


Thread Tools  Display Modes 
05052011, 07:54 PM  #1 
Newbie
Join Date: Apr 2011
Posts: 7
Rewards Points: 10

Help with daily actual output from the furnace
Hello Sir,
I have very old Gas furnace: LENNOX gas furnace Model: G20Q3/4E1003 Made on year 1990 The Furnace capacity =100,000 Btu/hr. My house is 30 yrs old, 2008 square feet. I got the gas usage 263 ccf during 41 days from 02/24/11 to 04/06/11. The total heating degree days were 1183 during this period. The house inside temp was about 67 F. Does anyone know how to calculate daily actual output from the furnace? Is there any equation for my reference. Thank you in advance! Advertisement 
05062011, 04:58 AM  #2 
An old Tradesmen
Join Date: Oct 2008
Location: Somewhere
Posts: 32,238
Rewards Points: 5,880

While dividing therms by number of days gives a 6.41 therm per day average. Without knowing actual temps of each day. No way to know for anyone day, let alone the coldest day you had.
Advertisement 
05062011, 08:23 AM  #3 
Experienced
Join Date: Dec 2010
Location: Southern Michigan
Posts: 2,822
Rewards Points: 2,000

To satisfy your request a very lengthy explanation would be required, a more accurate accessment of the energy required to heat your home would be arrived at by doing a heat loss analysis whereby you evaluate the insulation quality of your entire building otherwise known as a "Manual J".
This link may help you understand the relationship of Heat Degree Days as it relates to heating requirements http://en.wikipedia.org/wiki/Heating_degree_day I know if you search there are programs which are free to homeowners as a (1) time use to evaluate your heat losses and heat gains. Mark
__________________
When its all said and done there is usually more said than done 
05062011, 10:17 AM  #4  
I'm Your Huckleberry
Join Date: Mar 2011
Posts: 5,884
Rewards Points: 2,270

Quote:
I'd have to do some research for heating mode btu's and capacity but I can tell you now for cooling capacity what is needed to give you an idea CFM (450 CFM heat pump, 400 CFM non heat pump to possible 350, verifiable) x 4.5 x (enthalpy A enthalpy B) would equal actual coil capacity in btu's. Then you'd divide that capacity by the actual rated capacity of the system (so if it was a 5 ton system than five tons would be 60,000 btu's) and you'd end up with your system effective btu capacity in percentage of the nominally rated 5 tons for cooling mode. 

05062011, 11:12 AM  #5 
Newbie
Join Date: Apr 2011
Posts: 7
Rewards Points: 10

Thanks for every input!
I saw the equation from Alliant Energy: Therm consumption estimated based on the following: Therms = (.85 X Cap X HDD X 24) / ((Ti  Td) * Eff X 100,000 Btu/Therm) Where: Cap = Furnace capacity in Btu/hr HDD = Heating Degree Days Ti = Inside temperature Td = Minimum design temperature Eff = Furnace Efficiency http://www.alliantenergy.com/UtilityServices/ForYourBusiness/EnergyExpertise/EnergySafety/010790 Does anyone know the meaning for 0.85? Thank you! 
05062011, 11:14 AM  #6 
Newbie
Join Date: Apr 2011
Posts: 7
Rewards Points: 10

Thank you! I know the actual temps of each day from weather station. Can I do it?

05062011, 11:15 AM  #7  
Newbie
Join Date: Apr 2011
Posts: 7
Rewards Points: 10

equation from Alliant Energy
Thanks for your input!
I saw the equation from Alliant Energy: Therm consumption estimated based on the following: Therms = (.85 X Cap X HDD X 24) / ((Ti  Td) * Eff X 100,000 Btu/Therm) Where: Cap = Furnace capacity in Btu/hr HDD = Heating Degree Days Ti = Inside temperature Td = Minimum design temperature Eff = Furnace Efficiency http://www.alliantenergy.com/UtilityServices/ForYourBusiness/EnergyExpertise/EnergySafety/010790 Does anyone know the meaning for 0.85? Thank you! Quote:


05062011, 11:16 AM  #8  
Newbie
Join Date: Apr 2011
Posts: 7
Rewards Points: 10

Thank you!
Thanks!
Quote:
Advertisement 

Thread Tools  
Display Modes  


Similar Threads  
Thread  Thread Starter  Forum  Replies  Last Post 
Carrier Infinity 69 Trouble Code 42  bodya1  HVAC  4  12052010 06:43 PM 
Oversized Furnace, Undersized Return Air vents and Low Heat Output.... ??  LabRat0116  HVAC  4  10042010 08:53 PM 
Oil fired furnace and hot water heater question  steveinpa  Plumbing  3  08102010 08:42 AM 
Help! with Concord 80+ gas furnace + TSTAT  joryeln  HVAC  0  09162009 12:23 PM 
Oil furnace / tank questions...  pure_energy1  HVAC  26  06222009 08:47 PM 