© Ron Blank and Associates, Inc. 2010
Please note: you will need to complete the conclusion quiz online at ronblank.com to receive credit
SUSTAINABLE BUILDING TECHNOLOGY REHAU’s sustainable building technology provides solutions for heating, cooling, snow and ice melting, plumbing, water supply, fire protection, fresh air supply, and the building envelope
Lance MacNevin REHAU Inc. 1501 Edwards Ferry Rd. Leesburg, VA 20176 703-777-5255
[email protected] www.rehau.com
RADIANT HEATING DESIGN AND CONTROLS AN AIA CONTINUING EDUCATION PROGRAM Credit for this course is 1 AIA HSW CE Hour
Course reh23c
AN AMERICAN INSTITUTE OF ARCHITECTS (AIA) CONTINUING EDUCATION PROGRAM Approved Promotional Statement: • Ron Blank & Associates, Inc. is a registered provider with The American Institute of Architects Continuing Education System. Credit earned upon completion of this program will be reported to CES Records for AIA members. Certificates of Completion are available for all course participants upon completion of the course conclusion quiz with +80%. Please view the following slide for more information on Certificates of Completion through RBA
• This program is registered with the AIA/CES for continuing professional education. As such, it does not include content that may be deemed or construed to be an approval or endorsement by the AIA or Ron Blank & Associates, Inc. of any material of construction or any method or manner of handling, using, distributing, or dealing in any material or product.
AN AMERICAN INSTITUTE OF ARCHITECTS (AIA) CONTINUING EDUCATION PROGRAM • Course Format: This is a structured, web-based, self study course with a final exam. • Course Credit: 1 AIA Health Safety & Welfare (HSW) CE Hour • Completion Certificate: A confirmation is sent to you by email and you can print one upon successful completion of a course or from your RonBlank.com transcript. If you have any difficulties printing or receiving your Certificate please send requests to
[email protected]
Design professionals, please remember to print or save your certificate of completion after successfully completing a course conclusion quiz. Email confirmations will be sent to the email address you have provided in your RonBlank.com account. Please note: you will need to complete the conclusion quiz online at ronblank.com to receive credit
COURSE DESCRIPTION
Thermal comfort through radiant floor heating will be the focus of this course. We will review applications and calculations of the design process for hydronic heating. Controls and zoning for an integrated system will be covered as well.
LEARNING OBJECTIVES
UPON COMPLETION OF THIS COURSE THE DESIGN PROFESSIONAL WILL BE ABLE TO: • Describe the advantages of using radiant floor heating (RFH) technology • List several application options for RFH including residential, commercial, civic, industrial, and institutional applications • Follow the design process for radiant heating systems to determine heat loss, floor temperatures, piping layouts, and fluid temperatures
• Explain the basic control systems incorporated in radiant heating systems
RADIANT FLOOR HEATING BENEFITS • Thermal Comfort
• Control of temperatures • Flexibility in applications and with heat sources • Efficiency
THERMAL COMFORT RADIANT FLOOR HEATING ADDRESSES ALL THESE THERMAL COMFORT ISSUES: • Inconsistent temperature from minute-to-minute (cycling) • Inconsistent temperature from one room to another • Inconsistent temperature within a room • Drafts or “wind” blowing when the heat turns on • Cold hard surface flooring – need slippers! • Restricted placement of furniture due to heat emitters • Noisy fans or ticking baseboard • Ugly air vents and return air grates • Dusty air and heat emitters • Dry air in wintertime
THERMAL COMFORT: A WARM FLOOR MAKES A WARM HOME RADIANT FLOOR HEATING (RFH) IS: • Quiet, no fans, no noise • Steady, with even temperatures throughout a room • Invisible, with no holes in floor, no moving curtains • Warm, with heat delivered through our feet
THERMAL COMFORT Radiant floor heating provides a more “correct” temperature profile in the space to deliver comfortable temperature distribution in the space 8 ft
8 ft
6 ft
6 ft
6 ft
6 in
6 in
6 in
°F
60
68
Optimal Temperature Distribution
75
°F
60
68
Forced Air or other Convective Heating
75
°F
60
68
Radiant Floor Heating
75
THERMAL COMFORT • • • • •
