U.S. Boiler Company Alpine ALP080B, Installation, Operating And Service Instructions

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103448-10 - 6/18
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X. Operation
B. Supply Water Temperature Regulation
B. Supply Water Temperature Regulation
1. Priority Demand
The Control accepts a call for heat (demand) from
multiple places and responds according to it’s “Priority”.
When more than 1 demand is present the higher priority
demand is used to determine active boiler settings.
For example, when Domestic Hot Water (DHW) has
priority the setpoint, “Diff Above”, “Diff Below” and
pump settings are taken from DHW selections. Active
“Priority” is displayed on the “Boiler Status” screen.
Priority Status Screen
Display
Boiler Responding to:
1st Sequencer
Control
The boiler is connected to the peer-to-peer
network. The boiler accepts demand from
the Sequencer Master.
2nd Domestic Hot
Water
DHW call for heat is on and selected as
the priority demand. DHW is always higher
priority than Central Heat. It also has higher
priority than the Sequencer Control when
DHW priority is “enabled” and “Boiler Piped”
IWH is selected.
3rd Central Heat Central Heat call for heat is on and there
is no DHW demand or DHW priority time
has expired.
4th Auxiliary Heat Auxiliary Heat call for heat is on and there
is no Central Heat or DHW demand. (NOTE:
May be user selected to be higher priority
than Central Heat.)
5th Frost
Protection
Frost Protection is active and there is no
other call for heat. Frost protection will be a
higher priority than Sequencer Control if the
Sequence Master has no active call for heat.
6th Warm
Weather
Shutdown
(WWSD)
WWSD is active and the boiler will not
respond to central heat demands. DHW
demand is not blocked by WWSD.
7th Standby There is no demand detected.
Table 26: Order of Priority
2. Setpoint Purpose
The Control starts and stops the boiler and modulates
the boiler input from minimum (MBH) to maximum (MBH)
in order to heat water up to the active setpoint. The
setpoint is determined by the priority (Central Heat or
Domestic Hot Water) and as described in the following
paragraphs.
3. Central Heat Setpoint
Upon a Central Heat call for heat the setpoint is either the
user entered Central Heat Setpoint, or is automatically
adjusted by a thermostat’s “Sleep” or “Away” modes
and/or Outdoor Air Reset or, an Energy Management
System (EMS) supplied 4-20mAdc setpoint.
4. Auxiliary Heat Setpoint
Auxiliary Heat is a second heating demand that may
be used to serve either lower temperature radiation
or warmer heat demands such as fan coils. Upon an
Auxiliary Heat call for heat the setpoint is either the
user entered Auxiliary Heat Setpoint or is automatically
adjusted as a thermostat’s “sleep” or, Away Modes or,
Outdoor Air Reset .
5. Outdoor Air Reset
If an outdoor temperature sensor is connected to the
boiler and Outdoor Reset is enabled, the Central Heat
and Auxiliary Heat setpoints will automatically adjusted
downwards as the outdoor temperature increases. When
the water temperature is properly matched to heating
needs there is minimal chance of room air temperature
overshoot. Excessive heat is not sent to the room heating
elements by “overheated” (supply water temperature
maintained too high a setting) water. Reset control saves
energy by reducing room over heating, reducing boiler
temperature & increasing combustion efficiency and,
reducing standby losses as a boiler and system piping
cool down to ambient following room over heating.
6. Boost Time
When the Central Heat Setpoint is decreased by Outdoor
Air Reset settings the Boost function can be enabled to
increase the setpoint in the event that central heat demand
is not satisfied for longer than the Boost Time minutes.
The Boost feature increases the operating temperature
setpoint by 10°F (5.6°C) every 20 minutes (field adjustable)
the central heat demand is not satisfied. This process will
continue until heat demand is satisfied (indoor air is at
desired temperature). Once the heat demand is satisfied,
the operating setpoint reverts to the value determined by
the Outdoor Air Reset settings. If Boost Time is zero, then
the boost function is not used.
7. Domestic Hot Water (DHW) Setpoint
Upon a DHW call for heat the setpoint is either the user
entered DHW setpoint or the Thermostat’s “Sleep” or
“Away” DHW setpoint. The optimal value of this setpoint
is established based on the requirements of the indirect
water heater.
8. Domestic Hot Water Priority (DHWP)
Some boilers are used primarily for building space
heating, but also provide heat for the domestic hot water
users. When the outdoor temperature is warm, the
outdoor reset setpoint may drop lower than a desirable
domestic hot water temperature. Also, often it is required
to quickly recover the indirect water heater. When DHWP
is enabled, heating circulators are stopped, the domestic
circulator is started and the domestic hot water setpoint is
established in response to a domestic hot water demand.
Priority protection is provided to allow the heating loop
to be serviced again in the event of an excessively long
domestic hot water call for heat.
9. “Setback” Setpoints
User adjustable Thermostat “Sleep” or “Away” Setback
Setpoints are provided for both Central Heat and DHW
demands. The Setback setpoint is used when the
EnviraCOM thermostat is in “leave” or “sleep” modes.
When setback is “on”, the thermostat setback setpoint
shifts the reset curve to save energy while the home is
in reduced room temperature mode. The Honeywell
VisionPro IAQ (part number TH9421C1004) is a “setback”
EnviraCOM enabled thermostat.