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  1. #1
    Join Date
    Aug 2012
    Posts
    11

    New Manual J produced to match installed equipment.

    I posted earlier about issues with a new home cooling. (Thanks for the advice, a company is coming thursday to measure). However, part of my question is that the original Manual J state a 86,0000/71,000 Btuh 80% furance would be installed. Instead a 66,000/54,000 Btuh furance was installed. I paid to have an independent Manual J done and it closely matched the heating requirement of 73,003 Btuh outuput and required an additional 1/3-1/2 ton A/C.

    When I questioned this with the builder, a new Manual J was produced by the builders HVAC company that stated I only need a the 66,000/54,000 3 TON furance and the old Manual J was a mistake and I shouldn't look at it. Yet this new Manual J lowers my cooling from 3 Tons to 2 Tons, yet they will leave the 3 Ton A/C in place.

    I have looked at the new Manual J and to my untrained eye it seems suspect with some of the numbers. If anyone with experiece has time to glance it over I'd appreciate it.

    House:
    Ramber Facing North
    Upstairs 2340
    Basement 2360
    Total footage: 4700
    50% 10' ceiling 50% 9' ceiling on main floor.
    R38 Attic
    R19 2x6 walls.
    7 Bedrooms
    Location SLC, UT

    Questions:
    Missing 40 Square feet of glass on back of house.
    3 Rooms on the main floor have zero heating/cooling load.
    Ceiling dropped from 28% of the heating load to only 6.9%.
    Ceiling dropped from 40% of cooling load to only 14.9%.
    No Latent Cooling is required.
    No GR/lb included on the new Manual J.
    Zero people for latent load.
    Original calculated on MJ8 new one on MJ7 by the same company.
    Sensible heat ratio of 1.00 (Not sure but I keep seeing .75 as the standard)
    etc....
    Attached Images Attached Images

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