Look for signs of "sooting" around the flue pipe transition

it does not require field calibration

Leveraging the Armstrong Series B design

and 0-75 PSIG

the PR-274-R2-VDC is designed for environmental resilience

Resideo VR8304M2501 Valve 320074-702 Look for signs of "sooting"The Resideo VR8304M2501 is a single stage gas valve engineered for precision in high capacity heating applications. This intermittent pilot dual automatic valve features a standard opening characteristic with a rated capacity of 240,000 BTU hr (at 1 in. wc p. d.), making it a reliable choice for commercial and residential appliances requiring robust fuel control. The VR8304M2501 operates on a 24VAC gas valve circuit and maintains a factory set 3. 5