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06-15-2010, 07:15 PM #14Regular Guest
- Join Date
- Jan 2010
- Athens GA
Load calc s have only come into their own in the last 10-15 years.
Before that there were no calcs done ande if a contractor wanted to soundv hi tech he counted alum siding as insulation.
Insulation codes came into being in the 1970's.
Before calcs furnaces were sized by the "bettor to be too big than too small method"
Non contractors swimply would not believe the number of 100,000-120,000 btu units that we collectly have torn out of homes and replaced them with 45-50,000 furnaces.
I had one job where two janitrol 120.000 furnaces were twined and I took the both out and replaced them both with one 60m hi eff furnace.
A/cs were all sized by rule of thumbs like one ton per 500 sq feet,or 600 sq feet.
I don't know for a fact but I can guess THAT THERE HAS NEVER BEEN A LOAD CALC DONE ON YOUR HOUSE. As far as insulation is concerned you probably have the minimum requirements done because it was 1989.
To the fellow that laughed at asking for the blueprints,I used to ask.Not everyone has their blue prints and you would be surprised at how many do.If I had them the load calc just went so much quicker and smoother.I'd say it cut at least an hour off the time required.
06-15-2010, 07:52 PM #15Regular Guest
- Join Date
- Jun 2009
- Albuquerque NM
06-15-2010, 08:24 PM #16Contractor locator map
How many times must one fix something before it is fixed?
06-15-2010, 09:31 PM #17
I am a homeowner and in my experience of 3 load calcs for my house (2 of which I did using Hvac-Calc), they are unlikely to differ much unless somebody makes a goof. Remember this is a model, and garbage in = garbage out.
Evidently the job of doing a Manual J is worth $XXX at the going rate of professional labor. Better to pay that than to size wrong. Lots of people do cut a corner and just size according to what was installed before. It's not the worst thing to do but sometimes people are unhappy with the results, for example the new system might have inferior humidity removal because of a different design. In my case a Manual J told me downsizing was appropriate and that has to help humidity removal.
Best of luck -- Pstu
06-19-2010, 11:20 PM #18Regular Guest
- Join Date
- Jun 2010
- Houston, TX
08-12-2012, 03:25 PM #19
08-12-2012, 03:27 PM #20
This AINT rocket science, but it is science nonetheless!!!