Oh man I need some help. I am at the end of my radiant heating install and I can not figure out which circulator to buy. I have 2 floors. First floor has 8 loops with two manifolds broken up into 2 sections with 4 loops each (avg loops is 240ft). The Second floor has 10 loops on it broken up into 2 sections of 5 loops each (avg loop is 250ft). The first floor requires 51,705 BTU and the second floor is 64,532 BTU. Any help would be great because I have no idea how to calculate the size pump I need. Thanks

Go to Borst engineering .com. They have a bunch of calculators, one specifically for radiant heating design that can cover multiple zones. It can help you get an idea about how much head your pump will have to overcome in all that tubing on both floors at the flows required to deliver the necessary heat... You may also need to run your house parameters thru their heat loss calculator to refine the information needed in the radiant calculator, like downward heat loss. READ THE INSTRUCTIONS! They are very detailed as the information you will need to input is very specific to get an accurate result...

Good Luck...

Thanks Ronmar!

Yes, pumps should be properly sized given the flow that they will need to provide and given the hydraulic friction head from the PEX size/length that they will expericnce at this flow rate. As stated in the software instructions, this can be very intimidating software at first blush. However, the instructions are detailed and thoudands of DIYer have accomplished successful designs using this software. Please don't hesitate to contact us if you have any questions. Here is the link to the software:

Borst Hydronic Radiant Floor Heating Design Software