# Inspecting HVAC Systems **URL:** https://forum.nachi.org/c/specific-inspection-topics/inspecting-hvac-systems/23.md [Latest](https://forum.nachi.org/latest.md) · [Categories](https://forum.nachi.org/categories.md) · [Tags](https://forum.nachi.org/tags.md) --- ## [About the Inspecting HVAC Systems category](https://forum.nachi.org/t/about-the-inspecting-hvac-systems-category/151015)
**Author:** [@system](https://forum.nachi.org/u/system)\ **Replies:** 5\ **Last updated:** [November 30, 2022, 7:21pm UTC](https://forum.nachi.org/t/about-the-inspecting-hvac-systems-category/151015 "2022-11-30T19:21:23Z")
--- ## [Duct Damage at the Attic](https://forum.nachi.org/t/duct-damage-at-the-attic/271713)
**Author:** [@malonso2](https://forum.nachi.org/u/malonso2)\ **Replies:** 4\ **Last updated:** [October 25, 2026, 7:21pm UTC](https://forum.nachi.org/t/duct-damage-at-the-attic/271713 "2026-10-25T19:21:55Z")
Not sure if this minor damage could be repaired with duct tape and/or if necessarily needs to be reported --- ## [ELF Earth Stove Log Furnace](https://forum.nachi.org/t/elf-earth-stove-log-furnace/256114)
**Author:** [@bhoefer](https://forum.nachi.org/u/bhoefer)\ **Replies:** 5\ **Last updated:** [September 12, 2026, 7:07pm UTC](https://forum.nachi.org/t/elf-earth-stove-log-furnace/256114 "2026-09-12T19:07:21Z")
Ran into this rather unique wood-burning log furnace yesterday (my first) at an inspection for a 1955 home. I am trying to find more about it, but not finding anything online. I am thinking it was original to the home, b… --- ## [Technical bulletin on corrosion of fuel lines](https://forum.nachi.org/t/technical-bulletin-on-corrosion-of-fuel-lines/270588)
**Author:** [@gromicko](https://forum.nachi.org/u/gromicko)\ **Replies:** 1\ **Last updated:** [September 10, 2026, 3:58pm UTC](https://forum.nachi.org/t/technical-bulletin-on-corrosion-of-fuel-lines/270588 "2026-09-10T15:58:13Z")
--- ## [Duct tape not for repairing ducts](https://forum.nachi.org/t/duct-tape-not-for-repairing-ducts/270277)
**Author:** [@bhill4](https://forum.nachi.org/u/bhill4)\ **Replies:** 28\ **Last updated:** [August 29, 2026, 2:46pm UTC](https://forum.nachi.org/t/duct-tape-not-for-repairing-ducts/270277 "2026-08-29T14:46:56Z")
The ductwork is improperly patched with duct tape instead of being mechanically secured and sealed, resulting in visible gaps and loose edges that cause air leakage and reduce HVAC efficiency. Repairs require correctl… --- ## [age of Trane HVAC unit](https://forum.nachi.org/t/age-of-trane-hvac-unit/105694)
**Author:** [@lreeves1](https://forum.nachi.org/u/lreeves1)\ **Replies:** 6\ **Last updated:** [August 28, 2026, 6:48am UTC](https://forum.nachi.org/t/age-of-trane-hvac-unit/105694 "2026-08-28T06:48:35Z")
--- ## [HVAC duct sealing at floor penetration](https://forum.nachi.org/t/hvac-duct-sealing-at-floor-penetration/270175)
**Author:** [@mzafar3](https://forum.nachi.org/u/mzafar3)\ **Replies:** 12\ **Last updated:** [August 24, 2026, 7:48pm UTC](https://forum.nachi.org/t/hvac-duct-sealing-at-floor-penetration/270175 "2026-08-24T19:48:31Z")
Hi guys, first post here and just trying to learn more and more everyday. Is my evaluation of the situation correct given the picture attached? The picture shows an HVAC duct passing through a conditioned bi-level (s… --- ## [Air handler suspended in crawlspace](https://forum.nachi.org/t/air-handler-suspended-in-crawlspace/266652)
**Author:** [@aponder](https://forum.nachi.org/u/aponder)\ **Replies:** 12\ **Last updated:** [August 8, 2026, 8:20pm UTC](https://forum.nachi.org/t/air-handler-suspended-in-crawlspace/266652 "2026-08-08T20:20:48Z")
I encountered an air handler today that was suspended by metal straps. It appeared the straps were fastened directly to the cabinet, but I couldn’t confirm since I couldn’t see it. My thinking is vibrations from the un… --- ## [PVC exhausting furnace and water heater](https://forum.nachi.org/t/pvc-exhausting-furnace-and-water-heater/269656)
