Does a "condensing" boiler have to have a minimum efficiency rating?

DaveinCO

Hello all,

One of my first posts here. I came across a curious question in my office. There is a manufacturer that just came out with a Copper Fin style boiler with Stainless Steel fin tubes. They are promoting this product as "condensing", but their promoted efficiency on this unit is 87.1%.

What agency (if their is one) dictates if/when a manufacturer can call their unit condesning. I thought it had to be 90%+ to be considered condensing.

I appreciate anyones thoughts!

GGross

If it captures heat from the exhaust gas such that those gasses cool and condense then it is a condensing boiler. For it to be sold as such it just needs to be this way by design. For example you can make an old school cast iron boiler condense, but it will rot out the heat exchanger, it would go against design. There were a run of mid efficiency condensing boiler in the late 80's early 90's i believe sold through the early 2000's. They aren't as common

Basically any boiler that is producing condensate is condensing, no matter the efficiency. "Condensing" isn't an efficiency label, though it typically coincides with boilers that are over 90% efficient. Also worth noting that running those boilers with high return temperatures will result in non-condensing operation. so even a condensing boiler can not condense if the system is set up like that. For your info a condensing boiler running high temp and not condensing also does not hit its rated efficiency rating, those ratings are not based on every installation

Jamie Hall

As @GGross says, calling a boiler "condensing" has absolutely nothing to do with its efficiency rating. All that tells you is that the boiler is constructed in such a way, and with materials which can withstand, exhaust gas temperatures below the dewpoint of the exhaust gas — typically around 140 F. If it can, and can be controlled to run that way, it is a condensing boiler.

ChrisJ

https://forum.heatinghelp.com/discussion/comment/1877405#Comment_1877405

But how can the exhaust gases be that cool unless the efficiency is above a certain point?

My 82% condenses sometimes, but it certainly won't for long and certainly not during steady state.

Jamie Hall

https://forum.heatinghelp.com/discussion/comment/1877410#Comment_1877410

Generally speaking you would be right, @ChrisJ — all else being equal. The point is that a boiler which is sold as a condensing boiler is designed to do so without corroding itself to bits in a week or two, and is equipped with controls which allow it to run the exhaust that cool.

So you can advertise it as a condensing boiler.

Now… whether or not it actually will run in condensing modes is another question altogether! That's not the point. It's a regulatory and advertising thing: certain designs can be advertised as and the regulatory folks treat them as "condensing".