Direct Start; Introduction; Procedure - Siemens LMV5 Series Technical Instructions

Technical Instructions
Document No. LV5-8000

Direct Start

Introduction

Direct start accelerates the startup sequence of the burner. If the LMV5 is configured for direct
start, the following cases enable this feature:
• A call for heat is received during shutdown (phases 62-78)
• A fuel changeover is requested while the burner is in operation (phase 60) or shutdown
(phases 62-78)
The LMV5 skips the remainder of postpurge and proceeds to prepurge without turning the
blower off.
On every startup, the LMV5 tests the blower air switch for proper operation. The switch
contacts are required to open during standby of the boiler and close during blower operation.
With direct start, the blower does not turn off before startup begins. A 3-way solenoid valve
must be installed using direct start to briefly divert air pressure to functionally test the blower
air switch.

Procedure

1. Install and wire a 3-way solenoid valve as shown in Figure 1.
Appendix A
Figure 1: Wiring a 3-way Solenoid Valve for Direct Start
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