Lochinvar Harmony - Manual (Page 20)

20
ROTATE TIME Default 24hr
• The Rotate Time only takes effect if the Auto Rotate type is Time
(see pg. 17).
• The default value is 24 hours and is appropriate for most systems.
With 24 hour rotation, at 2 am every morning, the Lead Stage will
change to the next stage in Auto Mode. Note: If you do not set the
system time (see pg. 21), the Harmony will assume it was installed at
2 pm.
• The Rotate Time is adjustable in one hour increments from 1 hour to
168 hours (7 days).
• If the Rotate Time is not 24, the Lead Stage will change to the next
stage in Auto Mode every time the Rotate Time has elapsed. For
example, with a 12 hour Rotate Time, the Lead Stage will rotate from
A to B after the first 12 hours of operation, and then from B to C
after the next 12 hours, and so on.
LAST STAGE HOLD Default 0
• The Last Stage Hold prevents short cycling of the Lead Stage
during low load conditions.
• Even at 1% modulation, most fully modulating units are outputting
at least 20% of their maximum output. Some units may be outputting
significantly more.
• In low load conditions, the system might require only 5% of the
output of one Stage. When the Harmony brings on the Lead Stage,
this is 20% of the output. The Set Point is quickly exceeded, and the
Harmony turns the Lead Stage off.
• To prolong the run time during this type of condition, use the Last
Stage Hold setting.
• The Harmony will allow the system temperature to exceed the Set
Point by the number of degrees selected, before the Lead Stage is
turned off.
• For example, with a Set Point of 160°F and a Last Stage Hold setting
of 20°F, the Lead Stage boiler will remain on, at low modulation, until
the Set Point reaches 180°F.
Avoiding Conflicting Boiler Limits
• The temperature limits set on the boilers MUST be set considerably
higher than the Harmony's Set Point for the reasons detailed below.
• The Harmony sensor is located in a common header some distance
from the boilers.
• As the water enters the header and travels to the sensor location,
energy is dissipated.
• Therefore, the temperature in the header will correctly be lower than
that registered by sensors in the boilers.
• In addition to the normal drop experienced between the boiler's
internal reading and that read by the Harmony sensor, the Last Stage
Hold setting must be accounted for. The boiler limit must be set
above the Set Point PLUS the Last Stage Hold PLUS the normal
drop experienced in the piping.
• Using the previous example of a Harmony Last Stage Hold with a
20°F Set Point, the boilers' limits must be set enough over 180°F to
prevent the boilers' internal limits being reached. In this situation,
the boiler high limit should be set at approximately 195°F to prevent
the difference in boiler temperature vs. header temperature causing
erratic operation.
-AUTO ROTATE PERIOD-
Value -> New Value
-AUTO ROTATE PERIOD-
Value -> New Value
- SYSTEM SETTINGS 2-
Setback
>Rotate Time
Last Stg Hold PRESS TO SELECT
ADJUST
Press to
show
setting
PRESS TO SELECT
ADJUST
Turn to
adjust
value
PRESS TO SELECT
ADJUST
Press to
select
new
- LAST STAGE HOLD -
Value -> New Value
- LAST STAGE HOLD -
Value -> New Value
- SYSTEM SETTINGS 2-
Rotate Time
>Lst Stg Hold
Password PRESS TO SELECT
ADJUST
Press to
show
setting
PRESS TO SELECT
ADJUST
Turn to
adjust
value
PRESS TO SELECT
ADJUST
Press to
select
new
IMPORTANT: The temperature limits set on
the boilers must be higher than the
Harmony Set Point. Read the section at
right for details that will prevent erratic
system operation.
SYSYSYSYSY
STEM SETTINGS 2STEM SETTINGS 2STEM SETTINGS 2STEM SETTINGS 2STEM SETTINGS 2