15
Furnace Condensation Drain
In some applications, condensation can form in the flue collection box, especially when furnaces are
located downstream of cooling coils or operate in a high-efficiency range. If condensation occurs in the flue
collection box, there are fittings in the bottom of the flue collection box to drain condensation out of the box.
The burner in the unit is provided with a condensation drain assembly located underneath this fitting for the
condensation to collect. The drain will need to be connected to field piping to handle the condensation
properly.
Consult your local code as to the proper drainage regulations of the condensation. A heated drain option is
available to prevent the internal drain piping from freezing. If drains are field piped, ensure that the field
piping is piped in a fashion to prevent the condensation from freezing. Do not plug the holes under any
circumstance as it will cause the burners to overflow.
The standard efficiency furnace drain (
detail A) is piped to the exterior of the unit via 5/16”
silicone tubing. A 1/4” female NPT fitting is provided external to the unit to allow for field piping if required.
If piping is added to the unit, freeze protection should be added to prevent damage to the field-installed
piping.
The high-efficiency furnace drain (
detail B) is fitted with a condensation float switch assembly,
located in the bottom main cabinet, from the factory. A condensation drain must be field piped through the
base of the unit using 3/4” PVC schedule 80 smooth fittings per the above requirements. A 2” deep trap
must be field installed downstream of the unit to ensure adequate flow.
NOTE: Seal ALL base penetrations with appropriate filler (caulk or all-purpose putty) to prevent
water from entering the space.
Figure 10 - Condensation Drain(s)
To test the factory-installed condensation float switch assembly:
• Turn the unit on, start the heating system. If the heating system does not run, verify the condensation
float switch assembly wiring is correct.
• Remove the condensation float switch from the assembly. Lift the switching arm with a screwdriver.
The heating system should shut off immediately. If not, check that the condensation float switch
assembly’s wiring connections are secure and tight. Re-check the float switch for proper operation.
1. Standard efficiency drain connection. 1/4” NPT trap recommended.
2. 1/2”, 3/4”, or 1” NPT gas connection depending on furnace size.
3. Factory-installed high-efficiency condensation float switch assembly and wiring.
4. High-efficiency drain connection. 3/4” PVC schedule 80.
5. After drain pipe installation, seal base penetrations with an appropriate filler.
Standard Efficiency Drain - Detail A
High-Efficiency Drain - Detail B
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