Air-to-Water Heat Pumps for Low Energy & Net Zero Houses
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Air-to-Water Heat Pumps for Low Energy & Net Zero Houses presented at: February 14, 2018 8:30-10:00 presented by: John Siegenthaler, P.E. Appropriate Designs Holland Patent, NY www.hydronicpros.com © 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.
• Most North America heating professionals are familiar with ductless mini-split heat pumps. • Most are also familiar with geothermal heat pumps • Very few are currently familiar with air-to-water heat pumps. Ductless mini-split heat pump ? www.johnstone.com air-to-water heat pump geothermal heat pump airconditioning-repair-nashville.com
This is not the case in other global markets… Global air-to-water heat pump market: According to JARN (Aug 2015) 2014 global market: 1,745,000 air to water heat pumps sold Japanese manufacturers [Daikin, Mitsubishi, Fujitsu, Hitachi, Samsung, LG, Toshiba] German manufacturers [Dimplex, Wolf, Viessmanm, Bosch,Vaillant] Canadian manufacturers [ThermAtlantic, Nordic] 2014 China market : 987,000 units (12% increase over 2013) 2014 European market: 232,000 units (5% increase over 2013) #1 France, #2 Germany, #3 UK Still only about 2% of heat sources sold in Europe Due to low gas and oil prices, AWHP are subsided in Europe based on CO2 reduction targets, rather than energy efficiency. Many current models use inverter drive variable speed compressors for capacity control. Some use EVI (enhanced vapor injection) compressors.
So what is an air-to-water heat pump? air-to-water heat pump air-to-water heat pump (in heating mode) (in cooling mode) OUTSIDE OUTSIDE INSIDE hot gaseous refrigerant INSIDE liquid refrigerant condenses to liquid changes to vapor releasing heat absorbing heat hot cold fan outside outside air condenser fan warm air evaporator cool outside outside air air condensate hot gas drain cool gas cool gas hot gas hot cold fluid fluid hot gas evaporator liquid refrigerant condenser warm heat to RV comp. heat RV comp. fluid building from TXV cool fluid circulator building circulator TXV hot gas condenses liquid refrigerant to liquid releasing vaporizes absorbing heat heat liquid refrigerant liquid & gaseous refrigerant liquid & gaseous refrigerant In heating mode: The heat pump extracts low temperature heat from outside air, and transfers it to a fluid stream (water or water & antifreeze) to be used by a hydronic distribution system. In cooling mode: The heat pump extracts low temperature heat from a fluid stream (chilling it), and dissipates that heat to outside air.
Why hydronics vs. forced air? Water is vastly superior to air for conveying heat this cut would destroy the load-carrying ability of the floor joists A given volume of water can absorb almost 3500 times as much heat as the same 2 x 12 joist volume of air, when both undergo the same 14" x 8" duct temperature change 3/4" tube
Self-contained air-to-water heat pumps OUTSIDE INSIDE warmer climate application (water in outside unit) OUTSIDE INSIDE image courtesy of SpacePak • Heating + cooling + DHW colder climate application • Pre-charged refrigeration system (antifreeze in outside unit) • some are 2-stage for better load antifreeze! protected! matching circuit • No interior space required to / from! • No interior noise load heat! exchanger
Split system air-to-water heat pump Heating mode: 1. condenser 2. circulator 3. expansion tank 4. aux element 5. controls Cooling mode: indoor 1. evaporator unit 2. circulator OUTSIDE 3. expansion tank INSIDE 4. controls Indoor unit outdoor unit Outdoor unit Heating mode: 1. compressor 2. evaporator 3. expansion device Cooling mode: 1. compressor refrigerant 2. condenser lineset 3. expansion device
Split system air-to-water heat pump European split system air-to-water heat pump supplying heating and domestic hot water -4 ºF outside, 113 ºF leaving water temperature www.NIBE.eu
It’s not just about matching BTU delivery to load… It’s about providing COMFORT Ductless mini-split heat pumps rely on forced air delivery. While generally acceptable for cooling, forced air delivery doesn’t provide optimal comfort for heating. www.amazon.com • There will be some temperature stratification from floor to ceiling. • Mini-splits blow cool air into spaces while defrosting outdoor unit. • Cold floors are a common complaint with forced air heating. • High wall cassettes do little to counteract natural downdraft from large window surfaces. • Forced air heating may aggravate allergies or other respiratory symptoms. • There will be some sound from forced air terminal units. Properly designed radiant floor, wall, and ceiling panels can operate with virtually no detectible sound.
Why is the “net zero” housing market defaulting to mini-split heat pumps rather than hydronics? source: Revision Energy Training programs for “net zero” houses often promote mini-split heat pumps as the only necessary heating & cooling system. They often discourage the “complication” and cost of hydronic systems. historicshed.com
Based on this - who can blame them ??
