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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.
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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.
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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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    Condensing Boiler Efficiency: Inflated?

    The equation for nat gas combustion is CH4(g) + 2 O2(g) -> CO2(g) + 2 H2O(l) + 891 kJ/mol. The efficiency is dependent on turning the water into a liquid.

    A tankless water heater has 40-50F inlet...
  27. The high velocity vendors would counter that...

    The high velocity vendors would counter that their duct systems have much less leakage than most residential systems. Even with a genduct installed fiber duct, how would you do the runout in the...
  28. Replies
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    Mixing is an issues with VAV systems such as...

    Mixing is an issues with VAV systems such as residential two-stage cooling. The low stage has less air flow, lower face velocities, less throw and as a result less mixing.

    All systems have...
  29. Mini-splits come in all sizes. Whether it is a...

    Mini-splits come in all sizes. Whether it is a mini-split, a conventional system, a high velocity system, the biggest single phase compressors are 5-tons. There are a few exceptions--Drake and Aaon...
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    Does a 2-stage dehumidify more than a high stage?...

    Does a 2-stage dehumidify more than a high stage? Probably not. For any given inlet db/wb, the higher the cooling relative to the air flow will reduce the dewpoint and dehumidification more.

    Net,...
  31. First, you have winters. Is the Unico being sized...

    First, you have winters. Is the Unico being sized with a heat pump only or is their backup heat.

    Second, have you also looked at mini-splits? Again the backup heat issue, but it would eliminate...
  32. Replies
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    Now when the furnace is communicating (e.g. ...

    Now when the furnace is communicating (e.g. iComfort), do you need to add a humidistat too, or is it already part of the iComfort package (or Infinity, or ComfortLink II)?
    the comfortlink II and...
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    Combustion Analyzer for '38 Buick

    Our '38 Buick failed inspection! CO had to be under 8.5 and were 8.46, close put ok. The HC was 21,005 when the limit was 14,000.

    We've been told it is probably an idle adjustment issue; it runs...
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    Price is always part of it, or we'd all be...

    Price is always part of it, or we'd all be driving Rolls Royces and Ferraris.
  35. Replies
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    Not sure how Daikin's mini-splits are different...

    Not sure how Daikin's mini-splits are different from Mitsubishi's, Fujitsu's, etc. Daikin does have a nice small reverse cycle chiller, the Altherma, but it is hyper expense.

    None of the...
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    This is one of the reasons I'm looking at...

    This is one of the reasons I'm looking at hot/cold water, to get a constant velocity or constant register throw; multi-stage/modulating furnaces and DX cooling/heating tie air flow to heat quantity...
  37. Replies
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    Two questions: What is a DF system and is 'on...

    Two questions: What is a DF system and is 'on demand dehumidification' a manual switch to the dehumidication leads or a separate device like this:...
  38. Replies
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    First, I wasn't critiquing your installs but...

    First, I wasn't critiquing your installs but highlighting that heat pumps are assembled units whose efficiency isn't influenced by installation unless faulty.

    Second, how does a furnace make air...
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    Airmech: the issue with the ducts is that a...

    Airmech: the issue with the ducts is that a comparison in the same house usually also improved other defects so an A to B comparison is not possible.

    ga-hvac: And how does your installation...
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    Other than being a well-insulated low mass...

    Other than being a well-insulated low mass boiler, how does the System 2000 run more efficiently than a mod-con?
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    The Choice The Voters Have In Delaware

    http://hvac-talk.com/vbb/attachment.php?attachmentid=127151&stc=1&d=1285095593
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    Would you care to offer an analysis to back that...

    Would you care to offer an analysis to back that up? It is unlikely there is a controlled comparison available; most install are new vs. old, have some ductwork changes, and the temps vary year to...
  43. Damn decimal points! A therm of natural gas...

    Damn decimal points! A therm of natural gas creates about 9.4 lbs of water from combustion. The 100mbtu rating is if the water is condensed to a liquid. If it remains a vapor (is not condensed) 9200...
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    Now that is a recommendation! Know anyone in...

    Now that is a recommendation!

    Know anyone in NJ? :)
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    It sounds like the he answered the AC question....

    It sounds like the he answered the AC question. However, what about the duct work? Sort of like putting a new 572 Chevy in to a rusty 75 Impala.
    ...
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    The answer is it depends on your local electric...

    The answer is it depends on your local electric rates. In neighboring PA, beenthere and others report the rates are so low people install heat pumps with electric resistance heating as backup. Here...
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    A couple of things. First, with a gas...

    A couple of things.

    First, with a gas furnace/heat pump it is either heating with the heat pump OR with the furnace. The cutover point will depend on your electric rate vs. gas rate, the...
  48. All outdoor packaged systems, commercial and...

    All outdoor packaged systems, commercial and residential, and unconditioned attic installs in cold climates are non-condensing. It is possible to install the later with heating wire to prevent...
  49. Not sure I understand your post. What are you...

    Not sure I understand your post. What are you saying?

    P.S.
    Don't really need a new car now and already have a 320CDI. They don't make them they we like them anymore...a shame. Hopefully that...
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    Why do you prefer the Biasi, why change the...

    Why do you prefer the Biasi, why change the burner or does it come with that burner, and isn't the Beckett NX an oil burner?
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