intelligent system design - madison ashrae · parallel 137.6 18.8 30.6 32.1 219.1 series free...

Intelligent System Design

Justin WiemanChiller Systems EngineerTrane, A Division of Ingersoll-Rand

Member AHRI Systems CommittesASHRAE Member since 2000

When you buy a HVAC System would you rather buy:

Individual HVAC Components An Entire HVAC System

air handlers

controls

chillers

piping

ductwork

Similar components, maybe, likely … Vastly different results!

Building System Solutions with and for customers

air handlers

controls

chillers

piping

ductwork

• First Cost

• Operating Cost

• Comfort

• Indoor Air Quality

• Acoustics

• Carbon Footprint

Design HVAC systems to optimize

the building’s performance“for life”.

Intelligent™ Systems

( )C

45%

B

42%

+D

12%

+A

1%

+1=IPLV

AHRI Conditions

Chilled Water: 54°/44°F (12°/7°C)

Condenser Water: 3 GPM/Ton

D= 25% Load @ 65°F (18°C)

C= 50% Load @ 65°F (18°C)

B= 75% Load @ 75°F (24°C)

A= 100% Load @ 85°F (30°C)

For example: Evaluate Real Chiller EfficiencyUsing IPLV or NPLV as a simple payback tool

1%@ 85°F

57%@ 65°F

57%@ 65°F

IPLV/NPLV – is it good or bad? … NEITHER; it is just a rating point

Simple Comparative Tool?

is simply WRONG!

How do the chillers in

your plant run?

Efficiency Calculations Index Rating vs. Real-World (because every project is unique)

1IPLV =

1%

A42%

B

12%

D+ ++

45%

C

Efficiency ComparisonIPLV/NPLV – Good or Bad?

IPLV (along with FULL load efficiency) is *good* for

determining minimum efficiency requirements such as in

ASHRAE Standard 90.1:

► Full load performance determines peak energy consumption, impacting

utility demand charges and ratchets

► Part load performance reduces energy consumption as the load and lift

decrease

IPLV is *bad* for:

► Energy analysis

► Accurately representing a chiller’s system energy use

► Indicating a financial payback

► Comparing VSD to non-VSD chillers

ASHRAE Journal December 2009

IPLV is Neither Good nor Bad. It is a Rating Point.

Efficiency Comparison

• Real Payback Require Real Analysis

TRACE 700

Chiller Plant

Analyzer

System

Analyzer

Building Energy

Analysis Tool

EnergyPlus

Integrated

Environmental

Solutions

Design tools available for accurate prediction.

Trane myPLV™Accurately Predicting Your Future

Chiller Part Load Performance

myPLV™

IPLV myPLV

Weather

Weighted average of 29 cities across the U.S.A,

represented 80% of chiller sales from 1967 to

1992.

Customized to your location (Global)

Building TypeWeighted average of all types based on a DOE

study 1992.

Closely matched building type capabilities(building use, chiller plant design)

Operation

Hours

Weighted average of various operations

with chiller plants only, taken from the DOE study

1992and BOMA study 1995.

Operational hours calculated

SystemsWeighted average of systems with and without

some form of economizer included.

Selectable number of chillers

condenser control strategy customizable

Assumptions Comparison

Performance is calculated based on national averages

myPLV™

• Because every project is unique

Accurate performance based on unique project needs!

• Performance value calculated

based on specific project

• Installation location

• Building type

• Operation conditions

• Chiller plant design

• Excel based

• Industry validated data

• Vendor agnostic

Real Life Example myPLV™ Approach

Real world

conditions for real

world buildings

Real Life Example myPLV™ Approach

Real world

conditions for real

world buildings

Approximate

Savings

Centrifugal

Chiller

= $3,155

Real Life

Example

myPLV™

Accurate

Estimate

Financial Payback

Calculation Made Easy

Why the Customer’s Like Low Condenser Flow

• System efficiency increases• Chiller works harder but is most efficient piece of equipment

• Lower flow equals less pumping energy and reduced pressure drops

• Pumps get smaller, so less horsepower

• Cooling towers get more efficient with smaller fans

• Cost of the job is reduced• Equipment costs go down

• Trane CTV stays about the same price or even cheaper

• Cooling towers are sized on flow, smaller with less gpm

• Pumps are smaller

• Pipe size is reduced

• Contractor costs go down

• A smaller cooling tower may require smaller concrete pad and footprint

• Labor to install smaller piping will be cheaper

• Outside sound levels are reduced• Smaller cooling towers generate lower dBA’s

• Additional capacity out of existing equipment

Quick Reference for Efficient Chiller Design

Tools available to help you

Cooling Tower Selection

Cooling tower cost can be reduced with lower condenser flow!

