1.6 BOILER ACCESSORY EQUIPMENT
1.6-1 ELEMENTS
The immersion type electric resistance heating
elements are mounted in a standard 150# flange
(300# flange if required). These elements are
held into this flange with brass fittings. Each
element hairpin is rated at 5 KW or 10 KW at
the rated volts. The incoloy sheath is a nickel,
chrome and iron alloy, which provides good
resistance to oxidation and has good strength
characteristics at elevated temperatures. By
virtue of its very high nickel content, the
material does not have a tendency to become
embrittled after prolonged exposure to
temperatures. Corrosion resistance of the
incoloy is attributed to the chrome and nickel
content of the alloy. This type of material was
chosen as a sheath material because of its
resistance to corrosion oxidizing conditions and
attacks from impurities in the various water
conditions. Each element is easily replaced by
using ordinary hand tools. This eliminates the
necessity of having a complete element bundle
as spare parts and also eliminates the necessity
of returning the element bundle to the
manufacturer for repair, although this service is
available.
1.6-2 BOILER COMPONENTS - GENERAL
The boiler equipment list in this manual lists
the components supplied with this boiler. A
description of the major components follows,
however, detailed information can be found in
each manufacturers literature data.
1.6-3 POWER PANEL WIRING
These circuits are broken down into branch
circuits of no more than 50 amps per circuit. A
distribution lug in the BE Series and a copper
bus bar in the BH Series is used to branch the
power to individual fuses and contactors in
each branch circuit. Each leg in each circuit is
individually fused with fast acting fuses to
interrupt power if required. The contactors are
then wired using high temperature wire to each
element circuit and bundle located in the
element flange discussed earlier.
1.6-4 CONTROL CIRCUIT WIRING
The control circuit voltage is 120 V, single
phase, and fed from a step down transformer (if
provided). The transformer=s primary side is
connected to two fuses located in the power
panel. One side of the secondary is grounded
and the other side feeds the control circuit
through the control circuit fuse. All of the
safety controls are wired in series so that any
one of the safety controls will shut down the
boiler if the limit is reached. Also, located in
the control circuit is a recycle relay (in some
cases the relay is built into the sequencer). In
case of power failure, the function of this relay
is to eliminate a sudden power load on the
distribution system. If a power failure occurs,
the recycle relay interrupts the control circuit
power causing the magnetic contactors to drop
out. Power is shut off to the elements until the
modulating motor has driven the sequencer
back to its original starting position. The relay
is then activated, and the sequencer will bring
the steps back on one at a time until the system
is again balanced. There is also a limit supplied
to be installed with the shunt trip on the main
circuit breaker in order to completely shut
down all power to the boiler. Refer to your
electric wiring diagram supplied.
1.6-5 SAFETY RELIEF VALVES
The safety relief valves are mounted on the top
of the boiler. These are a final safety device in
case the operator and other safety devices fail.
Such a failure will cause the pressure to rise in
the boiler to the set pressure of the relief valve.
The relief valve will discharge, so that the
boiler will not be able to generate pressure
beyond the set pressure of the relief valve.
1.6-6 LOW WATER CUT-OFF
The function of the low water cut-off is to shut
down the boiler if for any reason the water
level should drop below the normal operating
range.
