Safety issues? - Page 1
Forum section: electronics / general

author: edy
author_rank: Super Contributor
timestamp: June 06, 2016, 09:05:03 pm
content: Hi folks,I saw this setup in a dental/medical office and somehow it didn't seem to be a good way to do things. For one, I'm not sure if the ground lead broke off or was never connected, seems like they tinned the ends and then wrapped it around but it broke. There seems to be almost nothing holding the wires on. They are only an inch off the ground and potentially moving power-bar or cable may be swaying, shorting possibly, water contamination, corrosion. Not that high voltage-wise but still....I mean, it's a piss-ant power-supply but still, I guess it is too little to cause any damage? What do you think?

author: Monkeh
author_rank: Super Contributor
timestamp: June 06, 2016, 09:13:02 pm
content: And that's why you don't tin wires.

author: edy
author_rank: Super Contributor
timestamp: June 06, 2016, 09:41:05 pm
content: You'd think a "For Use On Medical/Dental Equipment" transformer/wall wart would be implemented a bit better. I'm not sure what that designation really means, actually, other than they can charge more money. If it's just a simple isolating AC transformer, with 10:1 windings ratio and current-limiting resistor/fuse?

author: engineer_in_shorts
author_rank: Regular Contributor
timestamp: June 06, 2016, 09:54:50 pm
content: Screened core

author: helius
author_rank: Super Contributor
timestamp: June 06, 2016, 11:52:10 pm
content: The main problem seems to be the implementation of the cabling rather than the transformer unit (which may have QC issues but they aren't evident externally). Yes, screwing on bare stranded wires is not going to be reliable, every EE knows that, and end users generally don't care.

author: Monkeh
author_rank: Super Contributor
timestamp: June 06, 2016, 11:53:32 pm
content: Quote from: helius on June 06, 2016, 11:52:10 pmThe screw terminal is perfectly fine.. the problem is that the wires are NOT bare.

author: Tomorokoshi
author_rank: Super Contributor
timestamp: June 07, 2016, 01:23:18 am
content: Offer to fix it for $375.

author: edy
author_rank: Super Contributor
timestamp: June 07, 2016, 02:29:02 am
content: These multi-strands connected to screw terminals make me nervous. I walked into a completely brand new medical/dental office that was just built and ready to open in a few days.... When I noticed a strange burning smell coming from the wall.It turns out, the idiot who installed the P.A. overhead speaker system had connected the +/- for one of the overhead speakers to the amplifier/pot volume controller and one of the tiny strands from one wire had shorted to the other. The wall was filled with various construction dust and debri, and that was enough to make quite a noticeable smoke signal. The volume control pot looked something like that shown below.Anyways, multi-strand wires connected to screw-terminals can be done improperly. Whoever did the job above tinned the ends for some strange reason, but as you can see it didn't quite work. The main cable should have been fastened to the transformer somewhere with a clamp, or around a double-hook, so that tension the cable wouldn't pull on the screw terminals directly. I would have expected a small "lid" or cover over the terminals, and some strain-relief system for the main cable.

author: Raj
author_rank: Frequent Contributor
timestamp: June 07, 2016, 05:28:42 am
content: Ill recommend rewiring those using lug crimps, and hot snotthough i would have totally changed the enclosure into a more secure one

author: ez24
author_rank: Super Contributor
timestamp: June 07, 2016, 06:31:08 am
content: Time to get a filling

author: Jasper
author_rank: Contributor
timestamp: June 07, 2016, 11:21:21 am
content: Quote from: blueskull on June 07, 2016, 06:15:42 amWell, for one the safety ground has broken off. Regardless of the voltage, the device connected might still need the ground to be safe.For another, this is a fire hazard — it could short out accidentally.