Low Condenser Flow - SummaryEfficiency

• 3 gpm/ton

• Chiller = 0.600 kw/ton

• Tower = 40 hp/500 tons = 0.060 kw/ton

• Cond pump = (1500 gpm * 20’ / 4000) / 500 tons = 0.015 kw/ton

• Evap Pump = (1000 gpm * 18’ / 4000) / 500 tons = 0.009 kw/ton

Total kw/ton = 0.684 kw/ton

• 2 gpm/ton

• Chiller = 0.620 kw/ton

• Tower = 20 hp/500 tons = 0.030 kw/ton

• Cond pump = (1000 gpm * 20’ / 4000) / 500 tons = 0.010 kw/ton

• Evap Pump = (1000 gpm * 18’ / 4000) / 500 tons = 0.009 kw/ton

Total kw/ton = 0.669 kw/ton

That’s a saving of 0.015 kw/ton (2.2%) and the installed cost is less!

myPLV version 3 - Condenser Flow Optimizer

Series-Counter Flow

Series-Counter Flow Questions

Efficient Chilled Water System - Maximized

What Delta Ts are needed?

What Temperatures are needed

How does it benefit energy performance?

Chilled Water Design Parameters

ASHRAE GreenGuide guidance

on parallel plants

Chilled water

12°F to 20°F ΔT

2.0 to 1.2 gpm/tonCondenser water

12°F to 18°F ΔT

2.5 to 1.6 gpm/ton

Series-Counter Flow

chiller plants

Chilled water

16°F to 22°F ΔT

1.5 to 1.1 gpm/tonCondenser water

15°F to 18°F ΔT

2.0 to 1.6 gpm/ton

What Temperatures Required

Remember the Rule of 2 to 1

For a given coil, a 1 degree increase in return water temperature requires a

supply temperature 2 degrees cooler

• Coil originally sized for 44/54 with a 10 degree delta T requires:

– 42 degree water for 13 degree delta T

– 40 degree water for 16 degree delta T

– 38 degree water for 19 degree delta T

• Low Flow Benefits

– Reduced pumping energy

– More tons out of the distribution pipes

Parallel-Parallel Chillers

55°F 37°F

98.9 o F

37 oF

62.9 o F Equal lift

CHILLED

WATER

RETURN

CHILLED

WATER

SUPPLY

55°F 37°F

37 oF

62.9 o F

85°F98.9°F85°F98.9°F

Series-Parallel Chillers

CHILLED

WATER

RETURN

CHILLED

WATER

SUPPLY

98.9 o F

37 oF

45.1 oF

53.8 o F

62.9 o F

85°F

Reduced lift = increased savings

55°F 37°F45.1°F

98.9°F 98.9°F

6% Reduction

Series-Series Chillers or Series-Counterflow Chillers

CHILLED

WATER

RETURN

CHILLED

WATER

SUPPLY

55°F 37°F

98.9 o F

37 oF

45.1°F

45.1 oF

54.8 o F

54.3 o F

85°F98.9°F 91.3°F

91.3 o F

Further Reduced lift = MORE savings!!

13% Reduction

Series-Series-Series Chillersor Series-Series-Counterflow Chillers

CHILLED

WATER

RETURN

CHILLED

WATER

SUPPLY

55°F37°F45.1°F

85°F98.9°F 91.3°F

EVEN Further Reduced lift = EVEN MORE savings!!

95.1°F 88.1°F

50.0°F 41.0°F

95.1 o F

45.1 oF

50oF

98.9 o F

50 oF

91.3 o F

41 oF

88.1 o F

37 oF

50oF

51oF

48.9oF

19% Reduction

Arrangement Pumps

Cooling

Tower

(kW)

Evap Condenser CH

(kW)

Chilled

Water

(kW)

Condense

r Water

(kW)

Total

Plant

(kW)

Paralle

l

Parallel 6,489 14 18 480 7,001

Series Parallel 5,827 60 18 480 6,385

Serie

s

Series Counterflo

w

Duplexes

5224 60 126 480 5890

Comparison of Power Requirements

Series-Series-Series Chillers70% load ~constant speed pump

CHILLED

WATER

RETURN

CHILLED

WATER

SUPPLY

49.6°F37°F42.7°F

85°F94.7°F 89.4°F

EVEN Further Reduced lift = EVEN MORE savings!!

