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Old 02-06-2008, 08:44 PM   #1
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Central Air Installation Question ???


After this past summer, we properly disposed of our window air conditioning units, with the intention of motivating ourselves to upgrade to central air. Well, I have started the process of getting estimates and have found each contractor has a different plan, each focusing on a separate aspect, which they believe is the most important in the cooling process. While each makes a valid point, (i.e. valid in the eyes of a homeowner who has little experience in HVAC) one of them must have the proper plan for our existing system and house layout. And this is where I need Help!!!!

Background:
House is a 1100 sq ft cape, with crawlspace and existing forced hot air heating. 2 BR upstairs with the plan to install a full bathroom. The furnace is on the 1st floor in a closet off the TV room. The furnace is 7 yr old Kenmore down-flow or counter flow. (Which I have found, is not the most effective type for cooling a home). After coming to the realization that the house\furnace is not the most likely candidate for central air, we want to proceed anyway as window units are not very efficient, plus we see this as an investment for re-sale...

So I do a bit of research before selecting 3 contractors for estimates. Can you help me decide which is the best option? What product line is the best?

#1 Estimate = $3400
2-Ton Compressor (HEIL products, 10yr Warranty), Coil, T-stat.
Their plan, remove the furnace and put the coil on the floor then reinstall the furnace on top of the coil. The air will then be pushed through the coil to the venting in the crawlspace and disperse throughout the house.
Working Time = 1.5 days
Availability = could get a small discount if work is done in Feb, I guess they are no too busy this time of year...

#2 Estimate = $2800
2.5-Ton Compressor, Coil, T-stat (Goodman Products, 7yr Warranty)
His plan, leave the furnace in place and put the coil in the crawl under the furnace. There is currently an elbow vent under the furnace, which he would cut away and replace it with a 15X15 square vent. Furnace will still push the air thru the coil, except now the coil is under the house in the new venting they are adding. He is the only one who had me turn the heat on to check the pressure of air in one of the bedrooms upstairs.
Working Time = 3-4 hours
Availability = tomorrow if I wanted it -- that is a bit shady, even though he had no negative complaints filed with the BBB.

#3 Estimate = 3950
3-ton compressor, coil. (RUUD, 10yr warranty)
Keep the furnace in place, but add the coil above the furnace. He said that the coil can be either side of the furnace, return side or "flow" side.
After reviewing the returns, (1st Floor return 24X24 and is located high on the wall, 2nd return is 12X12 and located in upstairs hallway at floor level), his main objective was to increase the flow of air being sucked back into the furnace from the upstairs return. So his price includes enlarging both the return vents and venting that will lead to the coil, and minimizing the air being pulled from the first floor return.
Working Time = 2 days
Availability = 4 wks. He is busy must mean something!!!!!
Ultimately, we are trying minimize the temp difference between upstairs and downstairs.

My Thoughts:
1st -- OK, smallest compressor, and sounded like he was not a big fan of getting into the crawl.
2nd -- Skeptical, took the time to examine the air pressure, sounded like he knew what he talking about. However, sounded like he wanted nothing to do with removing the furnace or venting in the closet and wanted all the work to be done in the crawl.
3rd -- Best Feeling -- largest unit. Concerned about something the other were not, the amount of air being pulled from the house, particularly upstairs.

Curious to know what the pros think, and the reasons why one choice is truly better than the next...

WorkOnIt

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Old 03-07-2008, 08:56 AM   #2
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Central Air Installation Question ???


i just caught your message...i'am a 30 year commercial tech in Manhattan/NYC area but i don't do installs and haven't gone near resisdential systems for years.the tonnage ranges they are giving you aren't that off but the difference between 2 and 3 tons is one will run longer(2) and the other shorter (3)to maintain the house.the window units you had if you totaled them up on the BTUs(12,000 btus=1 TON) and how they kept the rooms would give you an idea of the overall tonnage required.you can stay with the down draft type furnace with and A coil,but if i were getting it i would go with complete change out.keep in mind the register locations for the heat(it rises) will be supplying cooling and(cold air drops) i'am thinking the exsisting heat supplies are floor mounted.brand-wise it is like buying tires for your car a good install will last the life of the house,not that tires will the life of a car(pressure right and balanced on install).the furnaces are so advanced now the contractors can't keep up with the air side,reburning of the gas in the heating modes to bring up the effiecantcy.the install aspect locate the condenser on the shadiest side of the house after 12PM noon,cool mornings are OK but the hot afternoons will make it work harder cost more to cool.spec a SCROLL compressor in the condenser most have them anyway,but just something to mention.have all the exsisitng ducts connections sealed all the way into the registers if you go all new,and see if can have them throw in a new STAT in the deal "NO CHARGE"Honeywell Vision Pro 8000 for you to go with them....maybe a new humidifier if not the stat.keep getting bids and note the tonnages as you go they make their money on HOW LONG the install takes..the units,stats,humidfiers are all stock items they just grab off the shop shelves or that afternoon at the supply houses.take notes on quotes of how long for a complete change out even get HD in their for a quote..they push TRANE stuff them CARRIER and YORK our paying for the name.

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Old 03-07-2008, 09:44 AM   #3
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Central Air Installation Question ???


I'm not an a/c pro, but I'm curious as to why there is such a discrepency in the tonnage of the units. Have any of these contractors done a Manual J?
If a central a/c is oversized, it will run less, but will not be effective in removing humidity, resulting in a cold "clammy" feel. A larger unit will also require a larger electrical circuit.
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Old 03-07-2008, 04:04 PM   #4
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Central Air Installation Question ???


check out www.hvac-talk.com wall of SHAME and PRIDE for loads of residential installation pix from all aspects with comments from installers who do it for a living.
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