GB 17466-1998 General requirements for enclosures of electrical accessories for household and similar fixed electrical installations
Some standard content:
GB 174661998
This standard is equivalent to the international standard IEC670% "General requirements for enclosures of electrical accessories for household and similar fixed electrical installations" (1989) and its first revised version (1994). This standard is the same as IEC 670 (1989) in terms of format. The main differences between this standard and IEC 670 are as follows:
1. Ambient temperature for use
Chapter 1 of IEC 670 stipulates that "enclosures that meet the requirements of this standard are suitable for use in ambient temperatures that do not normally exceed 25°C and occasionally reach 35°C."
Taking into account the subtropical climate in some parts of my country, this standard raises the ambient temperature for use to "do not normally exceed 35°C and occasionally reach 40°C."
2. Writing format
IEC 670 does not have a chapter called "referenced standards". In order to be consistent with the chapters of IEC 670 and to facilitate search and comparison, this standard uses the chapter "referenced standards" specified in GB/T 1.1-1993 as Appendix B (Appendix to the standard). 3. Some of the standards cited in IEC 670 (1989) are old versions, and new versions are now available. According to the provisions of GB/T1.1-1993, "all standards will be revised, and the parties using this standard should explore the possibility of using the latest version." Therefore, the national standards formulated according to the latest IEC version are cited in the referenced standards. This standard was proposed by the Ministry of Machinery Industry.
This standard is under the jurisdiction of the National Technical Committee for the Promotion of Electrical Accessories Standardization. This standard was drafted by the Guangzhou Electrical Science Research Institute of the Ministry of Machinery Industry. The main drafters of this standard are Su Shihua and He Weien. This standard is entrusted to the National Technical Committee for the Standardization of Electrical Accessories for interpretation. GB 17466-1998
IEC Foreword
This standard was formulated by the 23B (plugs, sockets and switches) sub-technical committee of the 23rd (electrical accessories) technical committee of the IEC. This standard is based on the following documents:
Six-month procedure document
23B(CO)83
23B(CO)83A
Table quick report
23B(CO)89
23B(CO)89A
For details of the voting of this standard, see the voting report listed in the table above. The IEC standards referenced in this standard are:
One-month procedure document
23B(CO)90
Voting report
23B(CO)92
112(1979): Determination of comparative tracking index and proof tracking index of solid insulating materials under humid conditions 423(1973): External diameter of conduits for electrical installations and external diameter of threads of conduits and fittings 529(1983): Classification of degrees of protection given by enclosures Second revision 669-1 (1981): Switches for household and similar fixed electrical installations Part 1: General requirements 695-2-1 (1980): Fire hazard tests Part 2: Test methods - Glow-wire test and guide wire test 817 (1984): Spring impact tester and its calibration 884-1 (1987): Plugs and sockets for household and similar purposes Part 1: General requirements Other standards cited are:
IS0 2039-2 (1987): Plastics - Determination of hardness Part 2, Grignard hardness This standard 1994-07 first revision is based on the following documents: DIS (Draft International Standard) document
23B (CD) 193
For details of the vote on this revision, see the voting report listed in the table above. Voting report
23B(CD)199
1 Scope
National Standard of the People's Republic of China
General requirements for enclosures for accessoriesfor household and similar fixed electrical installationsGB 174661998
eqvIEC670:1989wwW.bzxz.Net
This standard applies to enclosures or enclosure parts of household and similar fixed electrical installations with a rated voltage not exceeding 440V for indoor or outdoor use.
Note: This standard can be used as a guide for enclosures with a rated voltage not exceeding 1000V. Enclosures that meet the requirements of this standard are suitable for use in ambient temperatures that normally do not exceed 35℃ and occasionally reach 40℃1. The enclosures referred to in this standard include covers or cover plates of exposed, concealed and semi-concealed mounting panels for electrical accessories within the scope of TC23. These covers or cover plates may or may not be part of the electrical accessories. This standard does not apply to the enclosures of combined devices with overcurrent protection devices within the scope of IEC SC17D (switchgear and control equipment), nor does it apply to busbar trough-type enclosures. This standard also applies to installation boxes used to install or suspend lighting equipment. This standard was originally only used for electrical accessory enclosures within the scope of IEC TC23, and can also be used as a reference for other TCs and SCs. Any enclosure that becomes an integral part of an electrical accessory and can provide protection for the accessory against external influences (such as mechanical impact, solid matter or water intrusion, etc.) should comply with the requirements of the relevant standards for the accessory. 2 Definitions
(See the figure in Appendix A)
This standard uses the following definitions:
2.1 Enclosures
Refers to housing components such as surface-mounted or concealed installation boxes, covers or cover plates, switches, sockets, etc., which, after assembly, can provide the electrical accessories and cables and/or wires with the corresponding level of protection against external influences and the specified level of protection against contact with the enclosed live parts from any direction.
