AAON RSMZ User Manual

15
RSMZ Technical Guide
SEQUENCE OF OPERATIONS
Modes of Operation
Overview
The RSMZ may be congured to operate as any one of six
possible modules in the control system. This conguration
automatically adjusts depending on the address of each module.
All systems will consist of either three modules or six modules.
RSMZ control is a three or six circuit cooling system with Reheat.
The six circuit system is eectively two, three-circuit systems
operating in parallel. There is some overlap of controls to ensure
that the two systems operate in the same mode.
Modules at addresses 1, 2, 4, and 5 will each control a variable
speed circuit (single Danfoss scroll compressor) and represent
half of the evaporative face. Superheat is controlled by DMQ,
and there is no Reheat.
Modules at addresses 3 and 6 have two tandem xed compressors,
full evaporative face through two parallel evaporators interlaced
with the variable compressor-controlled circuits. Each Evaporator
Superheat is independently controlled by a DMQ. These circuits
also have parallel Reheat with a three-way valve to Control Feed
to the Reheat coils or the condenser. 100% Reheat is possible.
Sequencing depends on the particular operation—Cooling Mode
or Dehumidication Mode.
Modes of Operation
There are three basic modes of operation for this module:
1. O Mode
2. Cooling Mode
3. Dehumidication Mode
When changing modes, the mode will rst be commanded to
RSMZ Module 1 and that module will then share the mode
change with the other RSMZ Modules so that all modules will
operate in the same mode. If RSMZ Module 1 goes o line for any
reason, then DX coil operations will be stopped for the entire unit.
Off (Stop) Mode
During Emergency O Mode, all compressor(s) will immediately
stop, regardless of run time.
During regular O Mode, all compressor(s) will turn o after
they have met their minimum run times. The condenser fan will
then be disabled and condenser fan control output will be set to
0V. The DX staging sequence will stop and the module status
will change to o.
During Off Mode, monitoring continues to provide status
information and alarms remain activated unless otherwise
indicated.
Cooling Mode
During startup of the Cooling Mode, the RSMZ receives
communication from the AAON unit controller to indicate
Cooling Mode which is then used to stage on cooling.
In Cooling Mode, the variable speed compressors are staged on
together. If additional cooling is needed, the compressors on the
tandem circuit will stage on.
Dehumidication Mode
During startup of Dehumidification Mode, the RSMZ
receives communication from the unit controller to indicate
Dehumidication Mode which is used by the compressor staging
sequence.
If the current state is “all compressors are o” for RSMZ Module
3 or 6, dehumidication will begin once the minimum o time
has been met for module 3’s or 6’s rst compressor (E1/F1),
the condenser fan will modulate to the minimum condenser fan
output value. Compressor E1/F1 for module 3 or 6 will then be
enabled.
If the current state is “compressors A, B, C, and D are active”
for modules 1, 2, 4, or 5, the compressors will modulate to the
minimum position, wait for the minimum run time to be met,
and then will turn o. The compressors will then be disabled and
turn o. Once the minimum o time has been met for modules
3 or 6 rst compressor (E1/F1), the condenser fan will modulate
to the minimum condenser fan output value. Compressor E1/F1
for module 3 or 6 will then be enabled.
If the current state is “all VFD”, and E1/F1 are active, module
3 or module 6 will wait for the minimum o time to be met for
module 3 or 6 compressor E2/F2. Compressor E2/F2 will then
be enabled.

AAON RSMZ Specifications

General

Brand	AAON
Model	RSMZ
Category	Control Unit
Language	English