COMMERCIAL HVAC PACKAGED EQUIPMENT Split...

Copyright © Carrier Corp. 2005

COMMERCIAL HVACPACKAGED EQUIPMENT

Split Systems

Technical Development Program

PRESENTED BY:

Ray Chow

Sigler


Section 7 Summary

Section 6 Installation

Section 5 Controls

Section 4 Accessories

Section 3 System Components

Section 2 System Basics

Section 1 Introduction

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SECTION 1

Introduction

SPLIT SYSTEMS


Objectives• Identify applications that utilize

the strengths of split systems

• Identify the components of split systems

• Understand the impact codes have onsystem application and selection

• Compare the differences in outdoorand indoor unit types

• Understand key installation issues

Section 1 – Introduction


Split Systems Components


Condensing Unit

Indoor UnitAHU (Fan Coil)

Indoor UnitFurnace And Coil


Split Systems

• Residential to large commercial

• ¾ to 120+ tons

• Applications– Cooling only– Cooling with heat– Heat pump– Furnace with coil

• Utilize packaged products in an applied manner



• ARI has categories for air, evaporative or water-cooled• Plus 4 ARI heat pump categories (not shown)

• 5 ARI cooling split system categories

ARI System Classification

FanEvapCompCond

Single Package

Split Systems


FanEvapComp

Cond+

RemoteCondenser

Cond+Fan

EvapHeat

Comp

Year RoundRemote Condenser

EvapCompCond+

Condensing Unitwith Coil

EvapCompCond+

Fan

Condensing Unitwith Coil + Fan

Cond+EvapHeat Comp

Fan

Year Round Condensing Unitwith Coil + Fan


SECTION 2

System Basics

SPLIT SYSTEMS


Liquid LineWarm-Temp., High-Pressure Liquid

Suction LineLow-Temp., Low-Pressure Vapor

FilterDrier

Indoor Unit

Outdoor Unit

Split System Basics

SightGlass

Liquid LineSolenoid Valve

Section 2 – System Basics


Why Use a Split System?

Flexibility• Aesthetics

• Duct design

• Performance

• Zoning



• Mix and match indoor and outdoor units

• Closely match load requirements

• Use only manufacturer’sapproved combinations

Flexibility

10-ton condensing unit12½-ton AHU

10-ton AHU

OR



Residential & Duct Free Systems



Condensing units include:• Controls

• Compressors

• Condenser Coil

Condensing Units



Typical Condensing Units



Typical Indoor Unit

Cased Evaporator Coils Packaged AHU

Central Station AHU



Heat Pump System

Outdoor Unit• Condenser in cooling• Evaporator in heating

Indoor Unit• Evaporator in cooling• Condenser in heating



Refrigerant Circuits

Single Circuit

Dual Circuit



Indoor Unit – Refrigerant Circuits


Single Circuit

TXV

LIQUIDLINE

Distributor

LIQUIDLINE

TXV

Filter Drier

Solenoid

Distributor

Dual Circuit


ARI Standards


Standard #

210/240

340/360

365

Applies to

Unitary Air Conditioners

Air Source UnitaryHeat Pumps (Air-Cooled)

Unitary Air Conditioners

Air Source UnitaryHeat Pumps (Air-Cooled)

