what is the digi- · digi-rtu address all pnnl1 four areas of rooftop units advanced controls 4640...

WHAT IS THE DIGI-RTU™

4640 South 59th Street | Omaha, NE 68117 402.502.2340 | bes-tech.net

The Digi-RTU is a Heating, Ventilation, and Air

Conditioning (HVAC) rooftop unit control kit that

is both a demand management and energy usage

device. It is designed to improve the energy

efficiency and demand requirements of a rooftop

unit as well as solve the humidity, common

noise, and frequent on/off issues of a rooftop

unit through modulating the capacity of a rooftop

unit to match the cooling or heating space

requirements.

DIGI-RTU

PERFORMANCE RECOGNITION

American Public Power Association’s

2011 DEED Energy Innovator Award.


DIGI-RTU ADDRESS ALL PNNL1 FOUR AREAS

OF ROOFTOP UNITS ADVANCED CONTROLS


- Integrates air-side economizers

- Controls supply fan speed

- Controls compressor capacity

- Manages Demand-Controlled Ventilation, CO2

- Demand Response signal enabled

- Fault Detection via existing BAS, IP thermostat or utilizing Digi-SFT

1Department of Energy's Pacific Northwest National Laboratory http://www.pnnl.gov/main/publications/external/technical_reports/PNNL-20955.pdf

Addresses ALL Four PNNL Recommendations for Advanced Controls of Rooftop Units

HOW THE DIGI-RTU WORKS


By intercepting heating

and cooling calls, the

Digi-RTU’s patented

technology manages the

compressor and fan

speeds to match the

space requirements.

As a result space

temperature and humidity

are best managed. DIGI-RTU KIT

MAIN APPLICATIONS


– Package rooftop units, water and air

source heat-pumps, split units

– HVAC rooftop units between 3 to 30-ton

– Up to four cooling stages

– Up to two heating stages

– Scroll & reciprocating compressors

– Existing space thermostat and BMS

DIGI-RTU ADVANCED CONTROLS FUNCTION


Modulating mechanical HVAC equipment to better match space

operating requirements is the accepted industry standard

Modulating fan and compressor is the energy efficiency strategy for all

climate zones

Cool and hot/dry climates … increased free cooling

Cool and wet climates … humidity and moisture control

Economizer Integration

Integration and management of the existing economizer

Extends existing economizer range by 30%

Fan Speed Control

ON mode - average fan savings are greater than 85%

AUTO mode - average fan savings are 70 – 80%


Demand Controlled Ventilation, CO2

CO2 sensor into the return air duct integrated with the

economizer satisfies ASHRAE 62.1 and CA Title 24 air quality

requirements

Fault Detection

Digi-SFT provides fault detection diagnostics and notification

or

Digi-RTU communicates with the existing BAS or IP enabled t-

stat for diagnostics and notification

Demand Response

The Digi-RTU is subordinate to the existing T-stat or BAS

system responding to all space /building cooling and heating

requirements

The load-limit factor for the rooftop unit is sent through the

BAS to the Digi-RTU, and can range from 50-100%




Existing Building EE Strategies, Platform & Equipment

Communicates with existing BAS platforms and existing installed

thermostats; programmable, IP etc.

Integrates with the original equipment HVAC controller

Mounts inside the HVAC rooftop unit

Compressor Optimization

Conforms to original equipment manufacturer recommendations

for speed reduction down to 45Hz

Programmed logic provides soft start & stop of the compressor

Extended compressor life and lowered lifecycle costs

Compressor modulation savings are double fan power savings

for a significant portion of the United States climate zones

Peak Demand savings of 4 – 5kW for an average 10-ton rooftop

BENEFITS OF USING A DIGI-RTU OPTIMIZER


For Utility Companies: – Lowers peak demand up to 65%

– Reduces kWh usage up to 65%

– Decreases carbon emissions

– Scalable, 3-hour install time

For Building Owners and Tenants: – Reduces electricity consumption and costs

– Better maintains space humidity and temperature which decreases comfort complaints

– Reduces compressor on/off cycling up to 75%, and reduces maintenance cost

– Reduces HVAC equipment noise in occupied space

OMAHA, NE

DIGI-RTU CASE STUDY –

PHARMACEUTICAL DISTRIBUTION CENTER


70% kW

decrease

-20

0

20

40

60

80

100

0

10

20

30

40

50

60

70

80

90

100

9/18 10/18 11/17 12/17 1/16 2/15 3/17 4/16 5/16

OA

T (

F)

