VRF Equipment & Applications

Ruben Willmarth

West Region Sales Manager

Toshiba Carrier Ductless & VRF

November 07, 2014 Billings, MT Joint Engineering Conference

CONTENTS

What is VRFGlobal Application ExamplesBenefits of VRF systemsSystem ComponentsControlsBasic Design PracticesASHRAE Std 15 & 34

“VRF” system is a short for Variable Refrigerant Flow system. Refrigerant flow is varied based on demand

- System where multiple (up to 50 indoor units) can be connected to outdoor units.

- Fan coils are controlled individually or by group controls.

- Refrigerant flows to the unit that is calling for heating or cooling.

WHAT IS VRF

VRF Technology Overview Two VRF System Types

Heat PumpHeat Recovery

Simultaneous Cooling & HeatingSingle Mode: Cooling or Heating Only

VRF Technology Overview Primary Components of a Heat Pump System

Outdoor Unit• Controls

Compressor Speed• Maintains

Operational Mode

Indoor Unit• Transfers Heating

and Cooling to Space

• Allows for Optimal Zoning

Controller• Controls Space

Temp and IDU Fan• Remote or Central

Outdoor unit

Refrigeration Pipe

(Liquid, Gas)

Indoor unit

Liquid line (fully liquid)

Each indoor unit can be controlled individually.

On/Off setting , Set point, Air volume, louver position can be set individually.

（ Operation mode priority : Cooling or Heating, not simultaneously in heat pump model）

Cooling : Expansion=Indoor unit Liquid line=Condensed liquid

Heating : Expansion=Outdoor unit 　 Liquid line =Condensed liquid　

Compressor

Typical VRF Heat Pump System

VRF Technology Overview How does VRF work?

Outdoor Unit• Houses multiple inverter driven compressors• Compressors change speed based on demand of indoor

units, which varies the refrigerant flow• Segmented ODU Coil for efficient heat transfer

Unit operates to match exact building load

Indoor Unit• Transfers heating and cooling directly to the space• Measures Return Air Temperature• Pulse Motor Valve (PMV) adjusts to meet setpoint• Filters and distributes the air

Unit operates to match exact building load

Flow Selector• Receives superheated gas and subcooled liquid, adjusts

flow direction to heat and cool• Allows for indoor unit to be in either cooling or heating

mode

Unit operates to match exact building load

Controller• Allows for indoor unit control at zone level• Takes user desired space setpoint, fan speed, mode

Unit operates to match exact building load

Typical VRF Heat Recovery SystemSimultaneous heating and cooling, uses cooling mode waste heat for heating

3 - Pipe

Heat Recovery Box

Typical VRF Heat Recovery System2 - Pipe

How does the outdoor unit respond to the varyingdemands and vary the flow of refrigerant?

The compressor(s) in the outdoor units are inverter driven which means that their speed can be varied by changing the frequency of the power supply to the compressor.

As the compressor speed changes, so does the amount of refrigerant delivered by the compressor.

Varying Refrigerant Flow

Stable Operation

HighReliability

High Efficiency

HighReliability

SYSTEM ADVANTAGES

In case of: Not all units are on.Example: office area is on, meeting room is off.

In case of: Orientation of buildingExample: East/West exposure

In case of: Decreased load.Example: office closed

OFF

Application:

Apartment,

Office building

Use Wherever Part Load Exists

: 4-way cassette type

: Hi-wall type

: Outdoor units

: Piping

(In case of cooling)

OFF

OFF

OFF

OFF

ZONING OPERATION OF VRF

- Comfort

- Design flexibility

- Energy savings (part load, heating)

- Cost effective installation

ADVANTAGES OF VRF

ADVANTAGES OF VRF

Rotary compressor Scroll compressor

COMPRESSOR COMPARISONS

Twin rotary compressor

OutIn

COMPRESSOR COMPARISON

Scroll compressor

Out

In

In

EASE OF DESIGN

Multiple types of Fan Coils and Sizes provides design flexibility for many different applications

ADVANTAGES OF VRF

ADVANTAGES OF VRF

Modularity of equipment allows for Staging of installation, Redundancy in operation

ADVANTAGES OF VRF

HX, and

ADVANTAGES OF VRF

TECHNICAL TRAINING

23

1200 apartments in 7 buildings

Recognized by China’s Ministry of Construction as being among the most cost-effective air conditioning systems available.

