6
NOTE: Some gas utility companies derate their gas for altitude,
making it unnecessary to install high altitude orifices. Call the
local gas utility company to verify BTU content.
FIELD INSTALLED COMPONENTS
When installing the boiler, the following components MUST be
used, if applicable:
1) Circulating Pump (Hydronic)
2) Tank Temperature Control (Hot Water Supply)
3) Loop Temperature Control (Hydronic)
4) Low Water Cutoff Device
5) Relief Valve
6) Pressure Gauge
7) Manual Gas Shutoff Valve (Supply)
Check the FEATURES AND CONTROLS section for further
information.
FIGURE 1.
PANELS AND COVERS
All panels and covers (e.g. control and junction box covers; front,
side and rear panels of boiler) MUST be in place after service
and/or before operation of the boiler. This will ensure that all gas
ignition components will be protected from water.
NOTE: Remove the two (2) sheet metal screws from the rear of
the top cover and discard them, see fig 1. This will allow removal
of the top cover without the use of tools. Also, remove the sheet
metal screw from the bottom of the front panel.
FEATURES/CONTROLS
The Legend 2000
®
is a low-pressure boiler (Category IV) to be
used as either hot water supply (domestic/commercial water
heating) or hot water heating (hydronic) application. Category IV
boilers operate with a positive vent pressure and with a vent gas
temperature less than 140°F (60°C) above its dew point. Category
IV appliances are often termed “High Efficiency” appliances.
This high efficiency is obtained from a unique heat exchanger
design consisting of multiple integral high-finned copper tubes
brazed in parallel into two brass manifolds. The condensate
from the heat exchanger flows downward into the vent collector
housing then into the plastic condensate drain and through the
attached flexible hose which must terminate at a suitable floor
drain.
ELECTRONIC IGNITION CONTROL
The Legend 2000
®
is controlled by the WHC 1502 ignition system,
fig. 2. The WHC 1502 is a solid-state ignition control that ignites
the main burner by energizing the Hot Surface Ignitor, fig. 3. The
ignition control system continuously monitors the current of the
ignitor and will not allow gas to enter the main burner until current
flow reaches the preset ignition temperature threshold. Once
the ignition threshold has been reached, the control system will
open the gas valve(s). After the main burner ignites, the control
system monitors the burner flame through the principle of flame
rectification. If a flame is not verified, the gas valve is immediately
closed.
FIGURE 2. FIGURE 3.
The control board provides a pre-purge period of twenty (20)
seconds and a post-purge period of twenty-five (25) seconds.
The flame establishing period is four (4) seconds.
This control is non-adjustable. Any attempts to modify the
performance, other than those listed in this manual, voids the
control warranty.
The 24 VAC circuitry of the ignition control system is protected
with a 3-amp fuse. If the fuse opens, a red LED located near the
fuse will light.
HOT SURFACE IGNITOR
The Hot Surface Igniter, fig. 3, is a device that ignites the main
burner by high temperature (>1800°F) [982°C]. The igniter is
made of recrystallized silicon carbide, and when 120 VAC is
applied to the igniter, sufficient heat is generated to ignite the
main burner. Although improvements have been made to
strengthen the igniter, it is still fragile and care must be taken in
handling the igniter to prevent breakage.
FIGURE 4.
BLOCKED FLUE SWITCH
The Blocked Flue Switch (BFS) fig. 4, is a single-pole, normally
closed pressure switch that will open its contacts when a rising
positive pressure of 1.0 in. w.c. (0.25 kPa) is encountered. The
contacts will close when the pressure falls below the fixed set
point of 1.0 in. w.c. (0.25 kPa) The BFS monitors the pressure
inside the venting system. If the venting system is blocked in
such a way that the build up in pressure exceeds the setting of
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