The second company knows how to install a 90%+ efficiency furnace in an insulated attic, and the second company does not.

A high efficiency furnace produces water condensate that could freeze if the attic is very cold. The condensate drain pipe can be kept work using electrical heat tape. It is much cheaper than building an insulated furnace room in the attic.

Thank you! That sounds right!

Depending on the code being used by your local jurisdiction, most newer codes require an enclosure around attic installed furnaces. Additionally, the enclosure will require a smoke/carbon monoxide detector, a pan under the furnace in case of leaking, and I would recommend adding an moisture alarm also.

The heat exchanger cracking is not usual and should be covered by the manufacturers warranty (usually20 years or lifetime).

The condensate drain tube freezing is the bane of attic installed hi-eff furnaces and can only really be avoided by using heat tape all along the drain (which is kinda difficult if it runs down inside a wall).

I've never heard of a code requiring a separate enclosure for an attic mounted furnace (certainly not where I live). Can you post an example of this?

Unfortunately I've been told it's not covered for us because the original homeowner did not register the furnace. Has anyone heard of a way around this oversight?

I've not heard of a code either, and neither company mentioned this as part of their plan.

HomeSweetHome360,

Whether the unit is truly covered by warranty would have to be investigated. In some cases the warranty coverage *if any* can vary among specific brands, and further among different models.

If the manufacturer was Goodman / Amana / or Daikin --- the following would *likely* apply. Outside of these terms (in the picture below) things that can disqualify you would be 'improper installation'. In addition, the manufacturer will not cover labor, nor will they allow you to do the work yourself. You will need a licensed HVAC contractor.

If you don't have either the aforementioned brands, the warranty coverage if any can widely vary when you are not the original home owner... or the one who purchased and had the 'original equipment' installed. (or if you prefer -- the previous owner of the home was the one who purchased and installed the furnace)

In addition to all that --- Furnaces are a *special case*. So do not think something of this length of warranty would apply to an air conditioner. (Things can change this was posted in 2020)

Realize, I am NOT saying you specifically are trying to do this yourself. I am looking many miles down the road when I say this.

I service the Katy, Texas area.

Even if the original homeowner registered the furnace, it is unlikely the warranty would be transferable to a new homeowner. In the case where the warranty is transferable, it usually requires a payment to the manufacturer.

Call you local code official about for the code requirements. You should have the contractor follow the code requirements even if you don't plan to file for permits.