Also, the setup of some of the key jumpers can actually keep the units from starting up. J12 and J13 jumper positions must be looked at together to determine the exact capabilities or operation of the unit. The different setup configurations are explained to familiarize technicians with the effects on unit operation.
SECTION 2: JUMPERS
TWO-STAGE UNIT JUMPER SETTINGS (J13 & J12): DEFINITIONS
J12 - Y1 POSITION:
This indicates the unit will recognize both Y1 and Y2 signals and operate 1st and 2nd stage based on the thermostat call.
J12 - Y2 POSITION:
This indicates the unit will recognize a Y2 signal only and operate 2nd stage with a Y call from the thermostat.
J13 (HEAT JUMPER) REMOVED:
Y1 signal activates 1st Stage
J13 (HEAT JUMPER) INSTALLED:
Y1 signal activates 1st and 2nd stage (Heating Mode only)
JUMPER POSITIONS AND OPERATION
J13 (HEAT JUMPER) INSTALLED
| Jumper | Position | T-Stat Call | Compressor Amps | Stage |
| J12 | Y/Y2 | Y1 & Y2 | 20.7 | 2 |
| J12 | Y/Y2 | Y1 | 20.7 | 2 |
Unit operates at full capacity without staging because the J13 (Heat Jumper) is installed.
*With an O call for Cooling, the unit will operate at full capacity because the J12 jumper is in the Y/Y2 position.
J13 (HEAT JUMPER) NOT INSTALLED
| Jumper | Position | T-Stat Call | Compressor Amps | Stage |
| J12 | Y1 | Y1 & Y2 | 20.7 | 2 |
| J12 | Y1 | Y1 | 15.2 | 1 |
The unit will not run with J12 jumper in Y/ Y2 position and the J13 (Heat Jumper) removed from pins.
Use of a single stage thermostat means J13 (Heat Jumper) must be in place and the Y call from the thermostat wires into the Y2 terminal.
*The Y/Y2 position means the unit works solely on the Y2 terminal. With only one wire to initiate the Y call, a single stage thermostat’s Y terminal wires into the Y2 terminal on the unit. If a 3 Heat/2 Cool thermostat is used, and by accident the jumper is in the Y/Y2 position, the unit will not recognize the Y1 signal.
J13 (HEAT JUMPER) INSTALLED
| Jumper | Position | T-Stat Call | Compressor Amps | Stage |
| J12 | Y1 | Y1 & Y2 | 20.7 | 2 |
| J12 | Y1 | Y1 | 20.7 | 2 |
Unit operates at full capacity without staging because the J13 (Heat Jumper) is installed.
*With an O call for Cooling, the staging of the unit would not be affected because the J12 jumper is in the Y1 position. 1ST AND 2ND stages will be utilized in cooling.
J13 (HEAT JUMPER) NOT INSTALLED
In order to operate both stages in Heat mode, the J13 (Heat Jumper) must be removed and the J12 jumper in the Y1 position.
In Cooling mode, compressor staging will utilize both stages with or without the J13 (Heat Jumper) installed across both pins.
*Compressor Amperage based on GT060/ H060 operation.
RECOMMENDATIONS:
In order to utilize staging capabilities in both modes, use a 3 Heat/2 Cool thermostat (units w/ Auxiliary Heat) or 2 Heat/2 Cool (units w/out Auxiliary). Place J12 jumper in Y1 position and remove J13 (Heat jumper).
SECTION 3: NOMENCLATURES
FIGURE A: GEOCOMFORT GT SERIES NOMENCLATURE
The eighth digit in your GEOCOMFORT MODEL number will determine whether your unit is a Water-Air Package unit or a Water- Air and Water-Water Combination unit. The Combination unit is signified with a 2 or 3 as the 8th digit (2 = No Desuperheater, 3 = Desuperheater factory installed). The Water-Air only unit is signified with a 0 or 1 as the 8th digit (0 = No Desuperheater, 1 = Desuperheater factory installed).
FIGURE B: HYDRON MODULE H SERIES NOMENCLATURE
The sixth digit in your HYDRON MODEL number will determine whether your unit is a Water-Air Package unit or a Water-Air and Water-Water Combination unit. The Combination unit is signified with a 2 or 3 as the 6th digit (2 = No Desuperheater, 3 = Desuperheater factory installed). The Water-Air only unit is signified with a 0 or 1 as the 6th digit (0 = No Desuperheater, 1 = Desuperheater factory installed).