ANSI UL 458 - Maximum Overload Without Trip; External Surface Temperature Limits Test

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UL COPYRIGHTED MATERIAL –

NOT AUTHORIZED FOR FURTHER REPRODUCTION OR

DISTRIBUTION WITHOUT PERMISSION FROM UL

37.3.2 A converter or inverter is to be mounted in an enclosure consisting of four vertical side walls at

right angles to each other, and a horizontal top and base of 1/2-inch-thick plywood or soft pine with a

nominal thickness of 3/4 inch. The interior surfaces are to be painted ﬂat black and the joints are to be

tight or sealed. The converter or inverter is to rest on the base with the walls and top in as intimate contact

with the converter or inverter as the conﬁguration on the converter or inverter permits.

37.3.2 effective April 13, 1993

37.3.3 A converter or inverter intended for ﬂush mounting is to be ﬂush mounted on a vertical surface and

the recessed portions are to be enclosed in accordance with 37.3.2.

37.3.3 effective April 13, 1993

37.4 Maximum overload without trip

37.4.1 A converter or inverter is to be operated under the conditions described in 37.1.1 – 37.3.3 at the

maximum load it can carry without resulting in the protector required by 20.2.1 to open the circuit –

ultimate trip current. During the test:

a) Transformer winding temperatures shall not exceed 140°C (284°F) for Class A insulation, or

165°C (329°F) for a Class B or F insulation, or 20°C above the value speciﬁed in Table 37.1 for

any other class of insulation.

b) The temperature of any component other than a transformer shall not exceed that speciﬁed in

Table 37.1 by more than 20°C (36°F).

c) A ﬂush-wall mounted converter or inverter shall also comply with the temperature limits

speciﬁed in Table 38.1.

d) A ﬁxed or stationary type unit shall not exceed the temperature limits speciﬁed in Table 38.1

by more than 20°C.

37.4.1 effective April 13, 1993

37.4.2 With reference to 37.4.1, readily accessible branch-circuit overcurrent-protective devices in a

secondary circuit shall be shunted during the test if they would open the circuit prior to the opening of an

internal protective device.

38 External Surface Temperature Limits Test

38.1 During the normal temperature test described in Section 37, Temperature Test, surface

temperatures shall not exceed the applicable values speciﬁed in Table 38.1. The results of a test that is

conducted at a room temperature of other than 25°C (77°F) is to be corrected to 25°C (77°F). See 37.1.8.

38.1 effective April 13, 1993

DECEMBER 14, 1993UL 45856