Secondary Heat Exchanger

[Michael Larson]

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.

[Marc D. Shunk]

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

[Michael Larson]

Originally Posted by Marc D. Shunk

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.

[David P. Valley]

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.

[Michael Larson]

Originally Posted by dvalley

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.