Metal flue terminal on a condensing boiler?

spinningsheep

Hiya all, not sure if I am in correct forum or if gas would be more appropriate but anyway...every morning I walk past a venue in the city centre where I live that has a flue terminal for a boiler on the wall with a cage over it (I assume as it is low ish level on pavement) and it is metal, yet there is a big plume of steam comes from it, even when the temp outside is 5 degrees plus, so must be a steamer, my question is, why is it metal? I was under the impression all condensing boilers had a plastic flue A) because of the much lower flue gas temperatures and because the acidic nature of the condensate in the plume would corrode a metal terminal. Am I wrong? Always makes me wonder. Also, the plume on SOME boiler flues I see is always greater than mine, and I run on a 55-70 flow depending on weather. Does a bigger plume mean more condensing?

Weird questions I know but hey

Ectophile

The more steam, the less it's condensing. I'm no expert, but have read elsewhere that condensing boilers should have a return temperature below 55C to ensure good condensing.

A boiler running flat out will always produce more steam than one that's just ticking over.

gas4you

Condensing boilers should have a plastic coated flue terminal guard fitted, where needed.