2.2 The part of the surface-mounting box enclosure that is installed on the installation surface. 2.3 The part of the flush-mounting box enclosure that is installed flush with the surface. 2.4 The part of the semi-flush-mounting box enclosure that is installed into the installation surface but a part of it is higher than the installation surface. Instructions for use:
1] Considering that some areas of my country have a subtropical climate, the ambient temperature for the use of electrical accessories for household and similar fixed electrical installations is stipulated to be "generally not exceeding 35°C, and not exceeding 40°C". The ambient temperature stipulated in this chapter of IEC670 is "usually not exceeding 25°C, and not exceeding 35°C". Approved by the State Quality and Technical Supervision Commission on August 17, 1998 and implemented on September 1, 1999
CB 17466—1998
2.5 Extension of the installation box Installation ring box extension collar The part of the housing that is used for installation and extends beyond the installation box. 2.6 Cover or cover-plate The part of the housing that is not integral with the electrical accessories and can fix the electrical accessories in the normal position or enclose them. 3 General requirements
The design and manufacture of the housing should ensure that when its accessories are installed according to normal use requirements, it can provide sufficient electrical and mechanical protection for the enclosed components and ensure that the user or the surrounding environment is free from danger. Check for compliance through all the relevant tests specified. 4 A note on the test
4.1 The tests specified in this standard are all type tests. The insulating material housing must be pre-conditioned for 10 days at ambient temperature and in air with a relative humidity between 50% and 85% before it can be tested.
4.2 Unless otherwise specified, the test shall be carried out in the order of the provisions of this standard using a set of three new specimens at an environmental overflow of (20±5)°C. 4. 3 Unless otherwise specified, three specimens shall be used for all tests. Only when all tests are qualified shall the specimen meet the requirements of this standard. If one of the specimens fails a test due to defects in assembly or manufacturing, the test and any previous tests that may have affected the test results shall be repeated. In addition, subsequent tests shall be carried out. The retest and subsequent tests shall be carried out with another three specimens, all of which shall meet the requirements of this standard. Note: The applicant may submit another set of (three) additional specimens at the same time as submitting the first set of specimens for use in case any test fails. In this way, the (applicant) does not need to apply again, and the test station can repeat the test with the additional specimens, and only when the unqualified items appear again will it be judged as unqualified. If the additional specimen groups are not submitted at the same time, if one specimen fails, it can be judged as unqualified. 5 Classification
The enclosure is classified as follows.
5.1 Classification by material properties
5.1.1 Insulating materials
5.1.2 Metal
5.1.3 Composite materials
5.2 Classification by installation method
5.2.1 Concealed installation
5.2.2 Semi-concealed installation
5.2.3 Exposed installation
5.3 Classification by installation nature
5.3. 1 Concealed installation in the following conditions: 5.3.1.1 Solid non-combustible walls and ceilings 5.3.1.1.1 Suitable for placement before building construction (e.g. suitable for pouring into concrete). 5.3.1.1.2 Suitable for placement after building construction (e.g. not suitable for pouring into concrete). 5.3.1.2 Solid combustible walls and ceilings
5.3.1.3 Solid walls, hollow ceilings, furniture, frame edges 5.3.2 Surface-mounted enclosures in the following conditions: 5.3.2.1 Non-combustible walls and ceilings
5.3.2.2 Combustible walls and/or ceilings and/or furniture 5.4 Classification according to the temperature range during installation 5.4. 1 From -5℃ to +60C
5.4.2 From -15℃ to +60℃
5.4. 3 From -25℃ to +60℃1
5.5 Classification according to the maximum temperature during the construction of the house 5.5.1 +60℃
5.5.2 +90℃
GB 17466—1998
5.6 Classified according to the protection against direct contact, against the ingress of solid matter and against harmful ingress of water, etc., according to the IP code of GB4208.
