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Rules of Thumb and Heating Formulas?

RayWohlfarthRayWohlfarth Member Posts: 570
Howdy Wall Citizens,
I have the first draft complete on my new book on Heating Rules of Thumb and Formulas. I was wondering if you have any rules of thumb, secret calculations, or formulas you like to use and think would be beneficial to other wrench twisters like myself. The book is about 180 pages already. I never knew how much we had to know.
Thanks
Ray
Ray Wohlfarth
Boiler Lessons
Click here to take Ray's class.
Click here to buy Ray's books.

Comments

  • MikeL_2MikeL_2 Member Posts: 168
    edited January 9
    Ray,
    How about the value of 231? Cubic inches in a gallon; add a decimal point & 2.31 feet water column equals 1 psi.
  • RayWohlfarthRayWohlfarth Member Posts: 570
    @MikeL_2 I like that thanks
    Ray Wohlfarth
    Boiler Lessons
    Click here to take Ray's class.
    Click here to buy Ray's books.
  • LeonardLeonard Member Posts: 505
    edited January 10
    Related, but uses basics to remember it.

    A cube of water 1 foot on each side weighs 62.4 pounds
    Area of bottom of cube is simply = (12x 12) =144 square inches
    So pressure on bottom is 62.4/144 = .4333 pounds/sq inch ( psi)
    That's .433 psi /foot of depth

    If using oil with a specific gravity of .7 that pressure is .7 x .4333 =0.30 psi/ft
    Which means a hose of that oil 10 ft tall will make 3 psi at bottom.
    (check SG, gasoline = ~.7 , think #2 oil is higher)

    I did so much sonabouy design work I can't forget water weighs ~ 62.4 #/cubic foot ---- ( this is it's density)
  • RayWohlfarthRayWohlfarth Member Posts: 570
    Thanks @Leonard I appreciate it
    Ray Wohlfarth
    Boiler Lessons
    Click here to take Ray's class.
    Click here to buy Ray's books.
  • LeonardLeonard Member Posts: 505
    edited January 10
    Interesting side note ( for teaching maybe)
    0.433 psi /foot of depth .... means 1,000 ft underwater it's 433 psi

    And at bottom of Mariana Trench , the deepest known point in Earth's oceans. 36,070 feet depth means pressure is ~15,600 psi
    (ignores that salt water is little heavier than 62.4 #/CF fresh water)
  • EBEBRATT-EdEBEBRATT-Ed Member Posts: 4,695
    Not hydronic but a piece of ductwork 1 square foot (12" x 12") will carry 1cfm with a velocity of 1 fpm. I use it all the time when I forget/can't find my ductulator.

    fuel oil 1" of vacuum for every foot of vertical lift + .5" vacuum for every foot of horizontal run.

    1000 btu/lb of steam. lbs of steam =lbs of condensate. lbs of condensate/8.33=gallons of condensate.

    Air handle capacity is 400-450 cfm/ton of cooling
  • GWGW Member Posts: 3,202
    You have the math constant for a 45 degree angle? 1.414? The plumbing pros use the math, the others hold tape measures in the air and give it their best guess
    Gary Wilson
    Wilson Services, Inc
    Northampton, MA
    www.wilsonph.com
    [email protected]
  • GWGW Member Posts: 3,202
    A chart I keep in my cloud
    Gary Wilson
    Wilson Services, Inc
    Northampton, MA
    www.wilsonph.com
    [email protected]
  • RayWohlfarthRayWohlfarth Member Posts: 570
    wow Im busy writing notes Thanks Lots of great ideas
    Ray Wohlfarth
    Boiler Lessons
    Click here to take Ray's class.
    Click here to buy Ray's books.
  • RayWohlfarthRayWohlfarth Member Posts: 570
    @JohnNY My hero lol
    Ray Wohlfarth
    Boiler Lessons
    Click here to take Ray's class.
    Click here to buy Ray's books.
  • Pressure drop = Longest run in feet. Add 50%. Times .04 . This is your head in feet. Dan says figure 6 feet per 100 ft of pipe.
    --------------------------------------------------------------------------------------------
    Formulas used to calculate annual energy costs:
    Natural Gas (BtuHr loss of House / AFUE of appliance) X (Htg Load Hrs /100,000) X .77 X Gas rate per 100 cf = cost to heat.

    L. P. Gas (BtuHr loss of House / AFUE of appliance) X (Htg Load Hrs /91,500) X .77 X Gas cost per gallon = cost to heat.

    Oil (BtuHr loss of House / AFUE of appliance) X (Htg Load Hrs /138,000) X .77 X Oil cost per gallon = cost to heat.

    Heat Pump (BtuHr loss of House / HSPF) X (Htg Load Hrs / 1,000) X .77 X Electric rate per kWh = cost to heat.

    Electric Resistance (BtuHr loss of House / 3.143) X (Htg Load Hrs / 1,000) X .77 X Electric rate per kWh = cost to heat.

    Cooling Costs (BtuHr gain of House / SEER) X (Cooling Load Hrs / 1,000) X .77 X Electric rate per kWh = cost to cool
    Often wrong, never in doubt.
  • RayWohlfarthRayWohlfarth Member Posts: 570
    Thanks @Alan (California Radiant) Forbes Appreciate it
    Ray Wohlfarth
    Boiler Lessons
    Click here to take Ray's class.
    Click here to buy Ray's books.
  • hot rod_7hot rod_7 Member Posts: 9,095
    Kw to btu X 3.41
    Heat= 8.33v (delta t)
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    The magic is in hydronics, and hydronics is in me
  • RayWohlfarthRayWohlfarth Member Posts: 570
    Thanks @hot rod_7
    Ray Wohlfarth
    Boiler Lessons
    Click here to take Ray's class.
    Click here to buy Ray's books.
  • jumperjumper Member Posts: 1,247
    Most important rules are maximum fpm for ducts and maximum fps for pipes. Flout them and you'll see.
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