Electric Heating Sequence Of Operations; Dehumidification Sequence In Normal And Alternate Mode; Reheat Operation Piping Schematic - Circuit #1 Shown - York ZR Series Installation Manual

R-410a w/smart equipment, 6-1/2 - 12-1/2 ton, 60 hertz

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Table of Contents

Closed

Solenoid

Valve

(SOL 1)

Accumulator

Figure 32: Reheat operation piping schematic - circuit #1 shown

Alternate mode

When the Unit Control Board (UCB) detects a need for

dehumidification via the field installed return/space humidity

sensor and there is not a call for cooling, the UCB energizes

SOL 3, SOL 2, and de-energizes SOL 1. (In the ZR150, SOL 4

is only energized when the discharge pressure in circuit #1

rises above 400 psig and de-energizes SOL 4 after the

discharge pressure falls below 320 psig). The unit then

operates with circuit #1 in reheat mode and circuit #2 in cooling

mode.

When there is a call for first stage cooling while there is still a

call for dehumidification, no operational change is made. The

call for cooling is ignored and the unit continues to operate with

circuit #1 in reheat mode and circuit #2 in cooling mode.

When there is a call for second stage cooling, the UCB de-

energizes the HGR, which de-energizes SOL 3 and SOL 2, and

energizes SOL 1. Both circuits now operate in the cooling

mode.

The indoor blower operation is always initiated upon a call for

first stage cooling, second stage cooling or dehumidification

(HGRH). The unit does not operate in the reheat mode if there

is any call for heating or two stage cooling.

On units with economizers, the unit will not operate in the

reheat mode if there is a call for cooling and the economizer is

operating as first stage of cooling. All safety devices function as

previously described.

Johnson Controls Ducted Systems

Evaporator

Airflow

Coil

Reheat

Coil

Refrigerant Flow

Reheat Valve

(SOL 3)

Compressor

Open

Solenoid Valve

(SOL 2)

Condenser

Check

TXV

Valve

Check

Valve

Table 25: Dehumidification sequence in normal and

alternate mode

Request

Dehumidification

One stage of cooling (Y1)

Two stages of cooling (Y2)

Optional Aux mode

The Aux mode available with hot gas reheat units introduces an

operating mode that considers the dry bulb temperature in the

space when choosing hot gas reheat staging. The Aux mode

reduces the amount of over cooling while maintaining humidity

control in the space. The Aux mode is only applicable when the

unit is setup in the Alternate reheat mode.

If there is a call for dehumidification and no call for cooling the

unit automatically reverts back to the Normal hot gas reheat

mode only allowing refrigerant stage one to run in reheat mode

and refrigerant stage two remains off.

If there is a call for dehumidification and a call for cooling the

unit remains in the Alternate hot gas reheat mode allowing

refrigerant stage one to run in hot gas reheat or

dehumidification mode and refrigerant stage two runs in

cooling.