Air ConditioningCondensing Units

Capacity Range

<65,000 Btuh

<65,000 Btuh

65,000 to <250,000 Btuh

65,000 to <250,000 Btuh

>135,000 to <250,000 Btuh


EER

)()(

WattsInputPowerTotalBtuhCapacityEER =

11.2EER25.9290EER

kW3.1)(22.8MBtuh290EER

(Watts)InputPowerTotal(Btuh)CapacityEER

=

=

+=

=

Example 25-ton condensing unit @ ARI conditions



Net vs. Gross Capacity

HeatIFMCapacityGrossCapacityNet

InputPowerTotal(Btuh)CapacityNetEERSystem

-=

=



BHP Required

Interpolate to derive bhp for 0.44 in. wg

bhp @ 0.44 in. wg = 4.00 bhp

AHU Size Airflowcfm

External Static Pressure (in. wg)0.0 0.2 0.4 0.6

rpm bhp rpm bhp rpm bhp rpm bhp028 10,000 615 3.12 641 3.36 692 3.87 743 4.41



Btuh274,12Watts

Btuh3.414Watts3,595

Watts3,595HeatIFM

0.83746)(4.00HeatIFM

EfficiencyMotor746)(bhpHeatIFM

=*

=

*=

*=

IFM Heat



Net Capacity

Net Capacity = Gross Capacity – IFM Heat

Net Capacity = 294 – IFM Heat

Net Capacity = 282 MBtuh



Total Power Input

Now calculate Total Power Inputusing data from previous slides

( )EfficiencyMotor

746bhpmotorperpowerOFM *=


kW29.5InputPowerTotalkW3.1kW3.6kW22.8InputPowerTotal

powerODFpowerIFMpowerCompressorInputPowerTotal

=++=

++=


9.6EERSystem

kW29.5MBtuh282EERSystem

InputPowerTotalCapacityCoolingNetEERSystem

=

=

=

System EER

System EER for the 25-ton example system:



SEER

Applies to:– Single phase power only– Capacity less than 60 MBtuh

Calculated at three conditions and cycle test:– 80/67° F return air, 95° F outdoor air– 80/67° F return air, 82° F outdoor air– 80/57° F return air, 82° F outdoor air– 80/57° F cycle test, 82° F outdoor air

Requires laboratory testing and is not calculated in the field.



FOR ALL 3 Æ AND WATER-COOLED UNITS ANDAIR-COOLED UNITS ABOVE 60 MBH CAPACITY

• Evaluate equipment efficiency at less than full capacity

• Applicable only to equipment withmore than one stage of capacity

• Weighted average of EERat each capacity step

• Equipment with greater number of capacity steps can moreclosely match the load requirements of the space

• Unless equipment is always operated at 100%capacity, a higher IPLV is preferred

IPLV


PARTLOADFACTORCURVE


Coefficient of Performance

• Applies to heat pumps that operate on 3-phase power only

• Measures efficiency while operating in the heating mode

• A higher COP indicates a more efficient heat pump

)()(

WattsInputPowerTotalWattsCapacityNetCOP =



HSPF:• Applies to heat pumps that operate on single phase power

and have a cooling capacity of < 5.5 tons only

• Is similar to SEER in that it measures the seasonallyadjusted efficiency of a heat pump

• Accounts for defrost and required electric heat

• A higher HSPF is a more efficient heat pump

Heating Seasonal Performance Factor



Energy Codes


Many codes rely on ASHRAE 90.1 thatsets minimum efficiency requirements.

Air-Cooled Split System Requirements• Performance requirements

< 65,000 Btuh 10.0 SEER 1Ø≥ 65,000 – < 135,000 Btuh 10.3 EER≥ 135,000 – < 240,000 Btuh 9.7 EER≥ 240,000 – < 760,000 Btuh 9.5 EER / 9.7 IPLV≥ 760,000 Btuh 9.2 EER / 9.4 IPLV

• Control requirements• Motor hp limits• Economizer requirements• Heat pump requirements


IAQ and Sustainability


• IAQ – ASHRAE 62– Limits maximum humidity to less than 65%– Indoor unit condensate control– Indoor unit ventilation capability

• Sustainable Design – LEED™– Require meeting ASHRAE 90.1 efficiency

and ASHRAE 62 IAQ features– Optimized energy performance and IAQ

Split System mix and matches providebetter humidity control and flexibility

to meet these requirements


SECTION 3

System Components

SPLIT SYSTEMS


Rules of Thumb

Section 3 – System Components

Rules of Thumb are considered to be guidelines only• Airflow:

- 400 cfm per nominal ton- Range of 300 to 500 cfm per ton- Today, 350 cfm per ton may be more

appropriate• Mix and Match:

- Nominal and one size up,sometimes one size down,others depend (consult the manufacturer)

• Line Length:- Keep them at 100 ft or less


Operating LimitsCooling only equipment:Maximum outdoor air temperatureMinimum return air temperatureMaximum return air temperatureSaturated suction temperature rangeMaximum discharge superheatMinimum discharge superheat

Typical saturated suction temperature rangefor air conditioning duty is 40 to 50° F

Heat Pumps:Maximum outdoor air operating temperature in heatingMinimum outdoor air operating temperature in heating

