We're having a problem with a empire direct vent fireplace insert. I will get the model number from the office tomorrow but for now I figured to get a thread started. The fireplace is a natural gas insert with two 4 inch liners going up the old chimney. The liners are about 17 feet long. The unit is spark ignition with a switch to force it to full time standing pilot if desired.
The problem is with the venting. If the unit sits for any length of time and there is a call for heat, the pilot is lit by the spark ignition. Up to that point all is well but when the main burner lights it flutters and affects the pilot and the burner will go out due to the flame sensor losing signal. If we turn the unit on and switch it to full time pilot for 8 minutes with out the main burner on this warms the venting up and it operates properly. There appears to be some kind of inversion going on with a cold start. Also the wind affects the operation in spark mode or continuous pilot mode.
I'm not sure how to remedy this. It currently has a breidert type cap on the coaxial chimney termination. I have been thinking about trying a star-kap.