Key Water Heating Charts

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KEY WATER HEATING CHARTS AND FORMULAS
by Rich Grimes 

It’s 2012 already and in this issue we will try to give you plenty of information and useful charts related to water heating. I don’t receive many requests so I am glad to accommodate on such a pertinent subject. The best part is that you won’t have to read too much from me as these charts and formulas speak for themselves! So here we go…

BTU

A British Thermal Unit (BTU) is a measurement of heat energy. One BTU is the amount of heat energy required to raise one pound of water by 1ºF. Water weighs 8.33 pounds per gallon so we can calculate that one gallon of water requires 8.33 BTU to raise the temperature 1ºF.

BTU CONTENT OF FUELS

ENERGY SOURCE                        BTU PER HOUR

COAL

1 Pound                                         =       10,000 – 15,000

1 Ton                                              =       25 Million (app.)

ELECTRICITY

1 KW                                              =       3,412

OIL

1 Gallon #1 Fuel                            =       136,000

1 Gallon #2 Fuel                            =       138,500

1 Gallon #3 Fuel                            =       141,000

1 Gallon #5 Fuel                            =       148,500

1 Gallon #6 Fuel                            =       152,000

GAS

1 Pound of Butane                         =       21,300

1 Gallon of Butane                         =       102,800

1 Cubic Ft. of Butane                     =       3,280

1 Cubic Ft. of Manufactured Gas    =       530

1 Cubic Ft. of Mixed                        =       850

1 Cubic Ft. of Natural                     =       1,075

1 Cubic Ft. of Propane                   =       2,570

1 Pound of Propane                       =       21,800

1 Gallon of Propane                       =       91,000

HORSEPOWER

1 Boiler Horsepower (BHP)            =       33,475 BTU

1 Boiler Horsepower (BHP)            =       34.5 Pounds of Steam @ 212ºF

1 Boiler Horsepower (BHP)            =       9.81 KW

COOLING

1 Ton of Cooling                             =       12,000

GAS INFORMATION

NATURAL             PROPANE

Specific Gravity                                                          =       0.62                    1.52

Flammability Limits (GAS/AIR Mixture)           =       4%-14%             2.4%-9.6%

Maximum Flame Propagation (GAS/AIR Mixture) =       10%                    5%

Ignition Temperature                                                =       1200ºF                950ºF

1 Pound of Gas (1 PSI)         = 28″ Water Column (w.c.)

1 Pound of Gas (1 PSI)         = 16 Ounces (oz.)

1 Therm = 100,000 BTU

 

ELECTRICAL INFORMATION

1 Kilowatt (kW)   =       3412 BTU Per Hour

1 Kilowatt (kW)   =       1000 Watts Per Hour

1 Kilowatt Hour (kWH) will evaporate 3.5 pounds of water from and at 212ºF

 

Amperage – Single Phase (1 Ø)      =       KW x 1000                   or      WATTAGE
                                                                         VOLTAGE                               VOLTAGE

 

Amperage – Three Phase (3 Ø)      =       KW x 1000                   or      WATTAGE
                                                                      VOLTAGE x 1.732                  VOLTAGE x 1.732

 

WATER HEATING FORMULAS

 

BTU Per Hour Requirement

BTU OUTPUT        =       GPM x Temperature Rise x 8.33 Lbs/Gallon x 60 Minutes

 

BTU INPUT           =       (GPM x Temperature Rise x 8.33 Lbs/Gallon x 60 Minutes)

% Efficiency

 

Heat Transfer Efficiency

% EFFICIENCY    =       (GPH x Temperature Rise x 8.33 Lbs/Gallon)
BTU/Hr INPUT

 

Heat-Up Time

Time in Hours      =       (GPH x Temperature Rise x 8.33 Lbs/Gallon)
                                               (BTU/Hr INPUT x % Efficiency)

 

Temperature Rise

Temp. Rise (∆T)   =           (BTU/Hr INPUT x % Efficiency)   

(GPM x 60 Minutes x 8.33 Lbs/Gallon)

 

GPH Recovery

Electric                =       (kW INPUT x 3412 BTU/kW x % Efficiency)

