18
2. With the unit operating, time the smallest dial on the
meter for one complete revolution. If this is a 2 cubic
foot dial, divide the seconds by 2; if it is a 1 cubic foot
dial, use the seconds as is. This gives the seconds
per cubic foot of gas being delivered to the unit.
3. ,1387 *$6+7*9$/8([6(&3(5&8%,&
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EXAMPLE: Natural gas with a heating value of 1000 BTU
per cubic foot and 34 seconds per cubic foot as determined
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Input = 1000 x 3600 / 34 = 106,000 BTU per Hour.
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sure all pilot burners are operating.
Main Burner Flame Check
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7ඍඕඍකඉගඝකඍ5එඛඍ&ඐඍඋඓ
Check the temperature rise through the unit by placing
thermometers in supply and return air registers as close
to the unit as possible. Thermometers must not be able to
sample temperature directly from the unit heat exchangers,
or false readings could be obtained.
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1. All registers must be open; all duct dampers must be
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unit operated for 15 minutes before taking readings.
2. The temperature rise must be within the range speci-
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ඌඑඎඎඍකඍඖඋඍඊඍගඟඍඍඖඛඝඔඡඉඖඌකඍගඝකඖඉඑක
With a properly designed system, the proper amount of
temperature rise will normally be obtained when the unit
is operated at rated input with the recommended blower
speed.
If the correct amount of temperature rise is not obtained,
it may be necessary to change the blower speed. A high-
er blower speed will lower the temperature rise. A slower
blower speed will increase the temperature rise.
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ඕඉකඓඍඌඖගඐඍකඉගඑඖඏඔඉගඍ
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The total external static pressure must be checked on this
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Total External Static Testing
1. Using a digital manometer measure the static pres-
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.
Mode
.
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2. 0HDVXUHWKHVWDWLFSUHVVXUHRIWKHVXSSO\GXFW3RVL-
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3. Add the two readings together.
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4. Consult proper table for quantity of air.
If the external static pressure exceeds the minimum or
maximum allowable statics. Check for closed dampers,
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