1、NEMA Standards PublicationNational Electrical Manufacturers AssociationNEMA opens on temperature rise at scale setting. Type B Thermostat: two pole opposite throw (two circuit); one pole opens and one pole closes on temperature rise at scale setting. Type C Thermostat: single pole double throw; one
2、throw opens and one throw closes on temperature rise at scale setting. Type D Temperature-limiting control: two pole single throw; both poles open on temperature rise at marked setting; must be manually reset; resettable at a temperature not lower than 120F (48.9C). Type E Temperature-limiting contr
3、ol: one pole single throw; opens on temperature rise at marked setting; must be manually reset; resettable at a temperature not lower than 120F (48.9C). Copyright 2008 by the National Electrical Manufacturers Association. DC 5-1989 (R1996, R2002, R2008) Page 3 Section 3 CONSTRUCTION 3.1 DIMENSIONS T
4、o meet the requirements of 3.2 and 3.3, the general configuration for the bases of Type A, B, and C controls shall be in accordance with the dimensions as shown in Figure 31. Figure 31 CONTROL BASE (Typical Outline of Control Base to Illustrate Required Dimensions) 3.2 MOUNTING METHOD Means shall be
5、 provided to permit mounting the control either directly on the water heater tank or on a flat metal pad attached to the tank. 3.3 MOUNTING MEANS Means shall be provided to enable Type A, B, and C controls to be secured to the water heater tank either by screws or by mounting such as shown in Figure
6、 32. Copyright 2008 by the National Electrical Manufacturers Association. DC 5-1989 (R1996, R2002, R2008) Page 4 Figure 32 DIMENSIONS FOR MOUNTING BRACKET TABS The projection of the thermostat shall be contained within the cavity of the mounting bracket base, as shown by the dotted line envelope in
7、Figure 3-1. Type D and E controls may be combined with the regulating control. 3.4 TERMINAL MARKINGS Terminal markings shall be as follows: Type of Controls Switch Action Terminal Marketing Switch Schematic A Contacts open on temperature rise 1 and 2 1 o/ o 2 Contacts open on temperature rise 1 and
8、2 1 o/ o 2 B Contacts close on temperature rise 3 and 4 o o 3 4 Contacts open on temperature rise 1 and 2 o 2 C Contacts close on temperature rise 1 and 4 1 o/ oo 4 Contacts open on temperature rise 1 and 2 1 o o 2 D Contacts open on temperature rise 3 and 4 3 o o 4 E Contacts close on temperature r
9、ise 1 and 2 1 o o 2 Copyright 2008 by the National Electrical Manufacturers Association. DC 5-1989 (R1996, R2002, R2008) Page 5 Section 4 PERFORMANCE AND RATINGS 4.1 PERFORMANCE AND RATINGS Controls shall comply with ANSI/UL 873, ANSI/UL 174, and CSA C22.2 No.110. Copyright 2008 by the National Electrical Manufacturers Association. NATIONAL ELECTRICAL MANUFACTURERS ASSOCIATION 1300 NORTH 17TH STREET, SUITE 900 ROSSLYN. VA 22209www.NEMA.orgTO ORDER ADDITIONAL NEMA STANDARDS VISITWWW.GLOBAL.IHS.COM OR CALL 1-800-854-7179/1-303-397-79565612_0514TB