Common suggestion for net zero houses…. Install a ductless mini-split air-to-air heat pump, with 1 or 2 indoor wall cassettes, and leave the source: Revision Energy interior doors open for heat distribution. from a green building website blog… “Leave bedroom doors open during the day If you want to heat your house with a ductless minisplit located in a living room or hallway, you’ll need to leave your bedroom doors open during the day. When the bedroom doors are closed at night, bedroom temperatures may drop 5 F° between bedtime and morning.” “If family members don’t want to abide by this approach, or don’t want to accept occasional low bedroom temperatures during the winter, then supplemental electric resistance heaters should be installed in the bedrooms.” The COPs of cold climate ductless mini- split heat pumps at sub-0ºF ambient conditions is seldom discussed. Maintaining heating capacity at sub-0ºF conditions doesn’t imply that COP is being maintained. historicshed.com
What happens to the COP of ductless mini splits at low ambient air temperatures? Site 1 : COP = 1.1 at 0 ºF Site 4 : COP = 1.8 at 0 ºF
Low ambient air-to-water heat pump yields good performance at low outdoor temperatures: At ambient = 0 ºF, leaving fluid = 120 ºF, COP =2.04
Low ambient air-to-water heat pump performance COP = 2.04 at 0 ºF ambient and 120 ºF leaving water temperature. Heat pump heat output: 40,500 Btu/hr Heat pump power: 5817 watts Btu Heat pump circulator: 40,500 COPHP+circulator = hr = 1.96 power: 200 watts ⎛ Btu ⎞ 3413 ⎜ hr ⎟ ( 6.042kw ) ⎜ Distribution circulator kw ⎟ ⎜⎝ ⎟⎠ power: 25 watts Higher than the measured COP of several ductless mini split heat pumps Total power to system: @ 0 ºF ambient. 6042 watts
Ductless mini-split heat pumps provide heating & cooling historicshed.com An air-to-water heat pump has the potential to provide: • Room-by-room zoning • Radiant & convective heat delivery • Zoned cooling (air & radiant delivery) • Domestic water heating • Pool heating in summer • Higher distribution efficiency • Fewer (if any) interior refrigerant piping connections
Several trends suggest that a growing market will emerge for air-to-water heat pumps. Here are some key indicators: 1. Growing interest in Net Zero houses: The typical net zero house has a very low loss thermal envelop, and a sizable solar photovoltaic array on the roof. Net metering laws - where they exist - allow owners of photovoltaic systems to sell surplus electrical power back to the utility at full retail rate. Thus, surplus kilowatt hours produced on a sunny summer day Source: Zerohomes.org could conceivably be “parked” on the electrical grid, and reclaimed to run a heat pump on a cold winter night with no technical or economic penalty. Space heat + DHW loads are so small it doesn't pay to put a gas meter on these houses. AWHP could provide heating, cooling, & DHW
Net Zero house in Seattle Source: www.tclegendhomes.com SPECS • 2,426 Square feet • 4 Bedrooms • 2.5 Baths • Radiant heat • Air-to-water heat pump • SIP construction • 9.5 KW PV system
What are the advantages of using hydronic heating in these houses? • Superior comfort: Radiant panel heating is better match to human physiological comfort needs. It’s not just about pushing Btus into a space to match heat loss. • Simple room-by-room (“wireless”) zoning is possible with many heat emitter options. Don’t have to leave all doors open for internal heat balancing. A limitation of single point heat/cool delivery such as wall cassette. • Very high distribution efficiency (A single ECM circulator operating on 10 to 40 watts supplies all heating distribution) • Non-invasive installation of small tubing (3/8” & 1/2” PEX, PERT, or PEX-AL-PEX) (Installing this tubing is like pulling electrical cable) • Easily adapted to renewable heat sources) (solar thermal, hydronic heat pump, biomass) • In many cases a single heat source can supply heating and DHW (fewer burners, less vents, less fuel piping) • Water-based thermal storage is easily adapted to “time-of-use” Electric rate structures. source: Wagner Zaun Architecture
What is distribution DISTRIBUTION EFFICIENCY? desired OUTPUT quantity Efficiency = necessary INPUT quantity Distribution efficiency for a space heating system. rate of heat delivery distribution efficiency= rate of energy use by distribution equipment Consider a system that delivers 120,000 Btu/hr at design load conditions using four circulators operating at 85 watts each. The distribution efficiency of that system is: 120,000 Btu/hr Btu/hr distribution efficiency= = 353 340 watts watt
The electrical input power for a circulator can be estimated: 0.4344 × f × ∆ P we = We = electrical input power (watts) f = flow rate (gpm) nw/w ∆P = pressure drop of circuit (psi) nw/w = wire-to-water efficiency of circulator A typical wet-rotor circulator with PSC motor has a maximum wire- to-water efficiency of about 25 percent. (ECM circulators will have significantly higher wire-to-water efficiencies) Consider a 200 ft long circuit of 3/4” copper tubing operating at 5 gpm with 180 ºF supply and 160 ºF return water temperature. It would have a pressure loss of 3.83 psi The required electrical input power to operate this circuit is: 0.4344 × f × ∆ P 0.4344 × 5 × 3.83 we = = = 33.2watts nw/w 0.25
A flow of 5 gpm in a circuit with a 20 ºF temperature drop is moving about 50,000 Btu/hr. The electrical input to a standard PSC circulator operating at 25% wire-to-water efficiency is 33.2 watts. The distribution efficiency of such a circuit is: Q 50, 000Btu / hr Btu / hr nd = = = 1506 we 33.2watt watt Compare this to a 4-ton rated geothermal water-to-air heat pump delivering 48,000 Btu/ hr using a blower operating on 1080 watts. The distribution efficiency of this delivery system is: Q 48, 000Btu / hr Btu / hr nd = = = 44.4 we 1080watt watt These numbers mean that the hydronic system delivers heat to the building using only 2.9 percent (e.g. 44.4/1506) of the electrical power required by the forced air delivery system. With good design it’s possible to achieve distribution efficiencies > 3000 Btu/hr/watt This will become increasingly important in low energy and net zero buildings...
