Radiant Floor Heating/Mechanical Room questions


I'm looking for some validation of my mechanical room design.  This is for a 3700 sq ft home with the heatloss done in RadiantWorks Pro.  As always, thanks for sharing your knowledge and experience with the group. We genuinely appreciate it.

-48k BTU heat loss
-15 Degree Delta T
-105 Degree Supply Temp
-20K BTU "Backloss"
-6 Zones (5k - 10k BTU each)
-All zones are 2-2.5 ft of head
-Polaris water heater hacked to supply 140-155 water

-Polaris 130K 34 Gal
-Sentry zone valves
-Alpha system pump (on constant pressure)
-Bumblebee on heat exchanger loop (at 105 setpoint, manually adjusted for outdoor temp)

-Given that the system should always be pushing more flow than the heat exchanger loop, am I right to have the system as primary and the heat exchanger as secondary? Or should they be switched?
I could use a taco 007-vr on the polaris side, and loose the bumblebee and secondary loop all-together, but the VR is 3X the cost of the bumblebee. Is the added complexity penny wise and pound foolish? Is there a cheaper circulator that does setpoint variable speed and is brass/stainless?
-I've got both the alpha and bumblebee oriented vertically. That adds a few bends to the system, but it's my understanding it will help ensure air bubbles travel toward the air eliminator. But with both pumps pulling water downhill (and thus pulling air bubbles down too) does it really help anything?
-Are there any other obvious flaws here that are making me look stupid (I've got thick skin, I can take it).
What should be done about backloss? My understanding is that some of that heat is truly lost, but that much of it is coming right back at you in the form of thermal mass. Is there a rule of thump for how much you get back? I've got slab, crawl space, and second story all in the mix, if that helps any.
-Polaris is available in 34 and 55 gal models. Without the hack, either model will cycle like crazy, taking less than a minute to overcome the 3 degree delta built into the system. With the hack in place, is the extra energy storage of the 55 Gal model worth the extra cost and space?

If I am understanding correctyly, you are wanting to use a hacked water heater to produce around 150 deg water to pump through a heat exchanger that your heating system pulls from for your home zone heating? If this is the case. You may want to add a thermostatic mixing valve on your supply mixing your heat return with your exchanger supply as to control your heating set point. Is this water heater also supplying your domestic water needs?  Is your radiant heat baseboard, inslab radiant? staple radiant? etc.  Different temperatures are desireable in each.  What is the efficiency of the polaris water heater?  What savings are you trying to accomplish verses a dedicated high efficient boiler with domestic priority. Help me understand the purpose of heating up and storing a mass of heat for your home heating needs.  About two decades ago the industry was enthrawled with heating mass to 180  with an internal heat exchanger (the heat transfer products voyager comes to mind) and then cooling both down to provide domestic and space heating. This "great idea" only lasted about ten years.  What you have here will work provided your space heating temps are not overshot but I am more concerened about efficiency.  Lets talk about this.


Radiant Floor Heating

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Nathan Marshall


Can answer: All radiant heat questions, from design, install, service. Have years of experience with baseboard, staple up, gyp crete and custom radiant design. Have worked with all of the popular boilers. I.E. Heat transfer products Munchkin, Triangle Tube Prestige, Lochinvar Knight, NY Thermal Trinity etc. etc. Pumping, Setback, OR, Zoning issues. And any plumbing question ever.


Plumbing and heating since 8 years old (with dad)

RPA NorthWestern Mechanical Association Associated Mechanical Engineers Yampa Valley Contractors Guild

Nate RPA Heat Transfer Products Rinnai Noritz Slant Fin TNT Tekmar Caleffi

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