When your feet are warm, your lower body is warm With RFH there is some warm air floating in lower portion of the room Still air means less heat loss from the human body to the air flow • Eliminates that “drafty” feeling caused by forced air movement There is less hot air at the ceiling, less “stratification” • Cooler air at head level is fresher, has more oxygen, is not as dry With RFH, the warmest air is at floor level 8 ft 6 ft
6 in °F
60
68
75
THERMAL COMFORT • Higher Mean Radiant Temperature (MRT) improves comfort in a space • Surfaces are warmer than with forced air • Bodies radiate less heat to walls and ceilings, therefore indoor air can be cooler and “fresher” • Indoor air does not have to be so hot for comfort • Use 68°F vs. 72°F indoor design temperature with radiant floors for most residential applications • This delivers improved comfort, increased efficiency
Pink Area is the approximate comfort zone
THERMAL COMFORT • Cooler air has higher Relative Humidity (RH%) in winter as compared with forced hot air. May be less dry skin, fewer dry throats • No ductwork is necessary • Influence of dust/pollen/allergens may be minimized • Hard surface flooring is comfortable and desirable • Easier to eliminate carpet and rugs from indoor spaces
ROOM CONTROL: DELIVERING COMFORT AND EFFICIENCY • In residential applications radiant layouts typically cover 250 ft2 per circuit of pipe: • The flow of water for each circuit is controlled by circuit valves built-in to the manifold • That makes room-by-room zoning is easy • Room-by-room temperature control optimizes comfort and efficiency • Occupants may desire some rooms to be warmer than others • Heat loads change with occupancy Typical radiant thermostat and distribution manifold
FLEXIBILITY: RADIANT HEATING GIVES CHOICES 1. FLEXIBILITY WITH APPLICATIONS: • Use in floors, walls or ceilings • Heat the entire building with RFH, or mix it with other hydronic emitters • Radiant is zoneable
2. FLEXIBILITY WITH HEAT SOURCES: • Almost any source of “warm” water can power a radiant system
PART 1: FLEXIBILITY WITH APPLICATIONS HEAT FLOORS, WALLS OR CEILING HEAT THE ENTIRE BUILDING OR PARTS OF IT: • Radiant heating can be installed in almost any building panel • Radiant heating may be used as the primary heating system, capable of 34 BTU/hr(ft2) or more • Radiant heating may also be used just for floor warming • In tiled or hardwood areas, controlled with floor sensors in the floor
PART 2: FLEXIBILITY WITH HEAT SOURCES EXAMPLES OF SUITABLE HEAT SOURCES:
• • • • • •
Condensing boiler (“Mod/Con”, for low temperature applications, high efficiency) Ground source heat pump (usually a perfect match of water temperatures) Electric boiler (easy to control and install) Non-condensing boiler (for mixed high temperature/low temperature applications) Solar collectors (with storage tanks and water temperature mixing control device) The first three are well-suited for radiant applications since low water temperatures can be easily controlled
EFFICIENCY: RADIANT HEATING CAN SAVE ENERGY 1. Lower average air temperature reduces heat loss: • Lower indoor air temperature = less heat loss (68°F for RFH vs. 72°F for FA) 2. More efficient use of boiler or heat source: • Condensing boilers operate in full condensing mode only with water return temperature less than 130°F, easily achieved with radiant floor heating • Ground source heat pumps operate more efficiently when the temperature required for heat distribution is not much higher than the fluid temperature coming from the ground 3. It’s more economical to move heat using water vs. air • Hydronic circulators draw less power than furnace blower fan, potentially saving hundreds of dollars per year on heat distribution costs
EFFICIENCY: RADIANT HEATING CAN SAVE ENERGY SAVES COSTS AND REDUCES GREENHOUSE GAS EMISSIONS DUE TO THREE KEY REASONS: 1. Lower average air temperature reduces heat loss 2. More efficient use of boiler or heat source 3. It’s more economical to move heat using water vs. air In addition: • Not pressurizing rooms (no fans) reduces infiltration heat loss (reduced ACH) • Zoning capability allows temperature reduction of rooms when not needed • Total savings can be up to 30% or more!
RADIANT HEATING IS ‘GREEN’ • Thanks to high efficiency, comfortable environments, better air quality, compatibility with renewable energy sources, and use of sustainable products • Leadership in Energy and Environmental Design (LEED) rating system recognizes the benefits of radiant heating.
