this specific 10k or 12k ohm-style immersion probe is utilized for both the inlet and outlet headers to monitor the temperature delta across the heat exchanger

While it provides the mounting locations for high-limit switches and igniters

A failed or tripped 1320547 limit switch often forces the blower into a continuous "on" state as a safety measure to dissipate excess heat

This valve utilizes an electronic ignition system to eliminate the need for a standing pilot

and LB-107228T

Johnson Controls VG2231VM292NGGA Valve Assembly 30067439-890 this specific 10k or 12kThe Johnson Controls VG2231VM292NGGA is a heavy duty 4 inch 2 way normally open flanged globe valve designed for precise flow control in demanding hydronic systems. Built with a rugged cast iron body and durable brass trim, this assembly handles high capacity chilled or hot water applications with a 150 Cv rating. The ANSI Class 125 flat faced flange connection ensures a secure fit for industrial piping. Performance is driven by a tandem mount spring