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Thread: Load-Calc????

  1. #14
    Join Date
    Aug 2001
    Troysp..The TOTAL heat gain is 35,477 btuh
    There for you need to remove 35,477 btuh to keep up with the heat gain. Latent and sensible heat have both been included in this total. If you were sizing just based on sensible heat, then it would be undersized because latent heat wasn't taken into consideration.
    Latent heat is basically humidity. It takes btu's in order to change the state of a gas to a liquid.

  2. #15
    Join Date
    Oct 2001
    New Orleans, LA
    What I'm saying is that he should size the unit by making sure that it's sensible capacity is large enough for the sensible load and then make sure that the latent capacity of the same unit is large enough for the latent load. Since his sensible to latent ratio is about 85%/15%, if he installed a unit that was right according to the total only and that unit had a sensible to latent ratio of say 70%/30%, he would not have the sensible capacity that he needed. I'm pretty sure that this is the same method followed by manual S. It's also the same advice given by Don Sleeth in the manual for his program.

  3. #16
    Join Date
    Oct 2001
    1079 Front Street Uniondale, N.Y.11553

    LIPA rebate

    Hey Pete:
    Sounds like you are almost there. But, remember you must adhere to the LIPA rebate parameters if you want that 14 SEER rebate.
    Take the sensible heat gain and divide by 77%. Then add 6,000 BTU (that they will allow) and that is the BTU heat gain they will allow for. Also remember you must not calculate for more than 20 degree differential. Meaning on the A/C side if you are deciding it is 92 degrees outside you cannot calculate as your default any more than 72. But they do give you that 6,000 BTu margin of error.
    Unfortunatly, that is the reason that most contractors on Long Island have decided to go 12 SEER because they can't be hassled by this process or they just don't know how to do Manual J and don't want to learn.
    It's like I have always said.."it's not that I'm so good. it's 'cause most of my compitition is so bad".
    On the heat side if you are going with zoning or BTu modulation or two speed technology you are going to be in the ballpark.
    My shop is real busy right now and the location of my business probably couldn't service you well. The jobs I am doing near your home are complicated Hydro-air and/or high velocity jobs, and they are construction type and I would not want to install a system that I could not service 100%.

    What we do in muti-story is put a boiler downstairs with a fan coil in the basement next to the boiler. This fan coil has dual for the a/c and one for the heat. Then I only have to bring two pieces of 3/4 or 1" copper to feed the heating coil in another air handler in the attic. I get two zones, I design the boiler around my heating coils and my a/c around the seer rating I want for the condensers. Therefore there is minimul contruction to get heat upstairs and no boxing in of duct work. The other beauty of this is if the homeowner wants a "in-direct" water storage tank then my boiler can handle that future expansion.Usually what happens is you size for the in-direct and and you put the boiler on "priority" for domestic hot water. These in-direct last forever and have the best recovery rate! Additionally, if you ever wanted to put in radiant heat let's say in your kitchen or baseboard in your basement as a seperate zone you have the boiler as the heart of the system and you are not locked into a warm air furnace. Gas hot water heaters are junk and last for 8-10 years.
    This method has become very popular around these parts and knowledgable contractors, builders and saavy homeowner know what it is about.
    If you want real hi-tech boilers you can look at "Viessmann" or "Budereus" or even those 90+% direct vent "Munchkins".
    The in-direct can be added later or you can get the whole package.
    This thinking is not new but more expensive but much more flexible in my opinion and for others who have done it. You gotta "think out of the box".
    It doesn't seem to me that your in a super rush to do this job based upon all the questions you are asking and the level of research you have done. You may want to keep on digging.
    E-mail me with any questions and I will try to help you.
    Brian Gelber

  4. #17
    Join Date
    Oct 2001
    Austin, TX 78745

    Load Calc

    Hello Pete. If you are interested you can get a software program online to do your own Load-Calculations. It will cost you $39 for the program and lasts 2 months. I have no affiliation with them, though. Hope it helps. The address is below.

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