5.7 Classification by suspension device
5.7.1 Without suspension device
5.7.2 With suspension device
Note: The provision of double or reinforced insulation is under consideration. 6 Marking and indication symbols
The enclosure shall be marked with the following:
The name, trademark or identification mark of the manufacturer or seller; a model number (which may be a catalog number); a degree of protection against the ingress of solid matter, if higher than IP2X; a degree of protection against harmful water ingress, if higher than IPX0 and a cover or cover plate supplied with the installation box; Where the IPXX degree of protection is reduced during normal use due to reasons such as plugging a plug into a socket, the IP symbol shall also be added:
“—15°C” or “—25°C”, as applicable. Where there is a degree of protection against the ingress of water, this level shall be marked on the outside of the enclosure so that the symbol can be clearly identified after the enclosure is installed and wired according to normal use requirements.
Other markings shall be visible after installation, including after removal of covers, cover plates, electrical accessories, etc.; the model number may be marked only on the packaging. The markings shall be durable and legible.
Details applicable to classification according to 5.3, 5.4 and 5.5 shall be given in the manufacturer's catalogue. Compliance is checked by inspection and by the following test. Rub the marking for 15 seconds with a cloth soaked in water and then rub it for 15 seconds with a cloth soaked in gasoline. This test is not applied to markings made by printing, casting, pressing or engraving. Further information on the normal use of the housing shall be given in the manufacturer's catalogue or operating instructions unless the content is self-explanatory.
Note: Gasoline is defined as the solvent hexane with a maximum aromatic content of 0.1 volume percent, a shell rosin butanol value of 29, an initial boiling point of about 65°C, a dry point of about 69°C, and a density of about 0.68 g/cm3. 7 Dimensional inspection
Under consideration.
8 Protection against electric shock
8.1 The enclosure shall be designed so that, after installation for normal use, any live parts of properly mounted electrical accessories or any parts of these accessories that may become live due to a fault shall not be easily accessible. This requirement does not apply to small screws, etc., which are insulated from live parts, which fasten covers or plates to mounting boxes. When tested only with the standard test finger, all enclosures with covers or electrical accessories shall have a degree of protection of at least IP20. When supplied, enclosures without covers, cover plates or electrical accessories shall be tested after the corresponding parts are installed as specified in the manufacturer's product catalog. Compliance shall be checked by observing the case and applying the following force to each part of the component that may be easily touched after correct installation: For a pair of IP20 enclosures, apply a force of 10N with the jointless test finger specified in GB4208; for a pair of IP30 enclosures, apply a force of 3N with a rod with a diameter of 2.5mm; for a pair of IP40 enclosures, apply a force of 1N with a steel trouser with a diameter of 1mm: In case of doubt, use an indicator with a voltage of 40V to 50V to show the contact with the relevant parts. 8.2 Enclosures with special provisions for easily touched metal parts, such as hooks for sensing loads, should be designed to prevent the easily touched metal parts from contacting live parts or parts that will be easily touched after insulation failure, except where the easily touched metal parts themselves can be reliably grounded. Compliance shall be checked by observation.
8.3 Metal covers or cover plates that become easily touched when insulation fails should be able to be connected to ground automatically through a low resistance connection during the fixing of the cover or cover plate.
Note: It is permitted to use fixing screws or other methods to ground the metal cover or cover plate. Check compliance by observation and the test of 9.2. 9 Grounding measures
9.1 In metal casings, any part that becomes easily accessible when the insulation fails shall be equipped with a reliable permanent grounding device. Check compliance by observation.
9.2 There shall be a low-resistance connection between the grounding terminal and the easily accessible metal parts connected to it. Check compliance by the following test.
A 25 A AC current shall be passed between the grounding terminal and each easily accessible metal part, and the no-load voltage of the AC power supply shall not exceed 12 V. Then measure the voltage drop between the grounding terminal and the easily accessible metal part, and calculate the resistance value based on the current and voltage drop. The grounding resistance shall not be greater than 0.05 0.