**Author:** [@ggilbert](https://forum.nachi.org/u/ggilbert)\ **Replies:** 28\ **Last updated:** [August 8, 2026, 3:20pm UTC](https://forum.nachi.org/t/pvc-exhausting-furnace-and-water-heater/269656 "2026-08-08T15:20:01Z")
I have heard twice now within the last few weeks that PVC and I am pretty sure I heard ABS are not acceptable for the exhaust systems anymore and as a inspector we should report on it not being correct material used. If … --- ## [Is a missing sediment trap a "safety hazard"?](https://forum.nachi.org/t/is-a-missing-sediment-trap-a-safety-hazard/186853)
**Author:** [@rcasebolt](https://forum.nachi.org/u/rcasebolt)\ **Replies:** 11\ **Last updated:** [August 6, 2026, 12:48am UTC](https://forum.nachi.org/t/is-a-missing-sediment-trap-a-safety-hazard/186853 "2026-08-06T00:48:19Z")
I’ve read through numerous discussion threads and understand the differences between “drip legs” and “sediment traps”. I also realize that some jurisdictions have different rules regarding these. So when you’re in a ju… --- ## [Shade for the condenser?](https://forum.nachi.org/t/shade-for-the-condenser/268624)
**Author:** [@clambrecht2](https://forum.nachi.org/u/clambrecht2)\ **Replies:** 28\ **Last updated:** [July 4, 2026, 11:56pm UTC](https://forum.nachi.org/t/shade-for-the-condenser/268624 "2026-07-04T23:56:06Z")
Saw this shade device in our local news today - seems like it would work. Curious if anyone would call it out if encountered during a home inspection. --- ## [Flexible duct connections](https://forum.nachi.org/t/flexible-duct-connections/267595)
**Author:** [@kackerman2](https://forum.nachi.org/u/kackerman2)\ **Replies:** 2\ **Last updated:** [May 16, 2026, 7:51am UTC](https://forum.nachi.org/t/flexible-duct-connections/267595 "2026-05-16T07:51:02Z")
Not super familiar with flexible B-vent ducting, but I’m pretty suspicious of these connections. Any thoughts? --- ## [Latest Acceptable Temp Differential](https://forum.nachi.org/t/latest-acceptable-temp-differential/267388)
**Author:** [@nalbarghouthi](https://forum.nachi.org/u/nalbarghouthi)\ **Replies:** 37\ **Last updated:** [May 13, 2026, 1:07am UTC](https://forum.nachi.org/t/latest-acceptable-temp-differential/267388 "2026-05-13T01:07:36Z")
Hello all, I’m studying for the national exam, and the material/books that I have contain different ranges for acceptable temp differential between supply and return. For testing purposes, I need to be able to determine… --- ## [How to Inspect Fireplaces, Stoves, and Chimneys Course](https://forum.nachi.org/t/how-to-inspect-fireplaces-stoves-and-chimneys-course/204955)
**Author:** [@gromicko](https://forum.nachi.org/u/gromicko)\ **Replies:** 1\ **Last updated:** [May 13, 2026, 12:16am UTC](https://forum.nachi.org/t/how-to-inspect-fireplaces-stoves-and-chimneys-course/204955 "2026-05-13T00:16:39Z")
--- ## [Duct material - 1955 midwest slab house](https://forum.nachi.org/t/duct-material-1955-midwest-slab-house/267440)
**Author:** [@tdeutsch](https://forum.nachi.org/u/tdeutsch)\ **Replies:** 23\ **Last updated:** [May 12, 2026, 5:57pm UTC](https://forum.nachi.org/t/duct-material-1955-midwest-slab-house/267440 "2026-05-12T17:57:39Z")
The boot or box below the register was steel, but I decided to stick my flashlight and camera in. The duct itself looks like some kind of rolled masonite or similar. The flakes on the transition between the box and the d… --- ## [Radiant ceiling heat?](https://forum.nachi.org/t/radiant-ceiling-heat/14349)
