Spider27 Posted June 19 Share Posted June 19 May I ask experienced members here on what amphere rating for the on/off switch and fuse need to be if I am using SMPS that outputs 156W, 24v x 6.5A? Do I need to use On/Off switch as well as fuse rated 250V and just over 6.5A? Thank you Link to comment Share on other sites More sharing options...
aussievintage Posted June 19 Share Posted June 19 (edited) 54 minutes ago, Spider27 said: May I ask experienced members here on what amphere rating for the on/off switch and fuse need to be if I am using SMPS that outputs 156W, 24v x 6.5A? Do I need to use On/Off switch as well as fuse rated 250V and just over 6.5A? Thank you Doing a quick calc at 230 volt. 156/230 = 0.67 amperes. That 6.5A figure is just the 24 volt DC side at 24 volts. So. probably a 1 amp switch/fuse rated for our mains voltage. Edited June 19 by aussievintage 1 Link to comment Share on other sites More sharing options...
Spider27 Posted June 19 Author Share Posted June 19 7 minutes ago, aussievintage said: Doing a quick calc at 230 volt. 156/230 = 0.67 amperes. That 6.5A figure is just the 24 volt DC side at 24 volts. So. probably a 1 amp switch/fuse rated for our mains voltage. Thank you very much for clear explanation. A quick question. Is there any harm to use higher rates amp switch/fuse than 1A, say 5A fuse and 3A switch? Link to comment Share on other sites More sharing options...
aussievintage Posted June 19 Share Posted June 19 57 minutes ago, Spider27 said: Thank you very much for clear explanation. A quick question. Is there any harm to use higher rates amp switch/fuse than 1A, say 5A fuse and 3A switch? Yes, the fuse should be only just big enough to not blow in normal use, i.e. at turn-on (when there may be a surge) and at high loads. The switch can be as big as you want. 1 Link to comment Share on other sites More sharing options...
surprisetech Posted June 19 Share Posted June 19 54 minutes ago, Spider27 said: Thank you very much for clear explanation. A quick question. Is there any harm to use higher rates amp switch/fuse than 1A, say 5A fuse and 3A switch? Fuse should not be higher rated. If you find that the 1A fuse blows because of initial inrush current, you should try a slow-blow fuse of the same rating. Higher rating on the switch is fine. 2 Link to comment Share on other sites More sharing options...
bob_m_54 Posted June 19 Share Posted June 19 55 minutes ago, Spider27 said: Thank you very much for clear explanation. A quick question. Is there any harm to use higher rates amp switch/fuse than 1A, say 5A fuse and 3A switch? No worries using a higher rated switch, but if you want the fuse to act like it's supposed to (prevent the equipment form bursting into flames) then you need to use the appropriate size fuse on the input. 1 Link to comment Share on other sites More sharing options...
Spider27 Posted June 19 Author Share Posted June 19 Thank you all. I now got the idea what fuse rating that I need to aim at. I might need to get 1A slow blow fuse because I tried to turn on the SMPS last night with 3A Fast blow fuse that laying around and it was working fine when turning on but blew the fuse when it was turning off. Link to comment Share on other sites More sharing options...
Spider27 Posted June 20 Author Share Posted June 20 Got the slow blow 1A fuse with 3A 250v rated switch and works fine. Thank you all very much. 2 Link to comment Share on other sites More sharing options...
aussievintage Posted June 20 Share Posted June 20 10 hours ago, Spider27 said: Got the slow blow 1A fuse with 3A 250v rated switch and works fine. Thank you all very much. Well done. 1 Link to comment Share on other sites More sharing options...
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