Parameter Explanations; Outdoor Reset Operation - Weil-McLain ULTRA ULTRA-105 Service Manual

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GAS FIRED WATER BOILER SERIES
See Figure 25, page 42 for procedure to access Parameter settings.

Parameter explanations

Fixed-temperature operation (outdoor tem-
perature sensor not installed) — To operate with
constant outlet temperature, set parameter 4 to
the required supply water temperature for the
system.

Outdoor reset operation

1. The closer the heating unit output matches the heat loss, the
less the swing in indoor temperature. Outdoor reset adjusts
the supply water temperature so the heat output from the
heating units matches the heat loss as the outdoor temperature
changes. The colder the outdoor temperature, the warmer the
water temperature, and vice versa.
2. The control module temperature parameters are named
T1xxx for boiler water temperatures and T4xxx for outside
temperatures.
3. Parameters 4 through 7 determine the water temperature
reset curve, as shown in Figure 27, page 45.
4. is the Outdoor Design Temperature
for the building location, used to calculate design heat loss.
Set parameter 6 ( T4
5. At the ODT, the boiler outlet water tempera-
ture must be at the
required output from the heating units.
Set parameter 4 ( T1 ) equal to the design water tem-
perature.
6.
temperature at which building heat loss
is required at this outside temperature.
Set parameter 7 ( T4
temperature, typically 60 to 70°F.
7. When outside temperature is at or above the
balance point temperature, the boiler outlet water tempera-
ture should equal room temperature — this would result in
zero heat output by the heating units.
Set parameter 5 ( T1 ) equal to the design room tem-
perature, typically 68 to 70°F.
8. Automatic temperature boost timing
Automatic temperature boost compensates for required
pick-up times and variations in heating load requirements.
It automatically increases setpoint temperature when a
call for heat exceeds a preset time (parameter 11).
See page 46 for further discussion.
Set parameters 4 to 7 as needed for the desired
reset curve. Make sure to set parameters 4 and 6
so the outlet water temperature is at design water
temperature when outside temperature drops to
the ODT (outdoor design temperature) or lower.
44
1 & 2
) equal to the ODT.
to provide
is the outside
building heat
) equal to the balance point
—
9. Boiler setpoint temperature (
The control module regulates the boiler outlet water to
the temperature required by the reset curve.
For outside temperature at or below the ODT — pa-
rameter 6 (T4
parameter 4 (T1 ).
For outside temperature at or above the balance point
temperature — parameter 7 (T4
temperature equals parameter 8 (T1 ).
For outside temperatures between parameter 6 and pa-
rameter 7, the setpoint temperature is on the reset curve
sloped line, between T1
See Figure 27, page 45 and Figure 28, page 45 for ex-
amples.
If a call for heat exceeds the time set in parameter 11,
the setpoint temperature will automatically be boosted
(increased) above the reset curve value as explained on
page 46.
The boiler may not operate as low as T1 , because pa-
rameter 10 (T
water temperature. If the calculated setpoint, T1 , is
less than T , the boiler shuts off. See parameter 10
explanation below.
Parameter 9 (T4
1. Location of the outdoor sensor may sometimes cause the
sensor to incorrectly detect outside temperature.
2. You can set parameter 9 to correct for this difference (up to
9°F more or less) if you believe boiler response needs to be
improved. Set a negative number to reduce the outdoor tem-
perature reading, a positive number to increase the reading.
Parameter 10 (T )
1. Use this parameter to set a minimum operating boiler outlet
water setpoint temperature.
2. When calculated setpoint temperature, T , is at or below
T the boiler shuts down (after operating a postpump
cycle).
3. To deactivate this parameter, set the value to 32.
Suggested outdoor reset parameter settings
1. Parameter 4, T1 — Set to the required supply water tem-
perature when outdoor temperature is at or below ODT
(outdoor design temperature).
2. Parameter 5, T1 — Set equal to the required room tem-
perature for the building.
3. Parameter 6, T4
temperature.
4. Parameter 7, T4
ture for the building (typically 60 to 70°F).
T1 )
), the setpoint temperature equals
), the setpoint
and T1 .
), sets a minimum operating outlet
)
— Set to the ODT outdoor design
— Set to the balance point tempera-
Part number 550-100-029/0810