Vulcan-Hart VHX24G5, MHB24G manual N9, N10, N11, N12, N13 go out, N14, N16, N17 go out

VHX SERIES STEAMER - ELECTRICAL OPERATION

NOTE: Relay K4 remains energized through K4(1) N.O. locking circuit.

1)N8 goes out. K4(1) N.O. contacts close and K4(1) N.C. contacts open.

2)High pressure light (control panel) goes out.

C.N11 lit. K4(2) N.O. contacts close.

1)K5 is energized (24VAC).

a.N12 lit. K5(1) N.O. contacts close.

a)Combustion blower starts.

7.N13 lit. When the combustion blower generates sufficient air pressure, the air pressure switch N.O. contacts close.

A.Ignition module is powered (24VAC).

1)Ignition module starts sparking.

2)N14 lit. Pilot voltage (PV) N.O. contacts close.

a.K7 is energized.

a)K7(1) N.O. contacts close.

3)15 sec. timer circuit (board level, solid state timer) energized and timing of pilot gas valve ON time begins.

a.K6 energized.

a)N15 lit. K6(1) N.O. close.

4)Pilot gas valve energized, pilot valve opens for gas to flow.

B.Pilot flame established. Micro amp flame "sense" current rectified to ignition module through ignition cable.

1)Sparking stops.

2)N16 lit. Main voltage (MV) N.O. contacts close.

a.N17 LED lit. Proves LLCO on water level board closed.

b.Main gas valve opens, burner lights and boiler begins to heat up.

C.15 seconds after ignition module energized, relay board timer circuit times out.

1)N15 goes out. K6 de-energized.

pilot, quickly cycle the reset switch to prevent the boiler from draining. If the pilot is not established within 90 seconds from the ignitor module being energized, the ignition module locks out power to the gas valves. The module remains locked out until the power switch is turned to OFF then ON and the manual reset switch is pressed to r e-start the ignition trial cycle.

D.As boiler heats up and builds pressure, some by-pass water/steam is produced which runs into the steam drain box. This causes the cold water condenser (CWC) solenoid to cycle, cooling the drain water and condensing any steam vapors before exiting the drain. The CWC solenoid is powered through the CWC cycling thermostat.

NOTE: On initial cold startup only, the boiler pressure may overshoot and cause the mechanical pressure relief valve to open momentarily.

E.As long as the ignition control module senses a burner flame, the internal main voltage (MV) contacts (N.O.) on the ignition module remain closed, and main gas valve stays ON.

NOTE: PV N.O. contacts are also closed, but K6 contacts are open to keep pilot valve closed.

8.Boiler steam pressure reaches upper limit set point of 10 PSI (Approx. 15 minutes).

A.Cycling pressure switch open.

1)N9, N10, N11, N12, N13 go out.

a.K5 de-energized.

a)K5(1) N.O. contacts open.

b.Combustion blower is de- energized.

a)Air pressure switch opens.

B.Ignition module is de-energized

1)PV and MV contacts open.

a.N14, N16, N17 go out.

b.Main gas valve closes, burner goes out.

c.K7 de-energized.

a)K7(1) open

a.Pilot valve closes, gas flow stops to pilot.

NOTE: If pilot ignition is not established within the allotted 15 seconds, the ignition module continues to spark. To attempt to relight the

9.Boiler steam pressure drops below lower limit set point of 8 PSI and the cycling pressure switch close.

A.Boiler steam pressure is maintained by the cycling of the pressure switch between the

Page 47 of 68 F24700 (October 2001)