SERVICE INSTRUCTIONS — SAFETY DEVICES
Figure 13
Rear View Propeller Type Unit
Limit Control (Overheat Switch)
The limit control, mounted on the left inner side panel (when
facing front of unit), will shut off the gas supply to the main
burner in the event of overheating. It is a single pole single
throw switch.The contacts open to shut the combination gas
control off in the event the unit should overheat. This limit
control should operate only when something is seriously wrong
with the unit. Anytime this control operates, correct the difficulty
immediately or serious damage may result. If the limit control
cuts off the gas supply during normal operation:
1. See that front louvers are open and that there are not any
obstructions in the air inlet or outlet.
2. Check actual input to unit against rated input.
3. Check to be sure fan motor is operating.
4. On propeller unit check that fan is not loose on motor shaft.
On blower unit check belt and sheave for tightness or
damage.
5. On propeller units check fan speed against speed on motor
nameplate. On blower units check blower speed against
Performance Tables on pages 14 and 15; check for
restrictions in ducts and for dirty filters.
6. Check to make sur the venting system and combustion air
piping is not damaged or blocked. Also check to be sure
unit is venting normally.
7. Clean heat exchanger tubes inside and out if necessary.
8. If items 1-7 do not solve the problem, check limit control
and replace if necessary. The control is accessible by
removing the left outer side panel, held in place by screws
at the rear of the unit.
2
4
PRESSURE SWITCH
SENSING TUBES
PRESSURE
SWITCH
JUNCTION BOX
TERMINAL
BOARD
SIDE PANEL
MOUNTING
SCREWS
GAS SUPPLY
CONNECTION
ACCESS PANEL
SIGHT GLASS
FAN
MOTOR
Heater Parts from ACF Greenhouses