**Author:** [@bmargiotti](https://forum.nachi.org/u/bmargiotti)\ **Replies:** 36\ **Last updated:** [May 9, 2026, 11:09pm UTC](https://forum.nachi.org/t/radiant-ceiling-heat/14349 "2026-05-09T23:09:21Z")
--- ## [Range hood exhaust with dampers?](https://forum.nachi.org/t/range-hood-exhaust-with-dampers/266942)
**Author:** [@dfreund](https://forum.nachi.org/u/dfreund)\ **Replies:** 2\ **Last updated:** [April 21, 2026, 11:31pm UTC](https://forum.nachi.org/t/range-hood-exhaust-with-dampers/266942 "2026-04-21T23:31:22Z")
4100 sq ft SFR, $7 Mil. 1994 build, 2 story, kitchen on 1st floor I’m trying to be as accurate with my narrative as possible but can just observe and report objectively what I saw if needed. When I was onsite, I could n… --- ## [SEVERE COIL DEGRADATION and MOLD](https://forum.nachi.org/t/severe-coil-degradation-and-mold/265179)
**Author:** [@fhart2](https://forum.nachi.org/u/fhart2)\ **Replies:** 39\ **Last updated:** [March 18, 2026, 5:49pm UTC](https://forum.nachi.org/t/severe-coil-degradation-and-mold/265179 "2026-03-18T17:49:26Z")
Carrier HVAC system installed in new house built in 2015 Located in SC near the GA line Second floor/attic space insulated with spray foam Furnace located in attic with spray foam directly above There is a door betwe… --- ## [Gas flex connector to furnace](https://forum.nachi.org/t/gas-flex-connector-to-furnace/18138)
**Author:** [@jcahill](https://forum.nachi.org/u/jcahill)\ **Replies:** 28\ **Last updated:** [March 10, 2026, 6:04pm UTC](https://forum.nachi.org/t/gas-flex-connector-to-furnace/18138 "2026-03-10T18:04:18Z")
--- ## [Questionable placement of gas line and vent termination for gas stove](https://forum.nachi.org/t/questionable-placement-of-gas-line-and-vent-termination-for-gas-stove/212823)
**Author:** [@ahowell1](https://forum.nachi.org/u/ahowell1)\ **Replies:** 16\ **Last updated:** [February 9, 2026, 12:08pm UTC](https://forum.nachi.org/t/questionable-placement-of-gas-line-and-vent-termination-for-gas-stove/212823 "2026-02-09T12:08:56Z")
This gas-fired stove vent termination and gas line routing appears to be installed improperly. I think that the vent pipe should terminate above the roof based on the pitch of the roof, but I am uncertain. Also, I beli… --- ## [gas furnace exhaust and intake](https://forum.nachi.org/t/gas-furnace-exhaust-and-intake/103632)
**Author:** [@kbrose](https://forum.nachi.org/u/kbrose)\ **Replies:** 12\ **Last updated:** [February 9, 2026, 4:25am UTC](https://forum.nachi.org/t/gas-furnace-exhaust-and-intake/103632 "2026-02-09T04:25:13Z")
I came across an intake / exhaust set up today that I have not come across before. The exhaust and intake come out the top of the furnace (photo #1) take a 90 degree turn and join in at a Y fitting (Photo #2) and termi… --- ## [HVAC Intake and Exhaust](https://forum.nachi.org/t/hvac-intake-and-exhaust/264274)
**Author:** [@mgruenfeld](https://forum.nachi.org/u/mgruenfeld)\ **Replies:** 16\ **Last updated:** [January 21, 2026, 10:38pm UTC](https://forum.nachi.org/t/hvac-intake-and-exhaust/264274 "2026-01-21T22:38:54Z")
Hi Everyone, Has anyone seen this before? I am not familiar with this. High efficiency furnace. Exhaust and air intake seem to be connected. See photos attached. I would appreciate it if anyone can help. … --- ## [Power D/C for air handler](https://forum.nachi.org/t/power-d-c-for-air-handler/264249)
**Author:** [@acox](https://forum.nachi.org/u/acox)\ **Replies:** 4\ **Last updated:** [January 20, 2026, 8:35pm UTC](https://forum.nachi.org/t/power-d-c-for-air-handler/264249 "2026-01-20T20:35:29Z")
Just inspected a home built in 2021, has heat pump system with air handler installed inside. The electric panel is not within reach or sight and no disconnect at the unit. I called it out as a defect - NOT citing code, b… --- ## [Intake air high efficiency furnace](https://forum.nachi.org/t/intake-air-high-efficiency-furnace/263366)
