1 HVAC System Installation & Best Practices in New Construction Anthony Stamatopoulos ACI New Jersey
2 This Session Outline: 1. HVAC system Design, Selection and Installation Learn to list the steps for proper design Understand the importance of each 2. Understand Field Practical Tests Timing and Examples of Testing and Field Verification Methods for Testing and Developing the Story 3. Answering you questions a lot if asked!!
3 Topics covered today will include: This Session Very Flexible Agenda Preliminary Concepts & Discussion Manual J Manual S Manual T Manual D Duct Design strategies
4 Lots of different issues Systems HVAC Design Space Structure Final Design Moisture Aesthetic Energy
5 I.D.P. What is an Integrated Design Process? Balancing of structural, mechanical, aesthetic and performance attributes of the building Assumed that Architect performs this function, but this is typically not the case
6 HVAC Design is an Iterative Process..There s decisive steps, but there has to be a lot of back and forth. Communication, Communication, Communication It s an Art!!
7 System Characteristics High performance homes have different space conditioning requirements (i.e. Energy Star Homes) Standard air distribution system design, selection, and installation practices don t address high performance homes fully. What is a high performance house? Answer 30% better than a code built house. This actually means almost any house built today. Need to engineer and install the air distribution system for improved air delivery at lower cfm s
8 System Characteristics System size sf/ton Air flow cfm/sf Air exchange rate ACH Historic Standard cool 7.5 Base House, Austin TX cool 5.5 Lab C, Austin TX (HP) cool.74 heat 4.9 YPG House, Yuma AZ (HP) cool heat Civano, Tuscon AZ Lab House E, Pittsburgh PA cool 2.4 IBACOS staff house, Butler PA cool 2.7
9 Criteria for a Quality HVAC System What are we looking for? Small, compact, straight, air delivery from the interior of the space, proper velocity, good mixing, R.H. control, temperature control and uniformity, proper air distribution to the space and mixing, pressure balance, static pressure across the coil within manufactures and design specs, balanced airflows between the supply and return sides of the system, operation within acceptable noise criteria, sealed ducts, properly charged equipment, proper burner operation, minimized conduction loses and gains, operation within acceptable friction rates, correctly sized equipment, correctly sized ducts and air terminal devices, aesthetic requirements, energy criteria, ease of installation..
10 Criteria for a Quality HVAC System..and hundred other things I didn t mention We are ultimately looking for proper operation, within the parameters outlined and a system that provides occupant comfort! How do we do that? By utilizing a process and using sound engineering principles and techniques!
11 Preliminary Design Discussion Ensure that all pertinent parties are present Review the plans Discuss the design and installation Discuss objectives, timing and goals.
12 Preliminary Design Discussion Set performance goals and responsibilities What is acceptable and what is not? What is the energy and system performance criteria? What are the aesthetic criteria? Determine expectations amongst builder and trades What is the process for accountability Testing and verification process (Commissioning)
13 Manual J Residential Load Calculation A Contractor s Guide to Simple Energy Modeling
14 Manual J What is Manual J? Who: ACCA the Air Conditioning Contractors of America What: A procedure used to estimate the heat loss and gain of conventional residential structures for the purpose of HVAC sizing Most widely used tool Relatively simple with lookup tables
15 Introduction What is Manual J? Theory: With an accurate heat loss and gain estimated, an appropriately sized HVAC system can be ordered. Fact: There is inherent safety factor in Manual J. We ve seen even accurately sized systems using Manual J v8 that are 150% larger than the peak load. Provides room-by-room airflows Load information is used to estimate energy requirements and annual operating cost.
16 Introduction What is Manual J Strengths: Simple, accurate calculation based off of data stored in look up tables. Weaknesses: Residential buildings with atypical design features are excluded. Active/Passive Solar Homes Atriums, Solariums Swimming Pools and Hot Tubs Inherent safety factor
17 Manual J Procedure Heat Loss/Gain of a Structure Enclosure Elements Air leakage System Losses/Gains Sun Position Latent & Internal Loads
18 Manual J Procedure
19 Manual J Procedure
20 Internal Gains Manual J v8 More detailed guidance on calculating people, appliances, and latent loads Little guidance on lighting People = 230 Btu Sensible, 200 Btu Latent Occupancy = Number of bedrooms +1 Ventilation = (7.5 x # or people or bedrooms +1) + 1cfm/100 ft/sq
21 Design Temperature Difference Denver CO - Manual J v7 vs. V8 vs. ASHRAE Winter MJv7 MJv8 ASHRAE 97.5% 99% 99% 99.6% 1 o -3 o 3 o -3 o Summer MJv7 MJv8 ASHRAE 2.5% 1% 2% 1% 0.4% 91 o 90 o 87 o 90 o 93 o
22 Are you Using Manual J v8 Correctly Do not over estimate. There s inherent safety factor built in! Pittsburgh Attempt to determine all attributes of the house IE) shading, exhaust, ventilation, temp of unconditioned space. Don t assume that leaky ducts = leaky envelope Use adjustment factor when duct surface area is less than Table 7. Consider orientation of the individual site if known Use plausible internal gains; day-to-day, time of day, activities, and events. Educate customers and clients on these issues.
