10 things not to do with hydronic radiant heating presented at: presented by: John Siegenthaler, P.E. Appropriate Designs Holland Patent, NY www.hydronicpros.com
February 14, 2018
© Copyright 2018, J. Siegenthaler, all rights reserved. The contents of this file shall not be copied or transmitted in any form without written permission of the author. All diagrams shown in this file on conceptual and not intended as fully detailed installation drawings. No warranty is made as the the suitability of any drawings or data for a particular application. 1. Don’t use floor heating under floor coverings with high thermal resistance. tube spacing • Suggest R= 2.0 ºF•hr•ft2/Btu TOTAL 4" covering resistance (all concrete layers) if boiler is heat slab source. 6-inch tube spacing 12-inch tube spacing • Suggest R= 1.0 Rff=0 Rff=0.5 60 ºF•hr•ft2/Btu TOTAL ! covering resistance (all Rff=1.0 40 Rff=1.5 layers) if used with Rff=2.0 renewable heat source 20 (heat pump, solar). (Btu/hr/ft2)
upward heat flux upward heat 0 0 10 20 30 40 50 60 70 80 90 100 Driving ∆T (Tw-Tr) (ºF)! Average water temp. - room air temp Rff = resistance of finish flooring (ºF/hr/ft^2/Btu) 2. Don’t use “plateless” staple-up method of installation • VERY limited heat transfer from tubing • The only place you’ll find this “technique” used is North America… 2. Don’t use plateless staple-up method of installation 140 ºF water (w/ plates)
8” o.c. tubing 140 ºF water (no plates)
Floor surface temperature profiles 100 ºF water (w/ plates) 90 90 100 ºF water (no plates) 86 86
82 82
78 78
74 74
70 70
3/8" ceramic tile
3/4" plywood
Proper use
4"fiberglass of plates can
70 ºF air temperature increase 3/8" ceramic tile heat output 3/4" plywood about 3X over
4"fiberglass plateless systems.
70 ºF air temperature 3. Don’t rely on “bubble foil” insulation. • “Radiant” insulation doesn’t work under a slab (what air space??)
• Dust accumulation reduces effectiveness (e.g., increases emissivity) in air spaces over time. • Nominal product R-value of 1.0. Some sources claim an “assembly” R value of 15, with generous assumptions on resistance of air spaces.
http://healthyheating.com/ Radiant_Design_Guide/ Radiant_heating_mistakes_to_av oid.htm#.Wl9cda2tpyp 4. Don’t leave tubing at bottom of slab. • Requires higher water temperature for same upward heat output. (next slide) • Increases downward heat loss
• Increases response time, which can exasperate temperature overshoot and undershoot.
Notice where the tubing is in this 6” heated concrete slab Lift tubing to approximately half slab depth during pour. 4. Don’t leave tubing at bottom of slab. Deeper tubing requires increased water temperature for a given heat output.
1/2" PEX tube 3/8" hardwood flooring
4" concrete slab
1" polystyrene insulation
Upward heat output Average circuit water Average circuit water temperature with temperature with tubing at tubing at ½ slab depth bottom of slab
15 Btu/hr/ft2 95ºF 102ºF
30 Btu/hr/ft2 120ºF 134ºF
sawn control joint crack forms here polyethylene sleeving WWF reinforcing wire matt tubing
tamped fill
6-mill poly moisture barrier underside insulation leave tubing and WWF at bottom of slab under control joint locations 5. Don’t route tubing under cabinets, refrigerators, or freezers, or within 6” of closet flanges.
towel warmer 206+10=216 ft. W D LAUNDRY KITCHEN 177+15=192 ft. 206+10=216 ft.
route tubing under subfloor 6. Don’t use “homemade” or poorly formed heat transfer plates. • The conduction bond between tube and plate is critical to good heat transfer. Proper installation of plates above and below floor 7. Don’t waste tubing by creating long “leaders” • Adds material and labor cost, and increases circulator head loss
Create “extended manifold” instead 7. Don’t waste tubing by creating long “leaders”
Create “extended manifold” instead 7. Don’t waste tubing by creating long “leaders”
Create “extended manifold” instead 8. Don’t use PEX with external EVOH oxygen barrier in combination with aluminum plates. • Roughly 10:1 ratio in expansion coefficients • Rapid water temperature changes in PEX tend to create “stiction” sounds.
• Use PEX-AL-PEX tubing instead. The coefficients of expansion are very close. • Ideally - use constant circulation and outdoor reset control of water temperature for very quiet system. 8. Don’t place tubing without an accurate layout drawing • Wasted time • Wasted materials • No future documentation • Unknown circuit lengths Tubing layout drawing… • All circuits labelled and measured
M BEDROOM M BATHROOM • Use different colors for each circuit 264+10=274 ft.
