Temperature Rise - Intertek MVM97 Series Installation Instructions Manual

Type fsp category iv direct or non direct vent air furnace

Table of Contents

2. While the furnace is operating at high fire rate, time and record one complete revolution of the gas meter dial measuring

the smallest quantity, usually the dial that indicates 1/2 cu. ft. per revolution. You will use this number to calculate

the quantity of gas in cubic ft. if the furnace would consume if it ran steadily for one hour (3600 seconds).

3. If the 1/2 cu. ft. dial was used, multiply your number x 2.

EXAMPLE: If it took 23 seconds to complete one revolution of the 1/2 ft. dial.

This tells us that at this rate, it would take 46 seconds to consume one cu. ft. of gas. 23 x 2 = seonds per cu. ft.

3600 (secs in 1 hour) / 46 = 78

This tells us that in one hour, the furnace would consume 78 cu. ft. of gas.

The typical caloric range for 1 cu. ft. of natural gas is around 1000 BTU. Check with your gas utility, if possible. In this

example, the furnace is consuming 78,000 BTUH.

NOTE: The final manifold pressure cannot vary by more than ± 0.3" w.c. for Natural and + 0.5" for LP from the

specified setting. Consult your local gas supplier if additional input rate adjustment is required.

4. Turn ON gas to and relight all other appliances turned off in step 1. Be certain that all appliances are functioning properly and

that all pilot burners are operating.

EMPERATURE

ISE

Temperature rise must be within the range specified on the unit rating plate. An incorrect temperature rise may result in

condensing in or overheating of the heat exchanger. An airflow and temperature rise table is provided in the Specification

Sheet applicable to your model. Determine and adjust temperature rise as follows:

1. Operate furnace with burners firing for approximately ten 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 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.

Decrease blower speed to increase temperature rise. Refer to Startup Procedure and Adjustment -Circulator Blower

Speeds for speed changing details.