One condenser head pressure module, Sequence of operation – Orion System One Condenser Head Pressure Module User Manual

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One Condenser Head Pressure Module

Technical Guide

Sequence of Operation

Input Commands (VCM-X Connection)

Condenser On/Off

Instead of a hard wired input signal to the Condenser Enable input,
the VCM-X Modular or VCM-X WSHP Controller communicates
to the Module via E-BUS communications. This signal indicates the
compressor(s) are called to run and drives the Condenser On/Off func-
tion.

Reversing Valve Enable On/Off

As with the Condenser Signal On/Off function, the VCM-X Modular
or VCM-X WSHP Controller communicates to the Module via E-BUS
communications and signals that the reversing valve has been energized
and that heating has been enabled.

NOTE: When the term “ON” is used, it means there is either

24 VAC on the appropriate Binary Input or a call-to-
run signal is being received from the VCM-X Series
Controller or VCM-X E-BUS Series Controller. When
the term “OFF” is used, it means there is either 0 VAC
on the appropriate Binary Input or the call-to-run signal
from the VCM-X Modular Controller or VCM-X WSHP
Controller has been removed.

Sensor Reading Routine

Up to four Head Pressure Sensors can be monitored, but only the highest
reading is used for control. This is because the way the units are physi-
cally designed, the air from the condenser fan fl ows through ALL of the
condenser coils. As a result, if you modulate fans based on the highest
reading, you will have enough airfl ow for all of the condenser coils.

Modes of Operation

OFF Mode

The Head Pressure Control Board is in the OFF Mode when the Con-
denser Input Signal is “OFF”. In this mode, all relays are off, the Analog
Output is 0 VDC for an Air Cooled Condenser or 2 VDC for a Water
Cooled Condenser, and the PWM Output is 0% Duty Cycle.

Cooling Mode

If the Head Pressure Controller has been confi gured for the Reversing
Valve to be energized in the Cooling Mode and to Fail to the Heat Mode
(Dipswitch 4 is set ON), then the Head Pressure Controller will be in
the Cooling Mode when the Condenser Signal input is “ON” and the
Reversing Valve Enable Signal is “ON”. In this circumstance, the Re-
versing Valve Enable Relay Output will energize for indication purposes.

If the Head Pressure Controller has been confi gured for the Reversing
Valve to be energized in the Heating Mode and to Fail to the Cool Mode
(Dipswitch 4 is set OFF), then the Head Pressure Controller will be in
the Cooling Mode when the Condenser Signal input is “ON” and the
Reversing Valve Enable Signal is “OFF”.

The Condenser Enable Relay will energize to enable the Condenser Fan
or Water Valve. In a water system, the Water Flow Valve will start at
75% for 3 minutes. The Condenser Output Signal will then automati-
cally adjust between 0 and 100% to maintain the desired Head Pressure
Setpoint. The Condenser Output Signal can be a 0-10 VDC, 2-10 VDC or
0-100% PWM signal provided by the appropriate output. Both outputs
mirror each other.

Heating Mode

If the Head Pressure Controller has been confi gured for the Reversing
Valve to be energized in the Cooling Mode and to Fail to the Heat Mode
(Dipswitch 4 is set ON), then the Head Pressure Controller will be in
the Heating Mode when the Condenser Signal input is “ON” and the
Reversing Valve Enable Signal is “OFF”.

In this mode, the Condenser Output Signal will go to 100% and remain
there until it leaves the Heating Mode.

NOTE: The Reversing Valve Dipswitch 4 setting determines

whether the Reversing Valve Dipswitch 4 Relay is ON
to Heat / OFF to Cool or ON to Cool / OFF to Heat.

NOTE: The Reversing Valve Enable output is for indication only

and is not wired to anything.