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Is there any requirement that an auxillary drain pan be positioned under the primary trap?

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I have been reading the code and see where it states that the auxilliary drain pan must be situated below the coil and extend no less than three inches on either side of the equipment.  In my system though, the primary drain line extends an inch or so beyond the drain pan such that when the drain line clogs, the discharge does not fall into the drain.  This to me defeats the purpose but the installer swears it is up to code.  The system is now a year out of warranty so when the drain clogged, and the primary shutoff switch failed and the drain pan shutoff switch failed, the installer said "too bad" and charged me for the system repairs.  I have yet to assess any structural damage and mold but they've already said they aren't liable for those either.

This system was purchased as a total replacement of the builder-installed system.  It included compressor, air handler and a two-zone ducting system with automatic dampers.  I also purchased the maintenance plan and we get the regular service visits like clockwork.  The first shoulder season after the system was installed we got a bad case of dirty sock syndrome and the installer replaced our coil with a teflon-coated version.  Today when we blew out the drain the debris included silicone caulk or glue, mastic, and a lot of metallic chips and grit, all of which appeared to be residue from changing the previous coil.

At this point I'm looking for any insight as to whether positioning the trap outside the boundary of the drain pan violates anything other than common sense so I can justfy asking them to reengineer the drain or pay for someone else to do it.

Thanks for any advice.
asked in Heating and AC by tdotrob (120 points)
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1 Answer

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Hi Tdotrob,

Everything failed at the same time… I’m sorry to hear that, it looks like your maintenance provider didn’t do much to prevent it… I’ve been there - http://checkthishouse.com/3879/furnace-ac-seasonal-inspection-do-you-trust-your-hvac-guy.html

Back to your question, I bolded section of a paragraph below stating that the protective pan has to extend 3” beyond the equipment’s footprint (from IMC - International Mechanical Code). This is a link to original paragraph from 2006 IMC - http://publicecodes.citation.com/icod/imc/2006f2/icod_imc_2006f2_3_sec007_par004.htm

There’s also a possibility that your jurisdiction requires something other than in the paragraph below, more or less protection.

307.2.3 Auxiliary and secondary drain systems.
In addition to the requirements of Section 307.2.1, a secondary drain or auxiliary drain pan shall be required for each cooling or evaporator coil or fuel-fired appliance that produces condensate, where damage to any building components will occur as a result of overflow from the equipment drain pan or stoppage in the condensate drain piping. One of the following methods shall be used:

  1. An auxiliary drain pan with a separate drain shall be provided under the coils on which condensation will occur. The auxiliary pan drain shall discharge to a conspicuous point of disposal to alert occupants in the event of a stoppage of the primary drain. The pan shall have a minimum depth of 1.5 inches (38 mm), shall not be less than 3 inches (76 mm) larger than the unit or the coil dimensions in width and length and shall be constructed of corrosion-resistant material.

    Metallic pans shall have a minimum thickness of not less than 0.0276-inch (0.7 mm) galvanized sheet metal. Nonmetallic pans shall have a minimum thickness of not less than 0.0625 inch (1.6 mm). 

  2. A separate overflow drain line shall be connected to the drain pan provided with the equipment. Such overflow drain shall discharge to a conspicuous point of disposal to alert occupants in the event of a stoppage of the primary drain. The overflow drain line shall connect to the drain pan at a higher level than the primary drain connection.
  3. An auxiliary drain pan without a separate drain line shall be provided under the coils on which condensate will occur. Such pan shall be equipped with a water-level detection device conforming to UL 508 that will shut off the equipment served prior to overflow of the pan. The auxiliary drain pan shall be constructed in accordance with Item 1 of this section.
  4. A water level detection device conforming to UL 508 shall be provided that will shut off the equipment served in the event that the primary drain is blocked. The device shall be installed in the primary drain line, the overflow drain line, or in the equipment-supplied drain pan, located at a point higher than the primary drain line connection and below the overflow rim of such pan. 

Exception: Fuel-fired appliances that automatically shut down operation in the event of a stoppage in the condensate drainage system.

It all refers to unit / coil dimensions, and there’s nothing about extending underneath the drain tubing attached to this unit. I can’t see your installation but in some cases it would be logical to go that extra step and widen the pan (if constructed in location) to provide more protection for a suspect area… or reroute the drain pipe so it’s still above some factory made safety pan. Some people do it, some will unfortunately not use common sense.

One thing the maintenance people should be responsible for is removing all the debris from inside the drain line, that’s one of the main items on the maintenance list; you paid them for cleaning it!

Just click "comment" below if you have more questions.

answered by darekrudy (21,730 points)