1 Be sure to note that the contact resistance between the test probe and the test part must not affect the test results. 2 Insulated enclosures with more than one inlet and a degree of protection higher than IPXD shall be equipped with additional provisions to ensure the continuity of the earth conductor. 10 Structural requirements
10.1 The enclosure shall have adequate mechanical strength. Compliance shall be checked by inspection and the test in Section 12. 10.2 Covers or cover plates used to ensure safety against electric shock shall be fixed in place by two or more independent parts, and at least one of these parts shall be able to be turned with the help of a tool. It is allowed to fix the cover or cover plate with only one part, but this part must be moved with the help of a tool and plays a major role in reliably fixing the cover or cover plate in the normal position. Compliance shall be checked by inspection.
Note: Tests for snap-on fixings are under consideration. 10.3 Enclosures with a degree of protection higher than IPX0 and equipped with corresponding glands or gaskets shall provide the required level of protection against harmful ingress of water after being fitted with electrical conduits or sheathed cables. Compliance is checked by inspection and the test of 11.4. 10.4 Exposed and semi-concealed enclosures of IPX1 to 1PX6 shall be designed to provide a drainage hole of at least 5 mm in diameter or at least 3 m in length and width and 20 mm in area:
G17466—1998
The location and number of drainage holes shall be such that one hole provides drainage regardless of the position of the enclosure. Compliance is checked by inspection, measurement and with a test rod. 10.5 Enclosures suitable for installation in hollow walls shall have a degree of protection of at least IP20. Such enclosures shall have suitable means for securing accessories, covers or cover plates. Compliance is checked by inspection and test. This test is under examination. 10.6 The enclosure shall have means for securing it to (or in) a wall or ceiling. The structure of the insulating material enclosure should be such that when it is installed with the predetermined fixings, any metal parts of the internal fixings are surrounded by insulation, and the insulation should protrude from the top of the fixings to a height of at least 10% of the maximum width of the fixing recess. Compliance is checked by inspection and measurement. 1D.7 If there are entry holes, these entry holes should allow the sheaths of the relevant accessories or cables in the conduit or enclosure used to connect the conduit to enter the enclosure and provide mechanical protection.
The conduit inlets (if more than one, at least two of them) should be able to accommodate conduits of sizes or size combinations specified in GB/T17194-1997.
Compliance is checked by observation and testing with corresponding cables or conduits. Note
The requirements of the electrical regulations are under consideration.
2 The appropriate size of the entry hole can also be formed by knocking out holes, suitable inserts or using corresponding cutting tools. 10.B Screw fixings of covers, electrical accessories, etc. shall be able to withstand the mechanical stresses that occur during installation and normal use. Compliance shall be checked by observation and the following tests. If necessary, the test inspection of 12.3 shall also be passed. Tighten and loosen the screw fixings:
-10 times for screws that engage with the threads of insulating materials and insulating material screws; 5, for various other screws.
Screws and nuts that engage with the threads of insulating materials and insulating material screws shall be completely removed each time and then re-tightened; self-tapping screws are allowed to be used as screws that can be removed by the user. Self-cutting screws are allowed to be used as screws that can only be tightened once. Use a suitable screwdriver to apply the torque in Table 1 for the test: Table 1
Nominal diameter of thread
>2. 8 and ≤3. 0
>3.0 and ≤3.2
>3. 2 and ≤3. 6
>3. 6 and ≤4. 1
≥4.1 and ≤4. 7
Nominal diameter of thread
>4.7 and ≤5.3
>5.3 and ≤6.0
>6.0 and ≤8. 0
>8. 0 and ≤10. 0
Column I applies to pop-up nails that cannot be tightened with a screwdriver with a blade wider than the screw diameter. Column I applies to other screws tightened with a screwdriver. [
During the test
, there shall be no breakage of the screw or damage to the screw head slot that can no longer be turned by a suitable screwdriver, and no damage to the thread or housing that would render the fixture unusable. The screws shall not be tightened with explosive force. GB17466—1998
11 Resistance to ageing, protection against aging, protection against ingress of solid matter and protection against ingress of water 11.1 Resistance to ageing and weathering conditions for enclosures of insulating materials and composite materials 11.1.1 Insulating materials and composite materials enclosures shall be resistant to ageing. Parts used only for installation, such as certain covers, shall be removed before testing. Compliance shall be checked by the following test:
After the enclosure is installed as required for normal use, it shall be tested in a heating box with ambient air composition and atmospheric pressure and natural ventilation. The temperature in the heating box is (70±2)℃. The specimen is stored in the heating box for 7 days (168 hours). An electric heating box is recommended.
