GE JP989 Series Technical Service Manual page 11

Sufficient air is needed for proper combustion and exhausting of gases through the flue (chimney)
of fuel-burning equipment to prevent back drafting. Follow the heating equipment manufacturer's
guidelines and safety standards such as those published by the National Fire Protection Associa-
tion (NFPA), the American Society for Heating, Refrigeration and Air Conditioning Engineers
(ASHRAE), and the local code authorities.
Note: The exhaust blower output is approximately 400 CFM (cubic feet per minute) without ductwork.
Each installation is different and ductwork affects blower output accordingly. Actual blower exhaust CFM
can be approximated using the graph below.
Step 1: Calculate the "equivalent duct length" using Table 1 on page 13 of these instructions for
your installation.
Step 2: Find the approximate intersection point of the blower exhaust performance curve with the
equivalent duct length to estimate the actual maximum blower output for your installation.
Examples: 50 equivalent ft of ductwork have approximately 320 CFM. 100 equivalent ft of ductwork
have approximately 265 CFM.
450
400
350
300
250
200
150
100
50
0
0
JP989 Downdraft Cooktop Exhaust Blower CFM
25 50
6-in. Diameter Equivalent Duct Length
6 in. Diameter Equivalent Duct Length
75 100
– 9 –
125 150
GEA00303