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Picking a fuse

James Evens
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From the 10 A fused Input it distributes to two PSU (total 250W) and 3 silicone heater mats (2x200W,1x500W). 

Is there a benefit of adding a fuse to the silicone heater?

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You want the fuse on the heater to be less than 10A and a possibly a type that burns/trips faster than the 10A from the source.

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Hi, I guess it depends on what the PSUs are running. If they are running machines, yes. If you add a fuse to the downstream resistive heater mats you are protecting the upstream PSUs. Depending on your access to kit (because in the UK you can get 1A or 2A domestic fuses from RS), I would put 3A fuses on each mat. It says Europe on your profile, so from P=IV, I=p/v > 500W / 220V = 2.27 A for the largest mat.

 

Need more info on your setup really. Supply voltages would help.

Edited by Triphase
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37 minutes ago, Triphase said:

Need more info on your setup really. Supply voltages would help.

220V.
PSU output and everything from there is individually fused. So just the mains wiring is in question. Also in between fused input and everything else will be a RCD.

The heater are controlled through a solid state relay and coupled with a thermal fuse which is rated for 15A and 146 °C. Wire gauge isn't set so using 10A capable cables won't be a problem. Cable breakage is still a possibility/concern but reduced by using high flex cables and drag chain.

 

[Input with 10A fuse atm.]->[RCD]->[splitted to PSU and heaters]->[SSR]->[drag chain]->[thermal fuse]->[heater]

 

So you would go with a 3A fast?

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Hi, it can't hurt to test a 3A fast 20mm HBC and see how you get on. If they pop really quick (not sure about the load resistance of your mats(almost a startup current)) perhaps a  'T' type fuse? Inserted right next to the heater. I'd expect the fuse next to the heater to pop before anything further up the chain.

 

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Settled now on:

[Input with 7A fuse]->[RCD]->[splitted to PSU and heaters]->[xA fuse (500W 3A, 200W&250W 2A,)]->[SSR]->[drag chain]->[thermal fuse]->[heater]

and the Camden Boss CFTBN Fuse holder with HRC fuses.

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