designing a doas/radiant system for american univ. law school€¦ · [ashrae 62.1-2010 user’s...

Designing a DOAS/Radiant System for American Univ. Law School Cindy Cogil, PE LEED BD+C SmithGroupJJR

Building The Case for DOAS

2 11/12/2013 | Illinois ASHRAE

Law School Program


Students

Library

Clinic

Faculty

Administration

Other

Instructional

Student Activities Library Career Center Faculty

Clinical Center Socratic Classroom Computer Lab Centers

Mock Trial Law Review Moot Court Food Service Events

Reading Room

Group Study

VAV Systems


Multiple Spaces Equation - Excess OA Explained

AHU

Instructional

Library

Ext. Office - enclosed

Int. Office - enclosed

Building:System Tag/Name:Operating Condition Description:Units (select from pull-down list)

w /o diversity w / diversityInputs for System Name Units System Diversity System

Floor area served by system As sf 8250 Default entry has been overridden.Population of area served by system Ps P 110 D 85% 94 Default entry has been overridden.Design primary supply fan airflow rate Vpsd cfm 8,665 93% 8,058 Default entry has been overridden.OA req'd per unit area for system (Weighted average) Ras cfm/sf 0.08 Default entry has been overridden.OA req'd per person for system area (Weighted average) Rps cfm/p 6.5 Default entry has been overridden.Percent increase in Vbz over minimum required 0%

Inputs for Potentially Critical zones

Zone NameZone title turns purple italic for critical zone(s)

Lecture classroom

Library ext. office - enclosed

int. office - enclosed

Zone Tag Z-1 Z-2 Z-3 Z-4

Occupancy CategorySelect from pull-down list:

Lecture classroom

Libraries Office space Office space

Floor Area of zone Az sf 1,650 2475 2,063 2,063Design population of zone Pz P (default value listed; may be overridden) 65 24.75 10.3125 10.3125Design total supply to zone (primary plus local recirculated) Vdzd cfm 1,570 2970 2,269 1,856Induction Terminal Unit, Dual Fan Dual Duct or Transfer Fan? Select from pull-down list or leave blank if N/A: Induction Termi Induction Termi Induction Termi Frac. of local recirc. air that is representative of system RA Er 0.50 0.50 0.50 0.50

Inputs for Operating Condition AnalyzedPercent of total design airflow rate at conditioned analyzed Ds % May need to manually edit Ds: 100% 100% 100% 80% 80%Air distribution type at conditioned analyzed Select from pull-down list: CS CS CS CSZone air distribution effectiveness at conditioned analyzed Ez 1.00 1.00 1.00 1.00Primary air fraction of supply air at conditioned analyzed Ep 1.00 1.00 1.00 1.00

ResultsSystem Ventilation Efficiency Ev 0.78Outdoor air intake required for system Vot cfm 1600Outdoor air per unit floor area Vot /As cfm/sf 0.19Outdoor air per person served by system (including diversity) Vot /Ps cfm/p 17.1Outdoor air as a % of design primary supply air Ypd % 18%

Potentially Critical Zones

Law School Sample ProgramAHU-1Design cooling w/critical zone at min. airflowIP

Add Zone

Show Values per Zone

Show codes for Ez

Delete Zone

VAV – Design Cooling Minimum Ventilation Requirements




Floor area served by system As sf 8250.5 Default entry has been overridden.Population of area served by system Ps P 110 D 85% 94 Default entry has been overridden.Design primary supply fan airflow rate Vpsd cfm 8,665 93% 8,058 Default entry has been overridden.OA req'd per unit area for system (Weighted average) Ras cfm/sf 0.08 Default entry has been overridden.OA req'd per person for system area (Weighted average) Rps cfm/p 6.5 Default entry has been overridden.Percent increase in Vbz over minimum required 0%



Lecture classroom





Lecture classroom


Floor Area of zone Az sf 1,650 2475 2,063 2,063Design population of zone Pz P (default value listed; may be overridden) 65 24.75 10.315 10.3125Design total supply to zone (primary plus local recirculated) Vdzd cfm 1,570 2970 2,269 1,856Induction Terminal Unit, Dual Fan Dual Duct or Transfer Fan? Select from pull-down list or leave blank if N/A: Induction Termi Induction Termi Induction Termi Frac. of local recirc. air that is representative of system RA Er 0.50 0.50 0.50 0.50

Inputs for Operating Condition AnalyzedPercent of total design airflow rate at conditioned analyzed Ds % May need to manually edit Ds: 23% 100% 100% 100% 80%Air distribution type at conditioned analyzed Select from pull-down list: CSCRW CSCRW CSCRW CSZone air distribution effectiveness at conditioned analyzed Ez 1.00 1.00 1.00 1.00Primary air fraction of supply air at conditioned analyzed Ep 0.25 0.00 0.00 1.00



