Component
Condensate trap, drain and pump
A condensing furnace makes water: several litres a day in cold weather. The trap, drain and, where needed, a condensate pump carry it away. When they block or freeze, water backs into the furnace, the pressure switch opens and the furnace stops, or water appears on the floor.
Short answer
Water around a condensing furnace almost always means the condensate path is blocked, frozen or has come apart. The furnace may still run for a while, then stop with a pressure-switch or drain code. Turn off a condensate pump that is overflowing, mop up, and call. Do not open the trap on a running furnace; it is part of the flue-gas seal.
Why condensing furnaces make water
Every furnace sold new in Canada is at least 95% AFUE, which is only possible by cooling flue gas until its water vapour condenses in a secondary heat exchanger. That water is mildly acidic and must drain continuously. Carrier's 59TP6C, for example, has a trap that must be installed in a specific orientation for each of the furnace's four mounting positions and ports that need cleaning annually.
How it fails
Blockage: sediment and biological growth in the trap or drain line, common on furnaces that have never been serviced.
Freezing: drain lines run through unheated spaces, and exterior drain terminations, freeze in cold snaps. Carrier's instructions include a winterization procedure using propylene glycol where a drain could freeze.
Pumps: a condensate pump has a float switch and a safety contact that stops the furnace if the reservoir overflows. A failed pump looks like a dead furnace.
Joints and slope: hoses that sag or drain lines without fall hold water and let it back up during a long high-fire cycle.
Documented codes that point here
- Carrier 59SC6A status code 23: pressure switch stuck closed
- Carrier 59SC6A status code 31: secondary pressure switch open or lockout
- Carrier 59SC6A status code 32.1: open main pressure switch (LPS)
- Carrier 59SC6A status code 34: ignition fault or flame loss
- Carrier 59SC6A status code 14: flame-loss lockouts during a heat request
- Carrier 59TP6C status code 31: high-heat pressure switch (HPS) open or slow to close
- Carrier 59TP6C status code 14: flame-loss lockouts during a heat request
- Carrier 59TP6C status code 23: pressure switch stuck closed
- Carrier 59TP6C status code 32.2: open main pressure switch (LPS)
- Carrier 59TP6C status code 34: flame lost after ignition
- Carrier 59TP7A status code 31: high-heat pressure switch (HPS) open or slow to close
- Carrier 59TP7A status code 14: flame-loss lockouts during a heat request
- Carrier 59TP7A status code 23: pressure switch stuck closed
- Carrier 59TP7A status code 32.2: open main pressure switch (LPS)
- Carrier 59TP7A status code 34: flame lost after ignition
- Carrier 59SP6B status code 23: pressure switch stuck closed
- Carrier 59SP6B status code 31: secondary pressure switch open or lockout
- Carrier 59SP6B status code 32.1: open main pressure switch (LPS)
- Carrier 59SP6B status code 34: ignition fault or flame loss
- Carrier 59SP6B status code 14: flame-loss lockouts during a heat request
- Carrier 59TN7A status code 31: high-heat pressure switch (HPS) open or slow to close
- Carrier 59TN7A status code 14: flame-loss lockouts during a heat request
- Carrier 59TN7A status code 23: pressure switch stuck closed
- Carrier 59TN7A status code 32.2: open main pressure switch (LPS)
- Carrier 59TN7A status code 34: ignition fault or flame lost after ignition
Related
Questions people ask
Is the water dangerous?
It is mildly acidic and can damage flooring and rust the furnace base, but it is not a gas or CO hazard by itself. The danger is running a furnace whose trap is not sealing; that is why it is left to a technician.
How often should the trap be cleaned?
Manufacturers typically call for annual cleaning as part of maintenance. Furnaces that produce a lot of condensate, or drain through a pump, benefit from a check before each winter.
Need this looked at?
Call BC Wide with the brand, model number and anything on the display. Or
Request service online with this page attached.