Natural ventilation can be carried out through the holes in the wall of the heating box: After the above treatment, the sample is taken out of the heating box and then stored at room temperature and relative humidity of 45% to 55% for at least 4 days (96 b).
The sample shall not have cracks visible to normal or corrected vision (without magnification), and its material shall not be sticky or greasy. The judgment method is as follows:
Use dry coarse cloth or the index finger to press on the sample with a force of 5N. There shall be no traces of cloth on the sample, and the material of the sample shall not stick to the cloth. After the test, the sample shall not have damage that does not meet the requirements of this standard. Note: The force of 5N can be obtained by placing the sample on one tray of the scale and placing a weight equal to the weight of the sample plus 5 more on the other tray. After that, press the sample with the index finger of the wife wearing dry coarse cloth to restore the sample to balance. 11.1.2 The cable entry hole guard ring with sealing membrane shall be securely fixed and small enough to be displaced by any mechanical stress or thermal stress in normal use.
Check whether it is qualified by the following test:
The guard ring shall be fixed to the shell before testing. First, the shell shall be equipped with the guard ring that has been aging treated as specified in 11.1.1. Then, according to the provisions of 11.1.1, the shell shall be placed in a heating box for 2 hours, and the temperature in the box shall be maintained at (40±2)℃. After this stage is completed, immediately use the end of the standard test finger with the size shown in Figure 1 of GB4208 but straight and without joints to apply a force of 30N to various parts of the guard ring for 5s.
During the test, the guard ring should not be deformed so that any live parts surrounded by it become easily accessible. For guard rings that are subject to axial tension in normal use, an axial tension of 30N shall be applied for 5s. The guard should not fall out during the test.
Then, repeat the test with the untreated guard. 11.1.3 It is recommended that the guard with sealing membrane at the cable entry be designed and made of materials so that the cable can be inserted into the enclosure even at very low ambient temperatures.
Note: In some places, this recommendation is considered mandatory due to the need to work under cold conditions. Compliance is checked by the following test:
The enclosure is fitted with a guard ring that has not been subjected to any aging treatment; guards without openings should be pierced appropriately. The enclosure is then placed in a freezer for 2 h at a temperature of (-15 ± 2) °C, or (-25 ± 2) °C for enclosures installed at -25 °C.
After this stage, the cable can be inserted while the enclosure is still cold. It should be possible to insert a cable of the maximum expected diameter through the sealing membrane of the guard into the enclosure.
After the tests of 11.1.2 and 11.1.3, the expansion ring and the sealing membrane shall not show deformation, cracks or similar damage that does not meet the requirements of this standard.
11.2 Moisture resistance
GB 17466—1998
1.2.1 The insulating enclosure shall be able to withstand the humidity that may occur during normal use. Check whether it is qualified by the following treatment:
Subject the enclosure to humidity treatment in a humidity cabinet containing air components and maintaining the relative humidity between 91% and 95%. The air temperature where the sample is placed shall be maintained at (40±2)°C. Before placing the sample in the humidity cabinet, the temperature of the sample shall be brought to this temperature. Place the sample in the humidity cabinet for 2 days (48 hours) for enclosures of IPX0 and other grades; for 7 days (168 hours) for other enclosures.
1 In most cases, the specimens shall be kept at the above temperature for at least 4 h before the humidity treatment to allow the specimens to reach the specified humidity. To obtain a relative humidity between 91% and 95%, a saturated aqueous solution of sodium sulfate (Na2SO4) or potassium nitrate (KNO2) may be placed in the humidity chamber with a sufficiently large contact surface between the solution and the air.
2 To achieve the specified conditions of the humidity chamber, the air in the chamber must be constantly circulated and an insulated chamber should generally be used. After this treatment, the specimens shall not show any damage that would affect their continued use. In addition, the insulating housing shall pass the following test: 11.2.2 Apply a DC voltage of approximately 500 V. After the voltage has been applied for 1 min, measure the insulation resistance. The insulation resistance shall be not less than 5 MO.
