McQuay AAF Installation Manual

Operation Manual

MicroTechTM U nit Ventilator Controller Sequences of Operation

AAF-HermanN elson Classroom Unit Ventilator Model AEQ, AED, Air Sour ce Heat Pump

Program UV1: Air Source Heat Pump with Electric Heat

OM 101-1

Group: Unit V entilator Part No.: 106101201 Date: July 1999

Table of Contents

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

General Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Software ID . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Setpoints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Air Source Heat Pump with Electric Heat . . . . . . . . . . . 3

Description of Operation . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Occupied or Tenant Override Operating Mode . . . . . . 3

Unoccupied Operating Mode . . . . . . . . . . . . . . . . . . . . 4

Emergency Heat Mode . . . . . . . . . . . . . . . . . . . . . . . . 4

Defrost Cycle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Discharge Air Low Limit Control . . . . . . . . . . . . . . . . . 4

Safeties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Sequence Charts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Introduction

This manual describes the sequences of operation for MicroTech controlled AAF-HermanNelson unit ventilators equipped with air source heat pump (ASHP) heating and cooling, and supplemental electric heating. Unit ventilators with this heating and cooling configuration will be AAF-HermanNelson model AED, AEQ.

Regardless of the AAF-HermanNelson model type, the Unit V entilator Controller (UVC) provided with these units uses program UV1***.

For more information on the MicroTech Unit Ventilator Controller, refer to Bulletin No. IM613, “MicroTech Unit Ventilator Controller.”

General Information

Software ID

The Unit Ventilator Controller Software must be compatible with the unit ventilator heating and cooling configuration. The software is identified by a program code and “software model” number printed on a small label attached to the controller. Model AE with ASHP heating and cooling uses program UV1***. The first wild card character defines the UVC communication type as follows: S = stand-alone, M = master / slave, and N = network code. The last two wild card characters denote the software version (numeric) and revision le vel (alphabetical) respectively . Program UV1*** comprises only one software model: MDL00.

Table 1. UVC Setpoints

Setpoint

Description Abbreviation

Occupied cooling setpoint OCS Hardware setpoint Room Setpoint -Ventilation cooling setpoint VCS Software offset (below OCS) Vent Clg Offset 2oF

Setpoints

Most UVC setpoints are either “hardware” or “software” adjustable. Hardware adjustable means there is an on-board potentiometer used for adjustment. Software adjustable means a PC equipped with Monitor software and proper cable connection is required to make an adjustment. Default software adjustable values are shown on the sequence charts. Hardware adjustable values shown on the charts are for example only. Several UVC setpoints are defined by offsets relative to other setpoints. Table 1 summarizes these setpoints and offsets.

Defined By Label

Default

Value

Occupied heating setpoint OHS` Software offset (below OCS) Occ RmT Spt Difl 6oF Unoccupied heating setpoint UHS Hardware offset (below OHS) Unoccupied cooling setpoint UCS Hardware offset (above OCS) Electric heat lockout EHLO Software setpoint OAT EI Ht Lkout 20oF Compressorized cooling lockout CCLO Not adjustable -- 59oF Ventilation cooling lockout VCLO Software setpoint OAT Vent Clg Lkout 64oF Ventilation cooling discharge air low limit VCLL Software setpoint DAT Vent Clg Low 55oF DX cooling discharge air low limit DXLL Software setpoint DAT DX Clg Low 45oF Outdoor air lockout OALO Software setpoint OALO Setpoint 35oF

Unocc Offset --

OM 101-1 / Page 2 (Rev. 7/99)

Air Source H eat Pump with Electric Heat

Description of Operation

Definitions

Control T emperature

In order to maintain more stable room temperature control, the MicroTech Unit Ventilator Controller (UVC) uses the concept of a “Control Temperature.” The Control Temperature is a weighted v alue equal to 19/20 room temperature and 1/20 discharge air temperature.

Setpoint Abbreviations

OCS Occupied cooling setpoint VCS Ventilation cooling setpoint OHS Occupied heating setpoint UHS Unoccupied heating setpoint UCS Unoccupied cooling setpoint VCLO Ventilation cooling outdoor air lockout setpoint EHLO Electric heat outdoor air lockout setpoint VCLL Ventilation cooling discharge air low limit setpoint DXLL DX cooling discharge air low limit setpoint OALO Outdoor air lockout setpoint

Software ID

Program: UV1*** Software Model: MDL00

Occupied or Tenant Override Operating Mode

The supply fan will run continually in the occupied or tenant override operating modes.

When the UVC is first energized it will perform a self-calibration procedure upon the OA damper actuator . The calibr ation procedure will take approximately 5 minutes to perform during which time the supply fan will not operate.

The UVC provides a compressor minimum on time of 2 minutes and a minimum off time of 3 minutes.

