Stack Limit (Safety Limit And Rate Limit); Outlet High Limit (Safety Limit And Rate Limit/Hydronic Only); Stepped Modulation Rate Limit - CleaverBrooks CFC Operation, Service & Parts Manual

CB FALCON

Stack limit (Safety limit and Rate limit)

Parameter
Stack limit enable
Stack limit setpoint
Stack limit response
Stack limit delay
STACK RATE LIMIT
If the stack limit is enabled, as the temperature approaches the
stack limit temperature, the Stepped Modulation rate limit
function (see "Stepped modulation rate limit" on page 46) is
active.

Outlet high limit (Safety limit and Rate Limit/Hydronic only)

Parameter
Outlet high limit enable
Outlet high limit setpoint
Outlet high limit response
OUTLET HIGH LIMIT CH PUMP CONTROL (HYDRONIC
ONLY)
Whenever the outlet high limit has been reached the CH pump
will be turned on. It will remain on until the outlet temperature is
lower than the outlet high limit setpoint minus 5°F.
OUTLET RATE LIMIT (HYDRONIC ONLY)
Whenever the outlet sensor is not used as the modulation
sensor, the outlet rate limit function is active. (This will occur
when modulating via the DHW sensor, the Header sensor, or
as a LL slave.) In these cases, as the outlet temperature
approaches the outlet high limit setpoint, the Stepped
Modulation rate limit function (see "Stepped modulation rate
limit" on page 46) is active.
750-265
Table 21. Limits and Rate Override: Stack Limit Parameters.
Disable, Enable, Enable single-non-safety
This parameter enables or disables the entire stack temperature limit function.
Disable turns off the Limit function.
Enable turns on the Limit function and requires a 10k dual safety NTC sensor.
Enable single-non-safety allows for 10kohm or 12kohm NTC sensor to provide limit (non-
safety) function.
Degrees or None
If the stack temperature reaches or exceeds the safety limit temperature given by this
parameter then the response defined below will occur.
Lockout, Recycle & delay
If the stack temperature exceeds the stack setpoint, then a response will occur. If the
selected response is a lockout, then the burner control locks out.
However, if the selected response is Recycle & Delay, the burner control recycles and holds
while waiting for a delay (see below) to expire, and after the delay it tries again (assuming
that demand is still present).
MM:SS
This parameter provides the delay time for the Stack limit.
Table 22. Limits and Rate Override: Outlet High Limit Parameters.
Enable, Disable
Enable function requires the outlet high limit sensor to be a safety check dual redundant type.
Disable allows for single sensor input to allow steam to use outlet as non-safety.
degrees or None
If the outlet temperature reaches the value given by this parameter then a response will occur
Lockout, Recycle & hold
This parameter selects the response. If lockout is selected, the burner control locks out. If
Recycle & hold is selected, the burner control recycles and waits for the outlet temperature to
fall. It will remain in this holding condition until the outlet temperature is lower than the outlet
high limit setpoint minus 5°F.
Comment
Comment

Stepped modulation rate limit

The Delta-T, Stack, and Outlet limit functions all use the same
stepped modulation limiting, which reduces the maximum
allowed modulation rate in five steps as the monitored
temperature approaches the limit.
The limiting performs as follows:
A range is determined by calculating:
range= Maximum modulation rate
- Minimum modulation rate
NOTE: The DHW maximum modulation rate is used when fir-
ing for DHW, and for other sources the CH maximum
modulation rate is used.
A step size is determined by dividing this range by 5:
stepsize=range/5
46