Hello Brian, I may only be complicating the issue, but I will share how I handled a similar issue with products at a previous employer. I worked on power distribution equipment with internal electronics. These products were tested to IEC 60950-1. The electronics for the product were typically protected with a single fuse. For products where the outlets were the same current rating as the input, the power to the outlet was tied to input power before the fuse. As such, opening the fuse did not affect power to the connected loads.
First, the device was marked in accordance with IEC 60950-1 section 2.7.6. The wording is "CAUTION: Double Pole/Neutral Fusing". This is confusing enough and it requires translation for each intended market. There is the option of using ISO 3864 No. 5036 with IEC 60417-5016 and the letter "N" to indicate neutral fusing., but that symbol combination is probably even more confusing to the general user. This marking is only intended for service personnel of the main equipment, not the connected loads. Second, the connected loads were plug connected. Those loads would either use the plug as the disconnect or they had a suitable switch or other disconnect device built in. Service personnel working on the connected loads were to follow the service instructions for those loads. The presumption is that the device is always plugged into a live outlet and must be disconnected before servicing. IEC 60950-1 makes that assumption and requires information to the service personnel on properly disconnecting power. I generally recommend against using two fuses with one on each phase. This can cause more confusion without necessarily improving the situation. Inevitably, under fault conditions, one fuse will open and the other will not. I would consider having service personnel with poor trouble-shooting skills as a foreseeable condition. If overcurrent protection is provided for multiple phases, the overcurrent protectors should all open and close together. This typically means a multi-pole circuit breaker. Fuses in general are not reliable as a disconnect device and I would hope that service personnel would know that. (Trusting people to know better is not necessarily wise.)<https://1drv.ms/p/s!Ap8stJM0LsH4jweDCsFPQUi1wPk9> Where there is an individual fuse for each phase, there should also be a multi-pole disconnect switch. Ted Eckert Microsoft Corporation The opinions expressed are my own and do not necessarily reflect those of my employer. From: Kunde, Brian [mailto:[email protected]] Sent: Friday, November 4, 2016 7:38 AM To: [email protected] Subject: [PSES] AC Mains Outlet fuses or daul pole breaker?? Greetings Experts. If we send 230Vrms out of a product to power an external device through an IEC Outlet connector and we need to provide Overcurrent Protection for this port internal to our device, can I use two fuses or do I have to use a double pole circuit breaker? Since our product can be used in a 220-230 Vrms power system which cannot guarantee polarity on the plug (such as Europe) or that the neutral will be grounded (some North American power systems for example), we have to have over-current protection on BOTH sides of the line (all current carrying conductors). But when we supply power externally to another device, it is possible that one fuse could open and the other side of the line is HOT to Earth. Someone working on the external device could put a meter across the line as see there is no voltage and assume the AC mains is OFF not knowing that one side of the line it still HOT to Earth. This could cause a hazardous condition. SO, this is the reason for my question. If our device supplies power externally to another device, can we use fuses which could cause the hazardous condition I explained above, OR must we use a Double Pole Circuit Breaker which opens all HOT conductors simultaneously? If I must use a breaker, what standard or rule dictates this requirement? OR is this even a scenario we have to be concerned about? Since the external device has a warning label to disconnect power cord before servicing, is this even something to be concerned about? BTW, my product is Laboratory Equipment (UL/IEC 61010-1) to sell on a worldwide market. 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