RESIDENTIAL APPLICATIONS • Basements • Slab-on-grade pours • Suspended floor overpour • Garages • Apartments
Residential bathroom with overpour
COMMERCIAL/ INSTITUTIONAL APPLICATIONS SOME EXAMPLES: • • • • • • • • • •
Hotels Offices Restaurants Warehouses Museums Day Care Facilities Retirement Homes Schools/Colleges Hospitals Prisons
Milwaukee Museum of Art
INSTITUTIONAL APPLICATIONS SOME EXAMPLES: • • • • •
Day Care Facilities Retirement Homes Schools/Colleges Hospitals Prisons
11,000 square foot retirement home in Elliot Lake, ON. Each suite has its own thermostat and room control
INDUSTRIAL APPLICATIONS SOME EXAMPLES: • • • •
Warehouses Garages Factories Hangars
RFH in warehouses and factories eliminates overhead unit heaters and infrared tubes which could be damaged by forklifts
CIVIC APPLICATIONS SOME EXAMPLES: • Fire Stations • Bus Stations
RFH in fire stations eliminates overhead unit heaters and infrared tubes and creates warm, dry floors for safety
SUMMARY EXPLAINING THE MAIN BENEFITS: • • • •
Comfort Control Flexibility Efficiency
• Typical applications • Radiant floor heating has advantages in all these applications
RADIANT HEATING DESIGN PROCESS • A standard process using calculated values for accurate heating system design • Sizing hydronic equipment always starts with the heat loss
• These equations apply to new construction, renovations and replacement work
THERMAL COMFORT ASHRAE Standard 55: “Thermal Environmental Conditions for Human Occupancy” says: “Thermal comfort is that condition of mind which expresses satisfaction with the thermal environment.” Boundaries for thermal comfort according to Standard 55: -Operative temperature: - Summer period: 71 - 80°F - Winter period: 66 - 77°F -Range of the floor temperature: 66 - 85°F -A good radiant design will stay within these limits
RADIANT HEATING DESIGN PROCESS Step 1 • 1a: Calculate Heat Loss of space (gives Heat Source size) • 1b: Radiant Panel Heating Requirement (BTU per hour per ft²) • 1c: Required Floor Temperature (how warm does the floor need to be?) Step 2: Radiant Panel Design: Determine PEX pipe size, pipe spacing, circuit lengths, and water temperature (designers will have several options) Step 3: Determine Flow Rates for circuits and the entire system Step 4: Determine Head Loss requirements Step 5: Choose Circulator (pump) to meet Flow Rate and Head Loss requirements
STEP 1a: HEAT LOSS OF SPACE BTU (BRITISH THERMAL UNIT) DEFINITION: • The amount of (heat) energy required to raise one pound of water one degree Fahrenheit • Common conversions: • 1 kiloWatt (kW) = 3,413 BTU/hr • 100 W = 341 BTU/hr • “Ton” of energy = 12,000 BTU/hr • Historically, a “Ton” is the amount of cooling achieved by melting 2,000 pounds (1 ton) of ice in one day
HEAT LOSS OF THE SPACE • Calculate both conductive and air infiltration heat loss according to relevant methods, based on the selected outside design temperature: • ACCA Manual J • ASHRAE • Design the heating system to heat the building at “Outside Design Temperature” • Outside Design Temperature (ODT) is the coldest outside temperature expected for a location for a normal heating season • It is not the coldest temperature on record, but rather the lowest one recorded for a particular locale over a 3- to 5-year period - ODT’s are published in ASHRAE Fundamentals, Chapter 14
CONDUCTIVE HEAT LOSS FORMULA: • Conductive Heat Loss = Area (ft2) x T #1 (°F) R-Value of material
- The designer needs to calculate the convective heat loss through every exterior panel and every panel with a temperature difference - Example: Garage at 60°F, house at 68°F - There will be heat loss from the house to the garage (and heat gain to the garage)
CONDUCTIVE HEAT LOSS NOTE: - Heat loss from the floor through the ground is known as reverse loss - Reverse loss through heated slab edges (slab-on-grade) can be calculated when soil conditions are known, using special equations (not shown here) - Reverse loss through heated floors can be calculated when soil conditions are known, using special equations (not shown here)
AIR INFILTRATION HEAT LOSS BASED ON NUMBER OF AIR CHANGES PER HOUR : • ACH = fraction of air volume changed in 1 hour • Designer must predict or estimate this EXAMPLE: • Volume = 1,000 ft3, 300 ft3/hr air changed per hour = 0.3 ACH • 0.3 - 1.0 ACH is typical range for residential • Some commercial buildings have multiple air changes per hour (≥ 1) • ACH will be determined by construction quality, mechanical ventilation, code requirements for usage, etc.
