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441 06 1003 02 (10/2001)
PrintedinU.S.A.
Please read these instructions completely before attempting installation.
Twinning Kit NAHA003WK.01
For Use With Furnace Models Using
Honeywell ST9120 and ST 9160 Electronic Fan Controls
Electrical shock hazard/Fire and/or explosion haz-
ard.
Turn off electric power supply at disconnect switch
or service panel before starting installation.
Turn off gas supply at field installed m anual gas
valve before starting installation.
Failure to follow this warning can result in property
damage, personal injury and/or death.
!
Installation or repairs made by unqualified persons
can result in hazards to you and others. In stallation
MUST conform with local building codes o r, in the
absence of local codes, w ith the National Fuel Gas
Code NFPA 54/ANSI A223.1,1990 or latest edition. In
Canada, National Standard CAN/CGA B149--1.
The information contained in this manual is in-
tended for use by a qualified service technician fa-
miliar with proper safety procedures and equipped
with the proper tools and test instruments.
Failure to caref ully read and follow all instructions
in this manual can result in furnace malfunction,
property damage, personal injury and/or death.
!
This twinning kit is intended to permit two identical gas furnacesto
be installedconnected to the sameduct work. Airconditioning can
be added by using one air conditioning evaporator coil sized for
the total air flow capabilities of the two furnaces.
Single and Two Stage Heating
Single or two stage heating is obtainable using twinning kit
NAHA003WK01. Follow the instructions located in the Twinning
Kit Installation section for proper hookup of desired thermostat
staging.
Furnace Installation
Refer to the Installation Instructions packed with the furnaces for
information about clearances, start --up and maintenance, gas
piping and vent installation.
CAUTION
Furnaces installed MUST be identical. They may be
installed on a raised platform or wood floor which
MUST be level. When side return is required, separate
return air drops MUST be made to both furnaces. Do
not use rear of furnace for the return air duct
connection.
CAUTION
Make sure blower motors are wired to operate on the
same speed tap.
CAUTION
Two furnaces must be plumbed with a single supply
gas shut off valve.
NOTE: When twinning kit has been installed, locate the adhesive
backed wiring diagram included in the kit and apply next to the
existing wiring diagrams in the furnaces.
TWINNING KIT INSTALLATION
The twinning kit contains (2) 36” wires of two different colors to
interconnect the electronic fan controls of the two furnaces. For
proper operation, and to avoid damage to the controls, be
sure to match Z1 to Z1 and Z2 to Z2 or C to C and H to H on
each fan control (see Figure 1 and Figure 2). The wires are
color coded to assist with this connection. Each wire is factory
terminated with a special crimped edge connector which will push
into mating connection positions on the edge of the circuit board
on each fan control. The length of these wires can be extended by
cutting and splicing sufficient additional wire to each lead.
An isolation relay is provided to protect the system’s thermostat
from possible overloading due to the combined valve and control
load of the two appliances.