I went to an account today, that has 4 MUA's. One was down, found a linkage knuckle broken, replaced. I just happen to take a look at the burner, and saw moisture in some of the orifices. Hmm, so I take a quick look at the other units and the same thing.
What would case moisture in the manifold? I wanted to open the drip leg feeding the gas train, but the are feed up though the roof and the drip leg was 40' in the air.
I wouldn't think there would be moisture at the orifices, being that the manifold is under a negative pressure.