Changing NO Contacts to NC Contacts in the Field

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Most relays used in industrial circuits have the ability to have their contacts changed from NO to NC in the field. In other words, a technician can remove several screws and mount the contacts upside down and they will change from NO to NC, or vice versa. Ill. 1 shows an example of this type of contact. This feature makes adding NO or NC contacts very easy. It also makes it simple to change a set of NO contacts to NC at the time it's needed. Since these contacts are actually cartridges, additional sets of contacts can be added to a relay at anytime as long as there is room. In some cases a second deck is added to the relay so more contacts can be added.

ADDING or CONVERTING CONTACT CARTRIDGES HAVING SWINGAROUND TERMINALS

General Instructions (Specific cases below.) 

1.1 Adding a contact cartridge:

As received, accessory cartridges are in the normally open mode with terminal screws adjacent to N.O. symbols. If normally closed mode is desired, convert contact as indicated in Step 1.2 below. When cartridges are inserted, the terminal screws must face the front. The clear cover may face either side. Don't install more than 8 N.C. contacts per relay. When installing one cartridge, locate it at an inner pole position. When installing 2 cartridges, locate both in inner or outer (balanced) positions.

1.2 Converting a contact to its alternate mode (N.O. / N.C.):	Screwdriver
Withdraw an assembled cartridge	Blade P	for replacement or conversion by
inserting the blade of a suitably-	w/Plate sized screwdriver under. of Terminal screw pressure plate. Slide	Screw cartridge out. See Figure 2. Back
the terminal screws out of the,	Cartridge cylindrical nuts a sufficient amount (approximately 2 turns
for a fully-tightened screw) to permit rotation of each screw & of Withdrawal nut assembly to its alternate
position. See Figure 3.	Contact Block
Above: Fig.  2
Terminal	N C Contact
Screw Symbol
Pressure Cylindrical
Plate	Nut
N.O. Contact
Cartridge	CID	Symbol
Housing
Above: Ill. 1: Example of contacts that can be changed from NO to NC in the field.

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