YORK YK — HIGH AMBIENT TEMPERATURE FLT

HIGH AMBIENT TEMPERATURE FLT is shown on the VSD display of the YORK YK water-cooled centrifugal chiller. It is one of the VSD display messages, and the manual treats it as a shutdown, listing its potential causes and remedies. The panel prints the message in this exact wording.

What the VSD monitors as ambient temperature is actually the temperature detected by a component mounted on the VSD logic board. The high ambient trip threshold is set for 140°F, so the fault indicates that the temperature detected at the logic board has reached that threshold and the VSD has shut down.

• Internal VSD fan failure.
• VSD water pump failure.
• Entering condenser water temperature which exceeds the allowable limit for the job.
• Plugged strainer. Very dirty condenser water can plug the standard 1.5” Y-Strainer, which contains a woven wire mesh element with 20 stainless-steel wires per inch.
• Plugged heat-exchanger. In cases where the strainer plugs frequently, the heat-exchanger may eventually plug or become restricted to the point of reduced flow.
• Low condenser flow. The VSD system requires 8 feet of pressure drop across the heat exchanger to maintain adequate GPM.

1. If the condenser water is very dirty and plugs the standard 1.5” Y-Strainer frequently, consider a dual strainer arrangement with quarter turn valves, which permits cleaning of one strainer with the unit still on-line.
2. Back-flush the heat-exchanger by reversing the two rubber hoses which supply condenser water to and from the heat-exchanger.
3. If the rust or sludge cannot be back-flushed, the heat-exchanger may need to be replaced.
4. Check the pressure drop across the heat exchanger: the VSD system requires 8 feet to maintain adequate GPM. If the pressure drop is less than 8 feet, correct the flow problem, or add a booster pump as is applied on retrofit chillers.

• High ambient trip threshold: 140°F, applied to the temperature detected by the component mounted on the VSD logic board.