What are the requirements for the ACSC100 condenser unit

Issue:

What are the requirements for the ACSC100 condenser unit

Product line:

ACSC100

Environment:

All Product models, all serial numbers

Cause:

Condenser issues

Resolution:

ACSC Condenser

NOTE: The highest temp of condenser air will depend on the operating conditions. The ACSC101 unit has a total cooling capacity of 5.3kW at 26.7C db/19.4C wb, assuming 1440 m3/hr of 35C condenser inlet, while consuming 2.4kW of power. That corresponds to a total heat of rejection of 7.7kW, and at that airflow rate we get a 16C differential across the condenser. So the leaving air temp would be approximately 51C.  That's based on normally operating conditions. If the condenser inlet airflow was hotter or slightly restricted it is possible to get higher temperatures. I estimate that the hottest possible would be about 55C. Caution must be taken to ensure the condenser intake is not in an enclosed space.  The space is typically an open return to the building air handling system.  As noted in the install manual the exhaust duct should be slightly higher vertically to avoid mixing with the condenser intake.

The SC condenser section normally moves up to 1440 m3/hr (850 CFM), assuming fans at 100%, and no additional external static pressure drop.  The temperature of the discharge air will depend on the inlet air conditions.  Assuming a 35 C (95 F) condenser inlet the exhaust air would be approximately 44 C (111 F) on the 50 Hz unit (ACSC101), again assuming 100% condenser fan speed, and no additional external static pressure drop, as well as the unit operating at maximum capacity.  Other operating conditions will have different results.

Q: Can I connect the SC ducts directly outside?

A: Yes, with certain exceptions.  The SC condenser cannot tolerate inlet air below 32 F (0 C) as the unit has no low pressure provisions.  Low ambients will cause the unit to potentially fail to start due to refrigerant migration.  Higher than normal temperatures at the inlet air hotter than 105 F (40 C) will cause higher than normal head pressures and effect the integrity of the unit.  In these conditions it is suggested that the exhaust only be ducted and the inlet draw air from the datacenter. Be aware to avoid a negative pressure in the space.

Q: Can you please advise what will be exhaust outlet temperature if the inlet temperatures are 28degC or 32degC (88F or 91F)?

A: Many factors will affect the exhaust temperature; therefore the easiest approach is to assume that the dT across the condenser remains the same.  With a 9 C delta I would estimate that the condenser exhaust temperatures would be approximately 37 C and 41 C respectively.

Note:  Inlet temperature

-105 F (40 C) – Maximum recommended

-Above this limit unit cooling capacity is significantly impacted

-32 F (0 C) – Minimum recommended

-Below this limit condensation can form in the SC enclosure.  Unit has no low ambient (flooded) controls

-Restricted airflow will reduce maximum unit cooling capacity

These limitations are necessary to ensure proper operation of the SC unit.  High inlet temperatures to the condenser limit the maximum cooling capacity of the unit and can lead to shut down.  The High Head Pressure Protection (HHPP) feature discussed earlier will proactively take steps to reduce the unit capacity, and thus the heat rejection requirement) in situations where the inlet temperature is too hot, or the airflow is overly restricted.

Inlet temperatures that are too cold can cause condensation to form on the enclosure and also cause erratic operation of the unit. The condenser maintains a target head pressure by modulating the speed of the condenser fans. When the inlet temperature is too low the fans can not slow down enough and then the unit will not control the temperature in the room properly.

Any pressure drop beyond the duct kit will reduce the condenser airflow and impact the unit performance. Up to 0.25” (63 kPa) of additional static pressure beyond the standard duct kit installation can be tolerated with only a small impact on the condenser performance. The maximum allowable condenser inlet temperature at that point is still below the rated temperature of 95 F (35 C).

You may need a booster or compensation fan maybe needed in many circumstances to prevent a significant reduction in performance.

When the condenser airflow is restricted, as discussed in the previous slide, the HHPP feature will proactively reduce the unit cooling capacity in an attempt to avoid a complete shut down.

Released for:APC USA