AIR INFILTRATION HEAT LOSS FORMULA: • Convective heat loss = 0.018 BTU x Volume ft3 x # ACH x T #1 (°F) ft3 (°F) how many ft3/hr of air changed each hour
• 0.018 BTU is a constant value for air ft3(°F)
STEP 1a: Total heat loss • Conduction loss + Air Infiltration loss = Total Heat Loss @ design conditions • We can use this value to size the heat source and the heat delivery system
STEP 1b: RADIANT PANEL HEATING REQUIREMENT FORMULA: • Radiant Heating Requirement =
Total Heat Loss Available ft2
• Note: Not all square footage is available for heating • No pipe under walls, refrigerator, kitchen island, bookcase • Available ft2 is less than Total ft2 (usually 90% - 95% of Total area) EXAMPLE: • Heat loss is 50,000 BTU/hr for a building with 2,800 ft2 total, and 2,500 ft2 of available floor area 50,000 BTU/hr = 20 BTU/hr(ft2) radiant panel heating requirement 2,500 ft2
STEP 1c: REQUIRED FLOOR TEMPERATURE FORMULA: Floor Surface Temperature = Required Output + Indoor Air Temperature 2.0
EXAMPLE: 20 BTU/hr(ft2) + 68ºF Air = 78ºF Floor Surface Temperature 2.0 2.0 represents the combined Radiant/Convective Heat Transfer Coefficient (HTC) and is valid for typical residential indoor air temperatures
REQUIRED FLOOR TEMPERATURE APPROXIMATE HTC VALUES FOR HEATED PANELS: • Radiant Floors: 2.0 BTU/hr2 (35 - 40% heat is transferred via natural convection) 2.0 represents the combined Radiant/Convective Heat Transfer Coefficient (HTC) • Radiant Walls: 1.8 BTU/hr2 (less natural convection than floors) • Radiant Ceiling: 1.6 BTU/hr2 (very little natural convection)
• These values apply to standard room temperatures in range of 65° – 72°F • For colder rooms (like a 55°F warehouse) the HTC will be even higher thanks to greater natural convection • For hotter rooms (like a 80°F greenhouse) the HTC may be lower
REQUIRED FLOOR TEMPERATURE FLOOR AREA TYPES AND TEMPERATURE LIMITS Floor Area Type • Perimeter • Occupied • Bathroom • Distribution
Temperature Limit 95ºF (35°C) 85ºF (29°C) 91ºF (33°C) 95ºF (35°C)
Heat Output (Max.) 54 BTU/hr(ft2) 34 BTU/hr(ft2) 46 BTU/hr(ft2) 54 BTU/hr(ft2)
• These temperatures can be considered as design upper limits • These limits should not be exceeded without an engineer’s approval • This table is used to illustrate maximum radiant floor heat output for various floor types
REQUIRED FLOOR TEMPERATURE FLOOR AREA TYPES • “Perimeter” • 3-foot area near outside walls • “Occupied” • Living area inside perimeter area • “Distribution” • Hallways • “No Radiant Heating” • Under walls, kitchen islands, pantries, refrigerators and freezers, permanent cabinets, bookcases, etc.
STEP 2: RADIANT PANEL DESIGN STEPS • First, determine panel construction type • How will the floor be built? Thick or thin slab? Dry panel? Joist space? • Next, research the floor coverings • Bare concrete? Carpet? Tile? What R-values? • Then the designer: • Selects the pipe size • 5 choices (3/8” to 1”) • Selects the pipe spacing • Tighter spacing helps to avoid floor striping, requires low water temperature, ensures better response time, may even protect flooring against hot spots • Calculates the water (fluid) temperature • Less pipe density may require higher water temperature, may cause striping • This step is done using software
RADIANT PANEL DESIGN STEPS • First, determine panel construction type • How will the floor be built? • Thick or thin slab? • Dry panel? • Joist space?
