CE marking / EU standards - internal connectors finger safe?? - Page 1
Forum section: electronics / projects

author: max_torque
author_rank: Super Contributor
timestamp: August 29, 2019, 04:13:50 pm
content: I'm trying to establish if internal 240VAC connections need to be finger safe for an EU approved (CE marked) industrial applicance?The unit cannot be opened without tools, is externally labelled "isolate supply before removing cover", and is not required to be accessed at all by the end user.There is a 240VAC pass through via a filter / power distribution box, that is a seperate enclosure within the unit, and i am looking for a suitable connector set to get power out from that box and routed onwards to the loads within the unit (each of which has it's own feed loom, consisting of L/N/E. When each load is plugged in, then the connector is finger safe, but if unplugged it isn't.Therefore, if you left the power on, used a suitable tool to remove the cover, unplugged one of the loads and stuck your finger into the socket left behind, you'd get a shock!Has anyone got any design / sign-off experience that's relevant? There is a lot of standards and certification documentation i'm wading through, but i can't find an explicit requirement to be finger safe internally once something is un-plugged??

author: krho
author_rank: Regular Contributor
timestamp: August 29, 2019, 04:30:39 pm
content: Isn't this the same as opening e.g a computer power supply when under the power?

author: MosherIV
author_rank: Super Contributor
timestamp: August 29, 2019, 05:57:45 pm
content: How about the 3 pin IEC socket commonly found as power leads on computer equipment.

author: Conrad Hoffman
author_rank: Super Contributor
timestamp: August 29, 2019, 07:48:01 pm
content: Don't know about the regs, but it's just good practice to prevent contact whenever possible. It sounds like the connector should be reversed so the inaccessible half is the one with the voltage present.

author: Neilm
author_rank: Super Contributor
timestamp: August 29, 2019, 08:38:25 pm
content: It may depend on the standard you are trying to meet to allow you to declare conformity to the LVD.If you are not sure then a risk assessment should be carried out. Would a service technician have a need to operate the unit with the cover off? Would they have a cause to disconnect the load?I have designed equipment to IEC61010 (test and measurement). In this sort of situation where I had dangerous voltages exposed to a technician fault finding, risk assessments were carried out. A service manual was written that highlighted each of these areas. It is company policy that only approved service centers get the service manual and they only get approved if they have been on the training course for that equipment which would highlight the problems. I would also try (if practical) to have an LED on the board that would light if power was applied or caps were charged to dangerous voltage - have LEDs on them helps discharge them as well.IEC61010 does have a section under documentation that says service personnel should have enough information to safely fault find, reassemble and perform any safety tests required to prove the unit is reassembled correctly. This has to be in place before the unit can pass - read the standard you are trying to meet.

author: max_torque
author_rank: Super Contributor
timestamp: August 29, 2019, 10:02:00 pm
content: I can't use IEC sockets because they are not "latching" connectors and the unit is subject to vibration, which could shake a non latching connector apart.The exact CE and cert requirements are being worked out at the moment, but it seems that there is a vast difference between stuff that is a legal necesity and what is best practice, and it seens "internal finger safe" is a chunk of that!As the power distro unit includes a master "safe" relay inside that is used to isolate all the outputs via the hardware Estop circuitry, we might be able to use some sort of micro-switch in that chain to automatically disconnect the outputs if the lid is removed. Ie that switch would have to be deliberately bypassed with a specific tool for bench top testing and fault diagnosis etc?

author: floobydust
author_rank: Super Contributor
timestamp: August 29, 2019, 10:20:34 pm
content: Figure out what safety standards apply to the product. Example 61010:6.2 Determination of ACCESSIBLE parts6.2.1 GeneralUnless obvious, determination of whether a part is ACCESSIBLE is made as specified in 6.2.2 to 6.2.4 in all NORMAL USE. Test fingers (see Annex B) and pins are applied without force unless a force is specified. Parts are considered to be ACCESSIBLE if they can be touched with any part of a test finger or test pin, or if they could be touched in the absence of a covering which is not considered to provide suitable insulation (see 6.9.1).If, in NORMAL USE, an OPERATOR is intended to perform any actions (with or without a TOOL) that could increase the accessibility of parts, such actions are taken before performing the examinations of 6.2.2 to 6.2.4.NOTE Examples of such actions include:a) removing covers;b) opening doors;c) adjusting controls;d) replacing consumable material;e) removing parts.Rack-mounted and panel-mounted equipment is installed as specified in the manufacturer's instructions before making the examinations of 6.2.2 to 6.2.4. For such equipment, the OPERATOR is assumed to be in front of the panel."I think you are covered with a warning sticker per 5.2:"If the instructions for use state that an OPERATOR is permitted to gain access, using a TOOL, to a part which in NORMAL USE may be HAZARDOUS LIVE, there shall be a warning marking which states that the equipment must be isolated or disconnected from the HAZARDOUS LIVE voltage before access."

author: max_torque
author_rank: Super Contributor
timestamp: August 30, 2019, 12:13:40 pm
content: I think we are going to err on the side of safety, and add an additional internal cover over the output connectors, and that cover will prevent the connectors from being touched or removed when it's in place, and that cover will also press on a micro switch that enables the main safety relay. Therefore to unplug an output connector, that cover must be removed, which means the outputs cannot be enabled, and it can be replaced after a disconnection, covering any outputs that might be disconnected, ie the unit can be tested with loads unplugged, but the cover must be in place for it to operate.A minor cost and additional complexity for a decent functional safety improvement during unit repair / test etc