ashrae presentation 082012...variable refrigerant flow (vrf) heat pump versus heat pump with heat...

11/12/2012

1

ASHRAE Presentation: VRF Overview

Mitsubishi Electric

Eric Veit

©2011 Mitsubishi Electric& Electronics USA, Inc.

General overview of VRF Technology

Review of Design Considerations

Benefits of VRF

Agenda

11/12/2012

2

Variable Refrigerant Flow (VRF)

Heat Pump

versus

Heat Pump with Heat Recovery

11/12/2012

3

Heat Pump

Outdoor Unit

Indoor Units

Controls System

Heat Pump

11/12/2012

4

Heat Pump

Outdoor Unit

Indoor Units

Controls System

Heat Pump Applications

Restaurants Lobbies

Others?

Churches

11/12/2012

5

Heat Pump with Heat RecoverySimultaneous Cooling & Heating

Outdoor Unit

BranchCircuit

Controller

Indoor Units

ControlsSystem

Heat Pump with Heat RecoverySimultaneous Cooling & Heating

11/12/2012

6

Heat Pump with Heat Recovery

Outdoor Unit

Branch Circuit

Controller

Indoor Units

ControlsSystem

Simultaneous Cooling & Heating

Heat Pump with Heat Recovery Applications

Schools Assisted Living Facility Offices

Others?

Simultaneous Cooling & Heating

11/12/2012

7

What is the purpose of each component?

• Controls compressor speed

• Controls condenser fan speed

• Controls pressure of refrigerant to maximize capacity and efficiency

Outdoor Unit

11/12/2012

8

• Separates refrigerant into gas and liquid

• Ensures units in heating receive superheated gas

• Ensures units in cooling receive sub-cooled liquid

Branch Circuit (BC) Controller

• Sense the space temperature

• Contain a Linear Expansion Valve (LEV) that automatically modulates

• Allow the precise amount of refrigerant through the

heat exchanger

• Filter and distributes air

Indoor Units

11/12/2012

9

• Integrated sequence of operation

• Takes input from the user and provides feedback to the system

Controls System

What system type requires a Branch Circuit Controller?

Which system type cannot provide cooling and heating simultaneously to connected units?

Is there any difference between the controls offered for Heat Pump Systems versus those offered for Heat Pump with Heat Recovery?

Recall

11/12/2012

10

VRF Design Considerations

Equipment Layout Diversity Ventilation Heating Efficiency

Equipment Layout


11/12/2012

11

20 Ton System

Ceiling Space

Rectangular Ductwork (DX System) 40” x 20”

Round Ductwork (DX System) 30” Round

-Piping (4 Pipe System) 3” CHWS&R, 3” HWS&R

3/ 1/8Piping (VRF) 1 8” Gas 1 ” Liquid

Equipment

LayoutDiversity Ventilation Heating Efficiency

Rooftop Equipment Weight

0

2,000

4,000

6,000

8,000

10,000

12,000

VAV RTU w/SS

VRF 4-PipeFan Coil

WSHP

Equipment Weight (lbs)

80 Ton System

Equipment


11/12/2012

12

Vertical Stack WSHPs

Equipment


Water-source VRF

Equipment


11/12/2012

13

• There are piping considerations for:

▫ Total System Piping Length

▫ Intermediate Lengths

▫ Elevation Differentials

Piping Lengths

Equipment


• Outdoor Units

▫ Consider location of unit

▫ Consider area drains and floor stands

• BC Controller

▫ Drain pipe connection

• Indoor Units

▫ Drain pipe connections

▫ Some styles include standard condensate lift mechanism

▫ All styles include contact for condensate alarm/safety switch

Condensation

Equipment


11/12/2012

14

Diversity


Solar Diversity

5 Tons Morning

3 Tons Morning

What is the sum of

the zone peak

loads?

5 Tons Afternoon

3 TonsAfternoon

What is the

block load?

Equipment


11/12/2012

15

OPEN OFFICE 101WORK ROOM 103

CONFERENCE

105 COFFEE

105A

Occupant Diversity

Equipment


OPEN OFFICE 101WORK ROOM 103

CONFERENCE

105 COFFEE

105A

What is the

sum of the

peaks?

Occupant Diversity

What is the

block load?

Equipment


11/12/2012

16

COOLING

HEATING

What

equipment is

running?

Waste Heat

Building Diversity

Equipment


• Connected Capacity:

▫ Connect up to 150% of the outdoor unit capacity.

• Actual Capacity:

▫ The actual system capacity is the capacity of the associated outdoor unit.

• A system cannot provide more than 100% of the outdoor unit’s capacity.

Designing with Diversity

Contact your local representative when designing at greater than

110% connected capacity.

Equipment


11/12/2012

17

Example:

• Indoor units totaling 14 tons can be connected to a 12 ton outdoor unit

▫ Connected Capacity = 14 Tons, 117%

▫ Actual Capacity = 12 Tons, 100%

• The maximum amount of cooling that can ever be provided at a single instant is 12 tons

Designing with Diversity

Contact your local representative when designing at greater than

110% connected capacity.

Equipment


Ventilation


11/12/2012

18

• Duct required Outside Air (OA) directly to space or indoor unit

▫ Always calculate entering coil temperatures

• Use Dedicated Outside Air System (DOAS),Energy Recovery Ventilator (ERV), or both to temper the air

• Adhere to local codes in designing ventilation

Ventilation

Equipment


Heating


11/12/2012

19

• Utilize manufacturer’s design software

• Minimize connected capacity for colder climates

• Outside Air

• Consider Building Warm-up

Special Considerations for Heating

Equipment


Efficiency


11/12/2012

20

• INVERTER-driven compressor matches compressor speed exactly to load

• Simultaneous cooling and heating allows heat recovery between zones

• All efficiency values now available via AHRI Directory

▫ http://www.ahridirectory.org

Efficiency

Equipment


Efficiency

System TypeRoof Top

UnitsAir-Cooled

ChillerAir-source

VRFWater-source

VRF

IEER 11.5 - 17.7 19.6

EER 9.7 10.3 10.9 10.5

IPLV - 14.2 - -

SCHE - - 18.6 N/A

20 Ton System

Equipment


11/12/2012

21

• Two-pipe System

• INVERTER Technology

• Multiple Indoor Units

• Variable Capacity System

• Zoning System

• Complete Control Offering

What are the benefits of VRF?

ashrae presentation 082012...variable refrigerant flow (vrf) heat pump versus heat pump with heat...

Documents