Maximum Operating Temperature Withstand Test
This test is to be performed on all SPDs.
Rationale
As part of their application, SPDs are exposed to various temperature ranges. The maximum temperature that an SPD can withstand is of particular importance when specifying SPDs for harsh environments.
For two-port and In-Line SPDs, it is important to understand how operating these devices at the maximum load current might effect their maximum termperature rating and operation due to the potential heating of internal components at maximum load currents.
Purpose
The Maximum Operating Temperature Withstand Test is performed to assess the capability of an SPD to withstand a maximum operating temperature as declared by the manufacturer.
Test Setup and Procedure
The SPD shall be energized at the declared nominal system voltage during this test. All internal or external, thermal or otherwise, disconnectors shall be in place during this test.
For one-port SPDs, the SPD is placed in a heated chamber for 24 hours at the declared maximum temperature provided by the manufacturer while the nominal system voltage is applied.
For two-port and In-line connected SPDs, this test shall also be conducted at the maximum load current into a resistive load while the SPD is placed in a heated chamber for 24 hours at the declared maximum temperature provided by the manufacturer.
During the Maximum Operating Temperature Withstand Test, the SPD shall be placed on a softwood surface covered with a double layer of white tissue paper. The orientation of the representative device shall be such as to create the most severe conditions representative of normal installation. Each representative device is to be loosely draped with a double layer of cheesecloth. The cheesecloth shall cover openings (for example, receptacle openings and ventilation openings). However, the cheesecloth shall not be deliberately pushed into openings.
For the purpose of the test, all SPDs are to be packaged and shipped as though they are ready for installation. That is, any over-current protection device (OCPD) or circuitry shall be installed during the test. For SPDs that rely on an OCPD that is incorporated into the electrical system, the test is to be completed with the OCPD(s) specified by the manufacturer. The OCPD shall be incorporated into or installed during the test.
Expected Results
Given the proper selection of the maximum temperature and/or maximum load current rating of the SPD, this test should not overstress the SPD or cause failure of the SPD.
During and following the Maximum Operating Temperature Withstand Test the SPD shall remain functional with no observable effects nor shall any of the following conditions result:
a. Emission of flame, molten metal, glowing or flaming particles through any openings (pre-existing or created as a result of the test) in the SPD that result in:
i. Damage to the cheesecloth such as broken threads, holes or breakdown of the structure of the cheesecloth
ii. Glowing of the supporting surface, tissue paper, or cheesecloth
iii. Flaming of the supporting surface, tissue paper, or cheesecloth
b. Ignition of the enclosure
c. Creation of any openings in the enclosure that result in accessibility of live parts
d. Loss of structural integrity to a degree that the equipment collapses or experiences such displacement of parts that there is a risk of short-circuiting or grounding of current-carrying parts
e. The supply voltage drops below the nominal system voltage as a result of a change in the SPD
f. Opening of any internal or external OCPD, circuit interrupt device or internal component of the SPD.
g. The temperature shall not exceed the maximum operating temperature of any of the components of the SPD.