Heat loss calcs.

Gordy_2

I do not notice that value changing in the slant fin program. This is not to say other programs do not factor this in. So I'm limited buy the heatloss program. Makes sense though.

Gordy

Gordy

A different way of using heatloss calcs.

I have been experimenting with my heatloss calculator "slant fin", which is not the best program for my existing radiant heat application I know.

Looking at sizing the lower, and upper end modulation for a future Mod/Con in my home. It seems that there is quite a difference from brand to brand in sizing, so I'm trying to find the best fit.

I took the set point values to extremes. Example for outdoor temps. I used 50* and calculated the structure losses to determine a low end modulation. Then I used the design temp.-10 for my area for the upper end modulation.
I also plugged in different room set points 72*, and 65*.
By doing this I came up with a low end modulation of 12,500,and high end modulation of 61,500 at a setpoint of 65*. For a setpoint of 72* I get a low end modulation of 18,000,and high end of 67,000.

Has anyone used a heatloss calculator in this manner?

Interestingly also the difference in total btu loss from using 72* verses 65*. It is always 5720 btus for my structure, no matter if the outdoor temp. is -50* or +50*, although structure losses are higher and lower of course the difference from 65* to 72* is always 5720 btus. Which lead me down a different path on the topic of setback saving money. Over a 24 hour period if I use a room setpoint of 65* verses 72*, I would save 1.68 a day or 50.00 a month rounded at present fuel cost. If I use setback from 72* to 65* for an 8 Hour period that equates to a savings of 17.00 a month.

This method is a bit unorthadox because this assumes same outdoor temps. for the given time periods. So dollars saved would be less.

Actually this whole thought process may be unorthadox using slant fin. That is why I bringth to share with the master minds here to disect, and blast holes in. Then I can learn, and regroup.

Gordy

Mitch_6

What type of radiant

heat do you have, most manufacturers, Stadler Viega and Weil Mclain for example have there own programs.

Mitch S.

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Gordy_2

Radiant type

Ceiling Radiant, and some floor.

Gordy

Unknown

Heat loss is linear with changes in Delta T.

No need to re-run the numbers, (though you can), you just divide your high end heat load by whatever you change the Delta T by.

Let's make the math easy. 70 degree room temp, -30 degree temp, for a 100 deg design delta T.

Your load at 60 degree outdoor temp (10 delta T) is 1/10 design. At 20 degrees, (50 degree delta T), it's half design.

Setback has a lot to figure in beyond straight delta T. the cruise down and cruise up, namely, which is dependant on load and mass. More mass, tighter house, less savings.

Gordy_2

LOL !

So basically, I used long hand to achieve short Hand. Thanks Rob!

Gordy

Boilerpro_3

Not true!

heat loss accelerates as it gets colder because the air leakage rate increases. Take a look at the air leakage charts and you'll see something like .3 ACH at 40F and 1 ACH at 0F. The draft in a chimney gets stronger when it gets colder..so will the draft through your home.

Boilerpro

Unknown

Well, you're providing makeup air for the boiler, right? Shouldn't affect the rest of the house much.

Most of our systems don't use chimneys anymore anyway

Seriously though, that's a good point that needs to be taken into consideration on many systems. Thanks Boilerpro!