Consider a design heating load of 30,000 Btu/hr Q 30,000 f= = = 3gpm • Assuming a common ∆T of 20 ºF across the heat emitters 500(∆ T ) 500(20) • Assume a homerun distribution system to 8 identical panel radiators • Each panel rad is 24” x 72” x 4” operating w/ average 8, 24" x 72" x 4" panel radiators water temperature of 110 ºF, (120 ºF supply & 100 ºF TRV return) yielding output of 3,850 Btu/hr each, total system heat output of 30,800 Btu/hr • Flow rate per panel radiator is 3/8 = 0.38 gpm 120 ft x 1/2" pex homerun circuits • Head loss of each panel radiator (balance valve partially closed) at this flow rate is 3.38 ft. • Assume each homerun circuit is 120 ft of manifold 1/2” PEX at 0.38 gpm, head loss = 0.8 ft. 3-40 watts station pressure regulated variable speed • Add 10% safety factor to head circulator loss for a total of 4.6 ft. • Circulator requirement is 3.0 gpm at 4.6 ft. • Even with an ECM circulator that’s 30% w/w efficient, this requires an input of about 8.6 watts heat source 0.4344 × f × ∆ P 0.4344 × 3.0 × 4.6 ( 0.43) buffer tank we = = = 8.6watt ncirculator 0.3 Btu 30,800 distribution efficiency = hr = 3581 Btu / hr 8.6watt watt
Why is the NA hydronics industry leaving its “best cards” on the table? 80,000 Btu/hr Btu/hr distribution efficiency= = 94 850 watts watt 8, 24" x 72" x 4" panel radiators Btu TRV 30,800 Btu / hr distribution efficiency = hr = 3581 120 ft x 1/2" pex 8.6watt watt homerun circuits 94 In this comparison the hydronic system manifold station = 2.6% uses only 2.6% of the electrical energy required by the forced air system for pressure regulated 3581 variable speed equal heat transport (source to load). circulator
Several trends suggest that a growing market will emerge for air-to-water heat pumps. 2. The 30% federal tax credits on geothermal heat pump systems ended December 31 2016: That removed a significant purchasing incentive, and forces geothermal heat pump systems to compete against other types of heat pumps in an unsubsidized market. https://www.geoexchange.org/wp-content/uploads/GEO-Industry-News-January-2018.pdf “The GHP industry experienced a 50% loss of residential sales during the year (2017), with hundreds of layoffs and thousands more jobs in jeopardy.” THIS CHANGED 2/9/18 There’s a possibility this tax credit could be reinstated. NYSERDA does have $1500 / ton (cooling capacity) GSHP rebate program at present. https://www.nyserda.ny.gov/All-Programs/Programs/ Ground-Source-Heat-Pump-Rebate Do you want to build your business model on the assumption that subsidies will always be there?
Several trends suggest that a growing market will emerge for air-to-water heat pumps. geothermal heat pump 3. Air-to-water heat pumps are typical installed cost = $X significantly less expensive to install compared to geothermal heat pumps: This is especially true if vertical boreholes are required for the earth loop. In my area, these holes cost about $3,000+ per ton for drilling, air-to-water heat pump pipe insertion, and grouting. typical installed cost Additional cost is incurred for = $(30% to 50%)X connecting multiple vertical piping loops, and routing piping back to the location of the heat pump. Replacement of any affected pavements or landscaping also needs to be factored into the cost of installing a geothermal heat pump system.
Several trends suggest that a growing market will emerge for air-to-water heat pumps. Here are some key indicators: geothermal heat pump typical installed cost = $X 4. Diminishing returns: As home heating loads decrease due to better thermal envelopes, the difference in annual heating cost between heat pumps operating at seasonal average COPs that vary by perhaps 1.0 or less, decreases. The incrementally lower operating cost of the higher performance heat pump may not amortize the higher installation cost within the expected life of the system. air-to-water heat pump typical installed cost = $(30% to 50%)X
You don’t pay for COP! (you pay for kilowatt•hours) The annual savings in heating energy between two heat pumps with different seasonal average COPs can be estimated using this formula: Where: ⎡ 1 1 ⎤ S = savings in seasonal heating energy (MMBtu*) S = load ⎢ − ⎥ load = total annual heating energy required for the building (MMBtu*) COPL = seasonal average COP of heat pump having the lower of the two COPs ⎣ COPL COPH ⎦ COPH = seasonal average COP of heat pump having the higher of the two COPs * 1 MMBtu = 1,000,000 Btu Example: A house has a design heating load of 36,000 Btu/hr when the outdoor temperature is 0 ºF, and the indoor temperature is 70 ºF. The house is located in Syracuse, NY with 6,720 annual heating ºF•days. The estimated annual space heating energy use is 49.7 MMBtu. Assume that one heat pump option has a seasonal average COP of 3.28. The other heat pump has a seasonal COP of 2.8. ⎡ 1 1 ⎤ ⎡ 1 1 ⎤ S = load ⎢ − ⎥ = 49.7 ⎢ − ⎥ = 2.6MMBtu / year ⎣ COPL COPH ⎦ ⎣ 2.8 3.28 ⎦ The cost savings associated with an energy savings of 2.6 MMBtu/hr depends on the cost of electricity. For example, if electricity sells at a flat rate of $0.13 / KWHR, the cost savings would be: 2.6MMBtu ⎛ 292.997KWHR ⎞ ⎛ $0.13 ⎞ Cost savings = ⎜⎝ ⎟⎠ ⎜⎝ ⎟⎠ = $99 / year year 1MMBtu KWHR Can the added cost of the higher COP heat pump be recovered in a reasonable time?
Diminishing returns of higher COPs Example house: 36,000 BTU/hr design load at 70ºF inside & 0 ºF outside Location: Syracuse, NY (6720 heating degree days) Total estimated heating energy required: 49.7 MMBTU / season Average cost of electricity: $0.13/kwhr Distribution system: radiant panels with design load supply temperature = 110ºF AIR-TO-WATER HEAT PUMP OPTION Based on simulation software, a nominal 4.5 ton split system air-to-water heat pump supplying this load has a seasonal COP = 2.8. Estimated installed cost = $10,600 (not including distribution system) GEOTHERMAL WATER-TO-WATER HEAT PUMP OPTION: Based on simulation using simulation software, a nominal 3 ton water to water heat pump supplying this load from a vertical earth loop has a seasonal COP = 3.28. Estimated installed cost = $11,800 (earth loop) + $8750 (balance of system) = $20,550 (not including distribution system) Deduct for 30% federal tax credit: ($ -6165) Net installed cost: $14,385 (not including distribution system) Annual space heating cost: AIR-TO-WATER HEAT PUMP (COPave= 2.8) = $676 / yr GEOTHERMAL HEAT PUMP (COPave = 3.28) = $577 / yr Difference in annual heating cost: $99 / year Difference in net installed cost: $3,785 Simple payback on higher cost of geothermal HP: 3785 / 99 ≈ 38 years Without subsidies the estimated difference in installed cost is $9,950 With reinstated 30% federal tax credit the difference in installed cost is $3785 Initial difference in annual heating cost: $98 / year Draw your own conclusions….
