McQuay RAR47C Installation Manual

Installation and Maintenance Manual IM 835

Enthalpy Energy Recovery Wheel Option

McQuay Applied RoofPak™ Systems Heating and Cooling Units and Rooftop Air Handlers

Type RPR/RFR/RDR 015C-075C, RAR 800C-802C and 47C

Group: Applied Systems Part Number: IM 835 Date: March 2006

Contents

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Arrangements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

System Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Wheel Construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Purge and Pressurization . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Drive Motor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Frost Protection Option . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Variable Speed Frequency Control . . . . . . . . . . . . . . . . . . . . . 4

Alternate Frost Protection Measures . . . . . . . . . . . . . . . . . . . . 4

Startup and Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Prestartup Checks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Servicing Control Panel Components . . . . . . . . . . . . . . . . . . . 6

Replacement Parts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Bearings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Drive Motor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Drive Belts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Seals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Variable Frequency Controller . . . . . . . . . . . . . . . . . . . . . . . . . 6

Wheel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6

Enthalpy Wheel Removal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8

MicroTech II Sequence of Operation . . . . . . . . . . . . . .9

Enthalpy Wheel Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Exhaust Fan Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Energy Recovery Bypass Damper Control . . . . . . . . . . . . . . 11

Typical Wiring Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . .12

Appendix . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13

Power Twister Belt . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

McQuay and MicroTech are registered trademarks of McQuay International.

DesignFlow, Hi-F, Protocol Selectability, RoofPak, SelectTools, SpeedTrol, SuperMod, UltraSeal, and VaneTrol

Microsoft is a registered trademark of Microsoft Corporation.

are trademarks of McQuay International.

Windows is a trademark of Microsoft Corporation.

Introduction

This manual provides installation and maintenance information about the enthalpy energy recovery wheel option (“enthalpy wheel”) featured on the following McQuay Applied RoofPak™ models:

1 RPR/RFR/RDE 015C - 075C Packaged Heating and

Cooling Units

2 RAR 800C - 802C and 47C Rooftop Air Handlers

General installation amd maintenance information on the rest of the unit is found in the following manuals:

• IM 738 for Packaged Heating and Cooling Units

• IM 487 for Rooftop Air Handlers

• IM 696 for MicroTech™ II Controls

• OM 137 for discharge air control for MicroTech II

Controls

• OM 138 for space comfort for MicroTech II Controls

Figure 1: General Layout - (Approximate dimensions which vary with options)

Top

McQuay IM 835 1

Introduction

Arrangements

Three arrangements are offered for the enthalpy wheel:

1 Single enthalpy wheel with economizer and bypass (see

Figure 2). This arrangement is available for all units.

2 Single enthalpy wheel without economizer (100% outdoor

air unit) for airflow up to about 7000 CFM. This

Figure 2: Arrangement #1

OA Filter Rack

arrangement is available on sizes 015 - 040C and 800 802C only.

3 Dual enthalpy wheel without economizer (100% outdoor

air unit) for airflow exceeding about 7000 CFM (see Figure 3). This arrangement is available on sizes 015 040C and 800 - 802C only.

Enthalpy Wheel

Return Air Economizer Dampers

EA Filter Rack

Figure 3: Arrangement #3

OA Hood

OA Filter Rack

Side EA Economizer Dampers

(not shown)

Exhaust Air (EA) (at negative pressure)

OA Dampers

(2) Enthalpy

Wheels

Plenum EA Fan

EA Filter Rack

2 McQuay IM 835

System Description

When a unit is equipped with an optional enthalpy wheel (see Figure 2), ener gy recovery is provided by drawing outside air across half of the enthalpy wheel and drawing exhaust air across the other half. Latent heat and sensible heat are transferred from the hotter and moist exhaust air to the colder and dry outside air during winter conditions. Latent heat and sensible heat are transferred from the hotter and moist outside air to the cooler and dry exhaust air during summer conditions. Energy recovery control consists of starting and stopping an exhaust fan, modulating the speed of the exhaust fan, starting and stopping an enthalpy wheel, optionally controlling the speed of the enthalpy wheel and opening and closing a set of bypass dampers. The outdoor dampers are controlled in the normal manner. For more information, refer to OM 137 or OM 138. Also see “MicroTech II Sequence of Operation” on page 9.

Wheel Construction

Your McQuay enthalpy wheel is delivered completely assembled and ready to run. The wheel is built to provide many years of trouble free service following proper installation and performance of the minimal maintenance requirements.

Definitions

The following are descriptions of various components related to the enthalpy wheel construction (see Figure 4):

Bearing, external - The wheel and bearing rotate on the shaft, no field lubrication is required.

Brush seal - The seal used for both the circumferential seal and the inner seal in the cassettes. They are constructed of nylon brush and configured to seal against the enthalpy wheel band in the case of the circumferential seal, and against the wheel face in the case of the inner seal. These seals are full contact seals, have an integral clip, and they are clipped to the cassette face panel cutout (concumferential) or to the (inner) post.