24 Short Cycles Marginalizes part load performance Creates stratification and stagnation Degrades humidity control Requires larger ducts Increases installed cost Uses more energy Decreases equipments life Oversized Systems
25 Manual S Selection of Equipment & Capacity We ve Completed Manual J calculations Select Equipment Based Upon Final Manual J Loads, Manufacturer s Data and Energy Requirements Images courtesy ACCA
26 Manual S Equipment Selection Bridge between Manual J and Manual D Obtain detailed manufacturer s information and review it to be sure you have what you need Detailed capacities for heating & cooling equipment Combination ratings for cooling & heat pumps Evaporator coil info Fan performance info at different speeds & external static pressures
27 HVAC Sizing Chart Don t use this method Preparing your sizing chart: 1) Print out this page. 2) Leaving the page intact, carefully cut out the holes on the dotted lines. 3) For operating instructions see bottom of page. 1 1/2 to 2 ton 2 1/2 to 3 1/2 ton Sizing Chart Operating Instructions 1) Stand on the curb.* 4 to 5 ton 2) Hold the sizing chart approximately one foot from your face. 3) Look at the house through each hole. If the house fits in a hole, that's the size unit to use. *If the curb is not available - ask the homeowner where a curb would be if there was one
28 Better homes but less comfort? Space Conditioning Why Size Correctly We are working outside the traditional design and engineering environment Loads are less than 30% of past Windows are twice as cool New equipment is multi-speed and smarter than most of us Lower utility bills Fewer Maintenance problems. IE) short cycling, cost Quieter House Improved Comfort
29 Space Conditioning What is correct sizing Sizing requires every element of the system to be addressed Equipment capacities Duct sizing Registers and return grills Is the system zoned? Are there any energy requirements? Can the equipment handle the ventilation load, if there is one?
30 Space Conditioning Why Size Correctly Humidity control and IAQ Reduced cooling load reduces dehumidification potential Humidity control is important to controlling condensation and biological activity.
31 Space Conditioning Why Size Correctly Efficiency Poor system selection can cause occupants to force the system to adapt. Constant fan Higher/lower temperature Homeowner tuning of registers Oversized equipment tricks T-stats Oversized equipment doesn t reach peak efficiency EER = Output Btuh/ Input W SEER = Cooling Produced (btu) / KWh used AFUE = Annual fuel Efficiency Ratio
32 Manual S Residential Equipment Selection Guidelines Equipment should be sized as accurately as possible Sized to calculated sensible load (50% of the unused latent capacity could be added to the sensible capacity) If the total cooling load is 15% larger than the equipment capacity, move to the next larger size All units should be ARI rated Try to select the highest efficiency available cfm will be matched to equipment selected
33 Equipment Selection Example Manual J Peak Heating and Cooling House Loads Room-by-Room Loads & Required Airflows Manual J Loads Total required heating output 65,540 Required sensible cooling output 29,362 Required total cooling output 36,058 Newhouse Manual J calculations back of house facing east, inground basement, bay window options Peak Heating Load Peak Cooling Load Room BTUH % of total CFM BTUH % of total CFM Study 4, % 82 1, % 39 Rec Room 8, % 175 1, % 71 Bath % % 4 Storage 3, % % 21 Family 6, % 137 5, % 210 Kitchen/Nk 4, % 86 4, % 161 Dining 4, % 96 2, % 89 Living 4, % 99 2, % 93 Foyer 1, % % 36 Library 2, % 55 1, % 54 Pwdr % % 7 Mstr Suite 7, % 161 4, % 164 Dressing 1, % 38 1, % 43 W.I.C 1, % % 32 Util % % 7 Bed2 4, % 82 2, % 96 Bath % % 18 Bed3 3, % 72 2, % 89 Hall 1, % 38 1, % 46 Bed 4 3, % 72 2, % 89 not used 0 0.0% % 0 Totals 65, % 1,335 36, % 1,370
34 Equipment Selection Example Size furnace to meet peak heating load for the house 69,000 x 0.90 = 62,100 Newer Literature will only show one number, (after internal losses) 91,000 x 0.90 = 81,900 Manual J Loads Total required heating output 65,540 Required sensible cooling output 29,362 Required total cooling output 36,058 90UGFA3/4-100
35 Equipment Selection Example Size condensing unit & matching indoor coil to meet peak cooling load for the house 63 WB = 75 DB & 50-55% RH 67 WB = 80 DB & 50% RH You may have to Interpolate!! Manual J Loads Total required heating output 65,540 Required sensible cooling output 29,362 Required total cooling output 36,058 Sensible Capacity = 31,600 x 0.98 = 30,968 BTUH Total Capacity = 40,500 x 0.98 = 39,690 BTUH
