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Supplemental and Obsolescence Digest 174

QMB Fusible Panelboards

Branch Switch Replacement

Class 4620

Guidelines

STEP 1: Determine the panelboard interior type. If the date of manufacture is not known, compare your switch with the pictures below to determine the mounting rail direction. Only mounting rails that face outward will accept the Series D2 switch and its required mounting rail extension bracket.

STEP 2: Order a replacement switch from page 13-5.

 

Table 13.7:

Panelboard Interiors

Illustration No.	Interior Catalog No. Prefix	Designed For Switch Type	Switch Availability/Order Information
1.	Type QM in 31-inch wide box built before 1961.	Series 1-4 30–200 A Maximum	NOT AVAILABLE Series D2 switches are not compatible replacements for this application.
2.	Type QM in 31-inch wide box built after 1961 and before 1984.	Series 1-4 30–200 A Maximum	NOT AVAILABLE Order Series D2 switch from page 13-5.
		Series D2 30–200 A Maximum	Order Series D2 switch from page 13-5. (Many still stocked in DS.)
3.	Type QW in 38-inch wide box built before 1984.	Series 1-4 30–200 A Maximum	NOT AVAILABLE Order Series D2 switch and plug-on extension assembly from page 13-5.
		Series 1-4 400–600 A	NOT AVAILABLE QMB3400LA available order only from Lexington.
		Series D2 30–200 A Maximum	Order Series D2 switch and plug-on extension assembly from page 13-5.
4.	Type QMB in 35-inch or 38-inch wide box built after 1984.	Series E1 or E2 30–800 A	Order from Digest page 9-34.

 

Table 13.8:

1		2
Type QM (31-inch Wide) Manufactured Before 1961 Panelboards manufactured before 1961 have the interior mounting rails facing inward (toward the bus). Switches and circuit breakers that fit in this interior type are obsolete.		Type QM (31-inch Wide) Manufactured After 1961 But Before October 1984 Panelboards manufactured after 1961 have the interior mounting rails facing outward (away from the bus). This interior accepts Series 1-4 switches and Series D2 switches (shown above with required rail extensions). Order the Series D2 switch (includes mounting rail extensions) from page 13-5.
3		4
Type QW (38-inch Wide) Manufactured Before 1984 Type QW panelboards were built to accept bolt-on 400 A and 600 A Series 1-4 switches. 30-200 A Series D2 switches may be installed as shown using the plug-on extension assembly from page 13-5.		Type QMB Manufactured After October 1984 Series E1 panelboards will accept only Series E1 or E2 switches. Order from Digest page 9-34.