Several trends suggest that a growing market will emerge for air-to-water heat pumps. 5. Air-to-water heat pumps are significantly less disruptive to install compared to geothermal heat pumps: Horizontal earth loops require large land areas and major excavation. In my area, vertical earth loops cost about $3,000+ per ton for drilling, pipe insertion, and grouting. Additional cost is incurred for connecting multiple vertical piping loops, and routing piping back to the location of the heat pump. The drill “tailings” usually have to be removed from the site. Replacement of any www.thegeoecchange.org affected pavements or landscaping also needs to be factored into the cost of installing a geothermal heat pump system.
Several trends suggest that a growing market will emerge for air-to-water heat pumps. 6. As home space heating loads get smaller, the domestic water heating load becomes an increasingly higher percentage of the total annual heating energy requirement. Water heating Some estimates put the DHW load at 25-30 percent of COP = 1.0 the total annual energy requirement in a well insulated modern home. Most ductless mini-split heat pumps cannot provide domestic water heating, but a properly configured air-to- water heat pump can. A standard electric water heater providing domestic water heating in a situation where the heat pump can not, delivers heat at a COP of 1.0. If that energy was instead attained through an air-to-water heat pump, it could be delivered at a COP averaging perhaps 2.5 over the year. For a family of 4, needing 60 gallons per day of water heated from 50 to 120 ºF, and assuming electrical energy priced at $0.12 per KWHR, Water heating the difference in annual domestic water heating cost between these scenarios is $270. COP = 2.5+
Several trends suggest that a growing market will emerge for air-to-water heat pumps. 7. The high COP cited for some Example of a commercially geothermal heat pumps doesn’t available earth loop flow center. include the power required to move 4, UP26-150 circulators (370 watts flow through the earth loop. each) = 1,480 watts pumping power input. The ANSI 13256-2 standard for geo heat pump COP includes an estimate for the power required to move flow through the heat pump - BUT DOESN’T INCLUDE ANY ALLOWANCE FOR THE EARTH LOOP PUMPING POWER. The high flow and head required in some geothermal earth loops requires substantial circulator power. Example: A specific water-to-water geothermal heat pump has the follow listed performance information: Earth loop entering temperature = 30ºF Entering load water temperature = 100 ºF Flow rate (both evaporator and condenser) = 9 gpm Heating capacity = 27,700 Btu/hr Electrical power input = 2370 watts Based on a typical earth loop, the pumping requirement is 10.5 gpm at 35.5 feet of head. This equates to an estimated pump input of 287 watts. Btu Btu 27700 27700 COPHP only = hr = 3.42 COPHP +loop pump = hr = 3.05 ⎛ Btu ⎞ ⎛ Btu ⎞ 3413 3413 ( 2.37kw ) ⎜⎜ hr ⎟ ⎜ ( 2.37kw + 0.287kw ) ⎜ hr ⎟ kw ⎟ kw ⎟ ⎜⎝ ⎟⎠ ⎜⎝ ⎟⎠ Nominal 11% drop in “net” COP
Other (unique) air-to-water heat pumps
Split system air-to-water heat pump Nordic air-to-water heat pump INDOOR UNIT compressor refrigerant-to-water heat exchanger reversing valve controls desuperheater (for DHW) OUTDOOR UNIT (major components) air-to-refrigerant heat exchanger fan
Bring your own condenser... ThermAtlantic Energy Products, Inc.
Bring your own condenser... Heating mode Heat pump routes heat to buffer tank absorbed! Heat delivered from buffer (low temperature)! heat tank to low temperature load chilled water air handler ON air source heat pump! OFF outdoor unit temperature sensor zone! OFF thermostats manifold controls valve actuators ON electric! boiler zoned radiant ! ON DX2W module ON! ceiling panels buffer tank open (supplemental)! closed open
Bring your own condenser... Cooling mode Heat pump chills buffer tank rejected! heat Chilled water delivered to air handler for latent cooling, & mixing chilled water to radiant panels for sensible cooling chilled water air handler ON air source heat pump! ON outdoor unit zone! ON thermostats manifold controls valve actuators ON electric! boiler zoned radiant ! ON DX2W module OFF ceiling panels (cooling mode operation) buffer tank partially! open partially! open mixed
Heating performance: (inverter drive scroll compressor unit) leaving water temperature 95 ºF 95 ºF 131 ºF leaving water temperature 131 ºF 80000 5 4.5 4 60000 heat output (Btu/hr) 3.5 3 COP 40000 2.5 2 1.5 20000 1 0.5 0 0 -5 5 15 25 35 45 55 65 75 -5 5 15 25 35 45 55 65 75 outdoor temperature (ºF) outdoor temperature (ºF) Heating capacity COP Increases with: Increases with: a. warmer outdoor temperature a. warmer outdoor temperature b. lower load water temperature b. lower load water temperature
Heating performance: OUTSIDE INSIDE HEATING MODE outside air load water temperature! "lift"! (less is better) load water outside air Anything that reduces the “temperature lift” increases both the heating capacity and COP of the heat pump. Low temperature distribution systems are critical to good performance.
