Thread: New Cat IV Burning Smell

I fired up a new Cat IV furnace in new construction and got a bad plastic burning type smell. The smoke detector went off so I shut it down. I fired it up again about 15 minutes later and no smell, no smoke detector alarm. All was good. Has this happened to any of you and what's to make of this?

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Manufacturing oils, dust, etc. on the heat exchanger in the air stream. This is very common on new systems and sometimes on the first use of the season here in a/c land. Not sure why it would smell like plastic.

Start up odors are mentioned in the manufacturer's Installation
Instructions & User's Manual.

Personally, would never be the "one" (if not the contracted installer) to do the "first fire" of an interrupted installation of new construction fuel fired FA furnace. Secondly, prior to first fire-up of shut-down system, unoccupied or following construction activities - would always check ventillation of the ducting system (fan only mode) and ventillate same prior to actually "firing up".

However, in new construction - not yet finished at the time of installation - it is not uncommon to find the FA furnace to be tagged out with a warning - and to find the air filters set in place still with the plastic on same (to keep clean) - or to find same set adjacent, and the registers & returns covered (sometimes obstructed/sealed behind the grilles) In an effort to keep the system clean/free of dust, debris, destructive fumes/vapors, during final finishing activities, for which other means of ventillation should be provided (such as finished in place wood flooring, other building finishes, etc.). It also isn't uncommon for the floor finishers, esp. when using "swedish finishes" to block off all the supplies & returns - as the toxic vapors from the curing process can settle and linger for long periods of time - when they fail to return themselves to do the opening of the home and the required complete controlled ventillation, evacuation verification of the toxic, noxious curing vapors - the smells and off-gasing of settled finish curing vapor pockets in/on metal ducting when circulated and esp. when heated can be rather "plastic burning-like" in odor, grab at the back of your throat, and are noxious.

If its not installed as a true DV (alternate to Cat. IV installation -- i.e. exterior CAZ intake on the same plane as the exhaust vent), the intake may also be temporarily covered - so as to protect entry of damaging vapors into the heat exchanger.

Newer construction always verify the intake & exhust are actually clear - including building papers as well as ex. finish materials -- which may hve been installed after the intake & exhust vent systems, with the terminal just set-in place not truly & fully installed - or capped off during construction to prevent dirt, debris, rodent, insect, and/or water entry, etc. from other phase construction/trades work, as building is still unconditioned..

Thanks all.