Presentation on theme: "Presented By Darren Alexander Twa Panel Systems Inc. April 15, 2011 ACG 7 th Annual Conference on Total Building Commissioning COMMISSIONING ACTIVE BEAMS."— Presentation transcript:
Presented By Darren Alexander Twa Panel Systems Inc. April 15, 2011 ACG 7 th Annual Conference on Total Building Commissioning COMMISSIONING ACTIVE BEAMS
Introduction to Active (Chilled) Beams Fan energy savings De-coupled ventilation systems Principles of operation Active beam benefits Suitable areas for active beams Psychrometrics Condensation risks DOAS Information resource Placement within the ceiling Inherent comfort with active beams Beam acoustics 1/3 rd octave band analysis Installation & Maintenance Fastening beams to the structure T-Bar mounting detail Exposed / pendant type units Installation “Tips” Sample active beam packaging Beam mounted with aircraft cable IOM and precautions Coil maintenance Unit cleanliness prior to start-up Agenda
Air-side control and measurement Ducting for equal static pressure Vary primary air pressure for capacity control? Recommended CAV damper types Damper “Tips” Acoustics Balancing and confirmation Challenges Water-side control and measurement Self-regulating thermal capacity Modulating water flow Challenges “Tips” for easier commissioning Start-up Sample start-up sequence Shop drawings and schedules as a tool for commissioning Sample spaces serviced by active beams Agenda
Introduction to Active Beams De-coupled ventilation systems Energy UsageNoise LevelOutputComments Fan Coil UnitsMedium/HighMedium 32-64 Btuh/ft 2 Adaptable solution VAV Systems LowLow/Medium32-64 Btuh/ft 2 Very efficient all-air system VRV System (Variable Refrigerant Volume) HighMedium 48-64 Btuh/ft 2 Possible high maintenance costs Active Beams Low 32-125 Btuh/ft 2 Very low maintenance costs
Introduction to Active Beams Principles of operation
Introduction to Active Beams Active beam benefits 1) Lower overall air volume processed by the primary air handling unit. (0.25-0.5 cfm/ft 2 ) 2) Higher entering chilled water temperatures: (55°F-61°F). 3) Lower hot water temperatures: Select beams for cooling duty, then choose appropriate hot water temperature for heating. (i.e. usually less than 120°F. Beam discharge air should be less than 15 o F warmer than room design temperature to limit the risk of stratification. 4) Suitable for use with water-to-water heat pumps, and has the potential to double the COP of a dedicated chiller loop. 5) Self regulating secondary capacity: Approach = Room Temperature - Supply water temperature 6) VAV control: Can be used to strictly limit room air velocity, provide linear temperature control, and additional fan energy savings for areas with highly variable latent loads. (i.e. Labs, Boardrooms, coffee rooms, classrooms, etc…)
Introduction to Active Beams Suitable areas for active beams Yes / Maybe Spaces with moderate latent loads High sensible loads Office spaces Schools Desktop farms Labs – Check Psychrometrics and codes No Kitchens Atriums Zones with high latent loads Locker rooms Pool areas Entry vestibules Computer rack rooms Areas with high ceilings (i.e. >14’)? Patient Recovery Rooms (YES?)
Introduction to Active Beams Psychrometrics Option 1Option 2 Primary air dew point 48°F51.5°F Room air dew point 55°F57.8°F Secondary CWT55°F58°F Dehumidification 0.002 lbs/lb DA RESET FOR ENERGY SAVINGS!
Introduction to Active Beams Condensation risks Areas of greatest condensation risk: 1) Near points of entry to the building 2)At the perimeter, with mixed-mode ventilation 3)Structures with poor building envelopes, including retrofit applications 4)In areas with highly variable latent loads: Board rooms Lunch / coffee rooms Etc… Condensation prevention strategies may include: 1)De-activation of secondary chilled water supply, by zone, via loss of dew-point from sensors mounted to CWS lines. (… or via combination: DB / RH zone stats, or other…) 2) Tempering secondary chilled water supply by zone via: Three-way mixing valve Injection pumps 3) Etc…
Introduction to Active Beams DOAS Information Resource 1)http://doas.psu.edu/http://doas.psu.edu/ 2) Not all primary air handling systems are DOAS!
Introduction to Active Beams Placement within the ceiling P2 drops rapidly moving into the room P3 = ½ at 3ft into occupied zone
Introduction to Active Beams Inherent comfort with active beams Active Beam Diffuser
Introduction to Active Beams Beam acoustics Active beams can be very quiet! Chart reports acoustic values without room attenuation effect
Introduction to Active Beams 1/3 rd Octave band analysis Owens Corning Acoustic Testing Acoustic test standards may include: ISO3741 ASHRAE Std. 70 Reverberant chamber ( No Attenuation ) Manufacturer A = Worst Case 2’ x 8’ – D nozzle @ 1.20”w.c. Peak in the 2.5 KHz Band Lw (dB) = 39.1 LwA (dBA) = 38.8 NC = 24 !