RADIANT PANEL DESIGN STEPS SPECIAL CONSIDERATIONS FOR SUSPENDED SLABS
12” OC
6” thick concrete slab 3/4” PEX pipe
Side view of 6” thick slab with 3/4” PEX pipes
6” thick
12” width
AREA CALCULATION EXAMPLE: • 6-Inch thick slab has 72 in2 of concrete per foot length (6” x 12” = 72 in2) • Cross-sectional area of 3/4” PEX pipe = 0.601 in2 • Area of 3/4” PEX pipe installed every 12 inch = 0.601 in2 pipe per 72 in2 concrete • Percentage of concrete displaced by PEX pipe = 0.601 in2 / 72 in2 = 0.8%
RADIANT PANEL DESIGN STEPS • Next, research the floor coverings • Bare concrete? Carpet? Tile? What R-values?
RADIANT PANEL DESIGN STEPS Then the designer: • Selects the pipe size • 5 choices (3/8” to 1”) • Selects the pipe spacing • Tighter spacing helps to avoid floor striping, requires lower water temperature, ensures better response time, may even protect sensitive flooring against hot spots • Selects the maximum circuit lengths • Calculates the water (fluid) temperature • Less pipe density may require higher water temperature, may cause striping • This step is done using software
RADIANT PANEL DESIGN: PIPE SIZE Pipe Size 3/8” 1/2”
% Used 10% 70%
Applications Used in dry panel systems, joist-space, bathrooms Most common for residential “wet” systems
5/8”
9%
Larger residential, small commercial “wet” systems
3/4”
9%
Most commercial, industrial systems
1”
2%
Very large commercial, industrial systems
Table represents average usage of pipe diameters for radiant heating applications across North America
RADIANT PANEL DESIGN: PIPE SPACING Typical Pipe Spacing, using 3/8", 1/2" or 5/8" PEX pipes Residential Slab On Grade (thick pour)
6 - 8" Perimeter, 8 - 12" Occupied; 6” bathrooms
Residential Overpour (thin pour)
See below:
•
Overpour with Tile
6 - 9" spacing throughout to prevent striping
• Overpour with Carpet
6 - 8" Perimeter, up to 12" Occupied, based on heat load (more pipe = more efficiency)
• Overpour in Bathrooms
6" spacing throughout for high output
• Under Exterior Cabinets
12" under all “cold wall” cabinets
• Under Interior Cabinets, Pantries
Usually no pipe here
Dry Panel Installation
Usually 8" throughout
Joist-space installation
8” spacing throughout, with 16” joist centers
Commercial Slab On Grade
Depends on heat loss, 12” typical (18” possible)
RADIANT PANEL DESIGN: CIRCUIT LENGTHS Typical Maximum* Circuit Lengths • 3/8”: 250 feet • 1/2”: 330 feet • 5/8”: 400 feet • 3/4”: 500 feet • 1”: 500 feet *There is no absolute Maximum circuit length. • The farther the fluid travels in the pipe, the colder it becomes • The practical maximum circuit length depends on pipe diameter, heat loss for that circuit, and pump capability to keep the ΔT #3 within 20°F • A faster flow rate or larger diameter pipe reduces the heatloss per foot of the fluid travelling through the pipe • Larger pipe contains more fluid and more BTU’s for each foot of pipe in the floor
STEP 3. HYDRONIC FLOW RATES CALCULATING THE FLOW RATE TO DELIVER THE REQUIRED BTU’S • Hydronic Flow Rate Formula: BTU/hr = USGPM FD x 60 x SH x T(fluid) • Units: lb. x min x BTU x ºF gal hour lb x ºF • FD = fluid density (of the mixture) • SH = Specific heat of fluid (of the mixture)
• FD = 8.34 lb/gal for water, at 60°F • SH = 1.0 BTU/lb(°F) for water, by definition of a BTU • T (fluid) = 20°F for most hydronic systems
HYDRONIC FLOW RATES Hydronic Flow Rate Formula (simplified for water): BTU/hr = USGPM 8.34 x 60 x 1 x 500 x 20ºF BTU/hr 10,000
= USGPM
NOTE 1: US gallons are 3.8 l; Imperial gallons are 4.54 l, about 19% larger
All hydronic tables and graphs are based on US Gallons (USGPM) NOTE 2: These values apply only to water systems. Antifreeze will change these calculations
STEP 4: PIPE HEADLOSS • How much pressure (head) is required to make the water flow at the required flow rate? • Pressure is expressed in “feet of water head”
• 10 foot head = 4.4 pounds per square inch (psi) • 1 psi = 2.307 feet of head • System headloss values are found in tables and charts by the equipment manufacturers, such as: • Pipes • Heat sources • Air eliminators • Manifolds, etc.
