AC unit for 450 sqft clip this post email this post what is this?
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Posted by nickt (My Page) on Fri, Feb 29, 08 at 15:02
We are being told that the smallest AC units available are 1.5 ton. But, we only have 450 sq ft to cool (bedroom, bathroom closet suite w/ 9 ft ceilings and an office with a 11 ft vaulted ceiling). Would a 1.5 unit (placed in the attic space) be grossly inefficient? Can you use strategic placement of the thermostat to try to get more dehumidification and prevent short cycling? Can you just blow the extra air out an attic vent or something?
We have looked into mini-splits and are concerned that a single unit would not be able to cool all four spaces effectively. Multiple units would just be overkill.
Any advice would be greatly appreciated.
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Posted by mikenew (My Page) on Sat, Mar 1, 08 at 8:19
It's hard for me to believe you can get all that in 450 sqft. there are multi zone mini splits that may help in this application, otherwise you can bring in some outside air and condition it to offset the oversizing
Frigidaire vs Lennox gas furnace clip this post email this post what is this?
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Posted by lynnt (My Page) on Fri, Feb 29, 08 at 21:48
I live in the Washington DC area, in a 50-year-old 2300-sq-foot rambler. A service rep from my HVAC company shut down my 20-year-old Kenmore 80 1000-btu gas furnace this afternoon. He had run a camera on a cable up the burner flues into the heat exchanger, and showed me what he said were cracks: lighter lines among the black soot and more than a bit of rust. Although the monoxide alarms around the house and in the furnace room have not complained, he said the furnace was unsafe and must be replaced immediately.
OK, I can buy that the poor thing is at end of life. Question #1, do you agree that it had to be shut down immediately, or is this a pressure sales tactic? He didn't cut any wires, just turned off the breaker and the thermostat; is it safe for me to turn it back on?
Question #2, the sales rep is offering the following replacements, all 1000-btu Frigidaires (which I understand are made by Nordyne). What do you think of these furnaces, and does the price sound reasonable? They include running the required new exhaust PVC for the 93%er, plus all include $350 for running about 20 feet of flexible ducting to a badly-served dining-room addition.
80% 2-stage FG6TA096C12B $3500
80% 2-stage variable FG6RA096CVBA $4410
93% 2-stage FG6TC080CVBB $4550
The same company will replace my aged gas hot-water heater with a new 50-gal model for about $900, and add a system humidifier for about $650 if I do these at the same time as the furnace work. Comments?
Another company prefers Lennox furnaces; they say all I need is a 90K BTU furnace due to the increased efficiency these days -- though the old furnace was sized before the dining-room addition was built. They say the 80% Lennoxes are sturdy and far more reliable than the fancy Energy Star models. They are proposing:
80% G40 $2300
90% G51V $3400
and will do my hot-water heater for $625 along with the furnace replacement.
Is this apples and oranges? I really appreciate your input, and apologize for the long writeup. Both companies have good records in the area, and both have been around for more than a decade.
Lynn
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Posted by ryanhughes (My Page) on Fri, Feb 29, 08 at 22:56
The Lennox prices sound a bit low. Make sure you know what you're getting. Get all of it in writing: parts, materials, warranty, permit, etc. etc. Both brands are fine in my opinion. You really aren't comparing apples to apples; you have a "builder" Lennox or a SINGLE stage Lennox (I think the G51V is a good one--variable speed, 92.1% AFUE, etc.). The Frigidaire units are dual stage, which provides more comfort (low stage and high stage).
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Posted by mikenew (My Page) on Sat, Mar 1, 08 at 8:30
The tech had to shut you down for liability reasons but your not going to endanger your family by turning your heat on it is physically impossible for combustion product to get in your airstream in that furnace as the indoor air passing through your heat exchanger is positive pressure the worry is your indoor air making it into the combustion chamber and causing the flame to rollout but there should be safeties in place to shut down if that happens
Manual 'J' and Foam Insulation clip this post email this post what is this?
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Posted by lsufan (My Page) on Fri, Feb 29, 08 at 21:46
New house under construction. Live in South Louisiana. Most windows on North side of home. Foam under the roof deck(5-6 inches) and in the walls(3-4 inches) of a two story 6000 sq. ft. home. Manual J performed by several HVAC contractors...all provide for 5 ac units (varying tonnage)for a total tonnage of 16-18 tons! Told that the Manual J program does not always take into account the significance of the foam insulation....told program makes no allowance for anything with R value greater than 19.
Told by foam contractor that 16-18 tons of ac way high...suggest we could get away with as little as 6-8 tons. BTW, going with American Standard 18 SEER units with variable speed handlers.
What gives? Would think that we could get away with much less tonnage and number of units.
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Posted by mikenew (My Page) on Sat, Mar 1, 08 at 8:15
Manual J only knows what it is told and they don't know what to tell there is an R value to your structure period and that is what you need to know the foam contractor needs to talk to your HVAC guys. Kinda discouraging that five companies can't figure that out, SCARY!
do you think it's possible to keep the same refriderant lines that run from the condensor and air handler? they run inside interior walls and there is no real access to the crawl space on second floor where the handler is from an exterior wall.
Thanks for your help.
Both in and out need to go. Best to let a pro do it but maybe he would let you help him! Maybe let you wire it?
__________________
IAQ/HVAC for the past 13 years and still learning
Replacing an old condensor
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Hello, I am curious...I have 2 trane condesors outside from 1988. One still works fine, however the other can't hold a refridgerant charge for more than a month. Was told that we probably had to replace the unit. Was wondering if that just meant just the unit outside or if the air handlers inside needed replacing as well. Also is that something I could do myself or would it be wise to have a professional do it? Thanks for any help, as it is very appreciated.
mike n
AC Repair AC Coil Leaking
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If you replace the condensor the evaporator definitely needs to go as this is probably leaking also and the efficiencies of the equipment will not match and there are warranty issues also. If the lineset is properly sized there is no reason you can't keep it but it is possible it's not the right size make sure you check it yourself
mike n
If the charge is leaking out in a month then the leak is freakin' huge and it should be pretty easy to find it. They said you would 'probably' have to replace it? Did they locate the leak?
Depending on where the leak is it could be repairable easily enough if it's on exposed copper. (big IF) The thing is it will still cost you an unpleasant ammount of cash to do it.
...so I'm going to agree with the guys below here...
If the thing is 20 years old consider this an early wake up call before summer hits and just try and figure out how your going to pay for a new unit. Replace the inside and outside unit. No point in having a system that old and you pay to have the condenser replaced only to find next year your going to have to have the air handler replaced when you could have saved a few bucks now on trip time and labor and had it all done at once.
The thing with fixing a leak on an old system is that it stands a good chance of happening again :/
Michael
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