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Message
Another HVAC Question for OT Experts
Posted on 9/20/15 at 8:21 pm
Posted on 9/20/15 at 8:21 pm
Building a new home, approx. 2500 sq. feet downstairs with one bedroom approx. 300 sq. feet upstairs.
Suggestions on size, type unit. Also, the upstairs will rarely be occupied, if that matters in your opinion.
Suggestions on size, type unit. Also, the upstairs will rarely be occupied, if that matters in your opinion.
8
Posted on 9/20/15 at 8:52 pm to FreeState
I am building the same size house but it really depends on the material you use. Are you using traditional attic insulation or going spray? What type of windows will you use and what direction does you house face? A good HVAC company will run a Manual J to determine the heat and cooling load and recommend equipment based off that. You can't rely on guys that use a rule of thumb for sizing equipment anymore. I didn't worry as much about brand as I did the installing company. The day the equipment is installed is the most important day of the units life and could mean the difference between seven years of service or twenty.
Posted on 9/20/15 at 8:52 pm to FreeState
Use the rule of thumbs.
Stand on the street in front of your home, hold a thumb up at arms length and try to block out your house from your vision. For each thumb it takes to block out the house you need one ton of AC.
That should work or you could consult with a professional HVAC man.
Stand on the street in front of your home, hold a thumb up at arms length and try to block out your house from your vision. For each thumb it takes to block out the house you need one ton of AC.
That should work or you could consult with a professional HVAC man.
This post was edited on 9/20/15 at 8:53 pm
Posted on 9/20/15 at 8:56 pm to ruzil
I've never heard that.
It's about 1 ton per 600 sf. maybe 500 sf.
ETA: for the OP, consider about a 4 - 5 ton unit downstairs, maybe even two 2 ton units. For the 300 sf room upstairs, consider one of those window type units that you typically see in motels.
It's about 1 ton per 600 sf. maybe 500 sf.
ETA: for the OP, consider about a 4 - 5 ton unit downstairs, maybe even two 2 ton units. For the 300 sf room upstairs, consider one of those window type units that you typically see in motels.
This post was edited on 9/20/15 at 8:59 pm
Posted on 9/20/15 at 8:59 pm to FreeState
Is recommend 1.5 tons.
Posted on 9/20/15 at 9:01 pm to FreeState
I'd go a half to full ton over what you need. With the way the heat is here during the summer it would be nice and keep up a whole lot better.
Posted on 9/20/15 at 9:01 pm to East Coast Band
quote:
It's about 1 ton per 600 sf. maybe 500 sf.
It's 1 ton per 500 but that could change depending on a variety of factors such as insulation type, ceiling height, etc.
Posted on 9/20/15 at 9:04 pm to daviddsims
daviddsims, I am putting 6 inch bats in the walls, 6 inch bats in ceiling, and blowing an addition 12 inches in ceilings. 6 inch stud walls, 3/4 inch plywood, with basic wrap plus 1 inch styrofoam outside. Outside that, 1 x 6 treated siding, sort of a ship lap. Also, caulked every joint.
Front of house faces east. Back faces a lake, west. Also, the overhang on the house is at least 2 feet, all the way around with a hip roof.
Front of house faces east. Back faces a lake, west. Also, the overhang on the house is at least 2 feet, all the way around with a hip roof.
This post was edited on 9/20/15 at 9:07 pm
Posted on 9/20/15 at 9:07 pm to FreeState
5 ton downstairs - ductless mini split upstairs.
Posted on 9/20/15 at 9:09 pm to RodFarva
Oversizing is as bad as undersizing.
Posted on 9/20/15 at 9:11 pm to RodFarva
quote:
With the way the heat is here during the summer it would be nice and keep up a whole lot better.
Bad idea for lot's of reasons.
Cooling a house isn't just about dumping cool air in. It's about being comfortable and part of that comes into play with moisture control. Oversized air conditioners don't run for a long time because they reach the cooling temp faster and then shut off leaving a lot of moisture in the air. Properly sized air conditioners run longer and in turn work longer to take that moisture out.
There have also been studies that show you don't save money using a bigger A/C to cool off faster.
This post was edited on 9/20/15 at 9:13 pm
Posted on 9/20/15 at 9:27 pm to stout
quote:
Bad idea for lot's of reasons. Cooling a house isn't just about dumping cool air in. It's about being comfortable and part of that comes into play with moisture control. Oversized air conditioners don't run for a long time because they reach the cooling temp faster and then shut off leaving a lot of moisture in the air. Properly sized air conditioners run longer and in turn work longer to take that moisture out.
This X 1000, I replaced a perfectly good system in a house I bought because it was too big and the humidity stayed much too high, the house stays dry and cool, the electric bill went down a small amount.
Posted on 9/20/15 at 9:28 pm to Martini
quote:
5 ton downstairs - ductless mini split upstairs.
Not sure about the downstairs tonnage, but the upstairs mini-split is the only way to go. Just be sure to get some kind of wall mount for to hold the remote.
Posted on 9/20/15 at 9:40 pm to WeeWee
Go with a Lennox HVAC unit.
Posted on 9/20/15 at 9:42 pm to stout
Oh I'm sorry you're right. Not. Having a 30 degree split is still going to take the air conditioner a fair amount of time to perform that.
Posted on 9/20/15 at 9:44 pm to stout
quote:
for lot's of reasons.
Cooling a house isn't just about dumping cool air in. It's about being comfortable and part of that comes into play with moisture control. Oversized air conditioners don't run for a long time because they reach the cooling temp faster and then shut off leaving a lot of moisture in the air. Properly sized air conditioners run longer and in turn work longer to take that moisture out.
There have also been studies that show you don't save money using a bigger A/C to cool off faster.
Hece why I said half to full ton. But assuming it's 100 outside during the summer(which it is) having a 30 degree split is hard to achieve.
Posted on 9/20/15 at 9:45 pm to RodFarva
quote:
Oh I'm sorry you're right. Not.
So I guess every study done on this ever is wrong and you're correct?
This post was edited on 9/20/15 at 9:46 pm
Posted on 9/20/15 at 9:56 pm to RodFarva
quote:
Hece why I said half to full ton
That can still cause short cycling even in 100 degree temps. Especially with a newer home and better insulation.
ETA: Systems today have larger condenser coils and evaporator coils so upsizing of the past isn't practiced anymore. I know A/C people used to recommend upsizing your air handler a half a ton over your condenser but that doesn't happen anymore with the efficiency of the newer systems.
This post was edited on 9/20/15 at 10:00 pm
Posted on 9/20/15 at 10:05 pm to FreeState
I hate my mini split, don't get one of those. I would probably get two units and put a zone kit on one of those so it will have two thermostats on the one unit. One for upstairs where it can run and keep that section seperate.
Posted on 9/20/15 at 10:20 pm to Libertariantiger
quote:What?
I hate my mini split, don't get one of those.
The right PTAC is the perfect solution for his upstairs needs. Just because somebody dies in a Porsche doesn't necessarily make all Porsches a safety risk.
Your suggested "solution" in inordinately complex and initially much more expensive and will be crappy to live with long-term from a "who's going to fix this?" standpoint. Other than that, it's brilliant.
This post was edited on 9/20/15 at 10:25 pm
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