Po

we

r (k

W)

Date

Without Digi-RTU With Digi-RTU OAT

Measured Power Consumption and Ambient Temperature

Pre - blue

Post - red

Ambient temperature

5-minute intervals

DIGI-RTU CASE STUDY –

PHARMACEUTICAL DISTRIBUTION CENTER


85% kWh

decrease

Pre blue

Post red

5-minute intervals 0

10

20

30

40

50

60

70

80

90

100

30 40 50 60 70 80 90

Po

wer

(kW

)

OAT

Without Digi-RTU With Digi-RTU

Comparison of Measured Power Consumption with and without Digi-RTU

SAN DIEGO

DIGI-RTU CASE STUDY – OFFICE SPACE


February - March 2014

43% kW decrease

Measured RTU Power for One Minute Interval

Pre blue line Post green line Ambient temperature red line

DIGI-RTU CASE STUDY – OFFICE SPACE


February - March 2014

71% kWh

decrease

Pre blue line Post green line

Daily Electrical Energy Consumption; Pre (blue ) and Post (red ) vs. Ambient Temperature

SAN ANTONIO TX


SEPTEMBER – OCTOBER 2012

BIG BOX RETAIL


Two weeks with

and two weeks

without

29.5% kW

decrease

0

10

20

30

40

50

60

70

80

90

100

0

1

2

3

4

5

6

7

8

8/2

78

/28

8/2

98

/30

8/3

19

/19

/29

/39

/49

/59

/69

/79

/89

/99

/10

9/1

19

/12

9/1

39

/14

9/1

59

/16

9/1

79

/18

9/1

99

/20

9/2

19

/22

9/2

39

/24

9/2

59

/26

9/2

79

/28

9/2

99

/30

10

/11

0/2

10

/31

0/4

10

/51

0/6

10

/7

OA

T, D

eg

F

kW

Before

After

AVG-OAT

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

kWh

9/23/12 (OAT = 78 F; weekend; after install)

9/26/12 (OAT = 80 F; weekday; after install)

9/9/12 (OAT =79 F; weenkend; before install)

9/11/12 (OAT = 79 F; weekday; before install)

DIGI-RTU INSTALL ASHRAE #2

BIG BOX RETAIL


Two days with and

two days without

74% kWh

reduction

VERMONT

BURLINGTON ELECTRIC – STUDY Office Building

0

1,000

2,000

3,000

4,000

5,000

6,000

7,000

8,000

9,000

kWh

Metered Savings = 65%

W/O Digi-RTU

With Digi-RTU

65% kWh reduction


- Equipment sub-metered

- Two weeks pre

- Two weeks post

- IPMVP

0

20

40

60

80

100

4-Aug 9-Aug 14-Aug 19-Aug 24-Aug 29-Aug 3-Sep 8-Sep

Avg

. O

AT

Date

Without Optimizer With Optimizer

EFFICIENCY VERMONT - STUDY Distribution Center

0

10,000

20,000

30,000

40,000

50,000

60,000

70,000

kWh

Metered Savings = 68%

W/O Digi-RTU

With Digi-RTU

68% kWh reduction


- Equipment sub-metered

- Two weeks pre

- Two weeks post

- IPMVP

0

10

20

30

40

50

60

70

80

20

-Se

p

22

-Se

p

24

-Se

p

26

-Se

p

28

-Se

p

30

-Se

p

2-O

ct

4-O

ct

6-O

ct

8-O

ct

10

-Oct

12

-Oct

14

-Oct

16

-Oct

18

-Oct

Avg

. O

AT

Without Optimizer With Optimizer

DIGI-RTU CONCLUSIONS


Digi-RTU is able to:

– Reduce peak demand up to 65%

– Reduce consumption up to 65%

– Improve room humidity management

– Improve room temperature management

– Reduce compressor cycling

– Reduce maintenance costs

– Reduce equipment noise


Bes-Tech, Inc. 4640 S 59th Street Omaha, NE 68117

402.502.2340

BES-TECH.NET

what is the digi- · digi-rtu address all pnnl1 four areas of rooftop units advanced controls 4640...

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