Stove Ventilation Blowing into Kitchen
I contacted my contractor at the beginning of November with this issue... it is still not resolved. No one (including Zepher customer service and the Zepher service man) can seem to figure out what is going on.
We had our kitchen renovated last year and are having problems with the exhaust fan. The contractor installed a Zepher AK8100AS (600cfm on max). Here is the situation... We have 8 foot ceilings. The vent hood is installed inside the cabinet above the stove and is 39.5 inches above the cook top. The exhaust exits the top of the unit in a 6" pipe (runs 12 inches), makes a 90 degree bend (perpendicular to the wall the stove is on) in the ceiling, runs to the next joist opening (18 inches ish), makes another 90 degree bend and runs 4 feet (parallel to the stove wall) to the outside of the house. There is what looks like a large dryer vent on the outside of the house with a single flap and a triangular shield. The only joint I can see in the cabinet is a joint... no screws or tape. I don't remember what is in the ceiling, but am fairly certain it is 6 inch pipe. The equivalent run is 67 feet, the manual say it needs to be less than 100 feet.
The vent is really loud when it is operating, and there are no appreciable differences in sound between the 3 speeds (the spec sheet gives the range of 1.4 - 6 sones for L/M/H). The vent appears to be blowing into the kitchen. When I light a candle and hold it up by the fan, the flame dances around, it isn't being pulled. It feels like air is blowing in when I put my hand next to the grate, and it will not hold a piece of paper against the grate. When I set the candle on the stove and blow out the candle, the smoke 'wallows' around and eventually dissipates into the kitchen... it isn't sucked up. The vent flap on the outside of the house opens when the fan is on.
The manual specifies the hood to be mounted 26-36 inches above the cook top... we are too high, but that should not be an issue if I am holding a candle close to the fan.
The Zepher service man says the hood is operating correctly and thinks it is an installation issue.
Zepher customer service thinks it is a ventilation issue... they say the ductwork must have been downsized to 4 inches I remember 6 inch ductwork... trying to figure out a way to see if it was downsized without knocking a hole in the ceiling....
Installer can't figure it out and need parts from the cabinet installer to lower the unit before he can start trouble shooting...
Another retailer suggested that with the two bends so close together there maybe some flow issues causing some of the air to blow into the house and some out of the house.
Does anyone have any thoughts?