11.2.3 Apply a voltage of substantially sinusoidal shape, with an effective value of 2 000 V and a frequency of 50 Hz or 60 Hz, for 1 min between the inner and outer surfaces.
At the beginning, the applied voltage shall not be greater than half of the specified value, and then rapidly increased to the specified value. No flashover or breakdown shall occur.
1 The high-voltage transformer used in the test shall be designed so that when the output voltage is adjusted to the corresponding test voltage and the output terminals are short-circuited, the output current is at least 200 mA. When the output current is less than 100 mA, the overcurrent relay shall not operate. 2 It should be noted that the effective value of the applied test voltage should be within the range of ±3%. 3 The glow that does not cause voltage drop can be ignored. When conducting the tests of 11.2.2 and 11.2.3, place a metal box in contact with the inner surface and another metal box not exceeding 200mm×100mm in contact with the outer surface. If necessary, the metal box shall be moved in order to measure all parts. During the test, care must be taken to ensure that the distance between the inner and outer metal foils is at least 4mm, but the distance measured through the insulating material is not included.
11.3 Protection against ingress of solid objects
Enclosures provide protection against ingress of solid objects corresponding to their IP classification. Compliance is checked by the following test:
11.3.1 The enclosure is mounted in accordance with the manufacturer's instructions and for normal use. Exposed enclosures are mounted on vertical surfaces with the open drain holes at the lowest position.
Concealed or semi-concealed enclosures are fixed vertically in suitable recesses as required for normal use. Enclosures with threaded glands or with sealing membrane retainers are fitted and connected with cables corresponding to the rated values of the accessories installed. The fixing screws of the enclosure are tightened with 2/3 of the torque specified in Table 1 of 10.8. The cable and/or conduit inlet fittings are prepared in accordance with the manufacturer's instructions. Parts that can be removed without tools are removed. The glands are not filled with sealant or similar substances. Instructions for use:
1 According to GB2423 standard and my country's specific environmental conditions, this standard stipulates that the flood test temperature is (40±2)°C. IEC670 stipulates that it is any value between 20°C and 30°C in the chapter on moisture resistance test. GB 17466-1998
11.3.2 It can prevent the diameter of the pipe greater than 12.5mm solid matter entering the enclosure shall be subjected to the test specified in GB 4208 for IP2X protection level.
During the test, the test ball shall not pass through any hole of the enclosure. 11.3.3 Enclosures that can prevent the entry of solid matter with a diameter greater than 2.5mLm shall be subjected to the test specified in GB 4208 for IP3X protection level.
11.3.4 Enclosures that can prevent the entry of solid matter with a diameter greater than 1mm shall be subjected to the test specified in GB4208 for IP4X protection level.
During the tests of 11.3.3 and 11.3.4, the test wire or rod shall not enter the enclosure through any hole other than the drainage hole. 11.3.5 Dustproof enclosures shall be subjected to the test specified in GB4208 for IP5X protection level at ambient pressure. If there are drain holes, they shall not be opened during the test. 11.3.6 The dust-tight enclosure shall be subjected to the test specified in GB 4208 for IP6X protection level at ambient pressure. The drain holes shall not be opened during the test.
11.4 Protection against harmful ingress of water
Enclosures with a protection level higher than IPX0 shall provide protection against harmful ingress of water corresponding to their IP classification. Compliance shall be checked by carrying out the tests specified in GB 4208 for protection levels IPX1, IPX2, IPX3, IPX4, IPX5, IPX6, IPX7 and IPX8. During the test, the specimen shall be installed as specified in 11.3.1. After the test, an inspection shall be carried out, which shall show that no water has entered the specimen significantly, or that the water has not reached live parts. The specimen shall then withstand the electrical strength test specified in 11.2.3. If the enclosure has drain holes, any water that has entered shall not accumulate and shall be discharged without endangering the entire assembly. For enclosures with a protection level higher than 1PX4, if there are drainage holes, the drainage holes shall not be opened during the test. Note: If the enclosure does not have drainage holes, consideration should be given to draining any water that may have accumulated. The test of this clause shall be carried out before the tests of 11.2 and 11.3. 12 Mechanical strength
The enclosure shall have sufficient mechanical strength to withstand the mechanical stresses occurring during installation and use. Compliance shall be checked by the tests of 12.1 and 12.2. If the enclosure is too large to fit into the test device shown in Figure 3 or Figure 3, the test may be carried out under the same conditions as specified in 12.1.1 or 12.1.2, but the spring chain specified in GB/T 2423.44-1995 shall be used and the impact energy shall be set to the value required by 12.1.1 or 12.1.2.