Fastening beams to the structure Drywall Upstream damper at SMACNA recommended minimum distance N.B. - Include seismic restraint where required by code
Installation and maintenance T-bar mounting detail Width Length
Installation and maintenance Exposed / pendant type units Coanda wings required for proper throw characteristics
Installation and maintenance Installation “Tips” 1.“Rough-in”: piping, ducting, concrete threaded inserts, and beams, prior to T-bar installation. Lower beams into T-bar for final positioning. 2.Store beams on-site indoors whenever possible, in a low traffic area, and otherwise covered for protection from the elements. 3.Leave plastic film on each unit to minimize site damage, and prevent coil / unit fouling. 4.Match beam label to schedule; - beams look alike! Confirm that the right beam is in the right room. Contractor suggestion: - Confirm packing slip matches shop drawing requirements upon receipt of material. 5.Limit flexible duct to no more than 10’. Avoid sharp turns in ductwork.
Installation and maintenance Installation “Tips” 6.Plan for access doors, and possibly welded-aluminum frames, with beams mounted in dry-wall ceilings. 7.Manage glazing surface temperatures by planning discharge configuration. With high quality glass, beams which discharge perpendicular to the glazing, are typically preferred. 8.Stainless steel flexible hoses allow for some adjustment within the ceiling grid.
Installation and maintenance Sample active beam packaging Units remain “as-new” until final commissioning and “turn-over”. Recyclable packaging materials. Face-to-face, and back- to-back crating mini- mizes shipping damage.
Installation and maintenance Beams mounted with aircraft cable Note protective film at inlet of unit mounted coil
Installation and maintenance IOM and precautions Read the manufacturer’s Installation Operation and Maintenance Manual Pay particular note of any precautions which have been identified as high risk conditions. (i.e. minimum two people to handle beams 6’ and larger, pulling on un-latched door may cause hardware failure, be cautious of sharp edges, limit flex duct connections to 10’ maximum, etc…) Do NOT circulate water through the beam mounted coil until the “mains” have been properly “de-greased” / flushed. Do NOT remove protective plastic film from beam body until the space has been appropriately cleaned, to minimize fouling of the coil DO lower the secondary chilled water temperature slowly to limit the risk of condensation damage during start-up. This list is NOT exhaustive, co-ordinate the start-up requirements with the mechanical consultant.
Installation and maintenance Coil maintenance Active beams require practically no maintenance. If the coil remains dry, as expected, there is very little risk of fin “bridging”. Recommended cleaning schedules typically involve lowering, or removing the perforated doors / panels, in front of unit mounted coil, at 6-Months, and 1-Yr., to establish a maintenance schedule. Areas with higher airborne contamination require more frequent cleaning. Often, cleaning schedules can extend to between 3-5 years in spaces subject to weekly housekeeping. Higher housekeeping frequency, reduces the intervals between coil maintenance.
Installation and maintenance Coil maintenance Vacuum with or without a “horse- hair” bristle brush
Installation and maintenance Unit cleanliness prior to start-up Leave active beams wrapped to prevent fouling unit or coil. Wipe unit with a damp rag to remove surface dirt, or vacuum with a horse-hair bristle brush. Do NOT scrub the paint. Damage to the finish may occur. A soft bristle brush and mild detergent with water, can be used to remove stubborn “smudging”, if required. Beams ship with repair kits for surface scratched units. Do NOT spray the unit directly with “spray-bomb” type matched paint. Use artist paint brush, supplied with repair kit, to apply the paint to the affected areas.
Ducting for equal static pressure Pt = Ps + Pv Pt= total pressure (”w.c.) Ps= static pressure (”w.c.) Pv= velocity pressure (”w.c.) If velocity pressure is kept negligibly low, then the same static pressure will hold throughout the duct. ( i.e. Only if transport loss can be neglected). Pv = 0,5 x r x v 2 Pv= velocity pressure (”w.c.) r= air density (0.075 lbs/ft 3 ) v 2 = air velocity (fpm) At < (590 fpm) duct air velocity Pv < (0.02”w.c.) At < (590 fpm) transport Ø = (5”) < (0.001”w.c/ft.) Ø = (8”) < (.0007”w.c./ft.) Low air volumes required for beams makes using round ducting practical and low air velocity achievable.
Air-side control and measurement Vary primary air pressure for capacity control ? CAV primary air flow is typically simple with orifice plate “Iris” type dampers. Varying the plenum pressure yields a non-linear capacity response. Tight control with variable plenum pressure is typically impractical.
