Red Spot Fuse Holders FAQ

• Select a rating of fuse link which is at least equal to the normal full load current of the circuit, including any allowances needed for harmonic currents, as in the case p.f. correction circuits.
• Ensure that the fuse link rating can withstand any over currents which may apply to the circuit, such as transformer in-rush currents, motor starting surges and repetitive cycle loads.
• When full cable protection is required, ensure that the fuse link rating is compatible with the selected cable, i.e. less than or equal to cable rating.

• Remove Red nylon insulating shroud to release cable sleeve.
• Remove cable sleeve.
• Fit cable sleeve over cable.
• Fit conductor into fuse base terminal and tighten cable clamping screw to secure.
• Replace Red nylon shroud taking care it holds the cable sleeve in position by locating the shroud in the groove provided by the sleeves.

• Ensure cable sizes are correctly chosen in line with the IEE Wiring Regulations (BS 7671), making due allowance for:

i. Grouping of cables (correction factor Cg).
ii. Ambient temperature / internal enclosure temperature (correction factor Ca).

• Ensure that maximum cable core temperature is restricted to 70°C or less.
• Ensure adequate cable length is provided for interconnections between fuse holders or other components. This will prevent possible heat input to the fuse holder which could result in overheating.
• If using multi-stranded cables / Tri-rated cables the bared strands should be crimped in thin wall copper ferrules in order to consolidate the strands. The following points should be taken into account:

i. The inside diameter of the ferrules should match that of bared cable ends.
ii. The ferrule lengths should be the same length as the cable entry tunnel in the fuse base terminals.
iii. The termination screw should compress the wall of the ferrules, providing further consolidation of the cable strands within the ferrule.

• When used in banks, ensure that the diversity factors recommended in BS5486 Part 11, Factory Built Assemblies, are applied. If the number of fuse holders banked together exceeds 12 a 0.6 diversity factor may be used.
• For applications when there is insufficient or no diversity applied, adequate compensation should be made by a combination of some, or all, of the following:

i. Utilise higher standard current rated fuse links, or motor rated fuse links.
ii. Increase the cable size.
iii. Ensure that fuse holders in the bank are separated by at least 5mm.
iv. Ensure that there is adequate spacing between fuse banks if they are stacked vertically. Typically, depending on rating, this would be 30-50mm.
v. Incorporate natural or forced ventilation.

• Sharp bends in cables, especially near termination points, should be avoided in order to prevent damage to cable cores or insulation and to ensure that no mechanical strain, is put on the contact block in the fuse
  base.
• The minimum torque values detailed in the attached table should be applied to cable terminal and fuse link fixing screws.

• Isolate the supply.
• Withdraw the fuse carriers and inspect fuse tags and carrier contacts for any signs of damage.
• Check all cable terminal screws and fuse link fixing screws to ensure that the correct torque has been applied.
• Wipe clean and remove any oxidation from the carrier contacts.
• Apply a small amount of a proprietary electrical contact lubricating grease after ensuring that all contact areas are clean.
• Re-fit the fuse carriers and re-connect the supply.