part 2 rtu vfd & economizers -...

Part 1: RTU Refrigeration cycle

Part 2 RTU Controls

Part 2 RTU VFD & Economizers

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Types Of Units Available

• Gas/Electric

• Electric/Electric

• Cooling Only

• Heat Pump

27½ to 50 Tons

Voyager™ Commercial Packaged

Rooftop Units

Odyssey™ Split Systems

Trane Model

0 20 40 60 80 100 120 140 160

Precedent™

Voyager™

Voyager™ III

IntelliPak™

IntelliPak™ II

20 130

90 150

27.5 50

12.5-25

capacity (tons)

3-10

HVAC Rules of Thumb

• Air - 1 CFM/SF

• Cooling (office) – 300/400 SF/Ton

• Cooling (office) 400 CFM/Ton

• Heating 25-35 btuh/sf floor area

• Outside Air – 20 CFM/person

• Toilet/Jan Closet – 10 air changes/hour

Condenser Coil Design

Cycle

Compressor Design

Model ‘K’ Compressor’s

Pre-Intellipak Units

Model ‘E’ Compressor’s

Model ‘R’

Typical Compressor Parts

Fewer parts than traditional reciprocating compressor

New Scroll Design

• Proper rotation of the scroll

compressor must be

established before the

machine is started.

Oil for a scroll • Use only Trane oil!!!!!

• Oil-45 for 3/D Scroll.

• Oil-42 for older Scroll.

•Call parts with you M#

Tandem Compressor Design

Scroll Design

How a Scroll Works

• General

• A 3-D compressor has two

scrolls. The top scroll is fixed

and the bottom scroll orbits.

Each scroll has walls in a spiral

shape that intermesh.

Thermostat

Diffuser

Exhaust

Air

Outside

Air

Supply Fan

Room

Cooling Coil

Return

Air

Heating Coil

Filter

Section

Boiler Pressure Reducing

Device

Compressor

Outside Air

Condenser

Simple HVAC System...

Connects to Controls...

Pump

Cooling Coil

Condenser Fan

Supply Duct

Return Duct

Cycle

Refrigeration Systems Options

Thermal Expansion Valve (TXV)

Dehumidification Option

(3, 4, 5, 7.5, 8.5 &10T)

True Hot Gas Reheat

Refrigeration Controls

High Pressure Control

Frostat (Evaporator Coil)

Crankcase Heaters

Precedent Refrigeration Options

Dehumidification Option • Allows for increased outdoor air ventilation.

Reduce humidity levels while increasing comfort

level in the space.

Cooling can operate without a demand for

dehumidification.

A separate Trane humidity sensor controls the

reheat coil.

The Dehumidification option can be monitored

and controlled through one of Trane’s many ICS

systems.

Precedent Dehumidification

Dehumidification Option

• The dehumidification option works

great on replacement jobs where an

existing building humidity issue

exists.

The ReliaTel™ Options module

controls the dehumidification

option. (Unit flexibility!)

3-way valve is accessible through

the easy access compressor section.

Hot gas reheat coil designed to pivot

to allow for easy access cleaning.

Coil in service position

Dehumidification Option

Coil in service position

Standard Unit Conditions

• Airflow 400 cfm/ton

– minimum 320 cfm/ton

– 450 cfm/ton for Heat Pumps

• 55 deg. F outdoor ambient for cooling

• Entering air 68 deg. F Db, 57 deg. F Wb

Supply Air

DB: 55 WB:__46.7__

Return Air

DB:_70____ WB___57____

Supply CFM

CFM:2250_

Capacity

Unit Rated BTU: ___60,000______

Actual BTU : 59737,5

BTU’s BTU/HR=4.5 x CFM x DELT (BTU/LB)

Tons Capacity/12,000

CFM CFM= AREA x VELOCITY

Area Rectangular Duct A=(L(inches) x W(inches))/144

Area Round Duct (PIE x DI. SQ.) / (4x144)

1 Phase Watts Watts = PF × amp × volt

3 Phase Watts Watts = V avg. x A avg x p.f. x 1.732

EER EER= output cooling energy in BTU/Input electrical energy in Wh

COP COP=Power output/Power input

BTU to Watts 1 BTU = 0.293071 Watts

24.3 btu/lb

18.4 btu/lb

4.5 X 2250 X 5.9=59737.5

Hp. of

Motor

Current - Full-Load (Amperes)

Direct-current Motors Single-phase Motors

115

volt

230

volt

550

volt

110

volt

220

volt

¼ 4.8 2.4

½ 4.5 2.3 7 3.5

¾ 6.5 3.3 1.4 9.4 4.7

1 8.4 4.2 1.7 11 5.5

1 ½ 12.5 6.3 2.6 15.2 7.6

2 16.1 8.3 3.4 20 10

3 23 12.3 5.0 28 14

5 40 19.8 8.2 46 23

7 ½ 58 28.7 12 68 34

10 75 38 16 86 43

15 112 56 23

20 140 74 30

25 185 92 38

30 220 110 45

40 294 146 61

50 364 18 75

60 436 215 90

75 540 268 111

100 357 146

125 443 184

150 220

175

200 295

System Problem (TXV) Suction Pressure Liquid Pressure Superheat Subcooling Amps R/H Control

Refrigerant Overcharge Normal ↑ Normal ↑ ↑ Normal

Refrigerant Undercharge Normal2 /↓ ↓ Normal2 /↑ ↓ ↓ ICE/Normal

Liquid Restriction (Dryer) ↓ ↓ ↑ ↑ ↓ ICE/Poor

Low Evaporator Airflow

(low load)

↓ ↓ Normal4 Normal ↓ ICE/Normal

Dirty Condenser Normal ↑ Normal Normal ↑ Normal

Low Outside Ambient

Temperature Normal4 ↓ Normal4 Normal ↓ Normal

Inefficient Compressor3 ↑ ↓ ↑ ↑ ↓ Poor

TXV Bulb Loose ↑ ↑ ↓ ↓5 ↑ Poor

TXV Bulb Lost Charge ↓ ↓ ↑ ↑ ↓ ICE/Poor

TXV Bulb Poorly Insulated ↑ ↑ ↓ ↓ ↑ Poor

Non-Condensables Normal ↑ Normal4 Normal6 ↑ Poor/Normal

System Problem

(Fixed)

Suction Pressure Liquid Pressure Superheat Subcooling Amps R/H Control

Refrigerant Overcharge ↑ ↑ ↓ ↑ ↑ Poor

Refrigerant Undercharge ↓ ↓ ↑ ↓ ↓ ICE/Poor

Liquid Restriction (Dryer) ↓ ↓ ↑ ↑ ↓ ICE/Poor

Low Evaporator Airflow

(low load) ↓ ↓ ↓ ↓ ↓ ICE/Normal

Dirty Condenser ↑ ↑ ↓ ↓ ↑ Poor

Low Outside Ambient

Temperature ↓ ↓ ↑ ↑ ↓ ICE/Normal

Inefficient Compressor3 ↑ ↓ ↑ ↑ ↓ Poor

Non-Condensables ↑ ↑ ↓ Normal6 ↑ Poor