Cast iron or steel?

How does one determine on-site what a furnace/boiler heat exchanger is made of, or is it a matter of having to look up the make & model at some point later? Some of these manufacturers make it a real research project, but since there’s a considerable lifespan difference it’s important to find out.

You are going way beyond the scope of a normal home inspection. Unless you are charging a super premium for your services, you can’t afford to supply all information about every single component in an inspection. I sure would not be offering estimated life expectancies either. All it takes is that one miserable client to blame you because the item didn’t last as long as you said it would.

Report what you see and move on.

Where did you learn that you have to find out this information?

It’s part of determining if a system is at or near the end of its designed life. Not a critical part, but I see some 20-year old oil fired boilers and it could be the difference between end of statistical life and might have a few good years left.

Right now I’m erring on the side of caution and advising budgeting for its eventual replacement but if there’s some trick to easily finding out what the heat exchanger is I’d appreciate the help.

I think it’s a very good and legitimate question and I have often wondered myself. Hopefully, someone chimes in with some helpful insight.

For me I just look, experience helps. I look underneath at the legs; I look for welding at the flanges. I look for female threaded cast iron where the supply and return pipes attach. For me its a case of you know it when you see it. In our geographic area we see the usual suspects of 6 to 10 different manufacturers…I just know them.

I agree with others that you’re really exceeding SOP but thats fine if you want to do so.
What does your information say about which lasts longer and by how much?

As far as lifespan goes I sometimes discuss this verbally with the client during the inspection, informing them of the industry average lifespan. But I often see equipment that has far exceeded it and is working just fine. I will add a comment in the report describing a furnace for instance as “older unit, budget for replacement” and I put the date of mfg. in the photo caption.

Determining the material is as Mark said a matter of experience. Cast iron and steel are very different materials and that affects their appearance and how they are assembled, which is how you will know which is which. Experience.
If you’re really interested then hire a boiler tech, maybe you can tag along on some service calls with them. You’ll learn a heck of a lot in a short time!