Manual J calculations

[sitman]

Does anyone know where I can get the means to do a manual J calculation to check for proper heat pump sizing ?
Also would like to find duct sizing / layout design help.
Thanks

[Wgoodrich]

I believe Ron is better equipped to answer this quesiton. Lets wait and see if he catches this one. In the mean time while you wait try reading a related post on this forum concerning the J-form of heat calculations.

http://www.selfhelpforums.com/viewtopic.php?t=55

Then after you are sure you want to do the j-form calc. try the following link for an auto calc of the j-form. Understand that I am not promoting this auto calc in any manner. Just providing what you asked for.

http://www.mrhvac.com/manualjshort.htm

Now that you have done that calc try the following and see how close you come to the answer in BTUs of HVAC.

Take the room times the length times 1.5 Then divide that by 2.930711. That should give you a rough idea the total BTUs needed for you home if located in the general area of mid america.

See how close that answer compares to your J-manual calculation. Just curious how they compare.

Meanwhile maybe Ron will have a better answer for us.

Good Luck Wg

Wg

[sitman]

Thanks !
You said to take the room times the legnth...
Do you mean legnth x width , or legnth x width x hight ?
Is this in feet ?

[Wgoodrich]

What you are trying to discover is the total cubic feet of your heated area. width times length times hieght. Then the 1.5 is the rough adjustment [seat of the pant style] for heating degree days of your area. Then you have to consider your heat loss of windows and doors. Often times the windows and doors may be omitted by the above calculation. That will give you the total watt power needed to heat you home then convert that to BTUs per the last calculation mentioned in prior post. Not saying it will be close just saying I would like an comparison from your manual J calculation to the calculation simplified as I mentioned out of curiosity sake only.

Good Luck

Wg