If enabled, an outdoor air lockout setpoint has been pro vided to force the OA damper to close when the OA temperature goes below the OALO setpoint (software adjustable). This feature is typically used only on valve control hydronic heat and or hydronic cool units. This feature is disabled by default in UV Model 00.

If provided, the optional ventilation lock out feature can ov erride UVC temperature control and keep the OA damper closed as required.

If provided, the optional exhaust fan output will energize when the OA damper opens and de-energize when the OA damper closes.

If provided, the optional auxiliary heat output will operate a normally open device. The auxiliary output will energize (close the device) when the Control Temperature is abov e the OHS. The auxiliary output will de-energize (open the device) when the Control T emperature is

F below the OHS.

The same UVC output is used for both the auxiliary heat output feature and the exhaust f an output f eature . Therefore , both f eatures cannot be used together.

Note: When switching from unoccupied-to-occupied mode the OA damper will remain closed for the first 5-minutes of occupied operation.

Morning Start

If the space is cool and heating is required, the unit will operate as described in “Heating Operation” belo w. The outdoor air (OA) damper will remain closed until the Control Temperature rises to within 3 of the OHS setpoint. Then it will be opened to minimum position.

If the space is warm and cooling is required, the unit will operate as described in “Cooling Operation” below. If the outdoor air is not suitable for free cooling, the OA damper will remain closed until the Control Temperature falls to within 3

F of the OCS setpoint. Then it

will be opened to minimum position.

Cooling Operation

Certified Drawing

When the Control Temperature is greater than the OHS setpoint and less than the VCS setpoint, the O A damper will be held at its minimum position setpoint (hardware adjustable). As the Control Temperature rises and cooling becomes necessary, the UVC will decide whether the outdoor air is suitable for free cooling by comparing the outdoor air temperature (dry bulb) to the VCLO setpoint.

If the OA temperature is less than or equal to the VCLO setpoint, the economizer will modulate as required to maintain the VCS setpoint (default = 2

F less than OCS). The Control T emper ature will rise if the outdoor air is too warm to satisfy the cooling load. If the OA damper is more than 85% open, mechanical cooling will be energized when the Control Temperature rises to the OCS setpoint.

If the OA temperature is warmer than the VCLO setpoint, mechanical cooling will be energized when the Control Temperature rises to the OCS setpoint. The OA damper will be held to the minimum position setpoint, except when the OA temperature is warmer than the VCLO setpoint and the Control Temperature is 3

F or more above the OCS.

In this unlikely situation, the OA damper will be closed. Once the compressor is energized, the start-to-stop (minimum on)

timer will override normal temperature control maintaining compressor operation for the minimum on time. The compressor will be deenergized when the Control Temperature f alls below the OCS setpoint.

Note: Regardless of the economizer state, its operation is subject to discharge air low limit control.

Note: During normal (non-alarm) operation, the compressor will be disabled if any of the following conditions exist:

• OA temperature less than the CCLO setpoint

• Discharge air temperature less than the DXLL setpoint

• Stop-to-start (minimum off) timer has not expired

• Emergency heat mode active

Heating Operation

When the Control Temperature is greater than the OHS setpoint and less than the VCS setpoint, the OA damper will be held at its minimum position setpoint.

If the Control Temperature f alls to 1

F greater than the OHS setpoint, the reversing valve will be energized in preparation for mechanical (heat pump) heating.

The compressor will be energized when the Control Temperature falls to 1

F below the OHS setpoint. Once the compressor is energized, the start-to-stop (minimum on) timer will override normal temperature control maintaining compressor operation for the minimum on time. The compressor will be de-energized when the Control Temperature rises above the OHS setpoint.

Normally, supplemental electric heat is enabled when the OA temperature drops below the EHLO setpoint. It can also be enabled by the emergency heat, defrost cycle, or “v ent cooling” discharge air low limit functions. If the electric heat is enabled and the Control Temperature drops to 2

F below the OHS setpoint, the two or three (optional) stages of electric heat will be energized as required. A “stage-up” interstage dela y timer (default = 30 seconds) must expire before each subsequent stage is energized. When the Control Temperature rises to 1

F below the OHS setpoint, the electric heat stages will be de-energized using a “stage-down” interstage delay timer (default = 30 seconds).

The OA damper will maintain its minimum position when the Control Temperature is within 3

F of the OHS. If the Control Temperature

falls to 3oF or more below the OHS, the OA damper will be closed. When heating is no longer required and the Control Temperature

rises to 2 energized. Note that in addition to the 1

F above the OHS setpoint, the re v ersing valve will be de-

F offset between the

compressor and reversing v alve de-energization points, a time dela y

OM 101-1 / Page 3 (Rev. 7/99)

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