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Friday, April 5, 2013

Would an AC Unit by any other name still be an AC Unit?

The one question we had during our Pre-Con meeting that wasn't answered was about how many AC units we would be getting and what their capacities were.  The pull sheet was ambiguous and I wanted to make sure I didn't get 1 unit that would be running constantly and die just outside warranty.  I also didn't want to finish more of the basement and have it work that much harder.

Our PM was on top of this and got us answer the very next morning.  The pricing manager said we would be getting one unit.  I was a bit puzzled by this for a few reasons.  One is that the High Hopes for our Highgrove Blog got two units and the math wasn't working out.

I'm not an HVAC Engineer but I can read the side of the box, just like the salesman at Best Buy.  Our house is listed at 3,500sqft (before adding 4" Extensions and Finished Basement).  Depending on Heat Load (a factor calculated based on Square Footage, Region, Building Materials, Occupants, etc.), the rule of thumb is 1 nominal ton or 12,000 BTU's of cooling per 600 sq. feet.  Give me a second while I take my shoes off to count.  ~3,600sqft = 6 tons or 72,000 BTU's.  In reality with the basement we are closer to 5,000sqft (never asked what our final square footage was).  So we would need  8 tons or 96,000 BTU's.

Emailed PM with picture from referenced blog above and just asked if he could verify because it didn't' sound right.  Again, got right on it and received the answer.  We do get 2 units but we get a 2 Ton and 2 1/4 Ton unit = 4 1/4 tons and 51,000 BTU's.  So we are getting nearly 50% of the cooling required for this sized house.  Hmmm????

The manufacturer's specifications match the math above, yet the engineer in Maryland that designed the house said this is appropriate.  Remember the factors that go into Calculating Heat Load?  Seems as if the Cooling Requirements throughout the country may have some variation and the HVAC pro's should determine what is required for each specific area.

Energy Star 3.0...
Question?  If you put all Energy star stuff in your house, does it mean you are Energy Efficient?

OBTW, the Energy STAR folks say the # should be 12,000 BTU's per 450-550sqft and says to add 10% if there is no shade, which we do not have yet.

These units are 14 SEER (Seasonal Energy Efficiency Ratio).  The SEER measures air conditioning cooling efficiency.  It is calculated by the cooling output for a typical cooling season divided by the total electric energy input during the same time frame. A higher SEER rating means greater energy efficiency.

An interesting Fact.  Comfort Maker (The Company RH uses), sells units between 13 SEER and 22 SEER.  Another interesting fact.  The 13 SEER model is NOT Energy STAR compliant but the 14 SEER is.  So just barely meeting the requirement.

Now back to the original question.  If these undersized units are working like dogs all the time (even though they are Energy STAR compliant), will our units really be Energy Efficient?  I think it would be like putting a Go Cart motor in a 3/4 Ton pick-up.  While the Go Cart would get great gas mileage in a little aluminum frame, I doubt it would be able to move the big truck and would eventually burn itself up.  Much like our units will...probably just outside their warranty period.


  1. With A/C you are better off with smaller units vs. bigger (oversized) ones. The smaller units will run longer and do a much better job with dehumidification vs a large unit that will have short run cycles and produce cold air, but will not dehumidify as well leading to cool, but clammy conditions inside the home.

    1. Good points, thanks. I think size is relative. A 5 Ton unit for this house would be a small unit and I don't think RH is going to spring for 3 - 2 1/2 Ton units (1 for each floor), which I would prefer for many of the reasons you mentioned above. My point is that in a house where most of the 1st floor has nearly 20ft ceilings and large windows, these units are grossly under sized to handle the spaces... especially the 2nd floor. All the hot air is going to rise unobstructed and broil our bedrooms. I have thought about getting an attic fan and installing it somehow in the basement to pull the cooler underground air up. We'll see how that goes. I guess, first things first...get the house built, then worry about how to cool it. At this rate, I will be worrying about heating it versus cooling it.

  2. Hi,
    Any details on water heater they are putting in? Brand and capacity...

    1. Sorry for the delay. We were out at the lot and then I had to find all our paperwork. Our Master Selection List (MSL) says the following: On page 1, it says IHD, Gas Water Heater as Community Feature (this means it may not be included in all communities but it is in ours). When you look at IHD on Page 2 you will see that IHD is a High Efficiency Water Heater but it also has a Note R27 which is on Page 3 which says its a 50 Gal Gas Water Heater with Power Vent. RH uses Bradford White water heaters: ttp:// Not sure which model. This is my interpretation of the MSL, I would confirm with the SR. An email usually works and you'll get a pretty quick response.