115° F55° F95° F

25 to 55° F275° F60° F

75° F–20° F



Outdoor Units

Residential1½ to 5 ton

Duct Free¾ to 5 ton

Commercial6 to 100+ ton



Semi-Hermetic Compressor

• Repairable

• CapacityControl


CylinderUnloader


Multiple Compressors

Dual Semi-HermeticReciprocating

Dual Scroll



Multiple Condensing Units

Dual Circuit Indoor Unit

1st Stage Condensing Unit

2nd Stage Condensing Unit



Hot Gas Bypass

• Protects system in low load conditions• Prevents coil icing• Injects hot gas at indoor unit• Activates at minimum step of cooling only

Condenser

Evaporator

LiquidSolenoid

Valve

Hot GasSolenoid

Valve

Compressor

DischargeBypass Valve

Filter Drier

SightGlass

TXV



Alternative Condensing Unit SolutionsWater-Cooled

Condensing Unit

To indoor coil

Compressor

From indoor coil

Triple-Split

Condenser



Heat Pump System

Heating Mode

Accumulator

Compressor

4-WayValve

Bi-flowFilter Drier

OU

TDO

OR

CO

IL IND

OO

RC

OIL

Accurator

TXV with bypassCheck Valves


Bi-flowTXV


Cooling Mode

Heat Pump System

Accumulator

Compressor

4-WayValve

FilterDrier

OU

TDO

OR

CO

IL IND

OO

RC

OIL

Accurator

Bi-flowTXV

Check Valves


TXV with bypass

Bi-flowFilter Drier


Indoor Unit – Air Handler

6 to 30 ton Packaged AHUwith limited options

Central Station AHU



IAQ Features

• Double-Wall

• Dual-Density Insulation

• Foil-Face Insulation

• UV-c Lamps

Double-Wall


UV-cLamps


Constant Volume AHU

• Variable pitch pulleyis set at required airflowat first unit start-up

• Fan then operates ata constant speed



VAV Application

VAV Terminal

Inlet Guide VanesVFD

COIL

MOTOR

SUPPLYFAN



VAV Requirements

Indoor Unit• At least two circuits• Equipped with capacity control valve(s)

LIQUIDLINE

FilterDrier

CapacityControl

Solenoid TXVDistributor

SightGlass



VAV Requirements

Outdoor Unit• Multiple stages of capacity

• Electric control of capacity stages

• Suction line accumulators

• Interface with VAV controller



VAV Controller

• Typically controls discharge air temperature

• Controls:– Compressors– Stages of capacity– Fans



Cased Evaporator Coils

Installed in duct“A” coil design, installed

on twinned furnaces



Residential Coils

Cased Uncased



SECTION 4

Accessories

SPLIT SYSTEMS


Economizer

• “Free Cooling”

• Control types– Dry bulb– Enthalpy– Differential enthalpy– CO2

• Demand controlledventilation (DCV)

Return air

Outdoor air

Section 4 – Accessories


Heating AccessoriesHot Water or

Steam Coil onPackaged AHU

Electric HeatAccessory onPackaged AHU



Furnaces

Horizontal Furnace

Twinned Furnaces


with downstreamcooling coil


Accessories

Plenum

Return AirGrille

Subbase

CondensateDrain



SECTION 5

Controls

SPLIT SYSTEMS


Controls - ThermostatSimple control requirements:

• Indoor fan

• Outdoor fan(s)

• Compressor(s)

• Liquid line solenoid

Section 5 – Controls


• Y2 initiates 2nd stage cooling

Two-Stage Thermostat• Y1 initiates 1st stage cooling



Capacity Control Solenoid Valve


• Y2 opens the liquid linesolenoid valve

• Y1 initiates 1st stage coolingAND opens the liquid linesolenoid valve


DDC Control


User Interface


SafetiesOutdoor Unit

– High-pressure switch

– Low-pressure switch

– Discharge gasthermostat

– Oil pressure switch

– Cycle protection

– Compressor over-temperature protection

– Circuit breakers


Indoor Unit–Motor protection

–Airflow switch


Low Ambient Control

• Proper operation of expansion device at low outdoor temps

• Minimum outdoor air operating temperature

• Maintain minimum SCT

• Low ambient controller – OFM motor controller

MINIMUM OUTDOOR-AIR OPERATINGTEMPERATURE

UNIT38AR

CONDTEMP

(F)

