PICK OUT A CIRC FOR ME

[jimde]

I need to figure out which circ would best suits my needs. I have to pump 160 feet from my solo plus 60 and 740 feet of pressurized storage to my propane furnace with a water to air exchanger through 1.25 inch thermopex. My heat calc is 80,000 btu for the house and I want to include my 700 sq/ft attached garage with enough gpm for moderate heat. I currentlty have a 50gal propane water heater which I will convert to a sidearm or use a indirect water heater next year. I hope I can use variable speed,but dont understand how to figure it out for proper sizing.

 

[jimde]

Oh , I forgot to tell you that my boiler is about 6 feet higher than my furnace.

 

[Gooserider]

If you look in the "Tidbits" sticky, you will find a link to a technical paper from Taco that goes through the entire process - it assumes you are starting from scratch, while you already have a lot of existing hardware, but that makes things easier in some ways as it fills in some of the variables in the equations for you...

Essentially you need to figure the head loss for your plumbing setup (which will take a LOT more data than you provided) and what kinds of flow rates you need to get enough BTU's to satisfy your loads - you then look at the pump curves and pick a pump that can supply the required flow rates at the specified head loss. For variable speed, you need to pick a pump that will AT LEAST meet the same requirements, (which are based on "worst case" conditions) at it's highest output....

Gooserider

 

[Tennman]

If you are EXCEL spreadsheet handy, I built a spreadsheet for the steps in the TACO instructions to compute the size of my pump based on headloss and BTU transfer requirements. You can play with length and # of elbows you expect in your system. This is directly from the TACO Technical Document TD10 you can find that online. After you compute the BTUs and headloss you use the graph to pick the pump. Pretty simple. PM your email address if interested in the spreadsheet. Pump I picked works fine AND based on the calculations my application required a larger pump than what the boiler supplier was recommending. Glad I did the calcs because I would never have been able to pump adequate BTU's to match the boilers capabilites.