Cooling performance: Daikin Alterma model ERLQ054BAVJU Daikin Alterma model ERLQ054BAVJU leaving chilled water temp = 59 ºF leaving chilled water temp = 59 ºF leaving chilled water temp = 55 ºF leaving chilled water temp = 55 ºF leaving chilled water temp = 50 ºF leaving chilled water temp = 50 ºF leaving chilled water temp = 45 ºF leaving chilled water temp = 45 ºF Energy Efficiency Ratio (EER) (Btu/hr/watt) 70000 14 13 65000 Cooling capacity (Btu/hr) 12 60000 11 55000 10 9 50000 8 45000 7 40000 6 60 65 70 75 80 85 90 95 100 105 60 65 70 75 80 85 90 95 100 105 Oudoor air temperature (ºF) Outdoor air temperatue (ºF) Cooling capacity EER Increases with: Increases with: a. lower outdoor temperature a. lower outdoor temperature b. Higher chilled water temperature b. higher chilled water temperature
Cooling performance: OUTSIDE INSIDE COOLING MODE outside air outside air temperature! chilled water "lift"! (less is better) chilled water Anything that decreases the temperature lift’ increases both the cooling capacity and EER of the heat pump. Warmer chilled water temperatures improve performance.
LOW-AMBIENT Air-to-Water Heat Pump Systems
evaporator outside! outside! air fan air Standard ! refrigeration compressor cycle condensor water out evaporator water in (main) TXV! thermal outside! outside! expansion air fan air valve vapor injection port EVI enabled! EVI allows compressor electronic expansion increased refrigerant valve condensor EVI mass flow into evaporator, & at lower water out refrigeration entering temperatures. water in cycle (main) TXV! refrigerant! thermal "sub-cooler" solenoid expansion valve sub cooled! valve liquid refrigerant
Freeze protection Simplest option: Use antifreeze solution in entire system OUTSIDE INSIDE entire system filled with antifreeze solution pressure relief valve air separator remainder of system air-to-water heat pump flexible connectors expansion tank fill / purge valves
Heat exchangers between heat pump maximum! approach! and distribution system temperature! difference! OUTSIDE (heating) INSIDE
My own installation... February 2015 Upstate NY -23 ºF air temperature -29 ºF wind chill Feb 7, 2018
Design objectives: 1. Be able to serve as heat source for building with 18,000 Btu/hr design load (via radiant floor heating). 2. Retain oil-fired boiler and allow simple manual selection of heat source. (flip of switch) 3. Provide zoned chilled water cooling for 1st floor office, and 2nd floor guest room. 4. Be equipped for BTU metering of energy from heat pump & KWHR meter of electrical energy to heat pump (to calculated COP, and EER)
Supporting the heat pump Treated lumber pedestal to keep unit above snow level Added 2 threaded rods w/ base flanges to stiffen pedestal
Piping details to keep condensate out of wall framing 1” FPT copper adapter 2” PVC sleeve wrap with electrical tape for tight fit 1” Chamflex hoses with offset to allow small movement foam sealant inside
high wall fan coil 1/2” FPT to propex adapter 1/2” MPT lines on air handler end of condensate drain hose HW-18-ECM (@ 2.1 gpm flowrate) 25000 20000 Heat ouput (Btu/hr) 15000 10000 5000 0 condensate drain direct 70 80 90 100 110 120 130 140 150 160 through outside wall Entering water temperature (ºF)
Importance of low temperature distribution systems
Heat sources such as condensing boilers, geothermal & ATW heat pumps, and solar collectors all benefit from low water temperature operation. 5.1 Coefficient Of Performance (COP) 4.9 4.7 4.5 4.3 4.1 3.9 3.7 3.5 100 105 110 115 120 125 Entering water temperature (ºF) 0.8 0.7 thermal efficiency (decimal %) 0.6 0.5 0.4 0.3 0.2 ambient air temp. = 30ºF! 0.1 solar radiation = 250 Btu/hr/ft2) 0 60 80 100 120 140 160 180 200 inlet fluid temperature (ºF)
“FUTURE PROOF” your hydronic systems... Select heat emitters, and design hydronic distribution systems so that they can supply design load output using supply water temperatures no higher than 120 ºF. Even lower design load supply temperatures are preferred when possible. This is especially important when renewable energy heat sources are used.
Water temperature ranges for various hydronic heat emitters • The heat output of any heat emitter always drops with decreasing water temperature. • There is always some output provided the supply water temperature is above the room air temperature. • There is always a trade off between the total surface area of the heat emitters in the system, and the supply water temperature required to meet the heating load. • More heat emitter area always lowers the required supply water temperature. 120 ºF, suggested maximum supply water temperature for modern systems traditional cast-iron radiators traditional fin-tube baseboard NOT RECOMMENDED fan-coils panel radiators ceiling heating wall heating underfloor tube&plate above floor tube&plate thin slab covered heated slab floor heating (bare slab) 80 90 100 110 120 130 140 150 160 170 180 190 200 • Don’t feel constrained to select heat emitters based on traditional supply water temperatures…
Slab-on-grade floor heating tube spacing 4" concrete slab 6-inch tube spacing 12-inch tube spacing Rff=0 Rff=0.5 60 upward heat flux! Rff=1.0 (Btu/hr/ft2) 40 Rff=1.5 Rff=2.0 20 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)
Don’t do this with ANY hydronic heat source! Heat transfer between the water and the upper floor surface is severely restricted!
Don’t do this with ANY hydronic heat source! Heat transfer between the water and the upper floor surface is severely restricted!
Hydronic heat emitters options for low energy use houses Most CONVENTIONAL fin-tube baseboard has been sized around boiler temperatures of 160 to 200 ºF. Much too high for good thermal performance of low temperature hydronic heat sources. Could add fin-tube length based on lower water temperatures. BUT... Fin-tube output at 120 ºF is only about 30% of its output at 200ºF
Hydronic heat emitters options for low energy use houses Some low- temperature baseboard is now available
Hydronic heat emitters options for low energy use houses Panel Radiators One of the fastest responding hydronic heat emitters From setback to almost steady state in 4 minutes…
Hydronic heat emitters options for low energy use houses Panel Radiators • Adjust heat output for operation at lower water temperatures. As an approximation, a panel radiator operating with an average water temperature of 110 ºF in a room room maintained at 68 ºF, provides approximately 27 percent of the heat output it yields at an average water temperature of 180 ºF.
