Working With DHPS and Other Variable Capacity Heat Pumps October 05, 2017 1
Housekeeping Welcome Safety Bathrooms Cell phones 2
Session Survey Instructions At the end of each session, you will be given 5 minutes to complete the session survey. 1. Open the HEF2017 app 2. Navigate to Agenda and select the session 3. Scroll down to Session Feedback 4. For each question, select answer and hit Submit 5. Show completed survey to BetterBuiltNW rep to earn points 6. Prizes awarded Friday to the top point earners See Challenge section in the app for activities 7. Assistance available at the BetterBuiltNW table 3
Learning Objectives: What you will be able to do 1. Differentiate benefits VRF systems vs DHPs 2. Size and select the ideal VRF system 3. Design VRF systems - Duct design and ductless unit placement 4. Avoid control system mistakes 4
How Not to Get Snake Bit: The Design and Installation Process Deciding - ducted or ductless Equipment sizing and selection System design Commissioning and controls 5
Differentiating Benefits VRF systems vs non-vrf
Central Systems Conventional Variable Refrigerant Flow Ducted Mini-splits Point-Source Systems Cassette Wall mounted (DHP) Floor mounted 8
All Heat Pumps Air source heat pump Compressor type VRF Driven Conventional Rotary/Piston Cold Climate Cold Climate Non Cold Climate Non Cold Climate Style Central Point source Central Gas Back Up Mini ducted Cassette Wall Mounted (DHP) Floor Mounted
VRF Benefits Conventional HP VRF HP Cold Climate VRF HP Variable Capacity No Yes Yes COP at 5F* 1.1 1.2 1.7 Noise* 60 db 50 db 50 db Capacity at 5Degress* 25% 50% 100% *Typical Values - there are exceptions in all categories 10
Room by Room Loads If a room has 15% of the load, it needs 15% of the capacity Without knowing the room by room heating and cooling loads, you can t size the system 11
02/03/12 15:20:00.0 02/03/12 18:35:00.0 02/03/12 21:50:00.0 02/04/12 01:05:00.0 02/04/12 04:20:00.0 02/04/12 07:35:00.0 02/04/12 10:50:00.0 02/04/12 14:05:00.0 02/04/12 17:20:00.0 02/04/12 20:35:00.0 02/04/12 23:50:00.0 02/05/12 03:05:00.0 02/05/12 06:20:00.0 02/05/12 09:35:00.0 02/05/12 12:50:00.0 02/05/12 16:05:00.0 02/05/12 19:20:00.0 02/05/12 22:35:00.0 02/06/12 01:50:00.0 02/06/12 05:05:00.0 02/06/12 08:20:00.0 02/06/12 11:35:00.0 02/06/12 14:50:00.0 02/06/12 18:05:00.0 02/06/12 21:20:00.0 02/07/12 00:35:00.0 02/07/12 03:50:00.0 02/07/12 07:05:00.0 02/07/12 10:20:00.0 02/07/12 13:35:00.0 02/07/12 16:50:00.0 02/07/12 20:05:00.0 02/07/12 23:20:00.0 02/08/12 02:35:00.0 02/08/12 05:50:00.0 02/08/12 09:05:00.0 02/08/12 12:20:00.0 02/08/12 15:35:00.0 02/08/12 18:50:00.0 02/08/12 22:05:00.0 02/09/12 01:20:00.0 02/09/12 04:35:00.0 02/09/12 07:50:00.0 02/09/12 11:05:00.0 02/09/12 14:20:00.0 02/09/12 17:35:00.0 02/09/12 20:50:00.0 02/10/12 00:05:00.0 02/10/12 03:20:00.0 02/10/12 06:35:00.0 Temp F 2,200 Sq. ft. House with a 12K DHP 85 75 65 55 45 35 25 Master Guest Kitchen Office House has low UA. Very tight. 12K ductless heat pump and low-efficiency ERV. About 900 kwh/year for space heat. 12
Home Geometry and DHP Performance Low Load House: 18K mini-split High Efficiency HRV What Could Go Wrong? 15
Home Geometry and DHP Performance Single Story Home 65 sq. ft. of glazing (26% of floor area Five surfaces exposed to exterior Design heat load around 2,700 BTU/hr. for this room alone 16
Home Geometry and DHP Performance POP QUIZ Q: How much 70 F air must you deliver to keep this room at or set point or 68 degrees? A: Too much Avoid creating thermally isolated rooms 17
Home Geometry and DHP Performance Which home is best suited for a central air handler inverter driven heat pump and why? 18
Benefits Turn to the person to your right and take turns answering the following question: What are the benefits of a variable refrigerant flow HP vs. a standard heat pump? 19
Comfortable customers if you do it right! 20
Size and Select The Ideal VRF System
% Heating Capacity Sizing heat pumps 120 Heat Pump Capacity and Outdoor Temperature 100 80 60 40 20 0 -----Cold Climate VRF-----VRF----Typical -13-4 5 10 17 25 30 35 40 47 Outdoor Temperature F 22