92.0°F 87.1°F

46.1°F 39.8°F

92.0 o F

42.7 oF

49.3oF

94.7 o F

46.1oF

89.4 o F

39.8 oF

87.1 o F

37 oF

49.6oF

50.1oF

48.6oF

Series-Series-Series Chillers70% load ~Variable Primary Flow

CHILLED

WATER

RETURN

CHILLED

WATER

SUPPLY

55°F37°F45.1°F

EVEN Further Reduced lift = EVEN MORE savings!!

50.0°F 41.0°F

91.9 o F

45.1 oF

46.8oF

94.5 o F

50 oF

89.4 o F

41 oF

87.1 o F

37 oF

48.4oF

50.1oF

44.5oF

4% Reduction

85°F94.5°F 89.4°F91.9°F 87.1°F

Free CoolingRefrigerant Migration or a Plate Frame

Base Design

Design Requirements

• 1400 ton building load

• 42/60 evap

• 85/2 gpm/ton cond

• VFDs

• N+1

Base DesignParallel-Parallel Chillers (identical)

60°F 42°F

CHILLED

WATER

RETURN

CHILLED

WATER

SUPPLY

60°F 42°F

85°F

98.9°F

85°F98.9°F

CHILLED

WATER

RETURN

CHILLED

WATER

SUPPLY

60°F 42°F

85°F

98.9°F

930 gpm

930 gpm

930 gpm

3 – 700 ton VFD chillers

Alternate Design

Configuration

• Qty 2 – 700 ton VFD chillers• 42/60 and 42/51 evap

• 85/1500 gpmT cond

• Qty 1 – 700 ton non VFD redundant chiller

• Free Cooling equipped

• 42/60 and 51/60 evap

• 85 / 1500 gpmT cond

• Series configuration

CHILLED

WATER

RETURN

CHILLED

WATER

SUPPLY

85°F

Free Cooling with No VFD (same price)

60°F 42°F51°F

111.7°F

98.2°F

60°F 42°F

98.9°F

85°F

CHILLED

WATER

RETURN

CHILLED

WATER

SUPPLY

Free Cooling DesignSeries-Counter-flow (free-cooling upstream)

930 gpm

1857 gpm

Off Design Condition

Building Loads

• 550 ton building load

• 38 WB

• 45°F Tower water available at max

airflow

Base DesignParallel-Parallel Chillers (identical)

60°F 42°F

CHILLED

WATER

RETURN

CHILLED

WATER

SUPPLY

60°F 42°F

52°F61.4°F

CHILLED

WATER

RETURN

CHILLED

WATER

SUPPLY

60°F 42°F0 gpm

0 gpm

730 gpm

3 – 700 ton VFD chillers

550

tons

CHILLED

WATER

RETURN

CHILLED

WATER

SUPPLY

Reverse Flow to Parallel in Free Cooling

Mode

60°F 42°F52°F

60°F 42°F

98.9°F

85°F

CHILLED

WATER

RETURN

CHILLED

WATER

SUPPLY

Free Cooling DesignSeries-Counter-flow (free cooling upstream)

0 gpm

730 gpm730 gpm

45°F 49.9°F

49.9°F

57°F

Bypass300gpm

300

tons250

tons

Arrangement Pumps

Cooling

Tower

(kW)

Evap Condenser CH

(kW)

Chilled

Water

(kW)

Condense

r Water

(kW)

Total

Plant

(kW)

Paralle

l

Parallel 137.6 18.8 30.6 32.1 219.1

SeriesFree

Cooling

Series* 65.3 19.3 36.15 37.4 158.2

Comparison of Power RequirementsOff Design

*Counter-flow during mechanical cooling mode, but flow is reverse and thus “in-line flow” during free-cooling mode.

28% Reduction in Energy Usage

Justin Wiemanjwieman@trane.com

Thank you for your time and attention!