Unless I have this wrong, the BPI CAZ depressurization limits and draft calculations are for gas boilers and furnaces. Up here in New England we have a lot of oil burners. It would seem that it would take a lot more negative pressure in a CAZ to get an oil burner to spill. I have flue pressures for oil of: <10 F at -15 Pa, 11 - 40F at -13 Pa, 41 - 60F at -11 Pa, 61 - 90F at -9 Pa, and >90F at -7Pa.
We see lots of fuel oil in the NC mountains where we have been training BPI for over 2.5 years now. After many discussions with several trainers i have come to the conclusion that the fuel oil burner should be classified the same as an induced fan furnace receiving a CAZ Depressurization limit of -15. However, High Retention Head Burners may allow this limit to go even lower. I would love an official BPI interpretation on this issue.
I have recently received a reply from Tony Peters QA for Affiliates for BPI who states that, "CAZ depressurization limits shall be identical for gas or oil fueled combustion appliances. An oil fueled combustion appliance shall not be classified as a mechanically assisted draft appliance. Please classify oil fueled combustion appliances as natural draft boilers or furnaces." He also says, "Draft calculations shall also be identical for oil or gas fueled combustion appliances. Please follow the acceptable draft test results chart found on page 10 of BA for all natural draft appliances."
Seems a bit odd to me, but he explains that, "if the oil fueled combustion appliance has been installed with a barometric damper connected to the vent pipe, it cannot support a -15Pa CAZ depressurization limit."