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059705–00 REV. B
UNDERSTANDING OPERATION CONCEPT
The Genesis Heat-Timer
®
is a microprocessor-based control designed to manage a low-pressure steam heating system. The control
can operate a steam boiler or a two-way steam valve using a “cycle” concept to provide the desired amount of heat to the building.
THE “CYCLE” CONCEPT
The “cycle” concept was created by Heat-Timer specifically to allow steam heating systems to overcome the inabilities of standard
thermostatic controls to cope with the unique challenges of low-pressure steam heating. Unlike water and air systems, steam systems
take time to build up a “head of steam”. Moreover, after the system starts heating up, it has momentum that takes time to dissipate.
This makes it difficult to control its temperature.
CYCLE LENGTH BASED ON OUTDOOR TEMPERATURE
By monitoring the outdoor temperature, the Genesis Heat-Timer
®
is able to anticipate the building heating needs. Each cycle period
(usually 60 minutes long, but adjustable depending on the type of radiation units) consists of a Cycle-ON segment and a Cycle-OFF
segment. The length of the Cycle-ON segment will vary with the outdoor temperature. The colder it is outdoor, the longer the
Cycle-ON segment.
The Genesis Heat-Timer
®
constantly checks the outdoor temperature by means of an outdoor sensor located on the exterior
of the building. At the same time, it monitors the heating system of the building by means of a heating system sensor. This
heating system sensor tells the control when steam has reached the furthest location in the building (or the hardest to heat area,
(see “Piping Diagrams” on page 72)
. Based on this combined data, the Genesis Heat-Timer
®
calculates the length of the ON cycle
and begins the steam cycle.
The Genesis Heat-Timer
®
also provides two adjustable outdoor temperature cutoff settings, one for daytime operation and one for
nighttime operation. When the outdoor temperature rises above one of the cutoff settings, the Genesis Heat-Timer
®
will not call for
any heat.
FIGURE 1
EXAMPLE 60 MINUTE CYCLE
Cycle-On
21 Minutes
Establish
Heat
Establish
Heat
Cycle-On
21 Minutes
Cycle-Off
39 Minutes
Cycle delayed until System
Temperature drops belows
System Set Point-Diff
1
5
2
60 Minute Cycle
(Cycle-ON = Cycle-OFF = 39 mins)
3
4
03
STEAM HEATING
