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Eclipse ThermJet Self-Recuperative, V5, Design Guide 208, 9/16/2011
2. Calculate the Blower Air Volume
The volume of air required will be dictated by the
maximum output required from the burner. This will be
the total of the air required for combustion plus the air
required for the eductor. The totals required are
shown on the appropriate datasheet. Multiply this
volume by the number of burners and this is the total
volume needed.
NOTE:
A minimum of 10% safety margin should be added
to the blower capacity.
Exhaust
The eductor provided with the TJSR is capable of pulling
all the exhaust gas through the burner and when set up
correctly will give approximately neutral pressure in the
furnace chamber. Using this method it is not possible to
use furnace pressure control.
An alternative method, where more precise furnace
pressure control is required, is to pull only 90% of the
exhaust gases through the burner. The remaining 10% of
exhaust gas would exit through an auxiliary flue with
furnace pressure control.
The furnace pressure should not be too high; a positive
pressure will force a disproportionate amount of exhaust
gases through burners that are in the off or low fire mode.
Exhaust ducting should not be connected directly to the
eductor outlet. It’s recommended that the exhaust duct or
cowl be at least 2" larger in diameter than the eductor
outlet. There should be at least a 2" vertical air gap.
Air Pressure Switch
The air pressure switch gives a signal to the monitoring
system when there is not enough air pressure from the
blower.
You can find more information on pressure switches in
Blower Bulletin 610.
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Eclipse supports NFPA regulations, which require
the use of an air pressure switch in conjunction
with other safety components, as a minimum
standard for main gas safety shutoff systems.
Step 6: Main Gas Shut-Off Valve Train
Consult Eclipse
Eclipse can help you design and obtain a main gas shut-
off valve train that complies with the current safety
standards.
The shut-off valve train must comply with all the local
safety standards set by the authorities that have
jurisdiction.
For details, please contact your local Eclipse
representative or Eclipse.
NOTE:
Eclipse supports NFPA regulations (two shut-off
valves) as a minimum standard for main gas safety shut-
off systems.
WARNING
