Справочник Пользователя для Honeywell L91D

9

60-2152—08

1. Only qualified service technicians should attempt to 

service or repair flame safeguard controls and 

burner systems.

2. Disconnect power supply before cleaning the 

potentiometer windings or wiper, or before replacing 

the controller potentiometer.

All controllers are carefully tested and calibrated at the factory 

under controlled conditions. If the actual operating pressure 

does not match the setpoint, move the main scaleplate slightly 

up or down until the setpoint agrees with the actual pressure.

Keep the cover of the controller in place at all times to protect 

the internal components from dirt, dust, and physical damage. 

Perform routine maintenance occasionally by inspecting and 

blowing or brushing away any accumulated dirt and dust. To 

assure proper functioning of the controller at all times, perform 

an operational check of the entire system during routine 

maintenance checks. Be sure to handle controllers carefully at 

the time of installation, during actual use, and during 

maintenance.

Occasionally, the windings or wiper on the potentiometer (two 

on the L91D) may need cleaning. Disconnect the power supply 

before removing the cover from the controller and before 

cleaning the potentiometer.

Solvent-type electrical contact cleaners can deteriorate plastic 

components and wire insulation and leave an oily residue that 

accumulates particulate matter (dust, etc.). The residue can 

break down to form various carbonaceous substances that 

cause early potentiometer failure.

Use of abrasive materials results in wearing of the 

potentiometer windings and accumulation of particulate matter 

that changes the resistance between the windings and the 

wiper.

1. Disconnect all power to the controller.

2. Loosen the cover screw below the main scaleplate and 

remove the cover.

3. Mark the wires to the external device (motor or valve 

actuator) and disconnect them from the terminal block.

4. Remove the screw holding the terminal block bracket to 

the top of the case (Fig. 8). Put this screw in a safe place 

because it will be needed later.

5. While careful not to damage the potentiometer wiper or 

any of the internal wiring, lift out the terminal block and 

bracket.

6. Before removing any potentiometer wires, carefully note 

and record (sketch) the position (off-center) of the active 

winding on the potentiometer and the location and con-

nections of all wiring terminals. The new potentiometer 

must be inserted and connected the same.

Example: In Fig. 9, the active winding is on the left half of 

the potentiometer; the wire from the left end of the wind-

ing is connected to the (W) terminal on the terminal 

block, and the wire from the right end of the winding is 

connected to the (B) terminal on the terminal block.

7. Loosen the (W) and (B) screws on the terminal block, 

and remove the two wires to the active winding of the 

potentiometer. Leave the wire to the wiper arm intact. 

8. Carefully unscrew the bolt that holds the potentiometer 

to the bracket. Make sure the potentiometer wires do not 

entangle with the wiper and bend it.

9. Carefully slide the old potentiometer off the bolt.

10. Carefully slide the bolt through the new potentiometer. 

Make sure that:

a. The off-center position of the winding on the new 

potentiometer is the same as the old potentiometer. 

(Consult sketch in step 6.)

b. The wiper will contact bare wires. (Rotate the potenti-

ometer on the bolts so the surface of the winding 

where the brown enamel was removed is toward 

you.)

11. Screw the bolt into the potentiometer bracket. Make sure 

the wiper is contacting bare wires (step 10.b); then 

tighten the bolt.

12. Connect the two potentiometer wires to the (W) and (B) 

terminals on the terminal block and tighten the screws. 

Make sure these wires are connected to the same termi-

nals as in the old potentiometer. (Consult sketch in step 

6.)

13. Carefully fit the hole in the bottom of the terminal block 

bracket over the screw protruding upward from the bot-

tom of the case (Fig. 10). Insert the screw (removed in 

step 4) through the hole in the top of the case (Fig. 8) 

and into the top of the bracket, and tighten it.

14. Reconnect the wires from the external device (motor or 

actuator) to the terminal block.

15. Replace the cover and tighten the cover screw. 

16. Reconnect power to the controller.