Carrier 58CTA/CTX instruction manual Orifice Hole

b.Run for 3 minutes in low-heat operation.

c.Measure time (in sec) for gas meter to complete 1 revolu- tion and note reading. The 2 or 5 cubic feet dial provides a more accurate measurement of gas flow.

BURNER

ORIFICE

A93059

Fig. 54 - Orifice Hole

d.Refer to Table 12 for cubic ft. of gas per hr.

e.Multiply gas rate cu ft. /hr by heating value (Btuh/cu ft. ) to obtain input. If clocked rate does not match required input from Step 1, increase manifold pressure to increase input or decrease manifold pressure to decrease input. Repeat steps b through e until correct low heat input is achieved. Re-install low-heat regulator seal cap on gas valve.

5.Set low-heat temperature rise. The furnace must operate within the temperature rise ranges specified on the furnace rating plate. Do not exceed temperature rise ranges spe- cified on unit rating plate for high-and low-heat. Determine the temperature rise as follows:

NOTE: Blower access door must be installed when taking temperature rise reading. Leaving blower access door off will result in incorrect temperature measurements.

!WARNING

ELECTRICAL SHOCK HAZARD

Failure to follow this warning could result in personal injury or death.

Disconnect 115-v electrical power before changing speed tap.

a.Verify unit is running in low heat per Step 3. Place ther- mometers in return and supply ducts as close to furnace as possible. Be sure thermometers do not see radiant heat from heat exchangers. Radiant heat affects temperature rise readings. This practice is particularly important with straight-run ducts.

b.When thermometer readings stabilize, subtract return-air temperature from supply-air temperature to determine air temperature rise.

NOTE: If the temperature rise is outside this range, first check: (1.) Gas input for low heat operation.

(2.) Derate for altitude if applicable.

(3.) Return and supply ducts for excessive restrictions causing static pressures greater than 0.50-in. wc.

58CT

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