Welcome! Here are the website rules, as well as some tips for using this forum.

# BTU formula

Options
Member Posts: 165
than that. High temps increase heat loss in the distribution piping, stanby losses on the boiler, and decrease the accuracy with which the system tracks the thermostat setpoint. There is also the approx 10% combustion efficiency that can be gained from running low temperatures. Condensing boilers usually modulate, and the modulation affects savings as well.

Adding propylene glycol to a system decreases the specific heat of the fluid. The manufacturer should have data tabulated.

When it comes to low temperature heat emitters, more mass = less responsive, so plates should outperform a thin pour, and a thin pour should out perform a slab. Low temperature response = savings. There are control "patches" to help higher mass systems perform better, though they will never achieve what a low mass heat emitter can.

Efficiency is a complicated concept when it comes to heating systems. It goes far beyond combustion efficiency.

-Andrew

• Member Posts: 171
Options
BTU formula

I am struggling to remember the fomuala for the amount of energy needed to raise 1 lb of water 1 degree. The defination of a BTU. I am trying to compare the operation cost of a system running at 120 degrees coampared to 180 degrees. Thanks Jeffrey
• Member Posts: 1,380
Options
You Got It...

The definition of the btu is the amount of heat energy required to raise the temperature of 1 pound of water 1 degree Fahrenheit.

For example, if you wanted to raise the temperature of 1 pound of water from 67 degrees F to 68 degrees, 1 btu ofheat energy would have to be added to the water. If, however, the water sample was 10 pounds, it would take 10 btus.

The general formaula is:

Btu = W x SH x Delta-t

Where W is the weight of the water in pounds, SH is the specific heat of the substance and the delta-t is the difference between the initial and final temperatures. The specifi heat for water is 1.0 and can therefore be ignored.
• Member Posts: 171
Options
Yea thats what I thought

but it is Sunday and you know. Thanks for the input. I just figure out that by operating a radiant system at 120 Gyp degrees campared to 180 degrees staple up( guys aroud here run their system at 180 to over come high heat losses.) It was a 14,500 btus difference for a cold start 70 degrees. Over a heating season that's a \$500.00 diffrence using propane at \$1.70 per gallon. Another reason to install low teperature radiant systems with condensing boilers.
Thanks for the help Eugene
• Member Posts: 1,380
Options
You are correct, Andrew

Not only is efficiency complicated with heating, but coling and everything else under the sun. It seems that if you ask 100 people to describe the term "efficiency" you will get 100 different responses.

For example, if you speak with air conditioning experts about the EER of an air conditioning system and exactly how to calculate it, you will undoubtedly get numerous opinions and solutions, all of which may very well be correct within the context of the particular application.

• Member Posts: 171
Options
You guys are all right!

I am just comparing the apples to apples that you can do with math. Now take into consideration outdoor reset, modualtion and constant circulation no how can you add all these to the equation. Very difficult but it would be nice to have these numbers to show potential customers the savings. I have been using more aluminum radiant panel over the last few year and I think they add to the efficiency equation also. They are very precise and are able to have alot more control(heat up and cool down). They are very responsive. So many variables to add to the equation.
Jeffrey
This discussion has been closed.