Shengshi Qiantang Garden3,840Tons

24

Jae Neung Education Building2,400Tons

25

Portal Commercial Development280Tons

26

26

Approx. 10,000 sq. ft

7 floor multi-tenantoffice building

Burt Hill Architects Office

27

27

Installed in subway passages and administration offices

Contracts extending to other lines

China Subway19,200Tons

Stable Operation

HighReliability

High Efficiency

HighReliability

DESIGNING WITH VRF

Designing for Energy efficiencyPerimeter/CorePres. Office

12 kBTU

VP Office14 kBTU

Foyer2.5kBTU

Women’s2.0kBTU

Men’s2.0kBTU

Coffee/Brk2.0kBTU

Office 1016.0kBTU

Office 1026.0kBTU

Office 1036.0kBTU

Office 1043.0kBTU

Office 1053.0kBTU

Office 1063.0kBTU

Office 1073.0kBTU

Office 1083.0kBTU

Office 1093.0kBTU

Office 1104.5kBTU

Office 1107.5kBTU

Conf.28.0kBTU

Corr2.0kBTU

Corr2.0kBTU

1

2

34

5

6

7

20 kBTU14 kBTU

12 kBTU

2.5 kBTU

13.5 kBTU

12 kBTU28 kBTU

Example: 40oF Ambient

Rejected

Heat

30

Ventilation Design

Delivering OSA directly to the space:

1. Best when it is Neutral temperature & Humidity (DOAS)

2. An ERV-only is OK in the West & South, if low fraction and high ceilings (mixing time)

3. Mild Climates can bring in small fraction untreated

4. Benefits are less ducting, more flexible application

• Ventilation Strategies with VRFRoom graphic w/Air into Corner

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Ventilation Design

Delivering OSA ducted to the Fan Coil:

1. Pre-Filtered, tempered air is best. (DOAS) 1. Allows selecting to meet Envelope load for max comfort

2. Air inlet point is before the filter on some ductless, so Filter is a must!

2. An ERV-only is Good in the West & South, but may need additional heat in the North

3. DOAS system or ERV+FC is best for Cold Climates

4. Mild Climates can bring in small fraction untreated (<30%)

5. Benefits are better humidity control, no extra grills

Ventilation Strategies with VRF

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Ventilation Design

1. DOAS approach allows us to split the ventilation load away from the Mechanical system by tempering the air first.A. Can use an ERV only for most applications

B. Can run OSA through a standard Fan Coil in Series for Neutral Air application, especially if not ducted to Fan Coils

C. Can apply Supplemental Heat for Cold Climate applications for Neutral Air, or even higher

DOAS using an ERV

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Heating Design

Heating with a VRF System:

-VRF is a Heat Pump, but….A. But it is not your Grandpa’s Heat Pump!

B. Capacity is better than traditional because of inverter compressors that can spin faster to compensate

C. De-rate due to ambient temperature is less, but must still be accounted for.

D. Auxiliary Heat to cover the <average

Heating Design Strategies

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Heating Design

1. The Design Heating in Billings is -20F

2. But the Average January Low is 16F

Heating Design Strategies- Avg. vs. Design:

“Avg. winter low in Billings, MT is 16F”

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Ventilation Design

When to use Auxiliary Heat? A. Rule of Thumb is start considering it at 15F design temp.

