General Description
1-4 750-137 (revised 2012)
Model S, CR & HSB Electric Boiler Manual
The following optional equipment can be furnished by Cleaver-Brooks. The Dimension Drawings (DD) and Wiring
Diagrams (WD) shows the optional boiler equipment:
1. Manual reset low water cutoff
2. Auxiliary low water cutoff (manual or auto-reset)
3. Low pressure alarm
4. Pilot lights for individual steps
5. Toggle switches to enable/disable individual steps
6. Solid state progressive sequencing step control
7. Preheat switch
8. Demand limiting controls or interface
9. Control cabinet door interlock
10. Boiler disconnect switch or circuit breaker (with or without shunt trip, shipped loose for field mounting)
11. Ground fault detection
12. Metering ammeter, voltmeter or KWH meter
13. Alarm circuit (with or without horn/silence push button)
14. Automatic surface blowdown system
15. Local/remote modulation switch
16. SCR controller
9. Pressure Control System Boilers with 1 and 2 stages of control are standardly provided with on-off
pressure controls. Larger boilers are provided with a solid state, propor-
tional, modulating step-type pressure control system. As the system
steam pressure varies, the pressure control system proportions the input
power to the boiler demand, by increasing (or decreasing) the number of
heating element groups (steps) in use.
Both control systems (on-off and proportional) have adjustable pressure
ranges. The on-off controls have fixed differentials. The proportioning con-
trols have adjustable proportioning ranges.
This proportional solid state electronic sequencers also have an adjustable
time delay between steps varying from 5 seconds up to 10 minutes.
These adjustable controls enable the boiler to be tuned to the system it
regulates in order to optimize boiler responsiveness and system operation.
The controller features rapid recycling after power interruption. When
power is restored, the boiler starts with all elements off. To prevent cur-
rent surges, the step control ensures that the element groups are switched
on, one at a time.
10. Pilot Switch and Pilot Lights Pilot lights are standardly provided to indicate “power on,” “high pres-
sure,” and “low water.”
11. Safety Valve The safety valve is properly sized according to the boiler’s electrical rating
and per ASME and National Board.
12. Built-In Condensate/make-Up
Tank and Feedpump (model CR boil-
ers only)
This includes a condensate return tank and feedwater pump, completely
wired and piped. The condensate return tank is provided with a float-type
make-up valve, drain valve, and the necessary condensate return, vent,
and overflow connections.
Component Description