Law School Sample ProgramAHU-1Design heatingIP

Add Zone


Show codes for Ez

Delete Zone

VAV – Design Heating Minimum Ventilation Requirements


DESIGN OUTSIDE AIRFLOW

VAV Systems


Multiple Spaces Equation – Excess OA Explained

AHU

Instructional

Library



541 388 161 161

1570

1877 1870

7

1870 (619 CFM unvitiated)

412

1158 2970

0

2970 2269

0

2269

1856

Series fan-powered box (typ of 3) to comply with ASHRAE Std. 62.1 & 90.1

VAV Systems


Uncertainly in Multiple Space Analysis

AHU

Instructional

Library



541 388 161 161

1570

1877 1870

7

1870 (619 CFM unvitiated)

412

1158 2970

0

2970 2269

0

2269

1856

Fraction of local recirculation air that is representative of system? RA = 0.5?

ASHRAE RP-1276


Fraction of local recirculated air that is representative of system RA, Er

Ventilation Rate Procedure Flow Chart


Multi-Zone Recirculating vs. DOAS

DOAS

Multi-Zone Recirculating

Determine max zone OA ratio, Zp

Determine ventilation efficiency, Ev

Determine occupant diversity, D

Calculate uncorrected OA, Vou

Vot = Vou/Ev

“Calculating ventilation rates for multiple zone systems can be complex and requires considerable judgment on the part of the designer.” [ASHRAE 62.1-2010 User’s Manual]



Floor area served by system As sf 8250 Default entry has been overridden.Population of area served by system Ps P 110 D 100% 110 Default entry has been overridden.Design primary supply fan airflow rate Vpsd cfm 1,362 100% 1,362 Default entry has been overridden.OA req'd per unit area for system (Weighted average) Ras cfm/sf 0.08 Default entry has been overridden.OA req'd per person for system area (Weighted average) Rps cfm/p 6.5 Default entry has been overridden.Percent increase in Vbz over minimum required 0%



Lecture classroom





Lecture classroom


Floor Area of zone Az sf 1,650 2475 2,063 2,063Design population of zone Pz P (default value listed; may be overridden) 65 24.75 10.3125 10.3125Design total supply to zone (primary plus local recirculated) Vdzd cfm 588 422 176 176Induction Terminal Unit, Dual Fan Dual Duct or Transfer Fan? Select from pull-down list or leave blank if N/A: Frac. of local recirc. air that is representative of system RA Er 0.50 0.50 0.50 0.50

Inputs for Operating Condition AnalyzedPercent of total design airflow rate at conditioned analyzed Ds % May need to manually edit Ds: 100% 100% 100% 100% 100%Air distribution type at conditioned analyzed Select from pull-down list: CS CS CS CSZone air distribution effectiveness at conditioned analyzed Ez 1.00 1.00 1.00 1.00Primary air fraction of supply air at conditioned analyzed Ep 1.00 1.00 1.00 1.00



Law School Sample ProgramDOAS-1Design cooling w/critical zone at min. airflowIP

Add Zone


Show codes for Ez

Delete Zone

DOAS Minimum Ventilation Requirements


27% SAVINGS COMPARED TO VAV

Dedicated Outside Air Systems


Key Features

• 100% OA distributed by ductwork to each zone

• Flow rate to each zone as required to ventilate and handle latent load

• Requires TER, per ASHRAE 90.1 • Decouples S/L loads in the space • OA supplied below space neutral

temperature

DOAS Unit w/ER

Building w/Decoupled

Sensible and Latent Cooling

Cool/Dry Vent/Latent

Parallel Sensible Cooling System

Minimum Ventilation Requirements


DOAS Supply Air Conditions

55F DPT / 64.5 grains

47F DPT / 47.9 grains

Maximum CFM required to: • Handle space latent load at desired space humidity ratio • Comply with ASHRAE 62.1

SF/# OA/# OA/SF # (1000 SF)ASHRAE 62.1 OA (1000 SF)

Cumulative OA/#

Latent Load, Btuh Wroom Wprimary DPTPrimary

Cumulative OA/# OA Wprimary DPTPrimary

% OA increase

Auditorium/Lecture Hall 25 7.5 0.06 40 360 9 6,200 64.5 39 41.7 14 560 48 47.1 56%Library 100 5 0.12 10 170 17 1,550 64.5 51 48.7 17 170 51 48.7 0%

Private Office 200 5 0.06 5 85 17 775 64.5 51 48.7 17 85 51 48.7 0%SA DPT 45-53F; need desiccant for SA DPT <=40F

Supply Air DPT DOAS


QL=CFM*0.68*(Wroom – Wprimary)

DOAS vs. VAV Minimum Ventilation Requirements


Lecture Classroom Library Ext. Office – enclosed

Int. Office – enclosed

Total OA Intake Required for System

VAV System (ASHRAE Std. 62.1)

