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Variable Flow Systems System Design For Energy Efficient Pumping Stephen Hart Managing Director, Frese Limited

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Frese Grundfos Sytem Design for Energy Efficient Pumping

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Variable Flow Systems

System Design For Energy Efficient Pumping

Stephen Hart Managing Director, Frese Limited

Presentation Outline

Introduction

• Energy & Comfort compromise

• Seasonal loads• Constant v

Variable Flow• VSP• Two port

valve• Balancing

Problem

• Fluctuating pressure losses in pipework

• Pressure control• Start Point• End Point• Mid Point

Solution

• Current CIBSE• Pump• Flow• Temperature• Pressure

• OPTIMA PICV Solution• At coil• Remote

Sensor• Sensor

Polling

Power savings

• Schemes• Constant

speed• DPCV

solution• PICV

solution• Power

calculations• Life Cycle

Graph

The Energy & Comfort Compromise

Maintain a comfortable indoor environment• Full load heating on demand• Full load cooling on demand•Effective ventilation• Silent system operation

Reduce system power absorption• Slow motors at low loads•Maximise ΔT at all loads•Prevent overflows at all times•Minimise system resistance

PROBLEMS AND SOLUTIONS

Typical Heating & Cooling Load Profile

Hours4000 60002000

Flow

%

0

100

75

50

25

8000

Variable Flow System(Start Point Control)

Variable speed pump and two port temperature control valves VSP (Constant Pressure)

∆p

25 100

Hset

Variable systemcharacteristics

Pump curvemaximum speed

H[%]

Q [%]P1[%]

Q [%]

Variable Flow System(End Point Control)

Variable speed pump and two port temperature control valves VSP (Constant Pressure)

∆p

Hset

100

Hmax

Variable systemcharacteristics

Pump curvemaximum speed

H[%]

Q [%]P1[%]

Q [%]

25

At Full Load

Unstable Temperature Control

Distance

Pres

sure

∆p

∆p

Underflow

Underflow

Overflow

Overflow

At Part Load

Differential Pressure ControlDPCV Across a Branch

As a rule of thumb, limit DPCV setting to 1.5 times the design ΔP of the index on each branch to secure authority at part load

Source: TA

Differential Pressure ControlDPCV Across a Modulating Valve

Perfect solution ensures authority of 1 on modulating valve but is expensive and adds to pump resistance

Source: TA

Variable Flow SystemPressure Independent Control Valve

∆p

One valve replaces:•Two port modulating valve•Automatic balancing valve•Differential pressure control valve

Frese OPTIMA PICV

Maintain minimum required ΔP for PICV and coil at design

Benefits - Design

• Less time to define the necessary equipment for a hydraulic balanced system (only flow data is required)

• No need to calculate valve authority

• Flexibility if the system is modified after the initial installation

Benefits - Installation

• No further regulating valves required in the distribution pipework when PICV is installed at terminals.

• Total number of valves minimized due to the 3-in-1 design

• Minimized commissioning time due to automatic balancing of the system

• No minimum straight pipe lengths required before or after the valve.

Benefits - Operation

• High comfort for the end-users due to high precision temperature control

• Longer life due to less movements of the actuator

• Less energy consumption due to faster response and increased system stability

MEASURING ENERGY SAVINGS

P49%H36%Q20% ↓=↓=↓

==∴

∝∴

×∝

or,

8P

4H

2Q

QP

QHP 2)

QH 1)

3

2

Calculating Power Absorption

17

Large system constant curve

TP 80-250/2

18

Large system constant pressure

TPE 80-250/2

19

Large system PV & remote sensor

TPE

80-2

50/2

20

TPE

80-2

50/2

PICV Large SystemEnd Point Control

If either A or B do not have the required ΔP then the pump controller will speed up the pump.

A

B

AB

21Running hours: 6.840 hours/year

Calculating Pump Energy Consumption

Hours4000 60002000

Flow

%

0

100

75

50

25

Load profileCalculation profile

8760 hours/year

8000

Constant SpeedDPCV

2612544261253238

50357515

1006

Pres. kPa

Flow[%]

Hours[%]

4960585067407430

Power W

Total 48815 kWh/year 100%

TP 80-250/2

Mid Point ControlDPCV

1162544144191220

50357515

1006

Pres. kPa

Flow[%]

Hours[%]

1730267043607030

Power W

Total 24278 kWh/year 50%

TPE 80-250/2

Start Point ControlDPCV

2202544220220220

50357515

1006

Pres. kPa

Flow[%]

Hours[%]

4040480058007030

Power W

Total 41605 kWh/year 85%

TPE 80-250/2

End Point ControlPICV

43254466

102154

50357515

1006

Pres. kPa

Flow[%]

Hours[%]

554123025504890

Power W

Total 11827 kWh/year 24%

TPE 80-250/2

Pump Electrical Energy Saving

Variable Flow Systems

System Design For Energy Efficient Pumping

Stephen Hart Managing Director, Frese Limited