Calculating Manual Load for Heating

Crissie

Hi, Looking for a free web based app so I can calculate / validate the my heating BTU's need. Getting different feedback from different contractors. The SlantFin web app doesn't work, it is frozen. Does anyone know of a different app? Thanks!

Jamie Hall

As I said in your other thread, don't try to use it on a smartphone. Download the program to your PC.

Crissie

Jamie Hall said:

As I said in your other thread, don't try to use it on a smartphone. Download the program to your PC.

I tried using it on a Desktop computer. It froze. unfortunately isn't working.

ratio

And as I said in your other thread, use the phone app.

Seriously, I can't speak about the web app, but at least the Android version of the phone app works. For me.

KC_Jones

I didn’t think the desktop one was even supported anymore?!  I tried getting it a couple years ago and it didn’t work then.

The phone/tablet app works great, I just opened it again to verify and it’s all good.

CMadatMe

To figure out the loss through a outside panel. ( Design Temp Indoor - Design Temp Outdoor) / Panel R-Value = Btu/hr Loss per sqft of outside panel. Take that and multiple by the total sqft of the panel. Make sure you take out windows, doors and plug them in separately. Then add all the losses together for the total outside panel loss. Yea, its that easy. Don't forget to calculate both ceiling and floor loss should there not be a conditioned space above or below

For infiltration factors. Per ASHREA .35 to 1. Take the cubic ft of the room x the factor. (R-19 Wall or tighter use .35, R-11 I'd use .75. Now add that to the rooms total outside panel loss and boom you have a basic launch point for the heat loss of the room. Software is great to save time but it's also carries fudge factors so they are about as accurate as doing the actual math manually. Do it both ways and let me know how far they fall apart.

This would be no different than using Longest run x 1.5 x .04 to figure circ pump foot of head for the critics out there.

Canucker

CMadatMe said:

To figure out the loss through a outside panel. ( Design Temp Indoor - Design Temp Outdoor) / Panel R-Value = Btu/hr Loss per sqft of outside panel. Take that and multiple by the total sqft of the panel. Make sure you take out windows, doors and plug them in separately. Then add all the losses together for the total outside panel loss. Yea, its that easy. Don't forget to calculate both ceiling and floor loss should there not be a conditioned space above or below

For infiltration factors. Per ASHREA .35 to 1. Take the cubic ft of the room x the factor. (R-19 Wall or tighter use .35, R-11 I'd use .75. Now add that to the rooms total outside panel loss and boom you have a basic launch point for the heat loss of the room. Software is great to save time but it's also carries fudge factors so they are about as accurate as doing the actual math manually. Do it both ways and let me know how far they fall apart.

This would be no different than using Longest run x 1.5 x .04 to figure circ pump foot of head for the critics out there.

I agree with that. As much as I like using the Slantfin app, it way over estimates infiltration unless you're aggressive with the numbers. The number it spits out is my max range and would try to find a unit the size below. @Crissie has the advantage of already knowing an accurate infiltration rate