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  1. What is the rule of thumb for the number for return grilles?

    Commercial office building with the return via a dropped ceiling plenum. It has a separate perimeter heating/cooling system (diffusers above windows) and central ventilation/cooling system with VAV...
  2. The answer is yes and no. Some more so than...

    The answer is yes and no. Some more so than others. The residential market doesn't have the cost structure built into for elaborate duct work or system design. The installers have guidelines in the...
  3. Call AKDuct for a contractor for the ductwork.

    Call AKDuct for a contractor for the ductwork.
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    Manual J takes a single steady state load. The...

    Manual J takes a single steady state load. The real world isn't like that. However, the residential HVAC sales model barely supports using Manual J. While duct work can sap 25% or more of a forced...
  5. Nordyne Annouces iQ Drive Zoning with Airzone

    They are using the Airzone Innobus modulating zoning. Never heard of Airzone before. Has someone here used it?

    http://www.airzoneusa.com/product_new.php#
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    Where do HTP and Triangle Tube fit in?

    Where do HTP and Triangle Tube fit in?
  7. In 2010 houses vary so much in their construction...

    In 2010 houses vary so much in their construction and the efficiency of their duct system you can't base it on floor space.

    When doing the analysis on an unconstructed building you can use the...
  8. You need a heating and cooling from the MJ8. You...

    You need a heating and cooling from the MJ8. You also need it room by room, and ideally with a knowledge of what the biggest issues are in each room. For example heat gain can be radiant from...
  9. Elaborating on that there are two types of...

    Elaborating on that there are two types of programs: one that calculates the maximum heat loss and heat gain (in btu/hr) for your climate and one that calculates that plus the actually energy usage...
  10. Question: has the design heat loss and heat gain...

    Question: has the design heat loss and heat gain been calculated?
  11. That would be expensive gas and relatively cheap...

    That would be expensive gas and relatively cheap electricity.

    The system you listed seemed pretty basic. How big is your budget?

    I'd pay attention to the ducts first. There will be a lot of...
  12. First: Where is the house? Second: Which way...

    First: Where is the house?

    Second: Which way is south?

    Third: What are you objectives: comfort, operating costs, installation costs?

    Fourth: What are the rates (including delivery and...
  13. Based on those numbers some where in the 30-35F...

    Based on those numbers some where in the 30-35F range would be my guess, around 22-26mbtu.
  14. What is the heat loss calculation for the...

    What is the heat loss calculation for the structure at different ambient temps? You know you will be at 17mbtu at 17F.
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    Gentleman, it is Sunday, the kindergarden is not...

    Gentleman, it is Sunday, the kindergarden is not in session.
  16. Replies
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    I was confused. Sounds like an argument for...

    I was confused. Sounds like an argument for reheat or separate dehumidifier, which effectively is cooling with with reheat.
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    He won't lose anything in SRECs; they are...

    He won't lose anything in SRECs; they are calculated on power generated regardless of whether it is used locally or fed to the grid. However, those PV kwh are the same cost as his other electricity....
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  19. -30F? North Pole.

    -30F? North Pole.
  20. Yes, but he would have to be on the North Pole or...

    Yes, but he would have to be on the North Pole or have a furnace sized for the neighborhood for it to work much below 30F.
  21. Replies
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    You may be right in some instances but for a...

    You may be right in some instances but for a different reason.

    The low stage uses the same size coil as a high stage with a lower airflow. As a result, the air has a longer dwell time of the coil...
  22. His heat pump would be cost effective at 10F....

    His heat pump would be cost effective at 10F. However, it seems that he probably has a loss of 1000btu/F. At 47F his small heat pump is already down to 28mbtu vs. a loss of 22mbtu. How far below that...
  23. A cubic meter is about 35 cubic feet; 100 cubic...

    A cubic meter is about 35 cubic feet; 100 cubic feet to the therm. You are paying about $1.35/therm, or about 1.35/1000btu. Your electric is about 2.2/1000btu.

    Your furnace is about a COP of...
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    PV in NJ isn't about energy, it is about SRECs...

    PV in NJ isn't about energy, it is about SRECs and money. You get the same money feeding it into the grid or using it. It isn't free.

    For comfort you can get a hydronic ground source heat pump and...
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    If you have NJ priced natural gas available at...

    If you have NJ priced natural gas available at $1.35-1.40/therm, it is virtually impossible to configure a cost effective ground source heat system.

    The first hurdle is to think of the ground...
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