SYSTEM SETTINGS
- SYSTEM SETTINGS 2-
Setback
>Rotate Time
Last Stg Hold
Value
Value
ADJUST
PRESS TO SELECT
ADJUST
PRESS TO SELECT
ADJUST
PRESS TO SELECT
Press to
show setting
Turn to
adjust value
Press to
select
new
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.
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- SYSTEM SETTINGS 2-
Rotate Time
>Lst Stg Hold
Password
- LAST STAGE HOLD -
Value
- LAST STAGE HOLD -
Value
ADJUST
PRESS TO SELECT
ADJUST
PRESS TO SELECT
ADJUST
PRESS TO SELECT
Press to
show
setting
Turn to
adjust value
Press to
select
new
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.
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.
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.
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