Sub panels

[RichE]

Our gently used bot will not operate. The guys at ShopBot say I need a dedicated neutral and a ground for proper communication. My home is a little older (1961) so my main panel has a single ground bus and no neutral.

After a little research (and yes, I do believe everything I read on the internet) I see that if a main panel has this configuration you can wire a subpanel and have an isolated neutral bus at the subpanel. I'm a little confused by this. What does this do for the circuit? It seems to me that having a neutral terminate like this would be useless.

Its time for me to get an electrician but I thought I'd see if anyone here could help me understand this question so when an electrician shows up I can explain to them what exactly it is I need and why. ShopBot techs did offer to talk to them if they have any questions tho. Those guys are great. Can't say that enough.

[Brady Watson]

http://www.talkshopbot.com/forum/showpost.php?p=132424&postcount=8

-B

[RichE]

Thanks. I read this to mean that I want to completely isolate the neutral to avoid the chance of applying current to the ground portion of the circuit. I guess I'm just confused about why there is even a neutral portion to the circuit. To my tired brain, isn't this equivalent to simply removing the neutral from any circuitry at the subpanel? What is the purpose of the neutral if it is terminated at the sub?

[backyard_cnc]

If you have a 220V main service panel in your house than you have a neutral otherwise you wouldn't have 110V as thats how it is derived ( the neutral is the centertap with 110v referenced either side of the 220V input). At the main service entrance/panel the neutral and your system ground (water pipe or grounding rods) are connected together but any further sub panels or circuits cannot have the neutral tied to ground otherwise you could create shock hazards that could kill. Most panels have a simple jumper strap that either grounds or isolates the neutral bus for the panel depending on its application. There can only be one grounding point in a standard household electrical system. Since you have to have a neutral it could be that if you have older not grounded circuits the individual plugs in your house may only have 2 wires, that would be a hot and a neutral. You can easily verify if you have this by turning off the power and pulling out an outlet for a look. ENSURE THE MAIN POWER BREAKER IS OFF OR RISK ELECTRICAL SHOCK. If it has only 2 wires, likely black(hot) and white(neutral) and no bare copper wire than you have ungrounded circuits but if the bare copper is also there and attached to the electrical box than you likely have what you need. There are simple plug in circuit testers available for only a few dollars at any Home Depot or Lowes etc that will give a quick good-no good indication of your wirings status.

If you look at the service entrance where the electricity comes to your house (at the meter pole) you should see three wires, 2 insolated and one likely bare. The bare wire is the neutral and the 2 insolated are your 220V feeders. The actual "safety ground" will be a smaller bare copper wire either attached to your plumbing or run outside to buried ground rods or plates. Your ground is not supplied from the electrics company but supplied at the site

gerald

[RichE]

That is good info. I had assumed the bare wire to my service entrance would be ground, not neutral. I haven't noticed a grounding rod or grounding wire to my plumbing but I will investigate further tonight.

I do indeed have a two wire system for the older circuits in my home. The newer circuitry (basement and kitchen) have been wired for three prong with the neutral and ground connected to the lone bus in my main panel. I do have the plug-in tester, the plugs I've checked show the appropriate configuration.

Hopefully I can get a good electrician and make this work. I'm afraid now that I might be in for a big bill to bring my main panel and existing circuitry up to code before they will put in a sub.

[RichE]

So it turns out a $2 part sent me on a wild goose chase. One of my receptacles in the shop was shorting internally. Sheesh. Where's my whiskey. Glad we got it figured out tho. Everything is working fine. I just need to figure out how to operate it now.

[curtiss]

Does one depend only on the ground at the panel to ground the Shopbot ?

I pounded in a 4' copper rod into the soil with a bit of rock salt around it for my ground.
Some use an 8' foot rod I believe. I water the area from time to time.


Can one have too much ground ?

[bruce_taylor]

YOU CAN'T HAVE TOO MUCH GROUND IN MY OPINION, but you could have not enough, I have two eight foot rods pounded in full length bonded together with a heavy gauge solid copper wire.

[Brady Watson]

In an ideal world, all grounds should be terminated at a single common point. This will help to avoid what is known as a ground loop. Ground rods can vary in their grounding potential if more than one is used in a system, just from the soil composition difference between the two...If you want to get nitty gritty about it. Ground loops are most often an issue with low voltage devices, like some of the ShopBot electronics, so grounding can be an issue for some.

I prefer to have a good solid ground that originates from the electrical system. You can get fancy and tie into the panel, or just pull off the electrical conduit where it is convenient. Avoid multiple ground connections - focus on one 'master ground' connection. If you need multiple take-offs or connection points, use a star connection configuration. If you have an Alpha or RBK Standard, you can use the ground bus bar in the control box as your grounding point. Otherwise, you should run a dedicated ground from the electrical system to the control box, terminating it to the metal case.

Run a ground to the control box from the machine chassis. Verify ground continuity from the control box to the router/spindle mounting plate. We want to make sure we have a good solid connection. Routers may have worn brushes with a gap, so this is why I prefer the plate. Now the chassis of the machine, control box and electrical ground are all on the same ground. If non-Alpha/RBK then tie chassis into the same ground that terminates on the metal part of the control box.

Your dust collection system should also tie into the same ground. In most cases, you can tie it into another spot on your electrical system to wick up that high voltage static, without causing an issue. But, if you don't tie off to the same ground point as the rest of the stuff there is still a possibility for a ground loop. This is because the static electricity has a much higher ground potential than let's say a 5v input switch.

I've seen a lot of 'creative wiring' over the years & plenty of problems as a result. If you like yourself even just a little bit, wire things up deliberately, correctly and with the right stuff. If you do it half fast, you'll pay the price later with gremlins that are hard to diagnose.

-B