2-11
BOILER SYSTEMS AND OPERATION
SL 30-175, SL 45-260 MODULATING GAS BOILERS
use the
Summer Shutdown
field to enter a threshold temperature for the
avoidance of heating during warmer times. this is typically set at 60° to 65°F
so as to eliminate excessive boiler cycling in marginal heating conditions.
use the
Minimum Temp.
field to optimize boiler run times on low mass loads.
Finned tube baseboards sink very little heat when operated below 100°F;
application of a “full reset curve” (e.g. 160°F right down to a 70°F room
target) would cause boiler cycling in light-to-moderate heating conditions.
set baseboard minimums at 100-120°F and aim for 4 or less cycles/hr. a
minimum setting can also be used to enhance home comfort with single or
excessive speed air handlers to avoid the cool blast effect. set the lowest
possible level for combustion efficiency.
10.
For all loads, select and enter a
Maximum
allowable temperature and on/
off
Supply Differential Temp.
note these values must be input; they are not
automatically assigned as done within some boiler controls. ensure the
Maximum takes account of the construction and safety requirements of each
application – e.g., 140°F max. for typical in-slab radiant floor, for avoidance of
thermal stress. the differential shall be set to offer a reasonable temperature
control range (suggested values: 20°F for high mass radiant // 30°F for low
mass baseboards // 16°F for dHW). ensure that the spread between the
Target
and
Maximum
temps is greater than one half of the
Differential
(e.g.
for a radiant floor
Design Supply Temperature
of 125°F and a
Maximum
of
140°F, a differential of 20°F (half of which is 10°F) fits nicely.
11.
avoid situations where the
Maximum
is close or below the potential target, or
the boiler will cycle off its (software) water high limit.
12.
Priority:- where more than one load is present, it is critical that a value be
entered to allow reasonable load scheduling
(see Section 2.6.1).
13.
at the lower end of the load 1-2-3 setup screen, there are 4 lines available
for “mapping” of sensor inputs.. For example,
“Indoor Temp. from …..Indoor”
indicates that the boiler will look for a signal from an indoor sensor on the
indoor sensor wiring contacts. Failing a valid signal, the screen will display
“Indoor Temp. …..Open”
, and there will be no effective indoor trim of the
reset curve. these lines do not require amendment at most installation sites.
the mapping feature allows reassignment of the sensor contacts to support
non-standard functions. For example, re-allocation of the Water temp. signal
from “(boiler)
Outlet
” to
“Secondary Loop”
will allow the throttle management
routine to manage a secondary loop temperature rather than the boiler’s own
direct supply temperature. use this when injecting into a commercial heating:
cooling loop. another possibility: two separate reset channels – each with its
own indoor trim. sensor ports open for such re-assignment are dHW, indoor,
outdoor and secondary loop.
14.
The final 3 lines are for the motorized mixing valve option. See separate
documentation for this.
15.
to compensate for altitude at the installation site, use the
Altitude
adjustment
feature, found in the front
Installer Setup
menu (several lines below
“Heat
Load Configuration”
. Key in the altitude – in hundreds of feet above sea
level. For example, an installation at 2,860 feet should be entered as “29” (as
rounded to the nearest hundred).
16.
two lines below
Altitude
adjustment is the field for amendment of the primary
pump heat purge time. To shorten the 5 minute post-firing period, reduce the
300 second interval to as low as 60 sec. similar adjustment of secondary
pump run time can be made in the
Heat Load Configuration / Configure Load
1,2,3
fields (down to zero sec.= off).
Summary of Contents for SL 30-175
Page 76: ...NOTES...