Fan-assisted Panel Radiators The “NEO”, just released from Runtal North America 8 tube high x 31.5” wide produces 2095 Btu/hr at average water temperature of 104 ºF in 68ºF room 8 tube high x 59” wide produces 5732 Btu/hr at average water temperature of 104 ºF in 68ºF room
Site built radiant CEILINGS… Thermal image of radiant ceiling in operation Heat output formula: q = 0.71× (Twater − Troom ) Where: Q = heat output of ceiling (Btu/hr/ft2) Twater = average water temperature in panel (ºF) Troom = room air temperature (ºF)
Site built radiant WALLS…
Site built radiant WALLS… Heat output formula: • completely out of sight • low mass -fast response q = 0.8 × (Twater − Troom ) Where: • reasonable output at low water temperatures • stronger than conventional drywall over studs Q = heat output of wall (Btu/hr/ft2) Twater = average water temperature in panel (ºF) • don’t block with furniture Troom = room air temperature (ºF)
Reverse indirect tank buffers space heating & significantly preheats domestic water (ZP1) (T1) Source: Turbomax tanks entire system filled with (ZP2) (T2) antifreeze solution OUTSIDE INSIDE point-of-use instantaneous water heater SPACEPAK (MV1) (SPC) ASSE 1070 (S1) valve DHW (S2) CW (P1) reverse indirect water heater / buffer tank Solstice Extreme (HP) flexible air-to-water heat pump connectors
Reverse indirect tank buffers space heating & significantly preheats domestic water DESCRIPTION OF OPERATION: (ZP1) (T1) Power supply: The Solstice heat pump, circulator (P1), and motorized valve (MV1) are powered by a dedicated 240/120 VAC 30 amp circuit. The heat pump disconnect switch (HPDS) must be closed to provide power. The remainder of entire system filled with (ZP2) (T2) antifreeze solution the control system is powered by 120 VAC 15 amp circuit. The main switch (MS) must be closed to provide power. The instantaneous water heater is supplied by OUTSIDE a dedicated 240 VAC / 60 amp circuit. INSIDE point-of-use Heat pump operation: Whenever the main switch (MS) is closed 120 VAC is instantaneous water heater passed to the multi-zone relay center (MZRC). The (MZRC) passes 24 VAC to (MV1) SPACEPAK the temperature setpoint controller (SPC) which monitor the temperature at (SPC) ASSE 1070 (S1) valve DHW sensor (S1) in the buffer tank. If the temperature at sensor (S1) is below 105 ºF, (S2) CW the (SPC) closes its contact, which completes a circuit between terminals 15 and 16 in the Solstice Extreme heat pump, enabling it to operate in heating mode. After a short time delay, circulator (P1) and motorized valve (MV1) will be (P1) supplied with 120 VAC from the heat pump. This establishes flow of the system’s reverse indirect water heater / buffer tank antifreeze solution through the heat pump. The heat pump verifies adequate Solstice Extreme (HP) flexible air-to-water heat pump connectors flow using its internal flow switch, and when adequate flow is proven, starts the heat pump in heating mode. The 120 VAC supplied to (MV1) opens the valve 240/120 VAC allowing flow between the heat pump and the headers of the thermal storage 30 amp circuit L1 L2 N L1 N G tank. The system continues in this mode until the temperature at sensor (S1) heat pump 120 VAC / 15amp circuit disconnect reaches 125ºF, at which point the contacts in the setpoint controller (SPC) open switch main (T1) (T2) (HPDS) switch turning off the heat pump, circulator (P1) and motorized valve (MV1). instantaneous (MS) water heater 240 VAC Space heating: Whenever the main switch (MS) is closed, 24 VAC is sent to 60 amp (P1) circuit L thermostats (T1, T2). When either thermostat calls for heating its associated N Solstice (MZRC) zone circulator (ZP1, ZP2) is turned on. Extreme heat pump (MV1) 15 16 17 18 Domestic water heating: Domestic water passes through the copper tubing coils suspended in the buffer tank. The tank temperature at sensor (S1) is (HP) (SPC) maintained between 105 and 125 ºF. Domestic water passing through the coil R C (ZP1) (ZP2) (S1) will be preheated (or at time fully heated) as it passes through this coil. Any sensor additional temperature rise of the domestic water is provided by the tankless electric water heater.
