Shenhui ground spike

[john banks]

If I am not mistaken these machines have a ground spike intended to be put in the ground outside, after seeing feedback about these machines on here we're going to start talking to them to get a 1280 setup like Rodne's. The Chinese imported machines resold in the UK seem to have their earth from the 3rd pin on our 230 VAC standard plugs. Would it be a simple case of wiring the ground internally to the power connector(s), and checking that the supplied power cables have a ground in them? I want it all to play nicely with my RCD and I require the machine to be properly earthed. Are all the panels on the machine earthed nicely?

[Rodne Gold]

We took a big drill , drilled the earth spike *we used a copper bar* deep into the ground and tied every ground we could find on the machine to it. Chassis, power supplys etc. Prior to doing that , I had odd issues with the laser , albeit we also have ground pins on our electricity supply , afterward all worked well. Do it that way , its not a major job.

[john banks]

Thanks. Does the machine also make a ground connection through the earth on your electricity supply as well and the earth spike is extra?

[Dan Hintz]

I would suggest hooking all machine grounds to the ground in the power line coming to the machine. Bonding the machine grounds to physical ground without ensuring their connected in the machine to the electrical ground can lead to differences in ground potential at various points in the machine. It's likely there is at least one common connection, and setting up as Rodney has done would be acceptable (although not to code, if you're in the US), but considering the QA of Chinese machines is questionable, I wouldn't bet my machin'e life on it.

In short, connect all machine grounds to the incoming electrical ground and play it safe.

[matthew knott]

Im not sure why you would need an earth spike! Certainly in the UK the earth from your mains supply is going to be much better than effectively making your own! The electrical earth in building would have been well tested when it was installed and is able to carry a large amount of current in the event of something going catastrophicly wrong with the wiring as it will blow 50a fuses. I guess if you where to add your own spike and connect it to the building electrical earth it would not hurt but i also cant see what you would achive. I suspect the earth spike is a requirement of countrys that dont have a decent earthing arrangement (if any at all) as i have been to some where there appears to be no earth at all! But overall in the UK you would be waisting your time drilling and fitting an earth spike!!

[George M. Perzel]

Hi John;
After many discussions with the Shenhui techs its very clear that they do not have a good understanding of the US electrical system. When I asked that my machine be wired for 110VAC operation for the auxiliary receptacles, it was not done and they sent me a 110 to 220 voltage converted instead. I have since wired the machine to fit my USWA 110VAC blower, air, lights, and vacuum. To be safe, install a ground stud on the rear of the machine if there is not one provided. Clean the paint away to insure good contact. Connect the incoming 220 and/or 110 VAC ground wires to this stud. Connect a ground wire from the chassis of the power supply to this stud. I also installed a separate 8 foot ground spike outside (4 feet away from machine) as mandated by Shenhui but think this is overkill as building ground is same potential-connected it anyway to ground stud. By the way, Google internet for ground rod installation to find fast, easy way to sink ground spike using water and time-6 hours.
Best Regards,
George
Laserarts

[Michael Hunter]

John

Are you buying the machine direct from Shenhui, or going through a UK distributor/reseller?

If you are buying from a UK firm, the importer (maybe that firm, or maybe another firm somewhere in the EEC) is fully responsible for making sure that the machine meets all the UK/European safety and radio interference requirements.
If the machine has been tested properly it will be CE marked and there will be a certificate listing the ISO standards that it has been tested against.
Note that the radio interference bit requires an actual test of a whole machine working properly - it is NOT a paper exercise.
The safety assessment ***should*** include checking all the earth bonding within the machine to ensure its safety in use, though sometimes the whole thing is effectively done from drawings and parts lists.
If you subsequently have any worries about safety, your local Trading Standards people will take it up with the supplier for you.

If on the other hand, you are saving pennies and buying direct from China, then you are a bit on your own. The best way here is probably to get a demo from the reseller and snoop around to see if there are any "extra" earth wires etc..


PS If you import directly and then sell or even give the machine away in a few years time, then *you* are responsible for safety compliance!

[john banks]

Thanks all.

There is no Shenhui resaler I'm aware of in the UK, but their material states they are CE and ISO certified. I hope to be saving a few (million) pennies by importing, but it requires more groundwork on my behalf. This thread is part of that preparation.

My background is not high voltage stuff but microcontrollers, but since the machine is not double insulated my understanding is that every metal panel must be earthed. Even my bathroom metal pipes are earthed as they should be, but they are not near to any 30kV sources whereas the panels on a laser machine are. I have heard that on some imported and resold smaller machines that some panels are being earthed through painted hinges and the earthing varies depending on hinge position, but the larger professional machines have proper earthing and RCD in the machine.

The resistance between the sockets I'll likely use and the earth at the distribution board is about 0.1 ohm, about 10m of 2.5mm^2 conductor (I'm ignoring the small reduction from about 50m of 2.5mm^2 conductor on the other side of the ring). From the distribution board there is 0.5m of 16mm^2 conductor to join the supply cables at the meter which is connected to an appropriately chunky cable going into the ground. I don't believe that me sticking a spike in the ground is going to be anything like as good quality as simply going through the earth pin on the plug attached to this lot of modern wiring.

[matthew knott]

You are spot on there, you can connect it straight up to a UK 3 pin plug, its intresting with the CE marking, who do you think polices it! The answer is no one really, as a company you can "self certify" you declare that your machine comes up to spec and stick a ce label on it! Theres a whole list of things like EMC checking that should be done but who knows if they are and in reality unless someone gets hurt nothing is likely to happen. A CE mark guarantees you nothing at all !

[Michael Hunter]

You are on pretty safe ground if the machine is certified - and even more so if the CE "certificate of conformity" is signed off by an accredited test house (rather than just the company).
If you are still unsure, you can ask to see a copy of the test reports, though many companies don't like to give these out as they show all the tweaks that were needed to get the sample machine through the tests.

The ground-bond-every-panel thing is often less about safety and more about stopping RFI leaking out and/or improving immunity to the static discharge tests. Personally, I would not worry about lack of grounding to front doors and similar that are well clear of any mains or high voltage wiring