12.1 12.1.1 Impact test for enclosures to be cast in concrete
The specimens shall withstand an impact test using a vertical hammer test apparatus as shown in Figure 4. The vertical hammer test apparatus shall be supported on a sponge rubber pad having a density of 538 kg/m3 and a thickness of 4 mm when not compressed. The test apparatus on the sponge rubber pad together with the specimens shall be placed in a freezer for at least 2 h. The freezer temperature shall be maintained at: (-5 ± 1) °C for enclosures classified according to 5.4.1; (-15 ± 1) °C for enclosures classified according to 5.4.2; (-251) °C for enclosures classified according to 5.4.3. After this period, each specimen shall be subjected to a vertically dropped hammer impact. The weight of the drop chain shall be 1 kg and the drop height shall be 10 cm. The first impact shall fall on the back of the enclosure and the other four impacts shall fall on the side walls at equal intervals. 1) IEC670.1989 stipulates 12 mm. This standard refers to GB420g-93, which stipulates 12.5 mm, so this standard also stipulates 12.5 mm.
2) IEC670:1999 refers to IEC817:1984, but IEC817.1984 has been replaced by IEC68-2-63.1991. GB/T 2423.441995 equivalently adopts IEC 68-2-63:1991: no such note. GB17466-1998
After the test, the specimen shall not have any damage that does not meet the requirements of this standard. Past: The surface layer of the small pits that will not reduce the isolation distance or electrical clearance to less than the value specified in the national standard of the electrical accessories to be installed and the small fragments that will not affect the protection against electric shock or the prevention of harmful water ingress can be ignored. Cracks not visible to normal or corrected vision (without magnification) and surface cracks and small dents in fiber-reinforced moldings, etc., are disregarded.
12.1.2 Compression test on enclosures classified in accordance with 5.5.2 Enclosures of this type are suitable for installation in hot molds or hot concrete and shall withstand the mechanical stresses occurring during concrete work.
Compliance is checked by the following test:
- The enclosure is exposed to a temperature of (90 ± 5) °C for 1 h. The enclosure is then allowed to cool to ambient temperature.
After the test, the enclosure shall not show any deformation or damage that would lead to non-compliance with the requirements of this standard. - The enclosure is then placed between two hardwood boards and loaded with a force of 500 N for 1 min. Care shall be taken to ensure that the pressure generated by the hardwood boards used in this test is evenly distributed over the surface of the enclosure without reinforcing it. After the test, the enclosure shall not show any deformation or damage that would lead to non-compliance with the requirements of this standard or that would impair its continued use. NOTE
1 During the above two tests, the casing may be installed in a special component (if any) for reinforcing the mechanical properties of the casing when the casing is buried, according to the manufacturer's instructions.
2 The special component used in this test shall be delivered together with the casing. 12.2 The casing specimens not to be cast in concrete shall be subjected to impact using the impact test device shown in Figures 1, 2, 3a and 3b. The impact element has a hemispherical surface with a radius of 10 mm and is made of HR100 Grignard hardness amide; the mass of the element is (15C ± 1) g.
The impact element is rigidly fixed to the lower end of a steel tube with an outer diameter of 9 mm and a wall thickness of 0.5 mm. The upper end of the steel tube is equipped with a pivot so that the steel tube can only swing in a vertical plane.
The axis of the shaft is located (1 000 ± 1) mm above the axis of the impact element. The Rockwell hardness of the impact element is determined using a ball with a diameter of (12.700 ± 0.0025) mm. The initial load is (100 ± 2) N. The additional load is (500 ± 2.5) N.
