Combining geothermal heat pumps and radiant

The Glitch:

A contractor needs to combine a single-speed water-to-water geothermal heat pump to a highly zoned radiant floor heating system.

As a fallback for being short on inventory, his supply house buddy tells him that there’s no need for an expansion tank in the earth loop because the HDPE piping has enough “give” to accommodate any expansion or contraction. He now envisions the HDPE expanding and contracting like a piece of unreinforced rubber tubing, and assumes that he can use this to his advantage on the load side of the heat pump. He pipes up the radiant floor manifold with leftover pieces of HDPE pipe as shown in Figure 1. He uses two fixed-speed circulators, one to supply each manifold station. Individual circuit zoning at each manifold station is done using manifold valve actuators, each wired to a thermostat.

Can you identify several problems with this approach and propose a better one?

Are you an ace troubleshooter?

Within the pages of this magazine, PM’s Hydronics Editor John Siegenthaler, P.E., will pose a question to you, our readers, to review a system’s schematic layout and discover its faults, flaws and defects. Discover archived “The Glitch & The Fix” exercises at its radiant-focused website, www.radiantandhydronics.com. Good luck!