Safeclip Fuses and Fuse Holders FAQ

Details: Category: Eaton Bussmann BS88 Fusegear

Safeclip Fuse Link Selection

Fuse Link selection

• 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.

Recommended minimum torque values

Rating	Fuse Link fixing screw		Cable terminal screw		Back connected stud

	Size	Torque	Size	Torque	Size	Torque


SC20	N/A	N/A	M6 grub screw	2,0Nm	M6	3,0Nm
			(Slotted)	(18 lb.in)		(27 lb.in)

SC32	N/A	N/A	M6 grub screw	2,0Nm	M6	3,0Nm
			(Slotted)	(18 lb.in)		(27 lb.in)

SC63	N/A	N/A	M8 grub screw	3,0Nm	M8	6,0Nm
			(Slotted)	(27 lb.in)		(53 lb.in)

SC100	M6	2,5Nm	3/8” grub screw	3,5Nm	N/A	N/A
	Pan head	(22 lb.in)	(Slotted)	(31 lb.in)

SC125	N/A	N/A	M12 grub screw	4,0Nm	N/A	N/A
			(Slotted)	(35 lb.in)

Note:	Conversion from Nm to lb.in.	1Nm = 8,85075 lb.in.

Safeclip Fuseholder Installation

Method of cabling

Front connected fuse holders

Remove Red insulating terminal shrouds and loosen the exposed cable clamping screws.
Fit bared conductor end into fuse base terminal, and tighten cable clamping screw to secure.
Replace clip action Red insulating terminal shroud

Cable selection and termination

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 flexible cables are used, their relatively fine strands must be given increased protection by the use of thin wall copper ferrules crimped over the conductor ends. The following should be taken into account:

i. The inside diameter of the ferrule should match that of the 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. These measures should ensure that the heat is adequately exported from the fuses.

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.

Important note

These products should be installed, commissioned and maintained by, or under the supervision of a competent person, in accordance with current Electricity at Work Regulations, IEE Regulations for the Electrical Equipment of buildings, Statutory requirements and any other specific instructions issued by GE Power Controls Ltd. These notes assume throughout that the product is isolated from the supply during installation or maintenance. It is essential that this is done before commencement of any work. Any covers, or other safety measures which are removed during installation or maintenance must be replaced on completion.

Safeclip Maintenance

Guidelines

To ensure satisfactory operation of these fuse holders throughout their service life, it is recommended that the following procedure be carried out at regular intervals (at least once a year) as part of a planned maintenance schedule. Where the environment or service duty is severe there may be a need for inspection at shorter intervals.

Procedure

Isolate the supply.
Withdraw the fuse carriers and inspect fuse tags and carrier contacts (SC100) for any signs of damage.
Check all cable terminal screws and fuse link fixing screws (SC100) to ensure that the correct torque has been applied.
Wipe clean and remove any oxidation from the fuse link blades or carrier contacts (SC100).
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.

Important Note

The use to which these products are put and their service environment are outside our control. Therefore, particular care should be taken to follow these guidelines during installation or maintenance. No responsibility can be accepted by GE Power Controls Ltd if these guidelines are not followed.

(From Red Spot catalogue.)