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Direct Digital DBT, %RH, and Condensate Control for a DOAS-CRCP system. ASHRAE Winter Meeting Symp. 3, Orlando-Feb. 6, 2005 Stanley A. Mumma, Ph.D., P.E. & Jae-Weon Jeong, Ph.D. Architectural Engineering Department Penn State University, @ Univ. Park, PA.

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direct digital dbt rh and condensate control for a doas crcp system

Direct Digital DBT, %RH, and Condensate Control for a DOAS-CRCP system

ASHRAE Winter Meeting Symp. 3, Orlando-Feb. 6, 2005Stanley A. Mumma, Ph.D., P.E. &Jae-Weon Jeong, Ph.D.Architectural Engineering DepartmentPenn State University, @ Univ. Park, PA

sam11@psu.edu; jqj102@psu.eduhttp:// doas-radiant.psu.edu

presentation outline
Presentation Outline
  • First thoughts when considering DOAS-CRCP control.
  • DOAS-CRCP design philosophy.
  • Summary of the design issues you may wish to consider.
  • Field experience with single zone controls.
  • Extension to multi-zone applications designed with a DOAS supply air temperature equal to the required design SA DPT. Why you ask!
first thoughts about control
First Thoughts about control?

Points list

Nyquist Plots

Stability and dynamic response

Schematics

Z and Laplace Transforms

Sequence of operation

Bodi Plots

BACnet

doas crcp design concept

High Induction Diffuser

20-70% less OA,

Cool/Dry Supply

DOAS Unit W/ Energy Recovery

Building With Sensible and Latent cooling decoupled

Parallel Sen. Radiant Cooling System

DOAS-CRCP Design Concept
issues that impact control
Issues that impact Control
  • Thermal comfort, temperature and humidity control.
  • DOAS SAT, neutral or cold.
  • Envelope, Internal generation (high or low occ. Density), & Geo. Loc.
  • Std. 62, and IAQ.
  • ADPI with low to very low air flow.
  • Condensation control.
  • Instrumentation for control and monitoring.
  • Controlled devices.
  • Desire for BACnet compatibility & Web Access.
  • Control hardware and software.
extension to multi zone facility
Extension to Multi-Zone Facility
  • Case 1, Low Occupancy Density Facilities such as Offices.
    • Maintain low SAT, i.e. EW with CC.
    • Modulate the panel inlet water Temperature rather than flow as in the single zone.
    • Space DPT sensing not required, provided DOAS supply conditions maintained, but condensation sensing is still needed in some perimeter spaces.
    • If movable sash facility, sash position sensing is required.
extension to multi zone facility14
Extension to Multi-Zone Facility
  • Case 2, High Occupancy Density Facilities such as schools.
    • Maintain low design SAT with capability of central “free” reheat, i.e. EW-CC-SW.
    • A critical space reset control will be discussed next. The intent is to minimize terminal reheat energy use.
slide15

Paper Figure 3

ReHt

EW--CC-- SW

CRCP

Is Terminal Reheat allowed? Yes!!! See ASHRAE Std. 90.1- 2004; Sec. 6.5.2.1 “If the air reheated does not exceed that required to meet ASHRAE Std. 62.1”

Space 1 of nDBT, %RH

slide16

OA h

ReHt

RA h,

EW--CC-- SW

CRCP

Operate the EW whenOA h > RA h, otherwise off

SpaceDBT, %RH

slide17

CC CV

ReHt

EW--CC-- SW

CRCP

Modulate the CC CV so no space %RH > 55%orno space DBT > 75

SpaceDBT, %RH

slide19

CRCP CV

ReHt

EW--CC-- SW

CRCP

Modulate the SW speed to hold at least one CRCPCV wide open

SpaceDBT, %RH

slide21

ReHt CV

CRCP CV

ReHt

EW--CC-- SW

CRCP

Modulate the CRCP CV & the ReHt CV in sequence to maintain the Space DBT @ 75F

SpaceDBT, %RH

conclusions
Conclusions
  • The single zone DOAS-CRCP system has been operating superbly now for over 3 years with the controls presented here.
  • Without a single incidence of condensation.
  • Maintenance free.
  • Based upon that experience, the control was extended to a multi-zone building utilizing low SAT. A CRITICAL ZONE DBT AND DPT RESET SCHEME
  • The many interacting local control loops in the reset control will require care (slow response) to avoid hunting.