Manufacturer's Stated Heating Capacity at 47 deg F (Btu/hr) SIZING VARIABLE CAPACITY UNITS Tonnage: Ignore the Nominal Rating 25,000 Comparison of Nominal 1-ton DHP Models "Rated" Capacity 20,000 15,000 10,000 5,000-23
Manufacturer's Stated Heating Capacity at 47 deg F (Btu/hr) Turn SIZING Down VARIABLE Ratio: CAPACITY The ratio UNITS of the highest output to the lowest output Comparison of Nominal 2-ton DHP Models 40,000 35,000 30,000 25,000 20,000 15,000 10,000 5,000 - "Rated" Capacity 24
BOISE DHP LOW OUTPUT SIZING Why Turn Down Ratios Matter 30000 25000 20000 15000 10000 5000 0 10 K low output 4K low output Design load:24 K@9F Nom Size 24K DHP Sizing 3300 hrs. 1529 hrs. <0 0-9 10 to 19 20 to 24 25 to 29 30 to 35 35 to 39 40 to 44 45 to 49 50 to 54 55 to 59 BTU/Hr Hours in bin Boise Hours in bin Seattle 1800 1600 1400 1200 1000 800 600 400 200 0 H o u r s i n T e m p B i n 25
Mild Climates the Lowest Output is SEATTLE DHP LOW OUTPUT SIZING Extremely Important 30000 25000 20000 15000 10000 5000 0 7 K low output 3K low output DHP Sizing Design load:15 K@27F: Nom size 18K 4375 hrs 2810 hrs <0 0-9 10 to 19 20 to 24 25 to 29 30 to 35 35 to 39 40 to 44 45 to 49 50 to 54 55 to 59 BTU/Hr Hours in bin Boise Hours in bin Seattle 1800 1600 1400 1200 1000 800 600 400 200 0 H o u r s i n T e m p B i n 26
% Heating Capacity Activity Why do you need capacity curves when sizing heat pumps? 120 Heat Pump Capacity and Outdoor Temperature 100 80 60 40 20 0-13 -4 5 10 17 25 30 35 40 47 Outdoor Temperature F -----Cold Climate VRF-----VRF----Typical Unitary----Green Speed 27
Designing VRF Systems: Duct Design and Ductless Unit Placement
Pressure - IWC Distribution 0.7 Fan Curve 0.6 0.5 0.4 0.3 0.2 0.1 0.0 1300 1400 1500 1600 1700 1800 CFM Fans are the heart of the system. They can break your heart, too. Photo credit: http://comm2.fantech.net/commercial-products/specialty 29
Fan Curve Table 30
External Static Pressure (ESP) External Static Pressure is the pressure (resistance) against which the fan has to operate.50 I.W.C II 31
Total ESP.50 IWC Coil Included in heat pump fan curve Filter.12 Return Grille Supply Grille Total Losses Available Static Pressure.03.03.18.24 IWC.50 The available static pressure is the amount of pressure left over to overcome the resistance of the duct system. Coils and filters have large pressure drops. 32
Airflow(CFM) CFM VS Static Pressure ECMs 2000 1800 1600 1400 1200 1000 800 PSC ECM 600 400 200 0 0 0.5 1 1.5 Static Pressure (IW) 33
Watts ECMs Are Not Magic 900 800 700 600 Watts VS Static Pressure 500 400 PSC ECM 300 200 100 0 0 0.2 0.4 0.6 0.8 1 1.2 Static Pressure 34
Why Four Fan Curves for One Unit? 35
This unit has four ESP settings with three fan speeds in each setting 36
Low Profile VRF Fan Curve Fan Speed 37
Activity What is the CFM in the ultra low ESP Setting at.08 I.W.C on high speed? 38
Moving air hates to make hard turns Photo credit: http://www.masterfile.com/stockphotography/image/600-01791391/aerial-viewof-freeway-intersection-highway-404-and-finch- Avenue-Willowdale-Ontario-Canada 39
Relax: We will show you a short cut Step 1: Calculate the Total Equivalent Length (TEL) Step 2: Calculate the Available Static Pressure Step 3: Calculate the Friction Rate Step 4: Determine how much air each duct section is carrying Step 5: Size the ducts 40
Comparison of Equivalent Lengths (ELs) EL=10 ft. EL=20 ft. EL=120 ft. 50 ft. has an EL of 50 ft. 50 ft. of 15% compressed flex has an EL of 100 ft. 0 10 20 30 40 50 60 70 80 90 100 120 EL in Feet 41
It s the Fittings that Matter The Most Most of the friction loss occurs at elbows, Ys, and other fittings. 42
Equivalent Length (EL) ACCA s Manual D assigns an EL to every type of fitting used in a duct system. If a fitting has an EL of 35, it has the same resistance as 35 feet of straight pipe. 43
