Yanche wrote:Hello Chris,
Assuming the design criteria on your radiation system temperature drop is 20 degrees the BTU you can transfer with the 1 inch pipe is:
BTU = 500 x 8.5 x 20 = 85,000 BTU
If you go the water to air approach be sure to select a low head loss coil. Post the specs on what you plan to use for radiation and I'll do a flow analysis. Good luck with the rest of your project. Looks great so far.
Great info! Thanks!
Here's my setup: Boiler is located in insulated garage/shop. 1-1/4" iron pipe from top of boiler (since that's the outlet size - keeping it simple) to air eliminator/tank and pump, about 4 feet of pipe and 90. Then transition to 1" copper for less than 10 feet before going into 1" pex (not pex-al-pex). The insulated pex runs 120' to the house where it transitions back to 1" copper for the 50' run to the furnace.
Based upon your analysis (and my reality), we are very close. My furnace is 72k BTU output (80k input). I have a 16x18 fan coil on the way, 1" inlet and outlet. This is the data I have for it: I bought it through an Ebay seller just up the road in Wisconsin, and the seller says it will make 129,000 BTU which either is a typo or optimistic. I estimate I'll be operating in the 1000cfm region at 180 water temp. As you can see, there is very little difference in heat output between 5gpm and 9gpm. I was originally targeting 8 to 10 gpm flow rates which was driving me towards a Taco 011 or Grundfos 26-96. But, upon further analysis and verifying I only have 72k BTU output heating the house just fine, I revised my flow rates required to between 5 and 7 gpm, which can be handled by a Taco 008 or Grundfos 15-58 (which I purchased). I also figure having a delta-T of more than 20 degrees is just fine - there is nothing else on the loop at this time, although I can add DHW or a separate basement zone later very easily.
Essentially, the 1" insulated pex run is THE resistance to the circuit. I added up all the copper and fan coil (which has very low head loss) and the head loss was about 3 feet.
The pex had a head loss of about 11 to 12 feet. I'd rather have had 1-1/4" pex or 1" pex-al-pex, but the seller told me that the 1" pex is what he installs for all the OWB projects and it's been enough for everything so far. Granted, it's likely true seeing as I only have 72k BTU heating 2800 sq.ft. of 2 story house, but to get enough BTU transfer for more than just house heating requires 8-10 gpm of flow and that requires a big pump. That just goes against my engineering principals - it's like driving with the parking brake on. But, the 1-1/4" insulated pex is even larger and stiffer than the 1" (which is already a bear to handle) and even more expensive. But, this pex is beautiful stuff - fully foamed inside a seamless polyethylene jacket: http://www.thermopex.com/
I just didn't trust some of the stuff sold on Ebay that's not much more than pex (or pex-al-pex) wrapped in some bubble wrap and stuffed through some cheap plastic flex drain tubing. I wanted to have peace of mind that I'd never have to worry about water inside the jacket.
I have been reading through Siegenthaler's book extensively and it is an excellent reference. Taco has some excellent "how-to" information as well. I will say that the "student" version software included with Siegenthaler's book is not real useful, though, for "real world" installations, but it is useful if you know how to fudge your input values into what it can cope with.