Installation manual

IM 178 / Page 9
Table 2. Controls, settings and functions (continued)
SYMBOL DESCRIPTION FUNCTION RESET LOCATION SETTING RANGE DIFFERENTIAL PART NO.
SPS6 Dirty filter pressure Sensors pressure drop across final filter bank and N/A Final filter section N/A 0–5" w.c. N/A 495450B-05
sensor sends signal to MicroTech controller. (0–1245.4 Pa)
1–6 VDC out
S1 System switch Shuts off entire control circuit (except crankcase N/A Main control box N/A N/A N/A 013550B-00
heaters).
TD9, 19 Part winding start Reduces inrush amp draw on start-up Auto Main control box 1 sec., fixed N/A N/A 282101D-01
timer (fans)
ZNT1, 2, 3 Space temperature Senses space temperature; sends signal to N/A In building space N/A 3K ohms at N/A See IM 483
sensors MicroTech controller. 77°F (25°C)
GAS HEATING CONTROLS AS Blower air switch Proves presence of combustion air. N/A Gas furnace control 0.4" w.c., fixed N/A N/A 330038B-00
section
FD Flame rod Senses pilot flame. N/A Gas burner assembly N/A N/A N/A 365577A-00 FLC Fan control Closes to energize fan when heat exchanger is warm. Auto Gas heating section Closes at 125°F65°F–220°F25°F (14°C) 340821B-00
(52°C) (18°C–104°C) adjustable
Opens at 100°F50°F–205°F
(28°C) (10°C–96°C)
High limit cutout Opens furnace control circuit on temperature rise. Auto Gas heating section Opens at 200°F 100°F–250°F25°F (14°C),
(93°C) fixed
FSG Flame safeguard Proves pilot flame and controls main gas valve. Manual Gas furnce control N/A N/A N/A See IM 684 or 685
section
GV1 Pilot gas valve Opens to allow flow of gas to pilot burner. Normally Gas heating section N/A N/A N/A 344884B-00
closed
GV2, 3 Main gas valves Open to allow flow of gas to main burner. Normally Gas heating section N/A N/A N/A See IM 684 or 685
closed
HL22 Filter high limit control Opens furnace control circuit on temperature rise. Manual Supply air section Opens at 125°F N/A 25°F (14°C), 479388B-01
(52°C) fixed
HL23 Final filter high limit control Opens furnace control circuit on temperature rise. Manual Final filter section Opens at 165°F N/A 25°F (14°C), 479388B-04
(74°C) fixed
HPR High pressure regulator Regulates pressure to main regulator. N/A In gas line before MPR As specified 10"–13" w.c. N/A See parts catalog
(2491–3238 Pa)
HP5 High gas pressure switch Shuts off burner if pressure goes above set point. Manual Gas heating section 8" w.c. (1993 Pa) 5"–35" w.c. 1"–3" w.c. See parts catalog
(1245–8718 Pa) (249–747 Pa)
LP5 Low gas pressure switch Shuts off burner if pressure goes below set point. Auto Gas heating section 4" w.c. (996 Pa) 3"–21" w.c. 1"–3" w.c. See parts catalog
(747–5231 Pa) (249–747 Pa)
ELECTRIC HEATING CONTROLS HL1, 4 & Secondary heater limit Breaks line voltage to heaters if temperatures are too Manual Electric heat section Cutout=210°F N/A N/A 654962B-01 HL11-14 control high. (99°C)
HL31-34 & Primary heater limit control Breaks control voltage to heat contactor if Auto Electric heat section Cutout=175°F N/A 30°F (16°C) 658245B-01
HL41-44 heater temperatures are too high. (79°C) fixed
Cutin=145°F
(63°C)
HS1 Switch (toggle), Shuts off electric control circuit manually. N/A Main control box N/A N/A N/A 237803D-01
electric heat