Goodman Mfg GHS8 XIII. Operational Checks, Temperature Rise Measurement, Adjustment Switches

TEMPERATURE RISE

Air temperature rise is the temperature difference between supply and return air. The proper amount of temperature rise is usually obtained when the unit is operated at the rated input with the “as shipped” blower speed. If the correct amount of temperature rise is not obtained, it may be necessary to change the blower speed.

An incorrect temperature rise can cause condensing in or overheating of the heat exchanger. Determine and adjust the temperature rise as follows. The temperature rise must be within the range specified on the rating plate or Product Data Book applicable to your model*.

HEAT EXCHANGER

RADIATION "LINE OF SIGHT"

SUPPLY

AIR

TSUPPLY

RISE = TSUPPLY - TRETURN

TRETURN

RETURN

AIR

Temperature Rise Measurement

1.	Operate furnace with burners firing approximately 15
	minutes. Ensure all registers are open and all duct dampers
	are in their final (fully or partially open) position.
2.	Place thermometers in the return and supply ducts as

To adjust the circulator blower speed, proceed as follows:

1.Turn OFF power to the furnace.

2.Select the heating and cooling blower speeds that match the installation requirements from the airflow table in the Product Data Book applicable to your model.

3.Relocate desired motor leads to the circulator blower heat and cool speed terminals on the integrated control module. (Terminals are identified as HEAT and COOL (hot)). If heating and cooling blower speeds are the same, a jumper wire must be used between the heat and cool terminals. This wire is provided in the literature package.

4.Connect all unused blower motor leads to the “PARK” terminals on the integrated control module. Any leads not connected to the “PARK” terminals must be taped.

5.Turn ON power to furnace.

6.Verify proper temperature rise as outlined in Temperature Rise section.

CIRCULATOR BLOWER FAN TIMING ADJUSTMENT

NOTE: Items in this section refer to the air circulator blower fan, NOT to the induced draft blower. The induced draft blower timing sequence is not adjustable. The circulator blower fan timing is adjustable only on models with optional “heating fan OFF delay” adjustment pins or switches. It is NOT adjustable in any other circumstances.

As shipped, the circulator blower fan will remain on for 90 seconds after the gas valve closes. When a call for cooling occurs, the circulator fan comes on and remains on for 45 seconds after the call for cooling ends. During normal heating operation, the circulator fan will come on approximately 37 seconds after the gas valve opens.

	close to the furnace as possible. Thermometers must not
	be influenced by radiant heat by being able to “see” the
	heat exchanger.
3.	Subtract the return air temperature from the supply air
	temperature to determine the air temperature rise. Allow
	adequate time for thermometer readings to stabilize.
4.	Adjust temperature rise by adjusting the circulator blower
	speed. Increase blower speed to reduce temperature rise.

90

SECOND

DELAY

150

SECOND DELAY

2

1

2

1

120

SECOND DELAY

180

SECOND DELAY

2
1
	NO
2
1
	NO

Decrease blower speed to increase temperature rise.

Refer to the following section for speed changing details.

CIRCULATOR BLOWER SPEED ADJUSTMENT

WARNING

TO AVOID PERSONAL INJURY OR DEATH DUE TO ELECTRICAL SHOCK, TURN OFF POWER TO THE FURNACE BEFORE CHANGING SPEED TAPS.

This furnace is equipped with a PSC circulator blower motor. This blower provides ease in adjusting blower speeds. The Product Data Book applicable to your model provides an airflow table showing the relationship between airflow (CFM) and external static pressure (E.S.P.) and a table for the proper selection of heating and cooling speeds. The cooling blower speed is shipped set on HIGH, and the heating blower speed is set as indicated in the Product Data Book. These blower speeds should be adjusted by the installer to match the installation requirements so as to provide the correct heating temperature rise and the correct cooling CFM.

Switches viewed in an upflow installation.

Adjustment Switches

XIII. OPERATIONAL CHECKS

WARNING

TO AVOID PERSONAL INJURY OR DEATH, DO NOT REMOVE ANY INTERNAL COMPARTMENT COVERS OR ATTEMPT ANY ADJUSTMENT. ELECTRICAL COMPONENTS ARE CONTAINED IN BOTH COMPARTMENTS. CONTACT A QUALIFIED SERVICE AGENT AT ONCE IF AN ABNORMAL FLAME APPEARANCE SHOULD DEVELOP.

BURNER FLAME

The burner flames should be inspected with the burner compartment door installed. Flames should be stable, quiet, soft, and blue (dust may cause orange tips but they must not be yellow). Flames should extend directly outward from the burners without curling, floating, or lifting off. Flames must not impinge on the sides of the heat exchanger firing tubes.

IO-242C 25 05/05