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When a 4 ton air conditioner cools like it's 5. The proof of how well these measures work can be found in case of the 2,300 square foot fixer upper in Pleasant Hill. With summer coming up the first thing the homeowners wanted to do was install a completely new HVAC system. The old system was a 30+ year old heat only system. It was quite literally unsafe because its return was not ducted. Instead is sucked air from the same room the water heater sat in.In addition the heating load was abnormally high. The windows were all single pane. And there were a lot of them, especially in the living room. There was literally no insulation in the walls and very little in the attic. A Manual J calculation with absolutely no fudge factors added dictated that a 5 ton system was needed. Even though 5 tons was called for, this couple wanted a system that sized for the upgrades that the house would eventually have. Based on that we installed a 4 ton system utilizing the existing ducts for most of the smaller first floor and installing all new ducts for the larger second floor. We employed literally every step listed on this page. The results were impressive. First we'll show you some of the particulars. Keep in mind that this was the very first major project being performed on a fixer upper.
This job was unique in that the homeowners wanted a fresh air intake system. The orange damper above on the right opens and closes the 20 inch return duct that goes to the house. The smaller 14 inch damper on the left opens and closes a duct that leads to great outdoors. When the fresh air system is turned on it disables the air conditioner, closes the return to the house and opens the return to the outdoors.
The duct above that goes horizontally to the right and terminates at the wall brings in 100% outside air through the opening you see in the corner picture. That opening was later screened and louvered. The result is that when it cools off in the evening they can flush the hot air out of the house with cool, filtered nighttime air. If they leave it running overnight it will chill the house for the next day and lessen air conditioner usage.
I go to great
lengths to make sure your system is airtight. As you can see the
boot's seams and where the boot meets the floor are all sealed.
Above is just one of the diffusers I talk about here. As you can see the open area makes up a huge percentage of the diffuser. The front blades are individually adjustable. If you were to point all of them straight at the camera you'd have an awful lot of the dark area behind it showing through. That's in stark contrast to a typical cheap diffuser.
Of course the star of the show is the furnace, evaporator coil and air conditioner. For comparison purposes let's first take an average five ton system. Roughly 30% of a typical air conditioner's capacity will be spent on moisture removal. (Also called latent heat removal. Click here for an explanation.) Another 15% (often more) will be lost to duct leakage. That leaves us with only 55% of the air conditioner's capacity devoted to sensible heat removal. In other words a typical 5 ton system delivers less than 3 tons of sensible heat removal to the living space. On the other hand this four ton system was delivering 82% of rated capacity in the form of sensible heat removal to the living space. That's 3.3 tons, which is more than a typical five ton system. As a result when summer rolled around and it hit 105 degrees outside they had no trouble maintaining 75 degrees inside.
That same boot from below. The thing
to take note of here is the reinforcement. You'd be amazed at
how often a contractor will cut a hole in the floor and do
nothing to support dangling pieces of the sub floor.
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