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X-XX UL
INSTALLATION INSTRUCTIONS
Molex® is a registered trademark of Molex Incorporated.
Copyright © 1998 Honeywell Inc. • All Rights Reserved
69-1204
ST7997
Oil Burner Mounted Electric Fan Timer
APPLICATION
The ST7997 Oil Burner Mounted Electric Fan Timer
integrates control of burner and circulator fan operations in
an oil furnace and is the central wiring point for most
electrical components in the furnace. The ST7997 mounts
on a standard four-inch by four-inch junction box typically
located on the oil burner. When used with the R7997
Integrated Oil Primary Controller and Ignitor, it provides
simplified wiring and field serviceability. The basic
purposes of the ST7997 are to monitor the thermostat for
heat, cool and fan demands, run the oil burner primary
control and run a two-speed circulating fan, as required.
The ST7997 also monitors a limit switch string that
energizes the circulating fan when the limit switch opens.
The ST7997 provides electronic air cleaner (EAC) and
humidifier (HUM) terminal connections for field installation
convenience.
SPECIFICATIONS
Electrical
Input Ratings
Supply Voltage:
102 to 132 Vac (120 Vac nominal), 60 Hz.
Supply Current:
100 mA maximum without loads connected to outputs.
20A maximum with loads connected to outputs.
Output Ratings:
Relay Contacts:
Circulator Heat or Cool Blower Speed Rating: 15A Full
Load Amperage (FLA) (0.75 pF)/30A Locked Rotor
Amperage (LRA) (0.5 pF).
NOTE: FLA rating is reduced by EAC load.
EAC:
1A maximum.
Circulator Continuous Blower Speed Rating:
8A FLA (0.75pF)/16A LRA (0.5pF).
Humidifier:
1A maximum.
Limit:
10A maximum.
L1/L2 (Burner):
20A maximum.
Thermostat Current:
Heat Mode: 100 mA (R7997 supplied).
Cool Mode: Cooling contactor load 500 mA maximum
(ST7997 supplied).
Cooling Contactor:
2 VA minimum, 12 VA maximum.
Molex® is a registered trademark of Molex Incorporated.
Fuse:
1A (automotive type ATO).
Delay Timings:
Heat On Delay: 45 or 60 seconds (fixed or field
selectable via DIP switch optional position 3).
Heat Off Delay: 60/100/120/150 seconds (four field
selections via DIP switch positions 1 and 2).
Cool On/Off Delay: 0/0 or 30/30 seconds (fixed).
Delay Timing Tolerances:
±5 seconds or ±20 percent, whichever is greater.
Environmental
Temperature Ranges:
Operating: -40°F (-40°C) to +150°F (66°C).
Storage: -20°F (-29°C) to +150°F (66°C).
Humidity:
90 percent relative humidity at 95°F (35°C),
noncondensing.
Approvals:
Underwriters Laboratories Inc. Component
Recognized: File 353.
Canadian Underwriters Laboratories inc. Component
Recognized: Pending approval.
Mechanical:
Dimensions (Fig. 1):
4-9/32 in. (109 mm) long by 4-1/4 in. (108 mm) wide by
3-27/32 (97 mm) high. See Fig. 1.