Go to 1: Detailed information on determining the Grignard hardness of plastics is given by 1502039-21\. Impact test device design requirements: A force of 1.9~2.0 N must be applied to the hemispherical surface of the impact element to keep the steel pipe in a horizontal position.
The specimen should be mounted on a square plywood with a thickness of 8 mm and a length and width of 175 mm, and the upper and lower edges of the plywood are fixed to the rigid clamps of the mounting bracket.
The mounting bracket weighs (10 ± 1) kg and is mounted on a rigid frame with a pivot, and the frame is fixed to the wall. The mounting bracket should be designed so that:
The specimen can be placed so that the impact point falls on the vertical plane passing through the axis of the pivot; a specimen can move horizontally and rotate around an axis perpendicular to the surface of the plywood; - the plywood can rotate around a vertical axis.
The cable entry hole without a cover hole remains open; if there is a cover hole, one of the holes is opened. The specimen should be installed so that the impact point falls on the vertical plane passing through the axis of the pivot. Let the impact element fall from the height specified in Table 2. 1) Since there is no standard equivalent to or equivalent to I502039-2:1987 in my country, this standard directly refers to IS02039-2. In the table,
Drop height
GB 17466--1998
Part of the shell to be hit
Ordinary accessories
A——-Part on the positive surface, including recessed parts. Other accessories
B—After installation in normal use, the distance between the protruding mounting surface and the wall shall not exceed 15 mm.Except for Part A C—After installation for normal use, the distance between the mounting surface and the wall is more than 15 mm but not more than 25 mm, except for Part A.
D—After installation for normal use, the distance between the mounting surface and the wall is more than 25 mm, except for Part A. Note 2: These impact energies are determined by the part of the specimen that protrudes the most from the mounting surface. This energy can be applied to all parts of the specimen except Part A. The drop height refers to the vertical distance between the position of the test point when the pendulum is released and the position of the impact point at the moment of impact. The test point should be marked on the surface of the impact element, that is, at the intersection of the axis of the pendulum steel tube and the axis of the impact element and the line perpendicular to the plane passing through the above two axes and the surface of the impact element. Note 3. In theory, the center of gravity of the impact element should be the test point, but in practice, the center of gravity is difficult to determine, so the above method is used to determine it. The impact should be evenly distributed on the specimen, but not on the fall hole. The impact method is as follows:
Five impacts on the A part: one impact at the center, and after the specimen is horizontally moved, impact once at the most unfavorable point between the center and the edge; then, rotate the specimen 90° around its axis perpendicular to the plywood, and impact once at similar points. Impact four times on the B part (if applicable), C part and D part) · After the cavity plywood is rotated 60°, impact one side of the specimen once, and after keeping the position of the plywood unchanged and rotating the specimen 90\ perpendicular to the axis of the plywood, impact the specimen and the other side again; ■ After the plywood is rotated 60° in the opposite direction, impact once on each of the other two sides of the specimen. If there is a wire entry hole, the specimen should be installed so that the distance between the two rows of impact points and the wire entry hole is as equal as possible. After the test, the specimen should not be damaged in a way that does not meet the requirements of this standard. NOTE 4 Damage to the surface which does not reduce the creepage distance or electrical clearance below the value specified in the national standard for the accessory to be installed, small dents which do not affect the protection against electric shock or harmful ingress of water, etc., may be neglected. Cracks which are not visible to normal or correct vision (without magnification) and surface cracks and small dents in reinforced fiber moldings, etc., may be neglected.
After the test of the glass lens (of the indicator window), the lens may be broken or displaced, but it shall not be possible to touch live parts with the test finger, with or without joints, under the conditions specified in 8.1. NOTE 5 Additional requirements for concealed installation boxes are under consideration. 12.3 Enclosures intended to suspend loads
12.3.1 Enclosures intended to suspend loads from the ceiling shall be designed so that the enclosure and the suspension can withstand a force of 250 N or a force specified by the manufacturer, whichever is the greater. Check compliance by the following test:
After the sample is installed on the suspension device according to the manufacturer's instructions, it is placed in the heating box and the screws are tightened to 2/3 of the torque specified in Table 1.
Then, the suspension device is loaded with a force of 250N or the weight specified by the manufacturer (whichever is greater) at a temperature of (90±2)℃.
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