Is it safe for the case to be not earthed?


#1

I have just finished building the ELV PPS5330 PSU kit which is both accurate and very solid. BUT… It uses a two-core flex to the unit that goes straight onto an input board. There is a type X2 capacitor across the transformer which comes from the two holes in the PCB held down by cable ties. The double pole mains switch is insulated and fused by a shrouded pcb mounted fuse. The board is held in two places with plenty of clearance from the base panel which has an insulated shield on it.

All this means is the steel case is unearthed. It is coated in a thick layer of quality paint, but it is still steel. There is a spade terminal internally for an earth lug. Is this safe? Should I put a ground lug on the back of the case and bond it to my power ground? Clearances and isolation are both substantial.

image


#2

Looking at the back of this kit:

image

Does it require that the USB is always plugged in? I suppose that creates a path to ground as well, though I’m not sure I’d want to dump a bunch of excess current through my laptop chassis…

(not to mention my computer is also on 2 prong power on occasion)


#3

Whoops, was overzealous with my amazoning, the above was for the DPS 5315. Can’t seem to fint a picture of the back of the PPS 5330


#4

Here it is. No computer connection on my PSU. It is a cheaper model. I think the USB board on the more expensive PSU is optically coupled so the ground does not go any further into the unit. On the back there is the heatsink air outlet and power only.

image

https://www.elv.de/prozessor-netzteil-pps-5330-komplettbausatz.html


#5

I can only add (AS3000) that if an appliance is deemed double insulated, then an earth is not required. For this particular kit, the power switch is double pole so it swtiches both the active and the neutral. They also point out the importance of the isolation plate mounted underneath the power PCB and the transformer (Bild 19). So this might put this in the double insulated realm.
You could also ask the ELV forum for that kit.


#6

It probably does count as double insulated when I think about it. The bolts that hold the power board on are insulated by the plastic feet, so they have gone to great lengths. It just feels wrong. As for the ELV forum. Well to be polite I would have to post in German and mine is still too rubbish to be honest. I do like these kits though. I have a function generator ready to be built and the frequency counter on order. Both bits of kit I need better examples of. Building kits makes a therapeutic change. Thanks for the response BTW.


#7

I’ve posted to the ELV forum before in English because my written German just takes too long. I like these kits too and have built quite a few over the years. I will be curios about the function generator.


#8

I will wait a while for the function generator as I keep procrastinating with the train project. When I retired I purchased a pile of kits electronic and otherwise. So much to do and less time than when I worked.


#9

The case looks metal if so then use an earth to the case and any metal parts IE transformer the earth is to protect the user and any metal parts that are exposed to mains power.
In the UK at 230 volts AC it is mandatory to use an earth.

Hope that helps Bob