I have a Weil McLain HE boiler, circa 1983. It's a power-vented unit and had a bunch of parts replaced (according to the service sticker) in the years leading up to buying the house in summer 2017. The manual was helpfully left by the previous owners, and it shows a pre-purge timer connected to the gas valve in the schematic. The 30-sec timer is still there, but no longer connected. (And untested, but cheaply replaced with an ICM102 or similar if it's not working.)
Incidentally, the gas valve runs a standing pilot, which wasn't the original configuration. Apparently it had a electronically-lit pilot from the factory. I'm guessing the tech who replaced the gas valve just did the simplest installation and disregarded the timer.
How important is doing a pre-purge? It's a shared flue with the natural-draft water heater. Both were checked for CO and correct drafting when I had an energy audit.
Thanks
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