From EL to Total Equivalent Length T.E.L. Total Equivalent Length (T.E.L.) is: the sum of all the individual ELs of the fittings and the length of the ducts along the air s longest path from the return grille through the supply grille. As a rule, you need to keep your T.E.L below 300. It is not: The sum of ALL the fittings in the duct system. Not necessarily the longest path in terms of distance, but the longest path in terms of restriction. 45
Activity 6F=25 ft. 1O=120 ft. 2J=65 ft. 35 ft 25 ft Air Handler 4A=35 ft. 15 ft 8A=30 ft. 8A=30 ft. Total Duct Length 25 35 15 10 -- -- -- -- 85 Fitting 6F 6N 5H 1O 4A 2J 8A 8A -- EL 25 10 45 120 35 65 30 30 360 Grand Total 445 46
Activity 6F=25 ft. 1O=120 ft. 2J=65 ft. 35 ft 25 ft Air Handler 4A=35 ft. 15 ft 8A=30 ft. 8A=30 ft. Total Duct Length 25 35 15 10 -- -- -- -- 85 O L D N E W Fitting 6F 6N 5H 1O 4A 2J 8A 8A -- EL 25 10 45 120 35 65 30 30 360 Grand Total 445 Fitting 8F 6N 5K 1I 4A 2J 8A 8A -- EL 15 10 10 20 35 65 30 30 215 Grand Total 300 47
48
49
50
Many Causes of Low Airflow
Courtesy of Advanced Energy
Courtesy of Advanced Energy
Courtesy of Advanced Energy
Courtesy of Advanced Energy
Courtesy of Advanced Energy
Courtesy of Advanced Energy
The Kinked Hose Syndrome
hy Do We Hang Ducts in Attics? 59
Duct Design Rules 1. Don t do stupid stuff 2. Pick a unit that can deliver required CFM at expected pressure 3. No 90 degree turns 4. Stretch the flex 5. Don t squish the flex 6. Use large return grilles and return ducts 7. MEASURE AIR FLOW 8. If you are counting: keep TEL below 300 feet 9. If using a Ductulator, use a.06 or.08 friction rate for design purposes. 60
DUCTED MINI-SPLIT DESIGN The School of Hard Knocks A 18K DHP was installed first Then, we added a 9K mini-ducted variable refrigerant heat pump. What could go wrong? 61
DHP System Design Use an appropriate number of indoor heads o In most homes, one head per floor is enough An optimal system often consists of: o 1 DHP in the main living area, +1 smaller unit in the master suite o 1 DHP in the main living area, +1 ducted minisplit serving bedrooms o 1 DHP in the main living area, plus small electric resistance heaters in the bedrooms o If using ER heaters, use smaller units (750w), control with digital wall T-stats 62
DHP System Design Orient heads to take advantage of throw and mixing o Place in largest, most open areas o Orient to blow down central hallways In rooms with high ceilings, place DHP < 8 off the floor to minimize stratification effects Don t set units set in Auto mode, leave in heating or cooling Set fan speed to auto fan, if lower capacity and efficiency will drop. 63
Avoid Control System Mistakes
Thermostats/Controllers: Not DUCTED MINI-SPLIT DESIGN What You re Comfortable With 65
DUCTED MINI-SPLIT DESIGN The School of Hard Knocks Perfect airflow flow in each room What could go wrong? 66
FUNCTION DUCTED MINI-SPLIT 42 and DESIGN Other Settings jjj Setting the unit to sense temperature at the T-stat: Function 42 has to be set to 01 and the t-stat icon has to appear on the screen High Insulation setting needs to be activated 67
Where Fans and Controls Collide 68
Controller pitfalls explained 1. If using a wall-mounted controller, make sure it senses temperature at controller and not at air handler 2. If there is an option for efficient home, ensure it is selected. Set to High Insulation 3. Always set to high insulation setting 4. Read the manual 69
Commissioning 1. Put system in high heat or high cool mode if available 2. Measure external static pressure 3. Measure delivery at each register (if you have a flow hood) 4. Measure temperature gains 5. Conduct a duct leakage test if applicable 6. Check refrigerant charge against published values. 70
Summary Why would a controller sensing temperature at the air handler affect efficiency? How can you check where the temperature sensor is on most controller models? 71
Resources Better Built NW Local Home Energy Rater DOE s Building America Solutions Center Bruce Manclark 72
Goal Setting What can you do in the next 24 hours? 73
Thank you Thank You Bruce Manclark info@betterbuiltnw.com 74