Column height = 10 feet
CONVERSIONS:
STEP 4: PIPE HEADLOSS SAMPLE HEAD LOSS TABLE FOR PEX PIPES Flow Rate
Flow Velocity
100oF (38oC) Water
GPM
ft/sec
head loss/100 ft of pipe
Pipe Size- 3/8" 1/2" 5/8" 3/4"
1"
3/8"
1/2"
5/8"
3/4"
1"
0.1
0.32
0.17
0.12
0.09
0.05
0.223
0.054
0.022
0.011
0.003
0.2
0.63
0.35
0.24
0.18
0.11
0.766
0.184
0.076 0.036
0.011
0.3
0.95
0.52
0.36
0.26
0.16
1.580
0.380
0.156 0.075 0.023
0.4
1.26
0.69
0.48
0.35
0.21
2.641
0.634
0.261 0.125 0.038
0.5
1.58
0.87
0.60
0.44
0.27
3.935
0.945
0.388 0.186 0.056
1.0
3.15
1.74
1.20
0.88
0.53
13.6
3.262
1.340 0.642 0.193
1.5
4.73
2.60
1.80
1.32
0.80
28.1
6.743
2.769 1.326 0.399
2.0
6.30
3.47
2.40
1.76
1.07
47.2
11.295
4.637 2.220 0.668
Match flow rate with pipe size for headloss per 100 feet of pipe length
STEP 5: CHOOSING A CIRCULATOR INFORMATION NEEDED:
• Flow rate required (Step 3) • Head loss to overcome at that flow rate (Step 4)
PRINCIPLE: • Select a circulator which meets or slightly exceeds the flow rate and headloss requirements of the hydronic system, without going under • Avoid oversizing circulators by more than 10% over actual system needs
STEP 5: CHOOSING A CIRCULATOR - All circulators have tested performance curves available - Find intersection of x GPM and y feet of head loss to check if a given circulator is correct - See how the system “curve” matches circulator performance curve - System “curve” must fall to left of the circulator performance curve (inside) - Ideally, the system “curve” will be in the middle and to the left of the circulator curve
RADIANT HEATING DESIGN PROCESS • Step 1 • 1a: Heat Loss of space (this also gives Heat Source sizing requirements)
• 1b: Radiant Panel Heating Requirement (BTU per hour per ft2) • 1c: Required Floor Temperature (how warm does the floor need to be?) • Step 2: Radiant Panel Design: Determine PEX pipe size, pipe spacing, circuit lengths, and water temperature (designers will have several options) • Step 3: Determine Flow Rates for circuits and the entire system • Step 4: Determine Head Loss requirements • Step 5a: Choose Circulator (pump) to meet Flow Rate and Head Loss requirements • 5b: Size Expansion tank for the volume of the system
NOTES ON SOLID HARDWOOD FLOORING OVER RFH POTENTIAL DESIGN ISSUE: • With some species/brands of solid hardwood, the Maximum acceptable design temperature on the bottom of the board is as low as 85ºF • This would produce a maximum floor surface temperature of 77ºF on the top of the hardwood board • 77ºF Floor Temp. = 18 BTU/hr(ft2) output • This is a safe limit for design with solid hardwood over radiant floor heating, when the hardwood selected has a Maximum acceptable design temperature on the bottom of the board of 85ºF MOST HARDWOOD CONCERNS ARE BASED ON TWO ISSUES: • Poorly design and controlled radiant systems with excessive water temperatures • Hardwood floors installed when thermal mass is still “wet”, or before acclimation to the space
NOTES ON SOLID HARDWOOD FLOORING OVER RFH POTENTIAL SOLUTIONS: • Installers can control the under-floor hardwood temperature with the programmable floor sensor thermostat and remote floor sensor set into the floor • Program Max Floor Temp. = 85ºF • Installer should use tighter pipe spacing to reduce localized hot spots • Flooring contractor should use Quarter Sawn hardwood boards, Maximum 2 1/2” wide • Flooring contractor must ensure that the hardwood acclimates to the space/relative humidity for 2+ weeks before installation (even longer with “wet” overpour) • Add dry panel heating to walls or ceiling as supplemental heat source
NOTES ON SOLID HARDWOOD FLOORING OVER RFH POTENTIAL SOLUTIONS: specify flooring tolerant of the required temperatures, such as engineered hardwood floors
Solid Hardwood Flooring
Engineered Hardwood Flooring
