238-47104-00A - Bradford White

SEQUENCE OF OPERATIONA 4 wire, double element heater wired for simultaneous operation is essentially two single element systems operatingindependently. The heaters are wired internally with two independent circuits, one circuit for each thermostat/elementcombination. When installed using a two wire service, the blue and red (or white) wires will be connected together,likewise black and yellow wires will be connected together.Sequence of Operation- Double Element, Simultaneous Operation, Single Phase, 4 wire service installation.1Line voltage from circuit one is appliedacross terminals L1 & L3 of the lowerthermostat. Likewise, line voltage fromcircuit two is applied across terminals L1 &L3 of the upper thermostat. ECO in bothupper and lower thermostat is closed, sothere is voltage at terminal L4 of eachthermostat and to one side of the upper andlower elements.Circuit one1Circuit twoECOClosedCircuit one2Thermostat closedat terminal T2Circuit two2Tank is cold therefore both thermostatsare closed at terminal T2 (calling for heat).This completes the circuit through thethermostats and allows current to flowthrough the elements.ECOClosedThermostat closedat terminal T23 Circuit oneWhen either thermostat is satisfied, it willopen at terminal T2, interrupting currentflow through the corresponding element. Asboth thermostats satisfy, the system will bein stand-by mode waiting for the next callfor heat. Thermostats will operateindependent of the other.3Thermostat openat terminal T2Circuit twoThermostat openat terminal T2Page 88