Air-side control and measurement Vary primary air pressure for capacity control ? VAV airflow solves the issue of over-cooling a space with un-tempered primary air. Plenum static pressure range (0.3”-1.2” w.c. max) VAV diversity advantage with tight P-band control. Eliminates last limitation of VAV systems.
Air-side control and measurement Recommended CAV damper types Iris Dampers – (angled multi-leaf blades) Iris Dampers Pressure independent – butterfly type
Air-side control and measurement Damper “Tips” 1.Size dampers for flow and pressure drop. i.e. Do NOT oversize the damper by simply installing a nominal duct diameter damper. Check range of flow control, step-down if required. 1.Venturi – style dampers are typically only used with labs, and narrow- band pressurization control. 3.Check for flow generated noise with larger pressure drops. Add duct silencers if necessary. 4.Consider VAV air valves for spaces with highly variable latent loads. Be aware of additional control requirements Consider “occupancy” type (i.e. 2-position) air valves for these spaces in an effort to manage control costs.
Air-side control and measurement Acoustics Watch for flow generated noise across Iris damper. Add duct mounted silencers if required.
Air-side control and measurement Balancing and confirmation Beams are considered a constant volume device. Apply a known plenum static pressure, and the cross-sectional area of each nozzle sums to yield the total primary air delivered by the beam. Adjust orifice ∆P for beams of common pressure; - their nozzle determines the primary air flow rate. Since the induction ratio is exceedingly difficult to field measure, the most accurate means of determining the primary air delivery, is to rely on the manufacturer’s plenum pressure vs. volume relationship, which is typically measured with a precision orifice. Confirmation of zone flow rates can be accomplished via a duct traverse at a node of common intersection. Flow hoods cannot be used to determine total air flow into the space due to the recirculation component of the room air.
Air-side control and measurement Challenges Nominal duct size vs. ∆P across Iris dampers. Zoning to minimize capital costs. Night-time set-back. Simultaneous perimeter heating with core cooling. Air-side free-cooling. Dew-point control.
Self-regulating thermal capacity (1365 Btuh) (682 Btuh) Example 1 Room Temp = 75 o F Water temp = 61 o F Approach temp = 75 o F-61 o F = 14 o F Capacity = X Room Temp = 68 o F Water Temp = 61 o F Approach temp = 68 o F-61 o F = 7 o F Capacity = 1/2X
Water-side control and measurement Modulating water flow Turbulent flow Laminar flow Single circuit water flow Non-linear Expensive Maintenance issues? Temperature controlled water Restricted to zone control Expensive Maintenance issues?
Water-side control and measurement Challenges Water-side free cooling Zoning Chilled water reset by zone Valve authority (Ensure that the control valves are sized based on Cv, NOT line size)
Water-side control and measurement “Tips” for easier commissioning 1.Use pressure independent flow regulating valves 2.Reverse-return piping can sometimes make life “easier” in each zone 3.Apply venting “liberally” Pressure independent water control valve (Constant Flow Rate)
Sample start-up sequence 1.Confirm start-up and operating sequence with the: plans, specifications, and consulting engineer. 2.Confirm primary air ducting is free of dirt and debris to prevent beam nozzle clogging. 3.Seal all duct leaks, and ensure all duct access ports are affixed to the duct to achieve specified duct leakage rates. 4.Slit protective film at the active beam discharge to allow primary air to enter the space. Do NOT remove the protective film, until the work space is in an “as- new” condition.
Start-up Sample start-up sequence (cont’d) 5.Do NOT operate the active beams for temporary heat without prior written approval from the consulting engineer. 6.Close all operable windows, and ensure building exit doors are sealed to assist in the envelope dehumidification. 7.Commission and operate the primary air handling unit for building envelope dehumidification. 8.Balance supply air ducting to each zone.
Start-up Sample start-up sequence (cont’d) 9.Ensure a clean environment within which the active beams will operate (i.e. no gypsum dust or other construction contamination) 10.Remove protective film from active beam units 11.Ensure piping “mains” have been flushed and “leak-tested”, prior to being connected to the beam coils 12.DO NOT UNDER ANY CIRCUMSTANCES FLUSH THE PIPING SYSTEM THROUGH THE BEAM MOUNTED COILS.
Start-up Sample start-up sequence (cont’d) 13.Confirm that all air has been removed from the distribution piping. Deliver excess water by increasing the pump flow, or by closing other zones to assist in the removal of air from the system. 14.Once the building envelope dew point has been reached, slowly lower the secondary chilled water temperature to the scheduled design value. Note that dehumidifying the building envelope may require several days, or up to a week initially, to completely dehumidify the space. 15.Confirm secondary water conditions regularly to ensure that it is properly filtered, and appropriately inhibited.
Start-up Shop drawings and schedules as a tool for commissioning
Sample space serviced by active beams Child care classroom, California