Form 2055 4 Revision Date 5/1/2015
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
manufacturer’s 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.
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 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.