MINIMUMOUTDOOR TEMP

(F)

Std.With

Motormaster®Control

Z007Z008Z012

808080

353535

-20S012 80

803535

D012 80 35


Motormaster® Control


Fan Cycling Pressure Switch

• Turn off #2 OFM motorwhen SCT falls too low

• DO NOT cycle #1 OFM motor on/off becausea speed control device is required

OFM Motor

Intermediate SeasonSCT Control Device

#2 #1



Wind BafflesWind baffles may be required in areas ofsustained high winds, at least onthe windward side.


WINDBAFFLE


SECTION 6

Installation

SPLIT SYSTEMS


Power SupplyMinimum Circuit Ampacity (MCA)

determines required wire size

MCA = (1.25 * Current of largest motor)+ Sum of all other loads

MCA of a condensing unit = (1.25 * RLA of compressor)+ (FLA of OFM motors+ Control amps)

MCA of indoor unit with electric heat = (1.25 * FLA of largest motor)+ (1.25 * FLA of electric heater)+ Sum of all other loads

Section 6 – Installation


MOCPDefines MAXIMUM size ofovercurrent protective device

A smaller device may be used, if nuisance trips are not a problem

MOCP = (2.25 * Current of largest motor) + Sum of all other loads

Round down to the next lower standard rating,but not lower than the MCA value



• Fuse or Circuit Breaker

Protective Device


Usage defined by code and availability

• HACR Breaker


CONDENSINGUNIT

Disconnect• Located within “line of sight”

• Field-installed or factory-supplied

• Fused or non-fused


Field-installed disconnect

Factory-installed disconnect

FUSEDDISCONNECTSWITCH


Installation

• Consult manufacturer’s instructions

• Locate indoor and outdoor unitsas close together as possible

• Keep refrigerant pipingas short as possible

• Provide adequate clearancefor service access and airflow



Sound

• Understand sound power (both indoor and outdoor)• Utilize sound reduction accessories when available• Consider the effect of sound when recommending

unit location• Isolate and support refrigerant tubing



ElevationLIQUID LINE – 38AKS012-024 UNITS

UNIT38AKS

MAXALLOW.

LIFT(ft)

LIQUID LINE

Max Allow.Pressure

Drop(psi)

Max Allow.TempLoss(°F)

012014016024

65678287

7 2

NOTE: Data above is for units at 45° F saturatedsuction and 95° F entering air.


LIQUID LIFT


Suction Riser

• Refrigerant velocity insuction riser must behigh enough to entraincompressor oil with therefrigerant

• Double suction riser orreduced diameter risermay be required

• Consult manufacturer’srecommendations



Maximum Length of Refrigerant Piping

• Piping length depends on the application

• Heat pumps – 100 linear feet

• Consult manufacturer’s recommendations



Long Lines Require:1. Liquid line solenoid valve(s)

LONG LINE = 75 LINEAR FEET OR LONGER

Lift vs. Run

Long Line Applications


LIFT

2. Suction line accumulator(s)


SECTION 7

Summary

SPLIT SYSTEMS


Summary

Section 8 – Summary

• Identified applications that utilize thestrengths of split systems

• Identified the components of split systems

• Discussed the impact that codes haveon system application and selection

• Compared the differences inoutdoor and indoor unit types

• Reviewed key installation issues


Work Session 1

Work Session 1

SPLIT SYSTEMS

Work Session 1Multiple-choice questions may have more than one correct answer; identify all correct selections.

1. A typical commercial split system includes _______.

a) an indoor unit only c) an indoor and an out unit

b) a compressor, an indoor fan, an evapora- d) a compressor, an indoor fan, an evapo-tor and condenser as one or more rator and condenser as a packagesections

2. True or False? All commercial split systems are at least dual circuit. __________

3. True or False? Net capacity will always be greater than gross capacity. __________

4. SEER applies to _____

a. units which are cooling and heat single phase units under 65,000 Btuh


Technical Development Program

Thank YouThis completes the presentation.

TDP-634 Split SystemsArtwork from Symbol Library used by permission ofSoftware Toolboxwww.softwaretoolbox.com/symbols

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