(Temperature Rise x 8.33 Lbs/Gallon)

 

Gas                     =                (BTU/Hr INPUT x % Efficiency)       

(Temperature Rise x 8.33 Lbs/Gallon)

 

MIXED WATER FORMULA

% of Hot Water Required      =       (Mixed Water ºF – Cold Water ºF)

(Hot Water ºF – Cold Water ºF)

 

WATER INFORMATION

1 Gallon     =       8.33 Pounds

1 Gallon     =       231 Cubic Inches

1 Cubic Ft   =       7.48 Gallons

1 Cubic Ft   =       62.428 Pounds (at 39.2ºF – maximum density)

1 Cubic Ft   =       59.83 Pounds (at 212ºF – boiling point)

1 Ft of Water Column (w.c.) = .4333 PSI

 

Water expands 4.34% when heated from 40ºF to 212ºF

Water expands 8% when frozen solid

 

OPEN VESSEL

BOILING POINT @ 0 PSI      ALTITUDE

212ºF                                    0 Feet (Sea Level)

210ºF                                    1000 Feet

208ºF                                    2000 Feet

207ºF                                    3000 Feet

205ºF                                    4000 Feet

203ºF                                    5000 Feet

201ºF                                    6000 Feet

199ºF                                    7000 Feet

 

CLOSED VESSEL BOILING POINT @ PSI @ Sea Level

BOILING POINT             GAUGE PRESSURE

212ºF                                    0 PSI

240ºF                                    10 PSI

259ºF                                    20 PSI

274ºF                                    30 PSI

287ºF                                    40 PSI

298ºF                                    50 PSI

316ºF                                    70 PSI

331ºF                                    90 PSI

ONLINE RESOURCES

There are an unlimited number of online tools and calculators for every mathematical formula. The internet is full of helpful resources to get the job done quicker. Here are a few links to some useful websites:

 

WEBSITE/PROGRAM                                         WEB ADDRESS

Amtrol Expansion Tank Sizing                                   http://amtrol.com/support/sizing.html

Engineering Toolbox Calculators                      http://www.engineeringtoolbox.com/

State Water Heater Sizing (Online)                          http://www.statewaterheatersizing.com/

AO Smith Water Heater Sizing (Online)            http://www.hotwatersizing.com/

Lochinvar Water Heater Sizing (Download)     http://www.lochinvar.com/sizingguide.aspx

 

Cylinder Calculator (Storage Tanks) / Other Math Calculators http://www.calculatorfreeonline.com/calculators/geometry-solids/cylinder.php

Electrical/Mechanical/Industrial/Civil/Chemical/Aeronautical Calculators http://www.ifigure.com/engineer/electric/electric.htm

B&G System Syzer (Piping/Pressure Drop Tool Download) http://completewatersystems.com/brand/bell-gossett/selection-sizing-tools/system-syzer/

B&G Selection and Sizing Tools (Pumps, Regulators, Steam and Condensate) http://completewatersystems.com/brand/bell-gossett/selection-sizing-tools/

Taco Pump Selection Wizard (Online Pump Selector)                                        http://www.taco-hvac.com/en/wizard_pumps.html

Lawler Mixing Valve Sizing (Online – account setup) http://www.lawlervalve.com/index.php?p=page&page_id=Sizing_Program

DSIRE Database of State/Federal Renewable Energy Rebates      http://www.dsireusa.org/

ASCO Valve Online Product Selector (Valves – solenoid, pilot, pneumatic, etc.) http://www.ascovalve.com/Applications/ProductSearch/ProductSearch.aspx?ascowiz=yes

 

SUMMARY

There is a lot of other information that we could add such as Steam. It is a viable heating source and there are several factors that must be considered such as operating pressure, steam trap and condensate line sizing and so on. We will have to do a separate article on Steam in a future issue.

The charts and information above are all essential to water heating. They are proven mathematical formulas of algebra and geometry. If you input the accurate information then the results will be correct. It is also good to use the online tools and calculators. They are true time savers.

Thanks and we’ll see you in the next article!

 

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