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What is a Pre-transfer signal and how is it used?

Pre and Post transfer signals are also known as Selective Load Disconnect signals. The signals provide Pre-transfer and Post-transfer time delay notification via dry set/s of form C contacts when transferring from Emergency to Normal and from Normal to Emergency.

ASCO Transfer Switches offer standard and optional accessories for pre-and-post Transfer signals depending on the type/series of the Transfer Switch; please see the below accessory information about the Pre and Post transfer signal.

Transfer Switch SeriesPre and Post Transfer SignalAdditional Pre and Post Transfer Signal Accessories
300 Series
Standard (1-Set of Form C contact)- 18RX (additional 2-Sets of Form C contacts)
- 18RX2 (additional 4-Sets of Form C contacts)
4000 SeriesOptional - Accessory 31Z (2-Set of Form C contacts)- 31Z4 (4-Sets of Form C contacts)
- 31Z6 (6-Sets of Form C contacts)
- 31Z8 (8-Sets of Form C contacts)
7000 SeriesOptional - Accessory 31Z (2-Set of Form C contacts)- 31Z4 (4-Sets of Form C contacts)
- 31Z6 (6-Sets of Form C contacts)
- 31Z8 (8-Sets of Form C   contacts)


The most common application of Pre-Transfer Signal are as follows:

1. Motor Loads - used for disconnecting the equipment that allows residual load-side voltage to decay to prevent high inrush currents.  The motor load is reconnected after a user-specified delay.
2. Elevator Controls - In order to avoid stranding passengers, it is necessary to provide a means for elevators to reach a building floor to allow passenger egress. The pre-transfer signal can interact with an ATS controller to signal elevator controls that transfer is about to occur. The elevator controls then send the elevator to the nearest floor of the building and open its door before power is interrupted.

You may also watch the video related to this (please see below).


For further information, you may contact Technical Support at 1-800-800-2726 then dial 3 or send an email to technicalsupport@ascopower.com

ASCO Power Technologies USA

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Range:
ASCO 7000 SERIES Power Transfer SwitchASCO 4000 SERIES Power Transfer SwitchASCO SERIES 300 Group G Power Transfer Switch
Explore more
Range:
ASCO 7000 SERIES Power Transfer SwitchASCO 4000 SERIES Power Transfer SwitchASCO SERIES 300 Group G Power Transfer Switch
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