Latent energy - Latent energy, in the context of enthalpy wheel discussions, is the work done by the wheel to transfer moisture from one air stream to another. Latent work is accompanied by humidity changes in the air streams.

Media - The chemical composite part of the enthalpy wheel which actually performs the latent and sensible exchange.

Outdoor air - The air stream that is brought in from the outside. Outdoor air becomes supply air after going through the enthalpy wheel.

Purge - A small segment of supply air defined by the gap between the inner seal on the outdoor air edge of the center post and the supply air edge of the center post. The purge angle is adjustable. The purge captures the small amount of supply air captive in the enthalpy wheel when the wheel moves from return to supply and routes it to return to minimize cross contamination.

Return air - The air stream that is returned from the building. Return air becomes exhaust air after going through the enthalpy wheel.

Rotor - The part of an enthalpy wheel that performs the energy exchange and consists of the wheel media, hub, spokes and band.

Sensible heat - Sensible energy, in the context of enthalpy wheel discussion, is the work done by the enthalpy wheel to transfer heat from one air stream to another. Sensible work is accompanied by temperature changes in the air stream.

Spoke - Flat metal member used to support the enthalpy wheel radially.

Supply air - The air stream that is supplied to the building space. Supply air is outdoor air that has been run through the enthalpy wheel.

Figure 4: Wheel Construction (Side-by-Side)

Spoke

Hub

Brush Seal

Cassette - The steel structure that houses the rotor. Cassettes

Media

are of punched sheet metal panelized construction. Enthalpy wheel - A generic name for an energy

conservation wheel. The term “enthalpy” refers to an air stream’s total energy (temperature and humidity level).

Exhaust air - The air stream that is exhausted to the outside. Exhaust air is building return air that has been run through the enthalpy wheel.

Heat wheel - Synonymous with an enthalpy wheel, energy conservation wheel, or total energy recovery wheel. Some heat wheels are sensible only wheels and should not be confused with McQuay total energy recovery wheels.

Hub - The center support of an enthalpy wheel.

McQuay IM 835 3

Enthalpy Wheel

(1) Currently, only the Over-Under configuration is offered on McQuay rooftop systems and air handlers.

Side-by-Side Configuration Purge Location

Cassette

Over-Under Configuration Purge Location

Drive Belt

Motor

Sheave

System Description

Purge and Pressurization

Pressurization is critical to minimize crossover from exhaust to supply and to allow the purge to operate.

Figure 5: Purge and Pressurization

Outside Air at Atmospheric Pressure

Any leakage must occur from outside to Exhaust Air due to pressure gradient

Plenum Exhaust Fan draws a negative pressure

Figure 6: Purge Detail

Supply Air

Adjustable Purge (See Detail)

Exhaust Air

NOTE: Maintain the pressure gradient to prevent cross contamination from the Exhaust to Outside Supply Air

Frost Protection Option

During extremely cold winter conditions, exhaust air stream frost formation becomes a possibility. Frost formation will act to plug or reduce air flow but it will not hurt the enthalpy wheel itself.

To circumvent this frost possibility, McQuay offers a factory installed frost protection option (MicroTech II VFD system) that will control the speed of the enthalpy wheel for you (see “Variable Speed Frequency Control” below). The sequence of operation is detailed in “Variable Speed Enthalpy Wheel” on page 9.

Variable Speed Frequency Control

A variable frequency drive is included with the frost protection option and it controls the speed of the enthalpy wheel. The unit has also been programmed for the recommended range of wheel speed operation. Typical wheel speed is 45 RPM, but the programming can allow for wheel speeds above or below 45 RPM. Check all factory settings to make sure they are consistent with the application.

Enthalpy wheel speed will be controlled by exhaust temperature measurement.

Adjust purge in this direction to decrease

OUTSIDE AIR

EXHAUST AIR

capacity and increase purge

Drive Motor

The enthalpy wheel comes standard with a constant speed drive motor which is prewired to turn in the proper direction.

Alternate Frost Protection Measures

If you choose not to have the frost protection option factory installed by McQuay, other frost protection measures must be considered.

Enthalpy wheel speed control functions to limit frost formation by reducing wheel performance to a level where the exhaust air temperature is kept above the dew point. Proper dew point control of exhaust air is determined by using psychrometrics (see Figure 8 on page 9):

1 Locate the winter design return air condition and outdoor

air condition and connect the two points on a psychrometric chart.

2 Determine the dry bulb temperature at which this line

intercepts the saturation curve.

3 Add 2°F and set dew point control at this point and vary

enthalpy wheel speed downward to control at or above this point.

4 Audit performance of the enthalpy wheel during actual

operation. If frost formation is never evident, it may be because design conditions are never reached. In such a case, it may be possible to gradually work dew point control down.

4 McQuay IM 835

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