B. Simple Answer is when heating Design Day exceeds capacity

C. ERV & DOAS can provide significant contributions.

Heating Design Strategies

“Avg. winter low in Billings, MT is 16F”

“Avg. winter low in Seattle, WA is 36F”

“Avg. winter low in Chicago, IL is 17F”

“Avg. winter low in Nashville, TN is 29F”

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Heating Design

Types of Aux. Heat:A. Electric Strip-Heater (Ducted Models only)

B. Hydronic Coil (can feed from an upsized DHW source)

C. Both of above can be placed in DOAS ducting for 90+F ventilation air if that meets the needed BTU’s!

D. Baseboard Heating Panels

A. Hydronic or Electric-All Fan Coils

E. Radiant Panels

A. Hydronic or Electric-All Fan Coils

F. Wall Heaters

A. Typically Electric-All Fan Coils

G. Or….Previously Existing Heating System!!

Heating Design Strategies-Aux Heat

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Heating Design

There are 3 ways to activate the Aux. Heat

1. Individual Space Response:1. Zone temp drops, Aux heat activates at Temp. A, then

deactivates at Temp B. Both must be less than heating setpoint

1. Outdoor Ambient Trigger. Aux heaters engage when FC is in Heating, Aux Heating system activated by separate Outdoor Ambient Thermostat.

2. BMS Control system activation. Can use custom logic for zone by zone response, minimize setpoint drift.

Heating Design Strategies-Aux Heat

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Heating Strategies

Heating Setback with VRF:A. A VRF system is different from a combustion heater because

it’s efficiency gets better at part-load.

B. When system is in recovery, system goes to full-load, which is less efficient than maintaining a constant temperature, but total heat loss is more.

C. So, optimum use is probably minimal setback during weekdays, and more of a setback over weekends & Holidays, or just a 2F setback period.

D. No setback during cold snaps to avoid using Aux Heat.

• Heating Design Strategies-Aux Heat

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Heating Strategies

Alternate to zone-level Aux. Heat-Put Outdoor Units in a Mechanical Room or “Doghouse”

• Heating Design Strategies-Aux Heat

40

Heating Design

Alternate to zone-level Aux Heat-Put Outdoor Units in a Mechanical Room or Doghouse:

A. Simplifies controls of Aux. Heat by having one set of controls and heat source.

B. Heater is typically a Gas unit heater, or other combustion unit

C. Backup isolates from Outdoor air at preset ambient temp.

D. Key Selection Criteria:

A. Size the Unit heater for 70-80% of Heat Load

B. Ducting system must be 0.2” esp max. in both modes

C. Activation temp typically below freezing, but maintain interior temp around 45F to avoid frost buildup.

D. Don’t forget to include a condensate drain, w/heat tracing

• Heating Design Strategies-Aux Heat

Refrigerant system DesignVRF and ASHRAE 15/34

In part, Standard 15, Safety Standard for Refrigeration Systems, strives to ensure a safe system by limiting the maximum quantity of refrigerant below that which is a danger to human occupants if a leak occurs.

Because VRF uses the Refrigerant as the transport medium, it is inherently a more refrigerant intensive product than most traditional HVAC. Std. 15 is the application guideline that ensures a safe design every time.

VRF and ASHRAE 15/34

Refrigerant Concentration Limit (RCL) R410A

R410A is a commonly used refrigerant for commercial VRF systems. Per Standard 34, Table 2, the safety classification of R-410A is Group A1 (meaning non-flammable and non-toxic). Even though R-410A is Group A1, its ability to displace oxygen could pose a danger to occupants if released in large quantities into smaller-volume spaces. Therefore, Standard 34, Table 2 has established an RCL for R-410A at 26 lbs of refrigerant per 1,000 cuft of room volume.

For Institutional Occupancies such as patient care areas of hospitals and senior homes, the RCL is cut in half, changing the RCL for R-410A to 13 lbs/1,000 cuft.

Smaller Capacity Systems Design for “Connected Spaces” Combine multiple smaller zones on a single ducted

fan coil unit One to-One Systems Diversity

Refrigerant Piping Layout Y-branching versus manifold

Isolate refrigerant circuit for Smaller Rooms R410A sensor and alarm, or isolation valves

VRF and ASHRAE 15/34

Stephen W. Duda’s article published in ASHRAE Journal, July 2012. Posted at www.ashrae.org. Applying VRF? Don’t Overlook Standard 15

Questions

?

Thank You