Step 5: Combustion Air System: Blower And Air Pressure Switch - Eclipse TFB030 Manual

It is recommended to check your local standards to verify.
Flame Sensor
Flame sensing is by flame rod (TFB030 & TFB075) or UV
scanner (all models).
The UV scanner must be compatible to the flame
monitoring control that is used. Refer to the manual of
your selected control for proper selection of the scanner.
■ If combustion air is preheated, the UV scanner
must be protected from high temperatures. Install
the UV scanner with a heat block seal and supply
cooling air. See Bulletin 834.
Flame Monitoring Control
The flame monitoring control processes the signal from
the flame sensor and controls the start-up and shut-down
sequences.
Eclipse recommends the following flame monitoring
controls:
• Trilogy series T600 (Instruction Manual 835)
• Veri-Flame series 5600 (Instruction Manual 818)
• Bi-Flame series 6500 (Instruction Manual 826)
• Multi-Flame series 6000 (Instruction Manual 820)
If other controls are considered, contact Eclipse to
determine how burner performance may be affected.
Flame monitoring controls that have lower sensitivity
flame detecting circuits may limit burner turndown and
change the requirements for ignition.
Flame monitoring controls that stop the spark as soon as
a signal is detected may prevent establishment of flame,
particularly when using UV scanners. The flame
monitoring control must maintain the spark for a fixed time
interval that is long enough for ignition.
Step 5: Combustion Air System: Blower and
Air Pressure Switch
The effects of atmospheric conditions
Blower data is based on the International Standard
Atmosphere (ISA) at Mean Sea Level (MSL), which
means that it is valid for:
• sea level
• 29.92" Hg
• 70°F.
If you are above sea level or in a hot area, the properties
of the air are different. As the density of the air decreases,
the outlet pressure and the flow of the blower decreases.
12
CAUTION
An accurate description of these effects is in the Eclipse
Combustion Engineering Guide (EFE 825). The Guide
contains tables for the effect of pressure, altitude and
temperature on air.
Blower
The rating of the blower must match the system
requirements.
You can find all the blower data in:
• Bulletin / Info Guide 610.
Follow these steps:
1. Calculate the outlet pressure:
When you calculate the outlet pressure of the blower,
you must calculate the total of these pressures:
- the static air pressure required at the burner
- the total pressure drops in the piping
- the total of the pressure drops across the valves
- the pressure in the radiant or immersion tube
(suction or pressurized)
- recommend safety margin of 10%
2. Calculate the required flow:
The blower output is the air flow delivered under
standard atmospheric conditions. It must be enough
to feed all the burners in the system at high fire.
Combustion air blowers are normally rated in terms of
standard cubic feet per hour (scfh) of air.
An example calculation follows the information tables
below:
Table 3.4 Required Calculation Information
Description
Total system heat input
Number of burners
Type of fuel
Gross heating value of fuel
Desired excess air percentage
(Typical excess air percentage @
high fire is 15%)
Air/Gas ratio
(Fuel specific, see table below)
Air flow
Gas flow
Eclipse TFB, V2, Design Guide 310, 11/14/2014
Unit of Formula
Measure Symbol
BTU/hr Q
- -
- -
BTU/ft q
3
percent %
-
scfh V
air
scfh
V
gas