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New to Radiant Heating Design & Install. Feedback requested

knobby44 Member Posts: 2
Hello All. I have been reading a lot of posts and trying to work on my system for a new ICF House build here in Northern Nevada near the Sierras. The house is coming along and coming close to getting the walls finished for my final pour and then on to trusses.

This last weekend we had quite a storm roll through and high winds for 3 days, so couldn't do much with foam blocks in 30-50 mph winds and worked on more of my radiant system design.

We have some snow in the winter and ranges from crazy winter last year at about 2ft on the ground at a time to 6" in a mild year.

I have been doing the Manual-J and loop layout in LoopCAD and think I am close to having that finalized with manifold locations chosen to be in centrally located common walls in different areas around the house. The system will have the following design criteria.
  1. Geothermal Heat Pump (GeoComfort 4T GWT048G11AAACRS W2W 2STAGE)
  2. 40 gal DHW Tank
  3. 80 gal Buffer Tank
  4. 5 loops of 3/4 HDPE buried in 750' trench (finished)
  5. Ceiling Radiant heating / Cooling (Loads are less than 10 Btu/hr/ft^2, so there is plenty of capacity if needed)
  6. Looking at going with controls from www.bravocontrols.com for the system (manifolds will have actuators to do highly zoned system. Floor Heating Manifold & Electro-thermal Actuator https://bravocontrols.com/shop/floor-heating-manifold-electro-thermal-actuator/)
  7. Basement & Garage have slabs poured with radiant lines.
  8. Considering Driveway snowmelt
  9. Have a Rinai i120 combi-boiler for backup heat and DHW and could fulfill the 120KBTU for the snow melt system.
  10. Considering Ceiling heat on the porch and patio under stucco soffit/ceilings
  11. High Desert environment (Low humidity, summer time between 10-15%, high humidity week rarely may be a dewpoint of 55ºF to 60ºF)
  12. Design Supply Temperature is ~90ºF -93ºF except for Snow Melt at
Main Floor Layout

Basement Layout

At this point, the system design and the layout of the plumbing and pumps, etc is what I'm grappling with.

I have read many of Siegenthalers articles on Plumbing & Mech and many other sources.

There are a couple of system designs that intrigue me for the Heating/Cooling valving and Buffer Tank configuration. Mentioned in these two articles are 3-way and 4-way systems that allow cooling by bypassing the tank in shoulder seasons (which are long here). I am leaning toward the 4-way system which has fewer components and should be better for reliability and cost.

Using “reverser valves” to switch buffer tanks

Details for bypassing thermal storage

I will have a supply line to my garage for the radiant loops for the garage and for Snow Melt from 2 different manifolds in the same location. I have a little issue in that I was not aware of the size line needed for my 113,000 BTU SM at the time probably needing 1-1/4" line for the heat carrying capacity and only put in 3" feeder tube to the location. I may consider using one 3/4" and one 1" line to use for the capacity between the two and think I can get those two lines through the pvc pipe I buried below the slab. If I use one line, then I may have to use some mixing valve in the garage to temper the flow to the garage during snow melt that could use 120ºF supply temps.

Things I don't have a grasp on at this point are the following:
  1. separation of the ground loop system from the buffer tank (maybe the same?)
  2. Controls programming
  3. Plumbing the system
  4. Thermostat control for zones (Looking at the Tstat 7 Thermostat, TSTAT7-H https://bravocontrols.com/shop/tstat-7-thermostat-tstat7/
  5. Loop control valve zoning

I am considering buying the controls for the system and starting to play with the programming and functionality for the Thermostats. I am looking at the thermostat above that has Temp & Humidity built into them for the rooms so that the thermostat can directly control the Loop actuators with the 5 built in relay outputs to control the zone temperatures. Since they are a communicating thermostat, they could be programmed to always be at a min or max temperature and keep the rooms idle that are unused or infrequently. (The house is larger than we need, so there will be a guest bedroom or two that are not used most of the time) Any thoughts on this for managing the different rooms for zone control? I know this may be overkill for this fine control, but will be good since the temperature of different comfort levels vary a lot between my wife and I and we will each have our own office space.

I am putting together a diagram tonight for the beginning of my system that will start with a combination of the 2 systems above.

Any feedback is welcome. Thanks for looking and all the information that is posted here.
Carson City, NV
Mechanical Engineer
Building ICF House


  • hot_rod
    hot_rod Member Posts: 22,105
    These Idronics issues are written by Siggy, this may be a deeper dive than those articles.
    more pages anyways.

    https://www.caleffi.com/sites/default/files/media/external-file/Idronics_27_NA_Air-to-water heat pump systems.pdf
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • knobby44
    knobby44 Member Posts: 2
    edited March 5
    Here's where I'm at in the construction as of today. Time to go stack more blocks.

    @hot_rod Thanks for the reference, I also found #30 this weekend and started looking through those again. What a wealth of information and some generalities. I will be reading through them both again this week as I am working through the schematic diagram to try and get everything in the correct place and post that once I think it's fairly complete. There are sure a lot of things to remember and tricks or requirements that I don't fully understand for component placement since I don't work in the trade and only have knowledge of all the articles read over the last 2 years preparing for this ICF house build. I have a little time to figure it all out, but the next few months will go quite fast I'm sure
    Carson City, NV
    Mechanical Engineer
    Building ICF House
    Alan (California Radiant) Forbes
  • tim smith
    tim smith Member Posts: 2,752
    edited March 5
    Great view over the mountains, time to put the parka on and get to work it looks like. Which air to water heat pump you looking at? I just got the specs on the LG that's now available and they look fair amount better than most I have seen. I would be happiest with Mitsubishi if they would ever get it tested and certified for NA market.