Secondary Heat Exchanger

From an inspection on Saturday. Tempstar model NUKK075DG05

Unit had been installed as propan in 1991 and converted to natural gas in 1992. The third pic says a secondary heat exchanger was installed in 2003.

  1. Do any of the HVAC guys here know if this unit came with a secondary heat exchanger originally? (it is apparently a 90+ furnace from my research)

  2. The unit is rated 75K BTU L.P. and only 60K BTU for the alternate fuel which I assume is Natural gas. Is that correct?
    (Most of the converted units I have seen don’t have this much difference between the two possible fuel sources and when I converted my own boiler I was suppied with a new rating decal for the new fuel source. N.G/L.P.

Thanks in advance for any enlightening comments.:slight_smile:

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All plus 90 furnaces have a secondary heat exchanger. That’s where the extra efficiency comes from.

That’s what I thought too Marc or they would be more like 85%. The hand written note messed with my head. It must have been a repair. Thanks.

On some further thought I was also wondering if the 60K input BTU was an alternate setting for the burner. let’s see what some of the HVAC guys have to say.

Keep in mind, that anyone can write “Secondary heat exchanger installed in 2003”.

Do not write down that the H/E was replaced 4 years ago. You have no clear evidence. Simply write down what you see written on the casing and recommend further evaluation when the unit is serviced.

I always recommend service and cleaning upon moving into the home and annually thereafter.

Thanks for your reply David. I agree that without some documentation the handwritten note is worthless. The home was empty and is now owned by a relo co. the note just seemed odd to me as did the lack of the proper input label for natural gas.

I always reccommend annual service of the equipment.