Weil-Mclain Gold Boiler question

Hey All
I have a question about a boiler. I fired this puppy up and i noticed after it ran for about 30 minutes and i had all the zones on that the pipe with the elbow coming out the left side about half way down was dripping water.
What is causing this? I believe it is the pressure relief valve but i am not sure. Not a Boiler pro. Can someone educate me some.

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I’d post your question on heatinghelp.com (Questions section)

The pros there are great, and very willing to answer questions of this nature.

Does not look like any relief valve I have ever observed it looks like a 90 with a plug in it.

If indeed it is a relief it would not be uncommon to see one start dripping as the water started to warm up. Some times they will stop on their own and some times not. Most MFG would recommend Relief valves be changed on a set periodicity. Most of the time it is never done.