1870

DOAS (ASHRAE Std. 62.1)

587 421 175 175 1358 (-27%)

DOAS (Latent Load)

893 340 142 142 1516 (-19%)

DOAS (Design) 893 421 175 175 1664 (-11%)

Parallel Sensible Conditioning


Options

Fan Coil Unit

Radiant Ceiling Panel

Parallel VAV AHU

Variable Refrigerant Volume Heat Pumps

Parallel Sensible Conditioning


Options

Fan Coil Unit


Parallel VAV AHU

Variable Refrigerant Volume Heat Pumps

Noise / Space Space/Control

Aesthetics

Radiant Ceiling Panels


Key Features

• Low mass / fast response • Active panel area limited to < 70%

ceiling area • Quiet operation • Increased zoning potential • Accommodates low floor-to-floor heights • Requires dew point monitoring

Air Handling Unit Selection


DOAS

DOAS AHU


Low Temp Supply

48 47

• Requires cold chilled water temp (potential chiller efficiency penalty) •High aspirating diffusers •May reduce active panel area for cooling load dominated

spaces, especially where ventilation rates can be reset • Can use standard AHU manufacturers

DOAS AHU


Slightly Lower than Space Neutral Supply

•Dual Wheel (passive dehumidification) • PDW dehumidifies and reheats (saves cooling capacity) •Uses conventional CHWS/R, more efficient chiller • Custom, proprietary equipment • TER in custom unit typically has higher efficiency than

in non-custom unit

DOAS AHU



Total energy wheel

Sensible energy wheel

•Dual Wheel (sensible) • Requires cold chilled water temp (potential chiller

efficiency penalty) • Custom AHU equipment • TER in custom unit typically has higher efficiency

than in non-custom unit

DOAS AHU



•Heat Pipe • Requires cold chilled water temp (potential chiller

efficiency penalty) • TER in custom unit typically has higher efficiency

than in non-custom unit • Lower maintenance than dual wheel • Slightly larger unit

Water Side Selection


Secondary Chilled Water Circuit


Separate, Dedicated Secondary Chiller Plant



Plate Heat Exchanger



Mixing/Injection Valve

Mixing / Injection Valve

Secondary Chilled Water Pump



Design Considerations

• Capacity is a function of installation • Be cautious of minimum mass flow

rates to maintain turbulence • Limit maximum circuit pressure

drop to 6-7 ft. wg (2-4 panels in series)

Capacity Correction Factors

Schematic Design – HVAC Analysis


High Efficiency DOAS/Radiant vs. High Efficiency VAV

DOAS/Radiant


Floor 1

Floor 3

Floor 4

Floor LL

Floor 2

DOAS/Radiant


VAV


Floor 1

Floor 3

Floor 4

Floor LL

Floor 2

VAV SYSTEM Yuma Flrs LL, 1 Law Library Nebraska Yuma Flrs 2, 3 Yuma Flr 4 AHU-1-1 ERAHU-2 ERAHU-3 AHU-1-2 AHU-1-3

Peak Population 1506 1394 1394 409 325

Area, sf 59889 58997 26853 63831 14064

Design Supply Air 38110 45870 20620 47200 14840

VAV


Initial Costs


Energy Consumption


Energy Costs


Life-Cycle Costs


End of Study 8/1/40

DOAS Supply Air Temperature


Optimization

• Low temperature supply can result in overcooling and higher reheat loads for certain space types where internal and envelope sensible cooling loads are low

• By adjusting the supply air upwards to ~66F, we decreased total active surface area by 13.7%.

BIM Documentation


Lessons Learned

BIM Documentation


Workflow Graphics

BIM Documentation


RCP Family Building

BIM Documentation


Ductwork Plan Piping Plan RCP Plan

BIM Documentation


Ceiling Coordination Exit Signs

Projector Screens

Wall Wash Lighting

Sprinklers

Radiant Ceiling Panels

Ceiling Cameras

Metal Infill

Recessed Lighting

Projectors

Wireless Access Points

Ceiling Speakers

Questions?


Condensation Prevention


Step 1: Condensation Prevention • Fix windows closed • Construct a tightly sealed building • Use airlocks/vestibules at main entrances • Maintain CRCP surface temperature above space dewpoint temperature (DPT) Step 2: Condensation Control • Multi-zone system strategy (Variable flow/constant temp)

1. Proximity switches detect open windows (more cost-effective than individual zone DPT sensors and faster reacting)

2. Then, if OA DPT exceeds space design DPT, the CRCP control valve serving that specific zone or collection of zones would be closed

3. Once windows return to closed position, the valve is permitted to modulate again following suitable time delay or confirmation that DOAS has returned space to design DPT

Condensation Prevention


Cooling Only & Heating/Cooling RCPs


Occupant-Based Controls


designing a doas/radiant system for american univ. law school€¦ · [ashrae 62.1-2010 user’s...

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