36 Equipment Selection Example Check furnace fan capacity to match with cooling equipment About 400 cfm/ Ton of AC, at 0.60 or more External Static Pressure Target = 1400 cfm
37 Equipment Selection Example Air resistance of indoor cooling coil will be used in Manual D calculations About 400 cfm/ Ton of AC Target = 1400 cfm
38 Manual D Procedure Theory Pressure Loss from Duct Friction Pressure Loss from Fan Speed Placed on same graph, lineintercept is best setting
39 Fan Curves
40 Fundamental Principles Fan is part of equipment package, and equipment is selected before ducts are designed Fan curve is known first, and duct system is designed to match resistance at desired flow rate
41 Available Static Pressure Builder ABC Homes Location Boon Town Model Plan 5000 IBACOS Friction Rate Worksheet Calculate the available static pressure for the duct system Calculate the friction rate Size all ductwork using friction rate and velocity limits Manufacturer's Blower Data (Lennox G40UH-48C-110) External Static Pressure (ESP) 0.60 IWC Device Pressure Losses Direct expansion refrigerant coil Electric resistance heating coil.. Hot water coil.. Heat exchanger.. Low efficiency filter. High or mid-efficiency filter. Electronic filter. Humidifier Supply outlet.... Return grille.. Balancing damper.... Other device. Subtotal IWC Available Static Pressure External Static Pressure (ESP) 0.25 IWC Total Equivalent Length (TEL) Supply duct TEL 230 Return duct TEL 180 Total. 410 IWC Friction Rate Design Value External Static Pressure (ESP) 0.06 IWC Comments 1575 cfm on high speed Lennox C33-48, wet coil
42 Equipment Selection Recap Select equipment that best fits the design loads of the house. Equipment should be chosen to closely meet the design loads generated by Manual J. The blower selection and setting will be an engineered best guess and will need to be verified through Manual D. Preferably size system for high speed. Bigger is not better, comfort is better Objective of Manual D is to size the duct system to work with the fan that is supplied with the HVAC equipment!
43 Manual D Duct Sizing Procedure We ve Completed Manual J calculations We ve Selected equipment based upon manufacturer s data Design duct system to match equipment 3. Images courtesy ACCA
44 High-Efficiency Air Distribution Centerline supply Central returns Less ductwork equals more airflow Perimeter supply Room by room returns More ductwork equals less air flow
45 Air Distribution Design Preliminary Principles Use ACCA s Residential Duct System Manual D Integrate the distribution system into the floor plan of the house Locate equipment and ducts in conditioned space Size system for balanced air flows and quite operation Use central return systems Understand duct design is an iterative back and forth process: velocity, friction, throw, diffuser
46 Sketch a Design Determine equipment location (access to equipment) Locate central supply and return locations & paths Zone(s) based on thermal loads Determine air terminal locations Structural details: Framing, plumbing, room layouts Aesthetic desires Air Distribution Design System Design Principles Study building plans and sketch design
47 Air Distribution design Room Air Distribution Register Selection Criteria Throw Terminal Velocity Pressure Drop Noise Higher performance does not have to cost more 900 Commercial 600 Residential
48 Air Distribution design Room Air Distribution Approach Impact of Boot on Outlet Performance Velocity Profile Throw Pressure Drop Noise
49 Holy Crap, now what? Know that residential register designers plan for a face velocity in the 600 to 700 fpm range Open throwing type registers are designed for face velocities in the range of 700 to 900 fpm If velocities are less than these ranges, then the diffuser is too big If velocity is too low, mixing will not occur Smaller register could increase static Register should be replaced and flows re-checked System rebalancing may be appropriate
50 Fundamental Principles Design resistance in duct system to match fan capacity Scan of figure 3-5 Friction Rate is pressure drop / 100 ft. of duct FR = PD x 100 TEL FR = 0.20 x 100 = IWC/
51 Fundamental Principles Ductulator Pressure drop is converted to a friction rate to size the ductwork properly Use Ductulator to size ducts Duct size at 1000 CFM and Friction Rate = 15
52 Fundamental Principles Effective length of elbow fittings Recalculate friction rate and duct size FR = 0.20 x 100 = IWC/ Duct size changes from 15 round pipe to 16 round pipe
53 A 200 ft. straight pipe is 200 feet long How Long is the Duct System? (from an air molecule's view) This 4 ft. section of pipe is how long?