NOTES ON CARPET AND UNDERPAD OVER RFH POTENTIAL DESIGN ISSUE: Thick carpet and inappropriate underpad insulate a heated floor, trapping the heat inside unless high water temperature is utilized. Inappropriate underpad may also fail prematurely over a heated floor POTENTIAL SOLUTIONS: • Thinner carpet has lower R-value and conducts heat better • Select the thinnest carpet which is acceptable to the customer
• Synthetic rubber (SBR*) underpad is recommended for use over radiant systems • Be sure to select flat SBR underpad (not rippled) *Styrene Butadiene Rubber
NOTES ON CARPET AND UNDERPAD OVER RFH POTENTIAL SOLUTION:
• A high quality underpad is better for the carpet, is more comfortable underfoot and is a more efficient choice when working with a radiant floor • SBR underpad is recommend for use over radiant systems • Longer-lasting • Conducts heat better • Typical thickness is 7/16” • Will handle the temperatures
RADIANT HEATING DESIGN FUNDAMENTALS REVIEW Step 1 • 1a: Calculate Heat Loss of space (gives Heat Source size) • 1b: Radiant Panel Heating Requirement (BTU per hour per ft²) • 1c: Required Floor Temperature - how warm does the floor need to be? Step 2: Radiant Panel Design: Determine PEX pipe size, pipe spacing, circuit lengths, and water temperature (designers have several options) Step 3: Determine Flow Rates for circuits and the entire system
Step 4: Determine Head Loss requirements Step 5: Choose Circulator (pump) to meet Flow Rate and Head Loss
requirements
RADIANT CONTROLS SELECTION Control theory Zoning components Thermostatic mixing Outdoor reset control Offer the most appropriate control for customer satisfaction and system performance. • There are many choices... • • • • •
RADIANT CONTROLS THEORY TYPE I: HEAT SOURCE CONTROLS THE FLUID TEMPERATURE 108°F Circulator
Primary loop
Adjustable Temperature Heat Source (outdoor reset)
Load (s) at same water Temperature
Zoning elements control the flow via manifold actuators or by the circulator
88°F
No water temperature mixing devices: Heat source controls its own output temperature • Fixed output temperature (set for highest annual demand) • Integrated outdoor reset control • Actuators or zone valves control flow
RADIANT CONTROLS THEORY TYPE II: HEAT SOURCE FLUID TEMPERATURE MUST BE REDUCED BEFORE THE FLOOR 180°F
108°F
Circulator
Primary loop
High Temperature Heat Source
Mixing Device
Low Temperature Load
Secondary loop
140°F
88°F
Water temperature mixing device options: • 3-Way Thermostatic Mixing Valve (TMV) • 2-Way Thermostatic Injection Valve • Floating Action (motorized 3- or 4-Way) Mixing Valve • Variable Speed Injection Pump Mixing
Zoning elements control the flow via manifold actuators or by the circulator
RADIANT CONTROLS THEORY FLOW CONTROL THROUGH ZONING
T-Stats
24 V Actuators
REHAU
Zone Box REHAU
Outdoor Reset Control
ABNA - NC
ABNA - NC
ABNA - NC
ABNA - NC
RFH SY STEMS
RFH SY STEMS
RFH SY STEMS
RFH SY STEMS
40 / 99
40 / 99
40 / 99
40 / 99
24V 3 W
24V 3 W
24V 3 W
24V 3 W
260166
260166
260166
260166
24 V Zone Valves
or
RADIANT FLOW CONTROL - ZONING CONTROLS THERMOSTATS AND ACTUATORS: • Allows control of each room or “zone” • Allows different temperatures throughout rooms • Accommodates solar gain or high occupancy • Must use special radiant thermostats – different calibration than air stats • One thermostat is a “zone” • Control flow through actuators on balancing manifolds • Coordinate multiple thermostats and actuators in a zone control module
RADIANT FLOW CONTROL - ZONING CONTROLS ELECTRIC THERMAL MANIFOLD VALVE ACTUATOR: • Wax melt thermal motor • No solenoid, no motor or gears • Normally Closed position • Operates with 24 VAC power • Blue-Brown are the power wires (24 VAC) • Green-Green are the end switch wires • Electrical circuit is completed when the actuator opens fully • Will complete another electrical circuit to activate pump relay • Red Tab holds actuator open to ease installation and is then thrown away
