Crestron electronic 1.5 Manual De Usuario

        

Installation & Operation Manual

When multiple boilers are installed, they can be wired together 
in a cascade sequence. A maximum of eight boilers can be 
controlled from a single control. In this application one boiler 
would be designated as the Leader control and all others would 
be designated as Member controls.

Once the Leader boiler receives a call for heat from the Enable 
input, the 0 - 10 VDC input, or ModBus, the control will 
determine what the set point will be. If outdoor air reset is 
desired, connect the outdoor air sensor to the terminals on 
the Low Voltage Connection Board on the Leader boiler. The 
set point will be calculated based on the programmed reset 
curve parameters. See the Crest Service Manual to program 
the reset curve. If outdoor air reset is not desired, do not 
connect the outdoor air sensor. A fixed temperature set point 
can be programmed into the control, or provided through the 
ModBus interface.  

If the water temperature at the controlling sensor is less than 
the set point + the turn-off offset - the off-on differential, 
the control will initiate a call for heat on the Cascade (see 
the Crest Service Manual for an explanation of the offset and 
differential). The Leader will energize the lead boiler on the 
Cascade. For a new startup this will be the Leader boiler.

The two (2) types of Cascade control are listed below:

Efficiency optimization is chosen when the application is such 
that overall heating efficiency is most important.  The Cascade 
will fire the boilers in a way that is the most efficient.  This 
allows more boilers to fire at one time, at a lower rate, thus 
more efficient.  This Cascade is also required when cascading 
boilers in a common vent application.

The Lead/Lag method is chosen when the application requires 
firing as few boilers at a time as possible.  This method will not 
bring on another boiler until the current number of boilers 
cannot meet the demand.  This Cascade is NOT allowed in a 
common vent application.

The parameters for both types of Cascade are adjustable. 

 

Reference the Crest Service Manual for a more detailed 
description of these adjustments.

To equalize the run time of all boilers on the Cascade, the 
firing sequence will automatically be changed at set intervals. 

For the first 24 hours after initializing the Cascade, the 
sequence will be changed every hour. After that the sequence 
will be changed once every 24 hours. 

For HW operation any boiler(s) in the Cascade can be selected 
to provide heat for a HW call. Select a boiler to be designated 
as the HW boiler. Connect the HW thermostat or sensor to 
the terminals on the Low Voltage Connection Board marked 
for the HW Thermostat or sensor. When the boiler receives 
a HW call, the Leader control will take that boiler out of the 
Cascade sequence. If another boiler is available, the Leader 
will start it up to take its place. 

The HW boiler will adjust its set point to the programmed 
HW set point and will adjust its firing rate to maintain this. 
Once the HW call has been satisfied, the Leader control will 
place that boiler back into the Cascade sequence. 

Night Setback and Ramp Delay operation of the boilers within 
the Cascade are available. Programming will be done through 
the Leader boiler. Refer to the Crest Service Manual for 
information regarding Night Setback and Ramp Delay.