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Software Revs 3,5,6,8,10, 12 Infinity /Evolution Troubleshooting (Rev. 2)

10-12-2006

• Evaluate structure for zoning suitability

Zoning system will not run or shuts down intermittently. “EXCESS STATIC PRESSURE”

appears in the last 10 faults

System may be held off until more zones are calling. If the zone or zones calling are not capable

of delivering the minimum required airflow, the system will wait until more zones call for

conditioning.

This system contains a Blower Cutback algorithm that will not allow the system to run in

extremely restrictive conditions. Blower Cutback is initiated when the blower has reached its

maximum RPM, and is unable to deliver the requested airflow. The blower sends a signal at the

maximum RPM which varies depending on the equipment installed. This usually occurs at

around 1200-1300 RPM.

The steps below occur when Blower Cutback has been initiated:

In furnace heating, or heat pump comfort heating, the system will stage down or shut down

immediately until more zones call for heat. In heat pump Efficiency heating, the airflow will be

reduced heat pump Comfort levels and stage down if that is not possible

In cooling, there is more airflow flexibility. The following process occurs in cooling mode:

• CFM request is reduced in 50 CFM increments (this reduction is visible in the status

screens) Static pressure display is not valid in this range and should be ignored since

the unit cannot deliver the requested airflow.

• If blower RPM is still above cutback levels, continue reducing CFM request about once

a minute

• Reduce CFM request down to minimum CFM described above

• If CFM is at minimum, and cutback is still in effect, begin the same airflow relief process

used for Airflow Limits and record EXCESS STATIC PRESSURE fault in last 10 system

events

• If minimum airflow cannot be achieved after this process, stage down to low and

continue until Cutback is no longer active, or shut off if necessary

Options if EXCESS STATIC PRESSURE is active in Last 10 Events:

• Decrease airflow limit setting to from MAX to something else. This will engage the

airflow management algorithm sooner and may allow the system to run longer.

• Evaluate duct design and make improvements where necessary

• Evaluate structure for zoning suitability

Zoning Situation: “AIRFLOW LIMITED, STAGEDOWN/SHUTDOWN OCCURRED” appears in

the Last 10 Faults:

Factory default airflow limit is High in each zone. This means that the zone is allowed to

deliver 200% of the maximum assessed airflow. For example, if the maximum heating airflow

is 2000 CFM and a zone’s relative size is 25%, the maximum airflow for that zone when set to

High is calculated to be 2000 CFM * 25% * 200% = 1000 CFM

If the airflow limit is set to MED, the max allowable airflow is 150%, if set to LOW; 100%. If set

to MAX, there is no airflow limit, but the system could still shut down in heating if the maximum

motor RPM is reached due to EXCESS STATIC PRESSURE.

If the equipment owner is not complaining about zones being under conditioned, then this

message should be ignored. It indicates that the airflow limit was exceeded for a zone and the

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