat, he indicated the programmable Edge should provide everything we need and from what I've read, it should include ability to control humidity. But you raise some good points. It sounds like I need to verify a thermidistat is being included... is this a separate sensor, or part of the thermostat itself and I just need to ensure I'm getting the right model (perhaps TP-PRH)? Regarding dryness from outside air infiltration... our house is pretty tight, but this could be coming from the windows... I'm also looking to replace them with more energy efficient vinyl replacements, so that may help that situation as well. I think I'll hold off on the humidifier until the HVAC and windows have been replaced, and then evaluate. Regarding tigerdune's comment about 80% furnace... if I recall the discussion regarding this proposal, the 96 was required to qualify for tax credit. If I were to opt for the hybrid, could this qualify based on the heat pump rating alone? Thanks, Brian
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udarrell
10 years ago
A heat gain/loss needs to be performed separately on both floors.

Normally the first floor requires less Btuh to cool than the 2nd floor area; in your case that may not be the reality.

Free Whole House or, 1st & 2nd Floor Areas' Load-Calcs performed separately.

You can easily reduce infiltration rates yourself, therefore, IÃ¢ÂÂd use 0.4 ACH (Air Changes per Hour) be sure to add the (Air Changes per Hour) CFM into the Ã¢ÂÂFresh Air Recommended Ã¢ÂÂline-slot, or it wonÃ¢ÂÂt figure the Infiltration & fresh air Btuh.
You can experiment with changing the design temperatures in both heat & cooling, (or start-over showing the New Retro-R-Values) also to see whether the equipment exceeds, at those particular temperatures & new retro conditions.

You can't save the completed calc, so when you think it's right, Print it. The Snipping Tool can be used to capture an on screen image of the completed calc., which may be uploaded to this thread.

The 2.5% summer design in Atlanta, GA is 92ÃÂ°F & 74ÃÂ°F wet bulb for about 43% RH; calc may show a lower design temp; use it.

Here is a link that might be useful: Free Whole House or Floor Area Load-Calc
tigerdunes
10 years ago
"A heat gain/loss needs to be performed separately on both floors.
Normally the first floor requires less Btuh to cool than the 2nd floor area; in your case that may not be the reality."

I agree with above.

Sounds like you have some ductwork sizing/design issues that should be pointed out to dealer for possible improvement.

If you are satisfied with the heating, then furnaces can remain. But if they are conventional furnaces, you will be limited to 13 SEER condensers with matching coils. I would want a good model that has full cooling BTUs for the rated size. Many don't.

IMO

A/C replacement

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tigerdunes

jbw35
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udarrell

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A/C replacement

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tigerdunes

jbw35Original Author

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jbw35
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