Hubbell ST - Manual (Page 11)

11
STEAM OPERATING CONTROLS
The steam operating controls are factory selected, sized, piped, and tested to ensure reliable
operation. Steam controls can be shipped loose, upon request, for in the field installation by others.
All steam components are factory plumbed with schedule 40 black iron pipe and ready for steam and
condensate connections. A cast iron ‘Y’ strainer with 20 mesh screen protects the steam controls and
coil from dirt and debris in the steam supply.
Traps
Two traps should be utilized in the immediate steam piping system of the water heater. The first trap in
the system is a drip trap that is designed to collect condensate from the main steam line before entering
the steam regulator. Additionally, a main condensate trap should be located in the condensate line after
the steam coil. This trap ensures that the steam remains in the coil and releases its energy before exiting
the coil and traveling down the condensate line. There are various types of traps available. The
following may be included in your water heater package:
1. Drip Trap
a. Thermostatic (Standard)
b. Cast Iron Float and Thermostatic type
c. Cast Steel Float and Thermostatic type
2. Main Trap
a. Cast Iron Float and Thermostatic type (Standard)
b. Cast Steel Float and Thermostatic type
c. Bucket
Steam Control Valves
1. Pilot Operated (Standard) – A high quality cast iron pilot operated steam control valve
comes with the standard unit. It is the most widely used type of valve for water heating
applications. In this type of valve, a temperature pilot device utilizes steam to operate the
main valve. No external power source is required other than steam. This highly dependable
temperature control system is suitable for most commercial and industrial applications.
2. Self Operating – This valve design includes a bulb and capillary assembly charged with a
thermally responsive vapor. The expansion / contraction of the vapor acts upon the valve
bellows in order to control the flow of steam through the valve. No external power is required
for operation.
3. Pneumatically Operated – In this configuration the building air supply feeds a factory
installed temperature controller that operates the steam control valve. The temperature
controller sends a precise air signal to the steam control valve which adjusts the flow of
steam into the heating coil. The temperature controller is fully adjustable from 50° - 250 ° F
and requires 20 psi air at a maximum consumption of 0.5 SCFM.
4. Electronically Operated – This control valve is similar to a pneumatically operated system,
except in this case the temperature controller is a sophisticated digital display electronic
device which outputs a 4-20 ma signal to a compact motor mounted on the steam control
valve in order to proportionally control the flow of steam to the heating coil. The temperature
controller displays set point as well as actual water temperature and is available with an
RS485 communications port for remote control.