• Show flow direction for each circuit shelves • Show control joint locations CLOSET 206+10=216 ft. W D LAUNDRY
1/2 BATH
213+10=223 ft. T thermostat
ENTRY
GARAGE KITCHEN
206+10=216 ft.
T thermostat 328+10=338 ft. 291+10=301 ft. DINING
317+10=327 ft.
LIVING ROOM ENTRY
263+10=273 ft. 307+10=317 ft. 10. Don’t use thermostatic mixing valves intended for DHW systems for mixing in hydronic radiant panel systems.
1" piping The problem(s): 1-inch thermostatic mixing valve with Cv = 3.0
anticipated flow rate in • Small thermostatic mixing valves each circuit = 1 gpm can have Cv values as low as 2.5.
• 2.5 gpm = 1 psi ∆P. 1" piping
• At 8 gpm ∆P = 10.2 psi
• At 12 gpm ∆P = 23 psi
• The thermostatic mixing valve is creating a large flow bottleneck.
• Small circulators only produce about 4-10 psi @ zero flow… 2 One more: Don’t use lightweight concrete Note: Standard structural 1.8 + concrete has density of approximately 140 to 150 for heated “thin-slab” floors. 1.6 lb/cubic foot, and an R-value of about 0.1per inch of thickness. 1.4 1.2 Lightweight concrete is made with aggregates such 1 + as vermiculite and polystyrene. These materials 0.8 0.6 0.4 + + significantly decrease the thermal conductivity of + the concrete, which impedes heat diffusion. R-valueper inchft./hr/Btu) (ºF/sq. 0.2 + ++ 150 lb/ft^3 concrete 0 106 lb/ft^3 concrete 0 20 40 60 80 100 120 density of concrete mix (lb/cubic foot) 75 lb/ft^3 concrete Floor Surface Temperatures 50 lb/ft^3 concrete 3/8" ceramic tile 150 lb/ft3 for thin-slab construction shown 1.5" slab using different light weight concretes. 25 lb/ft^3 concrete concrete 3/4" plywood 100 ºF water temperature in tubes 70 ºF ambient air temperature 84 84 4" fiberglass 82 82 80 80 106 lb/ft3 78 78 concrete 76 76 74 74 72 72 70 70 floorsurface temperature (ºF) 6 5 4 3 2 1 0 1 2 3 4 5 6 5 4 3 2 1 0 1 2 3 4 5 6 75 lb/ft3 distance from tube centerline (inches) concrete
3/8" ceramic tile
1.5" slab
3/4" plywood
25 lb/ft3 concrete 4" fiberglass What’s Wrong with This Picture? What’s Wrong with This Picture?
Everyone who considers themselves a hydronic heating professional has made mistakes as they’ve learned to assemble systems from thousands of products in almost endless combinations.
True professionals learn from their mistakes, as well as the mistakes of others. They make a constant effort not to repeat mistakes. They refine system designs by carefully examining proposed installations for such mistakes.
The images that follow are all drawn from real installations.
Many have no doubt disappointed their owners.
Look them over with a discerning eye for details that could be problems.
Keep in mind that there are usually several options for addressing a given installation requirement, and that it is not necessarily an “error” to select a method or product different from another hydronic heating professional. Is this a little known form of waste heat recovery? What do you see that’s wrong? Check out the electrically-operated pressure relief valve on this system… A modern hydronic system assembled using the “DESIGN-AS-YOU-SOLDER” approach… What’s wrong with the mixing valve here? It’s the same problem in this photo… The controls for an $80,000 heating system… How many zone circulators can “pull” through a 3/4” thermostatic mixing valve?
Do you think eight might be too many? Notice how the burner is turned on and off in the radiant floor heating system serving a 7000 square foot municipal building…
Interesting side note: The installing contractor also sells fuel oil… Question: Where was this guy during wiring codes class? Answer: He was in pipe sculpture class… What do you think is wrong here? Some situations defy description… in PM magazine: The Glitch & The Fix
Look for the Glitch in Look for the Fix in PM magazine (pmmag.com) the Radiant & Hydronics eNewsletter
zone valves
fixed speed varaible speed circulator pressure regulated zone circulator valves
12D
purge valves
cast iron boiler the GLITCH
cast iron boiler the FIX Thanks for attending today’s session recently released! 864 pages, full color textbook Thanks also to the Home Performance Coalition
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