RADIANT ZONE CONTROL MODULE LOW-VOLTAGE 24 VAC WIRING BOX: • Connect all thermostats and actuators into one box • 4-zone Zone Control Module • Low-voltage 24 VAC input/output • Controls actuators based on input from up to 4 thermostats (“zones”) • Mount nearby manifolds • Run thermostat wire to the manifold location into the zone control module
RADIANT THERMOSTATIC TEMPERATURE CONTROL 3-WAY THERMOSTATIC MIXING VALVE APPROPRIATE ONLY FOR SMALL SYSTEMS, LESS THAN 30,000 BTU/HR: • Valve blends supply and return water to provide fixed output temperature • Simple and fairly accurate • Fixed output temperature must be set manually • Not weather-responsive • Water temperature may be too warm or too cold • Probably too warm for most days • Limited flow capacity is based on low Cv ratings • 3/4” Valve Cv 1.8 • 1” Valve Cv 3.0 • Exceeding the Cv rating increases headloss and possibility of noise Note: Cv = Controlled Volume = GPM @ 1 psi loss
OUTDOOR RESET CONTROL WEATHER-RESPONSIVE CONTROL OF WATER TEMPERATURE FOR HYDRONIC SYSTEMS ADVANTAGES: • Comfort: • Fast response to changes in heat loss • Prevent room temperature overshoot • Steady room temperature
• Control: • Can integrate with room zoning • Boiler protection, floor protection • You may need 2- or 3-temperature systems
• Flexibility: • Can control high-temp. and low-temp systems simultaneously
• Efficiency: • Reduced water temperatures • Increased cycle times, better equipment life • Reduced thermal expansion noise and cycling
OUTDOOR RESET CONTROL WEATHER-RESPONSIVE CONTROL OF WATER TEMPERATURE FOR HYDRONIC SYSTEMS FUNCTIONS: • Outdoor reset control determines the Target Supply water temperature based on Outdoor Air temperature at that moment in time • This is based on design information for that project: • Outdoor design temperature • Water supply temperature at design conditions • Minimum/maximum water supply temperature • Minimum boiler return water temperature (if applicable) • Outdoor reset control ensures that the heat input matches heat loss at any moment in time • Not too cold, not to hot, just right • “Reset Curve” calculates the target water temperature • Outdoor reset control also protects boiler against cold return temperatures • Outdoor reset control also protects sensitive flooring against hot supply temperatures
OUTDOOR RESET CONTROL TWO VARIATIONS: • Floating action output • 3- or 4-way motorized valve output • Motor “floats” the valve back-and-forth • Motor is necessary to control valve • Variable Speed Mixing Control • Variable speed pump output operates an injection pump • All use outdoor temperature sensors to “reset” system target water temperature
OUTDOOR RESET CONTROLCOMPLETE SYSTEM COMBINE WATER FLOW CONTROL AND WATER TEMPERATURE CONTROL FOR AN INTEGRATED SYSTEM: 6
1
Components: 1 2 3 4 5 6
Manifolds Mixing Valve Outdoor Reset Control Outdoor Sensor Pipe Temp. Sensors Thermostat
3
1
5
2 5
4
Course Summary
NOW THE DESIGN PROFESSIONAL WILL BE ABLE TO: • Describe the advantages of using radiant floor heating (RFH) technology • List several application options for RFH including residential, commercial, civic, industrial, and institutional applications
• Follow the design process for radiant heating systems to determine heat loss, floor temperatures, piping layouts, and fluid temperatures • Explain the basic control systems incorporated in radiant heating systems
RADIANT HEATING DESIGN AND CONTROLS AN AIA CONTINUING EDUCATION PROGRAM Credit for this course is 1 AIA HSW CE Hour
Course reh23c
© Ron Blank and Associates, Inc. 2010
Please note: you will need to complete the conclusion quiz online at ronblank.com to receive credit
SUSTAINABLE BUILDING TECHNOLOGY REHAU’s sustainable building technology provides solutions for heating, cooling, snow and ice melting, plumbing, water supply, fire protection, fresh air supply, and the building envelope
Lance MacNevin REHAU Inc. 1501 Edwards Ferry Rd. Leesburg, VA 20176 703-777-5255
[email protected] www.rehau.com
