Chromalox CHPES-6A manual Testing Operation Of Sequencer, Optional Equipment For Steam Boilers

OPTIONAL EQUIPMENT FOR STEAM BOILERS

IF A CONTROLLER SEEMS TO OPERATE IMPROPERLY If the controller is suspected of operating improperly, it may be

further checked as follows:

1.Leave the controller installed where it is, but disconnect all power to the boiler.

2.Loosen the cover screw below the main scaleplate and remove the cover.

3.Disconnect the wires from the controller.

4.Connect an ohmmeter between controller terminals B and W to measure the resistance of the potentiometer in the controller. The ohmmeter should read about 135 ohms on an L91B.

5.Connect the ohmmeter between controller terminals W and R and raise the set point of the controller above the actual pressure being measured. The ohmmeter should read the full value of the poten- tiometer measured in step 4 (135 ohms for an L91B).

6.Slowly lower the set point of the controller while observing the ohmmeter reading. The resistance should drop to zero at some set point below the actual pressure.

7.An approximation of the proportioning range can be made by observing the change in set point required for a resistance change from zero to full value.

8.When the controller is operating properly, reconnect the wires, replace the cover, tighten the cover screw, and reset the controller to the desired value.

9.Reconnect power to the controlled motor.

Main Scale	Proportioning Range
Adjusting
Screw	Adjusting Screw

Main Scale	R
	W
Setting	B
Indicator

Sequencer (5-Step)

TESTING OPERATION OF SEQUENCER

1.With boiler off, remove wiring from pressure control on sequencer low voltage terminal board.

2.Turn on boiler to supply the voltage to the sequencer. Short ter- minal R and B for counterclockwise rotation and terminal R and W for clockwise rotation.

3.If sequencer operates under this test procedure, but when rewired to pressure controller and does not function, check pressure con- trol. Note that wiring is W-B and B-W-R-R between sequencer and pressure controller

BOILER SEQUENCE — SOLID STATE

Solid State Progressive Sequencer

The solid state progressive sequencer provides accurate elec- tronic control of multi-stage loads of the type used in Chromalox steam boilers. It features progressive sequencing (first on-first off) which equalizes the operating time of each load. This control gives visual indication of each energized stage by means of integral solid state light emitting diodes. In the event of power interruption, all heating elements are immediately de-energized for safety. When power resumes, the control will restage the loads one at a time.

Ohmmeter

Set Point

Increase

W R B

The solid state sequencer operates on 120V AC/60 Hz and each output is relay switched with a load rating of 125 VA at 120V AC.

The input to the sequencer is a 0-135 OHM potentiometer sup- plied on the operating pressure control. The sequencer has a sensi- tivity control which is adjustable from min. to max. This sensitivity control defines the amount of resistance (pressure) deviation allowed before adding or subtracting a load. Potentiometer resis- tance should decrease with increasing pressure. Connections are

Increases to

135 Ohms

Terminals are not Labeled, but Screw-Heads are

Color Coded Red (R), White (W) and Blue (B).

BOILER SEQUENCER (5 STEP) MOTOR DRIVEN RECYCLE FEATURE

The step control is designed to drop out all contactors when con- trol circuit is interrupted. On resumption of power, the camshaft rotates to the counterclockwise (ccw) limit, opening all the load switches. The recycle relay then energizes, pulling in the load con- tact, and finally the camshaft rotates clockwise (cw) to the position called for by the pressure controller energizing, in sequence, the required load stages.

made to red and white terminals of proportional pressure control. See Wiring Diagram 337-300164-452 for Boiler With Solid State Sequencer.

Solid State Sequencer

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