29
ComPac 9/04-12
Dual Unit Phasing
For applications where one controller operates two units, e.g., the CommStat 3 or LL357D.
The current model, LL357D2, does not require unit phasing. However, if other devices are
connected to the control system, phasing of the air conditioner is required. Earlier models; i.e.,
LL357, LL357A, require the unit to be properly phased.
1. Wire each unit as described in steps 1 through 3 above.
2. Test for proper phasing as follows:
A. Power up the units.
B. Using an AC volt meter set to the 300 volt scale, measure voltage between terminal
L1 on the compressor contactor of unit #1 and terminal L1 on the compressor
contactor of unit #2 If voltage is present, units are wired out of phase and must be
rewired.
C. If units are not in phase, turn off power and reverse the field power leads connected
to the internal circuit breaker on one of the units only.
D. Restore power and retest the phase (step B). When the voltage reads "0", the units
are in phase.
E. Turn off power and proceed.
CommStat 3™ Controller (See Figure 8c)
The CommStat 3™ Controller by Marvair
®
is a solid state control package designed to
operate a fully or partially redundant air conditioning system for a telecommunication cabinet
or shelter. The CommStat 3 Controller is factory programmed with standard industry set
points to facilitate installation. If desired, each of the set points can be quickly and easily
changed in the field by the installer. It can be used with Marvair’s ComPac
®
I or II unique
vertical packaged wall mount air conditioners or Marvair’s environmental control units. See
Commstat 3 Product Data Sheet for installation and programming instructions.
LL357D2 Lead/Lag Controller (See Figure 8b)
The Marvair
®
LL357D2 is a complete control package designed to operate a fully or partially
redundant air conditioning system. It consists of a two-stage heat and two-stage cool
electronic thermostat and a solid state timer. It can be used with either the Marvair ComPac
®
I vertical packaged wall mount air conditioner or our unique ComPac
®
II air conditioner with
built-in economizer. The LL357D2 provides environmental control and the security
demanded by the communication shelter industry for a backup unit. The lead/lag controller
insures equal wear on both air conditioners while allowing the lag unit to assist upon demand.
The LL357D2 is factory wired, tested, and mounted in an enclosure for quick installation.
Refer to the LL357D2 Product Data Sheet for complete installation instructions.
Thermostat/Sub-Base
•
Thermostat Range: 40°F(4°C) to 98°F (37°C)
•
Changeover differential: Adjustable, 3°F to 10°F (1.5°C to 5.6°C) between heating
and cooling. May be set apart for greater separation.
•
Inter-stage differential:
Differential is factory set at 2°(1.1°C) between heating or cooling stages (make and
break points).
Operating differential is approximately 1.9°F (1.1°C) between stages in heating and
cooling.
•
24 Volt Control
