These tests were developed to assess fire propagation characteristics of a group of cables for use in commercial, "non-combustible" buildings, industrial plants, nuclear plants, etc. The criteria for acceptance of course, differs with jurisdiction. The following are some of the tests that fall into this category:

1. IEEE 383
2. U.L. 1685
3. ICEA T-30-520
4. CSA, FT4
5. IEEE 1202

All of these tests have common parameters; height and width of tray, heat input (70,000 BTU/Hr), burner type/fuel conditions, duration of test (20 minutes), spacing between specimens (½ diameter apart), etc.

Differences include tray loading, burner orientation, performance criteria, etc. Table 1 compares these flame tests. Figure 1 is a typical test enclosure for these tests.

There is one other test method, i.e. IEC 332-3 which has some similarity with these tests, in that it is a vertical "tray" test, however, the number of these specimens are determined from the combustible material available. One other significant difference is that the required number of specimens (3.5m long) are mounted in front of the tray and if necessary at the back of the tray to account for the necessary number of specimens for the test. Generally speaking, armoured cables and some non-armoured cables that meet the requirements of the tests referred to earlier will also meet the IEC Test requirements. Figure 2 is the test enclosure used and Table 2 compares this test with CSA FT4 test.

It has been our experience that any of the Cable Tray Flame Tests mentioned earlier produce similar results: Why then have all these different tests? Why can’t the industry get together and come up with a single test? Our industry did attempt to do just that! Insulated Cable Engineers Association (ICEA) which is made up of members from US and Canada set up a Working Group 520 to study the effect of various differences and after years of work came up with a report P-56-520 December 1984, which suggested that many of the differences that existed did not change the outcome of the test for the pass/fail criteria. ICEA has published

T-30-520 – "Guide for Conducting Vertical Cable Tray Flame Tests – 70,000 BTU/Hour."

At this point it is necessary to mention that the CSA Tray Flame Test (FT4) was developed by the industry with participation of Ontario Hydro, and adopted by CSA. The test parameters are very similar to the earlier Ontario Hydro test, except for the tray loading. The cables are mounted on the centre 10" of a 12" wide tray, the number of specimens are greater, and the requirement more stringent – max. damage 1.5m (5.9 ft.) (see Table 1). The significant factor is that a much higher number of specimens are to be mounted. For example: for a 5mm diameter cable, CSA (FT4) test requires 63 specimens as opposed to 20 specimens for other tests (UL 1685, IEEE 383). See Figure 3 and Table 3.

It is important to note that in 1984, when the Task Force on Electrical Cables of the Standing Committee on Use and Occupancy set up by the Associate Committee on the National Building Code of Canada, in coming up with recommendations for performance of cable for installation in "non combustible" (commercial) buildings, concluded that the FT4 test performance was adequate for all installations, including return air plenums.

Some cable specifications require that the cable meet a flame test performance using IEEE 383 or UL 1685 test protocol, at a heat input of 210,000 BUT/hr. There are critical considerations as to how you get to this high heat input using these test protocols, particularly with reference to gas flow rates. In order to get the flame to impinge on the cable surface, one has to modify the gas input system. The aforementioned ICEA Group had addressed this issue and came up with a Guide T-29-520 which presumably addressed some of these concerns.

This test is being specified by some industrial cable users under the assumption that it will provide a greater margin of safety with regard to flame propagation. The test set up however, does not take into account the true tray loading which in practical terms is the important factor in determining the flame propagation characteristics. Granted the heat input is three times that of the standard 70,000 BTU/hr., but the tray loading is as the 70,000 BTU/hr. test. Flame impingement on the cable front is also questionable – the hotter portion of the test flame does not always impinge on the cables, and is cable diameter dependent.

The ICEA test configurations for 70K and 210K BTU/hr. are compared in Figure 4.

Recognizing the obvious inadequacy of the IEEE 383/UL 1685, IEEE/IAS formed a Task Group P1202 to address this issue to come up with an improved test.

At meetings in May 1989 and September 1989, several flame tests were considered. Presentations on CSA FT4, IEC 332-2 and FMRC tests, were made and considered. The Task Group chose the CSA FT4 test and the work to adopt this test with minor modification to put it in IEEE style was set in motion. After several meetings with industry participation, IEEE 1202 was published in 1991.

Table 1 highlights the differences in the test protocols of the major tray flame tests.

We have seen increasing use of IEEE 1202/CSA FT4 test for industrial and other types of cables and we are confident the trend will grow. There are years of experience using FT4 cables in all sorts of installations in Canada and the United States. UL has adopted this test in 1685 and on June 14, 1993 announced that manufacturers who have listings may choose to include it in their follow-up services, and the cables may be so marked.

CSA FT4 Test: * 7.5 ft. specimens

** Evaluation of fire damage is determined by char line. In IEEE 1202 blistering/swelling above the char is also included as fire damage.

 

Fig. 2 – Equipement d’essai au feu

Fire test rig.

Figure 3

Figure 4