Cold climate air-to-water heat pump system radiant panel mainfold station 1 • 2 zones of radiant panel heating (AH1) OFF • 2 zones of chilled water cooling • 80 gallon buffer tank • High efficiency variable speed distribution circulator (ZVH1) (ZVC1) • Direct-to-load supply side piping OFF radiant panel mainfold station 2 (ZVH2) (AH2) OFF HEATING MODE (ZVC2) All piping and components OFF conveying chilled water must be insulated and vapor sealed OUTSIDE INSIDE entire system filled with (P2) propylene glycol antifreeze solution spring check (ORC) SPACEPAK valve (S2) outdoor (S1) temperature (S3) sensor temperature sensors (SPC) (P1) heated buffer tank Solstice Extreme (HP) flexible air-to-water heat pump connectors
Cold climate air-to-water heat pump • 2 zones of radiant panel heating (AH1) • 2 zones of chilled water cooling • 80 gallon buffer tank OFF (ZVH1) • High efficiency variable speed distribution (ZVC1) circulator • Direct-to-load supply side piping (ZVH2) OFF (AH2) COOLING MODE (ZVC2) All piping and components conveying chilled water must be insulated and vapor sealed OUTSIDE INSIDE entire system filled with (P2) propylene glycol antifreeze solution spring check (ORC) valve SPACEPAK (S2) (S1) (S3) temperature sensors (SPC) (P1) heated buffer tank Solstice Extreme (HP) flexible air-to-water heat pump connectors
Cold climate air-to-water heat Description of operation: pump system Power supply: The Solstice Extreme heat pump and circulator (P1) are powered by a dedicated 240/120 VAC 30 amp circuit. The heat pump disconnect switch (HPDS) must be closed to provide power to the heat pump. The remainder of the control system is powered by 120 VAC / 15 amp circuit. The main switch (MS) must be closed to provide power to the 240 VAC 240/120 VAC 15 amp circuit 30 amp circuit control system. Both fan coils are powered by a dedicated 120 VAC / 15 amp circuit. The L1 L2 G heat pump L1 L2 N G L1 N G service switch for each air handler must be closed for that air handler to operate. disconnect 120 VAC / 15amp circuit switch main (HPDS) switch Heating mode: The mode selection switch (MSS) must be set for heating. This passes 24 (MS) VAC to the RH terminal in each thermostat. Whenever either thermostat demands heat, (P1) L1 L2 24VAC is passed from the thermostat’s W terminal to the associated zone valve (ZVH1, or L N ZVH2). When the zone valve reaches its fully open position its internal end switch closes, Solstice Extreme passing 24 VAC to relay coil (R1). Relay contact (R1-1) closes to pass 120 VAC to heat pump circulator (P2). Relay contact (R1-2) closes to pass 24VAC to outdoor reset controller 15 16 17 18 (ODR). The (ODR) measures outdoor temperature at sensor (S2), and uses this temperature along with it settings to calculate the target supply water temperature for the buffer tank. It then measures the temperature of the buffer tank at sensor (S1). If the (R2-3) (R1-1) temperature at (S1) is more than 3 ºF below the target temperature the (ODR) closes its (R2-1) relay contact. This completes a circuit between terminals 15 and 16 in the Solstice extreme heat pump, enabling it in heating mode. After a short time delay the heat pump (HP) turns (P2) on circulator (P1) and verifies adequate flow through the heat pump. After a short time transformer delay the heat pump compressor turns on it compressor. The heat pump continues to 120/24 VAC (MSS) 24 VAC operate until the temperature at sensor (S1) is 3 ºF above the target temperature calculated Mode by the (ODR), or neither thermostat calls for heat, or the heat pump reaches it internal high heat cool service selection (AH1) switch off switch (RC) L1 limit setting. Note: Neither air handler operates in heating mode, regardless of the fan L2 (R1) switch setting on the thermostats. G R G (RC-1) (R2) RC Cooling mode: The mode selection switch (MSS) must be set for cooling. This passes RH (ZVH1) 24VAC to relay coil (RC). normally open contacts (RC-1) and (RC-2) close allowing 24VAC service W M (AH2) switch from the air handlers to pass to the RC terminal in each thermostat. Whenever either G L1 L2 thermostat calls for cooling, 24VAC is passed from the thermostat’s Y terminal to the Y M G R G thermostat associated zone valve (ZVC1, or ZVC2). When the zone valve reaches its fully open (T1) (ZVC1) (RC-2) position its internal end switch closes, passing 24 VAC to relay coil (R2). Relay contact RC RH (ZVH2) (R2-1) closes to pass 120 VAC to circulator (P2). Relay contact (R2-2) closes to pass W M 24VAC to the cooling setpoint controller (SPC). The cooling setpoint controller measures G the temperature of the buffer tank at sensor (S3). If this temperature is 60 ºF or higher, the Y thermostat M (SPC) relay contact closes completing a circuit between terminals 15 and 16 on the Solstice (T2) (ZVC2) Extreme heat pump (HP) enabling it to operate. Relay contact (R2-3) closes between terminals 17 and 18 in the Solstice Extreme heat pump (HP), switching it to cooling mode. (R1-2) (ORC) R C The heat pump (HP) turns on circulator (P1) and verifies adequate flow through the heat (S1) pump. After a short time delay the heat pump compressor turns on it compressor and (S2) sensors operates in chiller mode. This continues until the temperature at sensor (S3) drops to 45 ºF, or until neither zone thermostat calls for cooling, or until the heat pump reaches in internal (R2-2) (SPC) R C low limit setting. The blowers in the air handlers can be manually turned on at the (S3) thermostats when the mode selection switch (MSS) is set to cooling. The blowers will sensor operate automatically whenever either cooling zone is active.
Dynamic Duo: hydronic heat pump + boiler This combination provides the following benefits: • The mod/con boiler can serve as a “peaking tool” to meet peak loads when necessary. • The heat pump can be smaller in capacity relative to design load. This is helpful in applications where the cooling load is significantly smaller than the design heating load. • Having a mod/con boiler as a secondary heat source provides full or partial backup if the heat pump is not operating. • The boiler’s electrical power demand is relatively small compared to the heat pump. This makes it more feasible to operate the heating system from a modestly-sized backup generator during power outages. • In areas where time-of-use electrical rates are available, it would be possible to operate the heat pump when off-peak rates are in effect, and avoid high on-peak rates by using the boiler as the heat source.
