We are building a house and I need to figure out if a pump is needed between the storage tank and the the mechanical board to supplement the Circulators for each zone.

If there are some good articles on how to calculate it I would appreciate it. Or, if there are suggestions I also appreciate that.

We have 3 zones downstairs and 4 zones upstairs with varying total lengths due to area size. All loops are less than 275 for 1/2" pex.

The largest zone has 1100 linear ft and the smallest has 180 linear ft. Total linear ft for all zones is 3800.

I am thinking of the Grundos Alpha2's for the circulators.

The 37 gallon Storage Tank will be in the same 6x9 room as the circulators.

Thoughts?

Thanks, Dean

Without knowing your HR floor heating system PEX layout and design flow rates, it isn’t possible to properly select a pump. However, it is unlikely that more than one pump would be necessary for the typical residential HR floor heating system if it is properly designed. We have free DIY HR floor heating system software on our website that can be used to select a pump. Please carefully read the associated software instructions. How is it that you already have HR floor heating system installed, but you didn’t get a properly sized pump specified as part of the HR design?

Borst Hydronic Radiant Floor Heating Design Software

Thanks for the suggestion to use the Borst site. It looks incredibly complete. I have made my first attempt by entering all of the data for the 7 zones in my house and clicked the solve button. Unfortunately the site just spins and I just get "wait" messages. After 15 minutes it has still not returned. Thoughts?

Ok... open a new window...try again and do solve after adding each room... and it is working. I will continue to move through the process. thanks, Dean

Yes, that calculator is quite a number cruncher and has about 5,300 lines of code. It fully adheres to the design methodology detailed in John Siegenthaler’s “Modern Hydronic Heating” and it will hydraulically balance your system with your pump.

Again, please carefully read the instructions and enter the pump performance curve (flow rate versus head) for the selected pump as indicated. Ideally, you should select a pump that places the pump’s Best Efficiency Point (BEP) at the total design flow rate and total design head loss as explained in the instructions. BEP should be indicated on the pump performance curve, but it is typically located near the center of the pump performance curve.

There are smart pumps like the Grundfos Alpha that can adjust pump performance somewhat based on the actual head loss, however, for minimum pump electrical usage and maximum efficiency, it is always best to select an ECM pump that operates at it’s BEP.