Puzzled over condensate

[inspectorwill]

Home is equipped with a vertically mounted York high efficiency furnace and A/C. The a-coil is above the furnace. Dual condensate lines are installed at the a-coil and a condensate line is also installed for the furnace. The primary condensate is plumbed to a bathroom sink drain. The secondary discharges at the eaves onto the driveway. When the furnace is operated, condensate drains from the secondary line installed at the eave of the home. When the a/c is operated, I can hear condensate draining through the bathroom sink drain. There is a slight kink in the primary condensate line where it attaches to the sink drain. I would think that if the kink doesn't obstruct flow for the A/C it shouldn't obstruct flow for the heater. Unless, more condensate is created by the heater which the kinked line can't accommodate or the heater condensate was plumbed to drain outside. Just puzzled and any thoughts are appreciated.

[Greg Booth]

The furnace drain is tied into one of the A/C condensate lines-right? Could it be tied into the secondary? Also, are there any issues with the method of tie-in to the DWV system at the sink ie. traps, air-gap etc?

[Nolan Kienitz]

Get rid of "any" kink in the primary condensate drain as it routes to the DWV below the sink.

Debris, mildew, etc. can collect (at the kink usually) and cause a flow restriction then things would back up and the flow would then start coming out of the secondary.

HVAC folks often us a heavy rubber-type hose (almost a radiator hose) and they will often have a kink or sharp bend from the PVC that is coming out of the wall below the bathroom sink to the drain just above the P-Trap.

Sometimes the turn is "too sharp" and causes a kink and thus possible restriction of condensate flow.

[inspectorwill]

Appears to be tied into the drain correctly although there is a kink in the line right at the connection to the drain. However, the A/C is draining correctly through the same line. I could not discern which condensate line the heater was tapped into because the space was tight and there were obstructions.