54 Fundamental Principles Pressure losses associated with devices must be considered FR = ( ) x 100 = IWC/ Duct size changes from 16 round pipe to 19 round pipe
55 Fundamental Principles Effective length of duct branch takeoffs from main trunks Effective length of elbow fittings Effective length of boot fittings
56 Fundamental Principles Calculate the total effective length, then calculate friction rate, then size all ductwork FR = 0.20 x 100 = IWC/
57 Air Distribution Design Comfort Pitfalls Performance and comfort can be determined by the ten worst decisions And not the twohundred good ones
58 A Good Duct Design Provides Quiet Efficient Comfort
59 Comfort TEMPERATURE DIFFERENCE BETWEEN ROOMS < 2 F IDEAL 4 F MAXIMUM SO USE A CONTINUOUS FAN? NO
60 Comfort comes from a designed system Duct System Must Be Designed to Deliver Correct Amount of Air to Each Supply Terminal AND Each Supply Terminal Must Be Carefully Sized and Located AND Each Supply Terminal Must Be Chosen With Adequate Mixing and Throw AND There Must Be an Adequate Return Path for Each Supply
61 Low System Airflow Energy & comfort Wrong Room Airflow - Comfort High system pressure drop Energy Noise Comfort Poor Room Air Delivery - Comfort Wrong fittings? Critical branch? Poor fan performance? Selection? Convenient to build, but not convenient to design Air Distribution design Potential Problems
62 Return Duct Field Measurements Room pressures With door closed, pressure across door should not exceed 3 to 5 pascals Return Duct Static Measure between the occupied space with all doors open and the fan cabinet. Should not exceed 20 pascals or.06 inches of water Return flows Measure return flows with flow hood. If airflows are less than 80% of system total flow, look for leaks.
63 Air Distribution design System Design Principles Provide return path Ducted return main Return path for each room Pressure Relief Transfer Grille
64 Bringing it Together Testing and commissioning is the back end of the process Successful space conditioning requires someone to lead the process. Many systems This is the look Head fine Coach and visual position inspections and is responsible can reveal for coordinating flaws, but the many other poorly coaches performing Offensive duct Line systems Coach have : Total major building flaws. load You and have duct to sizing Quarterbacks test or commission. Coach : Great installation team Receiving Coach : High performance return system Special Teams : Proper equipment size and fully commissioned
65 Tools of the Investigation With a few simple tools and an understanding of some basic principals, you can diagnose most problems. Fixing them may be a little bit harder, but you won t know until you discover what's happening. Duct Blaster : evaluate leakage characteristics Flow Plate : a good view of airflow across the coils Flow Hood : to measure individual register flows Velocity probe : measures air speed Differential temperature probe Digital Monometer
66 Air Distribution design Construction Concerns Commissioning System Airflow Room Airflows Supply Registers Total Leakage Leakage to Outside Supply Side Leakage Return Side Leakage Operating Leakage Leakage of the system should be less than 5% of Fan capacity
67 Air Distribution design Construction Concerns Testing & Commissioning System Airflow Room Airflows Supply Registers Insert Picture of Flow Plate HERE Verify Fan performance and system flows
68 Air Distribution design Construction Concerns Commissioning System Airflow Room Airflows Supply Registers Use flow hood measurements to balance, based of measured total flow
69 Air Distribution design Construction Concerns Commissioning System Airflow Room Airflows Supply Registers 50 FPM is the boundary of throw. Understand performance of your registers
70 Air Distribution design Construction Concerns Commissioning System Airflow Room Airflows Supply Registers Measure temperatures at supply and room discharge to determine impact of duct location
71 Air Distribution design Construction Concerns Commissioning System Airflow Room Airflows Supply Registers Room to Room Pressures Ventilation system airflows Measure adequacy of pressure balancing and return strategy
72 Why more problems now? Lack of design Installation doesn t match design Installation error Plans help, but we can find local deficiencies Poor maintenance Filters, dirty coils, poor balancing Drifting equipment specifications New equipment has different fan curves Better homes mean better designs are needed We are pushing the boundaries of what we can do with traditional forced air systems. It s the end as we know it.