Installation Instructions

ManualsBrandsGoodman ManualsFurnacesFurnace Twinning Kit

The Furnace Twinning Kit (FTK) provides the means for two gas furnaces

containing an Integrated Ignition control to operate at the same time from a

single thermostat. The two furnaces to be “twinned” must be

exactly the

same model with their circulating air blowers set to deliver the same air flow

at the same time. The furnaces may deliver different CFMs in the cooling

mode, if appropriate. THIS KIT CANNOT BE USED TO CONTROL MORE

THAN TWO (2) FURNACES. When properly installed, these furnaces will

achieve the operational and performance specifications described in the in-

stallation instructions. For items not covered in this manual, follow the instal-

lation instructions shipped with the furnaces.

This Twinning Kit Installation Instruction is divided into five sections. Section

I deals with furnace opening sizes, recommended filter sizes and maximum

CFM per furnace. Section II details the installation of the twinning kit. Sec-

tion III details the sequence of operation. Section IV provides checks and

possible repair procedures. Section V provides a point-to-point wiring dia-

gram.

SECTION 1 GENERAL INFORMATION

It is very important to properly size ductwork and to supply appropriate filters

for your furnaces. There are four possible ductwork configurations for twinning

your furnaces:

• Bottom Return

• Side Return - One Return per Furnace

• Two Side Returns

• Top Return

IMPORTANT NOTE: Back return duct installations to furnaces are NOT per-

mitted. Back return installations constrict airflow which leads to poor perfor-

mance and equipment damage. Back return installations are considered im-

proper installation and will void warranty coverage.

GENERAL NOTES

• Maximum CFMs are limited by a maximum filter velocity of 600 feet per

minute, or by circulator high speed at 0.5 inches External Static Pres-

sure (ESP) (whichever CFM is lower). THIS REQUIRES A HIGH VE-

LOCITY FILTER. THROWAWAY FILTERS MUST NOT BE USED. If us-

ing anything other than a permanent high velocity filter, consult filter

manufacturer recommendations for maximum allowable velocity.

• Actual CFM at the job should be established by carefully setting the

furnace input and measuring the temperature rise. The ESP/CFM Tables

in the furnace specification sheets and installation manuals are based

on side return(s) for a single furnace. For twinned installations - espe-

cially those with bottom return - the relationship between ESP and CFM

may be different. The most accurate way to estimate airflow on twinned

installations is to use temperature rise:

CFM =

BTUH Input

1.085 x (Supply Air Temperature - Return Air Temperature)

• Cooling CFM should be 350 to 450 CFM per nominal ton of cooling

capacity. Heating CFM must produce a temperature rise within the

range(s) specified on the furnace nameplate.

Bottom Return

In most cases, bottom return air to both upflow furnaces will be more

practical. When bottom return air is used, the furnaces should be set as

close together (0 to 3 inches) as is practical. This separation distance is

variable, depending upon the needs of the particular job.

See furnace specification sheet for furnace opening sizes, recommended

filter sizes, and maximum CFM per furnace.

Side Return (One Return per Furnace)

This is applicable only for the upflow models with less than five tons of airflow.

PREFERRED M ETHOD

Place the furnaces close together and install a return air drop to the outside of

each furnace (Figure 1).

Figure 1 - [Preferred Method] Single-Side Return Per Furnace Side

Cutouts are 14" x 23" (All Furnaces)

ALTERNATE M ETHOD

The alternate method is used when the installer is forced to use one return for

two furnaces (Figure 2). The maximum required spacing between the fur-

naces is 30 inches apart (approximately 28 x 24 return trunk duct).

Figure 2 - [Alternate Method] Single-Side Return per Furnace

Side Cutouts are 14" x 23" Furnaces are 30" Apart

NOTE: NOT FOR USE WITH TWO-STAGE VARIABLE SPEED FURNACES OR WITH 2-STAGE CONDENSING UNITS.

NOT FOR USE WITH FURNACES UTILIZING IGNITION CONTROL 50A55-289 (PCBBF112(S).

IO-656B

September 2013

FURNACE TWINNING KIT

INSTALLATION INSTRUCTIONS

WARNING

EACH FURNACE MUST BE EQUIPPED WITH ITS OWN

GAS SHUTOFF VALVE A S REQUIRED BY THE NATIONAL

FUEL GAS CODE.

Summary of content (4 pages)

PAGE 1
FURNACE TWINNING KIT INSTALLATION INSTRUCTIONS NOTE: NOT FOR USE WITH TWO-STAGE VARIABLE SPEED FURNACES OR WITH 2-STAGE CONDENSING UNITS. NOT FOR USE WITH FURNACES UTILIZING IGNITION CONTROL 50A55-289 (PCBBF112(S). WARNING EACH FURNACE MUST BE EQUIPPED WITH ITS OWN GAS SHUTOFF VALVE AS REQUIRED BY THE NATIONAL FUEL GAS CODE. The Furnace Twinning Kit (FTK) provides the means for two gas furnaces containing an Integrated Ignition control to operate at the same time from a single thermostat.
PAGE 2
Two Side Returns Two side returns per furnace is ordinarily used when only 8 or 10 tons of cooling are required and where a bottom return is not practical. The furnaces should be from 24 to 30 inches apart. Two side returns are applicable only for upflow models with five tons of airflow.
PAGE 3
Fan Sensor Wiring Installation Continuous Fan Operation Furnaces that are twinned using this kit cannot be setup for heatingcooling-continuous fan speed operation. Furnace will operate at the same continuous fan speed selected in the furnace control. 1. Route the two wire cable along the same path as the thermostat wiring to the twinning control. 2. Connect the two wires to the corresponding FAN/LED SENSOR INPUTS on the furnace #1 section of the twinning control.
PAGE 4
On the next stage 1 call for heat, furnace #1 is signaled to heat. This sequence alternates on successive cycles balancing run times on the furnaces. SECTION V POINT-TO-POINT WIRING DIAGRAM If a stage 2 (W2) call for heat is received at any time W1 is activated the R-W circuit of the non-firing furnace closes. If both stages energize or deenergize simultaneously, operation is identical to single stage operation above. Two stage cooling is analogous to staged heating but activates the R-Y circuits.