latching and non latching diagnostics

[key]

This is a microprocessor question I recenlty wrote. Can someone please explaine the difference between latching and nonlatching diagnostics.

[kcl]

A latching diagnostic results in unit shutdown after an alarm and requires the unit to be manually reset in order to perform a restart. Latching diagnostics are usually more serious alarms such as high head pressure, low refrigerant temperature, starter faults. Non-latching alarms will result in unit shutdown and after the microproceesor senses the alarm condition is corrected the unit will automatically restart without pressing a reset button. Non-latching diagnostics may be from loss of chilled water or condensor water flow. Manufactures will list which alarms are latching or non-latching in the operation manual.

[flange]

Most times a latching relay will require power to be turned off then back on to reset.

[key]

Thanx guys

[caosesvida]

on ddc systems the latching relays can be reset ( the ones that I work with anyway) from your terminal. On the stand alone units they may need to turn off and then on again, if there is not a reset (such as on hps).