towel warmer Heating + Cooling +DHW radiator air vent thermostatic operator air vent Self-contained (2-stage) TRV air-to-water heat pump w/ dual isolation valve mod/con auxiliary boiler Single thermal mass tank mod/con boiler PEX, or 2-stage temperature PEX-AL-PEX tubing setpoint controller (SPH) variable speed circulator (P2) Supplies: isolation and • flushing valves zoned space heating for potable side of HX • manifold station P&T single zone cooling temp. DHW (P3) (HX) • sensor domestic hot water (S1) (FS1) • automatic aux boiler buffer OUTSIDE INSIDE tank (P4) diverter N.C. valve A (DV1) AB 2 stage or inverter drive B N.O. heat pump very important (P1) spring-loaded check valves to avoid short cycling in Solstice SE cooling mode. air to water heat pump (AH1) Entire system filled with propylene (S2) single zone air handler for glycol antifreeze solution. cooling
Heating + Cooling +DHW Electrical Wiring 240 VAC L1 L2 N L1 N towel warmer 120 VAC radiator air vent thermostatic operator main switch (MS) air vent L (HP) TRV dual isolation valve (P1) N Solstice SE heat pump (RH2-1) 43 44 (P2) 5 6 mod/con boiler (Rdhw-1) (P4) (RH1-2) PEX, or 2-stage temperature (RB-1) (AH1) PEX-AL-PEX tubing setpoint controller (SPH) variable speed circulator (P2) mod/con isolation and boiler T (RH1-1) flushing valves for potable side (B1) T of HX manifold station P&T (P3) temp. DHW (P3) (HX) sensor transformer (S1) 120/24 VAC (FS1) 24 VAC (Rdhw) buffer OUTSIDE INSIDE tank (FS1) (P4) diverter valve N.C. A (SPH) R C (DV1) AB (S1) stage 1 (RH1) B N.O. sensor 2-stage Mode setpoint selection stage 2 controller (DV1) switch cool cool spring-loaded heat (P1) check valves (MSS) off off Solstice SE air to water heat pump RC RH (RH2) W (AH1) G (RB) (T1) Y single zone master (SPC) air handler thermostat R C (S2) for cooling (S2) sensor
Heating + Cooling +DHW Description of Operation Please read this later in the PDF Heat Source Operation: When the main switch (MS) is closed, power is available to the line voltage and low voltage portions of the electrical system. 24VAC is applied to power up the 2-stage setpoint controller (SPH). This controller (SPH) measures the temperature at sensor (S1) in the upper portion of the thermal storage tank. If that temperature is below the user-set stage1 setpoint (in this case 125 ºF), minus half the user-set differential (in this case half the differential is 5 ºF), then the stage 1 contacts in (SPH) close. For space heating operation, the (DPDT) mode selection switch must be set to heat. This passes 24VAC to the RH terminal of the master thermostat (T1). It also allows 24 VAC to pass from the stage 1 contacts in the (SPH) controller to energize the diverter valve (DV1) and relay coil (RH1). Relay contact (RH1-1) closes between terminal 43 and 44 on the Solstice SE heat pump turning it on in the heating mode. Relay contact (RH1-2) opens between terminals 5 and 6 on the Solstice SE heat pump allowing it to operate in heating mode. An internal relay within the heat pump turns on circulator (P1). Heat from the heat pump flows to the upper header of the buffer tank. The heat pump and these associated devices continue to operate as described until sensor (S1)in the buffer tank climbs to a temperature of 130 ºF, or if the master thermostat (T1) stops calling for heat. If, during a call for space heating from master thermostat (T1), the temperature at sensor (S1) in the upper portion of the buffer tank drops to 115 ºF, the stage 2 contacts in the setpoint controller (SPH) will close. These contacts complete a low voltage circuit powered through the boiler, and enable the boiler to operate in a fixed upper temperature mode. The boiler turns on circulator (P3) through an internal relay. The boiler continues to operate until the buffer tank sensor (S1) reaches a temperature of (130 ºF), at which point the boiler turns off, and so does circulator (P3). Note: The boiler will operate in this mode regardless of whether the mode selection switch is set to heat or cool. This allows the boiler to maintain a suitable temperature in the buffer tank for domestic water heating even when the heat pump is operating as a chiller. Space Heating Distribution: When master thermostat (T1) calls for heat, 24VAC passes from its W terminal to energize the coil of relay (RH2). Contact (RH2-1) closes to pass 120 VAC to circulator (P2). This circulator is set to operate in constant differential pressure mode to provide the necessary flow to any panel radiator that does not have its thermostatic valve fully closed. Circulator (P2) will automatically vary its speed to maintain approximately constant differential pressure across the manifold station serving the panel radiators. The thermostatic valves on each radiator can be used to limit heat input as desired. Domestic Water Heating Mode: Whenever there is a demand for domestic hot water of 0.6 gpm or more, flow switch (FS1) closes. This passes 24VAC to energize the coil of relay (Rdhw). Contact (Rdhw-1) closes to pass 120 VAC to circulator (P4). Heated antifreeze solution flows from the upper portion of the buffer tank will flow through the primary side of heat exchanger (HX), and transfer heat to the cold domestic water flow through the secondary side of the heat exchanger (HX). When the demand for domestic hot water drops to 0.4 gpm or less, flow switch (FS1) opens. This turns off relay (Rdhw) and circulator (P4). All domestic hot water leaving the system passes through a thermostatic mixing valve to limit the water temperature to the distribution system. Cooling Mode: For cooling operation the mode selection switch (MSS) must be set to cool. This passes 24 VAC to the RC terminal of the master thermostat. If the master thermostat is set for cooling operation, and calls for cooling, 24VAC is passed to its Y terminal. From the Y terminal, 24VAC passes to energize the coil of relay (RB). A normally open set of contacts (RB-1) close to pass 120 VAC to the air handler (AH1) turning it on. 24VAC also passes from the Y terminal of the master thermostat to energize cooling setpoint controller (SPC). Once energized, (SPC) monitors the temperature of sensor (S2) on the inlet pipe to the air handler. If that temperature is above 60 ºF the contacts in (SPC) close. This completes a circuit between terminals 43 and 44 in the Solstice SE heat pump, turning it on in cooling mode. The heat pump turns on circulator (P1) through its internal relay. All necessary devices for cooling operation are now active. The system remains in cooling operation until either the cooling demand is removed at thermostat (T1), or the temperature at sensor (S2) on the air handler inlet drops to 40 ºF, at which point the heat pump, circulator (P1), and air handler (AH1) turn off.
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