Thermador HMCB36FS Manual page 6

S E L E CTI N G T H E R I G H T H OOD
CHOOSING THE RIGHT CfM
1. POWER AND SIZE Of THE COOkTOP
The power of your cooktop, measured in BTUs (British thermal units), is perhaps the most important factor in determining CFM
(cubic feet per minute) needs for your hood.
PROfESSIONAL SERIES RANGES AND RANGETOPS
Thermador's Professional Series Hoods are tested and approved
to withstand the high heat generated by our Professional Ranges
and Rangetops.
Professional gas cooktops generally should have 1 CFM for every
100 BTUs.
Example: A Thermador 30" Professional Range with a
60,000 BTU Cooktop should have a 600 CFM Hood. It is
also important to note that this method assumes that all
burners are on high at the same time. Griddles and grills
generally require an additional 200 CFM.
30" PROFESSIONAL
WALL HOOD (600 CFM)
+
30" PRO GRAND
RANGE (60,000 BTU)
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MASTERPIECE® SERIES COOkTOPS
Thermador's Masterpiece Series Hoods are best matched with our
non-professional cooking products.
For electric and induction cooktops, and gas cooktops under
60,000 BTUs, choose a blower with a minimum of 100 CFM per
12" of cooktop width.
Example: A Thermador 36" wide Cooktop requires a
blower with a minimum of 300 CFM.
36" HOOD WITH
>_300 CFM
+
36" INDUCTION
COOKTOP
CHOOSING THE RIGHT CfM
2. COOkING STYLE
The appropriate airflow capacity is determined by evaluating the
cooking space and the occupants' cooking habits.
• More demanding cooks usually require more exhaust capacity to
handle moisture generated by boiling large pots of water or the
grease and smoke resulting from grilling or frying. This cooking
style could require a hood or downdraft system with airflow of 600
to 1300 CFM.
• High heat cooking or aromatic foods may require additional CFM.
Increasing capture area by 3" on each side is also a recommended
way to address this issue.
• For those who are used to preparing quick meals in a relatively small
kitchen, a hood with 400 to 600 CFM may be adequate ventilation for
the cooking space.
• If the cooking surface is in a peninsula or island, a larger capacity
hood can provide better capture when there are cross currents and
when the hood needs to be mounted higher. Downdraft ventilation
systems are also a good alternative.
3. LENGTH AND SIZE Of DuCT WORk
Proper performance is dependent upon proper ducting. Use a
qualified and trained installer.
• Do not use flexible duct; it creates back pressure/air turbulence and
reduces performance.
• Straight runs and gradual turns are best. Use the shortest route with
the fewest turns possible.
• Check local codes for makeup air requirements, if any. For more
information on makeup air, see page 42.
If using a 10" duct, Thermador recommends not exceeding 150 feet
of duct. Transitions, elbows and wall or roof caps are all factors that
will add more static pressure, therefore increasing your equivalent
duct run.
Example: Assume you have 30 feet of straight 10" duct with
two 90-degree elbows and an outside wall cap. To calculate
the equivalent straight duct run pressure, you would add
12 feet for each elbow, and 5 feet for the outside wall cap,
increasing your equivalent total run from 30 to 59 feet.
DUCT STATIC PRESSURE EQUIVALENTS
30' DUCT WITH 2 ELBOWS
AND AN OUTSIDE WALL CAP
=
59' OF STRAIGHT DUCTING
For more information on the equivalent duct lengths for commonly
used transitions, see page 41.
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