Hello everyone,

I got hired by a research lab to do the electronics work for an outdoor experiment. The equipment they use runs on 5 volts along with a mains line and some cheap mains transformers that feed the boards with a new 5V line every couple of meters.

The equipment and the boards are not well designed or high end at all. The electronics parts are extremely sensitive to esd (and they could have been easily shielded.) I've experienced several similar problems that point to bad design.

Now it turns out that it will be raining on the experiment day (the public are invited to participate.) I pointed out to them that a wet floor is a significant hazard to the people given that the equipment already has several problems and proposed an alternative design where the transformers are safely housed at the corners of the experiment floor and connected in parallel, supplying 5V to fewer grounded nodes. I haven't heard back from them yet (its been quite some time).

Should I quit this job if they decide to go on with the current wiring scheme?!

 

Can you point out any specific safety issues?

I don't see any in your post.

 

It will be raining that day. There will be about 20 cheap 120V transformers lying around in soaking wet floor -- which the people taking part in the experiment are standing on.

 

The only person who can make that call is you. Obviously, you are not happy with the configuration. I have been in situations where I was concerned about safety issues. Also, like you, I was "hired help", as in lacking authority. It sound like you have voiced your concerns. It's a tough call.

Do you have GFIs in place?

 

Yes, That's what they make ground fault outlets for. Most outdoor outlets have them.

 

Lestraveled - I am only testing the system indoors. I don't know about the actual place.

 

Whatever you do or wherever you are, install a GFI outlet.

 

Well there's lots of matters here that need proper consideration before any sensible conclusion can be reached.

In principle there is nothing wrong with standing transformers in rain and water. In most local substations (where the voltage are much higher) transformers are exposed.

However they and their connections are properly weatherproofed.

So question number 1 would be: Is this a temporary lash up and for how long?

In the UK 'mains' voltage is 230 but regulations require installations like yours need to be supplied from 110 volts (or less).

110 volt equipment is often in the rain on sites, but proper weatherproofing and connections are used.

Then there is the electrical reason for wanting to run mains cables out around the worksite.
To minimise power loss.
Would the supply cables to a 5V system loose too much voltage from a central 5V supply?

As to earthing, what are you expecting to happen?

 

could you put each transformer in a plastic bag for insulation to keep off the rain?

 

You could use a large 120V:120V isolating transformer indoors, able to cope with the total load.

 

The reason that people are not getting killed often from electricity in their homes is that there are multiple layers of protection. The casing of appliances insulate the user from deadly voltage. The three wire power distribution puts a ground shield around most appliances. Catastrophic failures are prevented with fuses or breakers. Then finally there might be a GFI. It is ludicrous if you strip these layers away so that something like a plastic bag is the only thing that will keep you safe.

Evaluate your electrical environment for the things that will kill you and the things that will save your life. If you are basing your safety on a piece of plastic that is designed to keep your sandwich fresh, you are in trouble.

Think it through.

 

the plastic bag has worked better for my lights in the front yard than the supposedly outdoor wireing. a plug and socket sitting in rainwater isnt a very good idea, even with a ul label on them.

 

alfacliff
I apologize for picking or your plastic bag idea. My point is there needs to be several layers of protection that are hopefully recognized by UL or the local electrical codes.

Imagine going in to a court of law and defending yourself because someone got killed.

 

and I dont see how the UL could defend themselvs over the safety of outdoor lighting plugs and sockets. they arent any differnt than indoor ones, and are subjected to rain and standing water. the plastic bag is just to substitute for a good insulating housing for the connection.

 

I don't know who or what UL are, but proper contractors use proper site wiring and connectors for the conditions.

 

UL is the under ruighters labratories, the group that passes on safety issues, they test and approve electrical eqauipment here in the US.

 

outdoor lighting plugs and sockets. they arent any differnt than indoor ones

I'm surprised. They are different in the UK.

 

UL is the under ruighters laboratories,..

Also know as Underwriters Laboratories.