**Author:** [@achand](https://forum.nachi.org/u/achand)\ **Replies:** 34\ **Last updated:** [December 26, 2025, 10:08pm UTC](https://forum.nachi.org/t/intake-air-high-efficiency-furnace/263366 "2025-12-26T22:08:47Z")
I observed this in one of the inspection today. The furnace is a high efficiency. It is drawing intake air from inside the room. Should the intake air vent not be extended all the way to the exterior? is this a defect? T… --- ## [Is coolant evaporating through hole dangerous?](https://forum.nachi.org/t/is-coolant-evaporating-through-hole-dangerous/263198)
**Author:** [@dshakhov](https://forum.nachi.org/u/dshakhov)\ **Replies:** 20\ **Last updated:** [December 24, 2025, 8:55pm UTC](https://forum.nachi.org/t/is-coolant-evaporating-through-hole-dangerous/263198 "2025-12-24T20:55:45Z")
Hello, My question is concerning a tiny leakage in a suction pipe inside the home right next to the furnace/evaporator cabinet. According to owner the hole is not even visible. It was detected by HVAC technician. The qu… --- ## [2 thermostats, 2 levels, no zoning?](https://forum.nachi.org/t/2-thermostats-2-levels-no-zoning/262626)
**Author:** [@dfreund](https://forum.nachi.org/u/dfreund)\ **Replies:** 10\ **Last updated:** [December 3, 2025, 3:50pm UTC](https://forum.nachi.org/t/2-thermostats-2-levels-no-zoning/262626 "2025-12-03T15:50:56Z")
11th month warranty inspection today on townhome-style condo. Living space on 2nd and 3rd floor. 2nd and 3rd floor each had a separate thermostat. One furnace/air handler in attic. AC was installed but I only tested the … --- ## [Condensate on furnace not going to a drain](https://forum.nachi.org/t/condensate-on-furnace-not-going-to-a-drain/262563)
**Author:** [@pbuffone](https://forum.nachi.org/u/pbuffone)\ **Replies:** 24\ **Last updated:** [November 30, 2025, 3:27pm UTC](https://forum.nachi.org/t/condensate-on-furnace-not-going-to-a-drain/262563 "2025-11-30T15:27:10Z")
Hi guys, new inspector here and this condensate line has me stumped. It seems to be going to the air intake vent pipe. Seems very odd. I can follow it out of the furnace to the pump and then it goes up to the intake. Thi… --- ## [Pennco Gas Boiler Age](https://forum.nachi.org/t/pennco-gas-boiler-age/229863)
**Author:** [@rguyer2](https://forum.nachi.org/u/rguyer2)\ **Replies:** 4\ **Last updated:** [November 28, 2025, 7:32pm UTC](https://forum.nachi.org/t/pennco-gas-boiler-age/229863 "2025-11-28T19:32:59Z")
At today’s inspection a Pennco gas boiler was at the property. I called the manufacturer for help with the age of the boiler. The rep said using their current decoder for serial numbers, this unit was manufactured in 1… --- ## [Rattling wall furnace](https://forum.nachi.org/t/rattling-wall-furnace/262443)
**Author:** [@ksilvas](https://forum.nachi.org/u/ksilvas)\ **Replies:** 19\ **Last updated:** [November 26, 2025, 3:44pm UTC](https://forum.nachi.org/t/rattling-wall-furnace/262443 "2025-11-26T15:44:40Z")
does anyone have any idea what’s going on with this wall furnace? This was on a coastal San Diego condo. The exterior temperature was approximately 60°, not very cold. The rattling started after the furnace had been runn… --- ## [Sweating air handler](https://forum.nachi.org/t/sweating-air-handler/88809)
**Author:** [@tmiller2](https://forum.nachi.org/u/tmiller2)\ **Replies:** 27\ **Last updated:** [October 24, 2025, 2:50pm UTC](https://forum.nachi.org/t/sweating-air-handler/88809 "2025-10-24T14:50:16Z")
[Next page](https://forum.nachi.org/c/specific-inspection-topics/inspecting-hvac-systems/23.md?page=1)