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archaic is a good word , do not see rcd, s, still see lots of fuses of all styles on main supplys , do not even see disconnects ( isolators ) next to equipment , a recent service call at a hospital to replace a thermostat on a freezer room , two seperate systems but a single stat mechanical type double throw, so to isolate requirers access to the roof 3 floors up and a key to access the roof and a ride in the elavator and a lot of walking from one end of roof to the other , and you need to turn off both sets of equipment as you dont know which is the supply to the stat , by the way in evey call i make if you want to start a manual defrost , you also need to find the condensing unit which is inevetiably on a roof 20 ft high is common , as the clock and i mean the old style paragon type is still in daily use here isalways locted at the condensing unit , they have not heard of a control panel defrost control etc and an isolator adjacent to the freezer room , , some of there stuff takes alot of getting used to , and then there are wild legs but that is a different story ,

3 phase moter will have resistance the same on all 3 legs .If not moter bad ,which i worked on a older trane which was a 208 230 volt 3 phase which hinding in the corner was a step up transfprmer 460 v 1 phase .running condenser fan '

Originally Posted by Slatts

From what I've read here I assume you don't use residual currant devices much over there?

The more I learn about the power reticulation system used in the States, the more it horrifies me.

We joke about using the earth wire as a neutral return path over here but nobody would actually do it.

It sounds positively 19th century...

In the US, the neutral is a grounded conductor, and the service neutral is bonded to an earth electrode for surges and lightning.

Earth can never be used in place of a neutral to the power transformer. Here, that neutral is a transformer secondary center tap, so that the full secondary voltage is 220v, and one end of the secondary referenced to the center tap is 120v, which is our basic residential voltage for lighting and small appliances. We send the two ends of that transformer secondary and the center tap neutral from the pole to the home. A two pole breaker provides 220v, and a single pole breaker referenced to the neutral gives 120 volts.

Does that help?

Originally Posted by SBKold

Timebuilder I have wondered this for some time now - about the seperate neutral 4 wire range and dryer cords.

I understand what you mean about not using ground as current path.

At the dryer electrical connection there is a jumper from ground to neutral so what did this really accomplish?

From what I've read here I assume you don't use residual currant devices much over there?

The more I learn about the power reticulation system used in the States, the more it horrifies me.

We joke about using the earth wire as a neutral return path over here but nobody would actually do it.

It sounds positively 19th century...

Originally Posted by R123

You really need to use a megger to check for grounded motors. If the motor has a very mild ground, the 9 volt battery inside your standard ohm meter isn't powerful enough to complete the circuit. A megger, which produces 250 or 500 volts, will be alot more accurate. There has been many times my high quality Fluke 87 won't show a ground but the megger will pick it up.

Couldn't agree more R123.
Mechs who rely on a multimeter to test resistance to ground (earth) run the risk of killing themselves or worse, their paying customer.

Here are a couple of links of links to the type of meters we're talking about:

http://www.hioki.com/product/field.html

http://www.myflukestore.com/c538/meg...p?currency=USD

They may be expensive but how much is your life worth to you and your family?

Originally Posted by jarganda83

I ohmed the new motor right out of the box. The motor only has 3 leads, black, yellow and brown. I just checked from one lead to another. I checked the old motot the same way, with the motor leads off.

Essentially Black is common, Yellow is run, and Brown is start...Brown to yellow "Should" have the most resistance. Black to Brown the second highest, and Black to yellow the least...A volt meter can pick up on a shorted motor, a grounded motor is a different animal...A short is a broken wire...A ground is a crack in the lacquer in the windings causing power to "leak" to ground...You need meg-ohm meter for that...The OP got blasted by a grounded motor, a shorted motor would blow the fuses or the breaker...

BTW most of this is my experience, there is no hard fast rule on wire colors, the schematic or hook up diagram doesn't lie...

Originally Posted by jarganda83

I ohmed the new motor right out of the box. The motor only has 3 leads, black, yellow and brown. I just checked from one lead to another. I checked the old motot the same way, with the motor leads off.

I guess there is a chance my meter was wrong, but I ohmed a different motor the same day because I wanted to compare numbers and it was about right. The only difference was the voltage. The old and new motor were 460 single phase. The compared motor was 208/240 single phase.

I knew somthing was up...

A single phase motor that uses a run cap has three wires, and two windings. One is a run winding, and the other is usually referred to as an "aux" winding, which has a function similar to a start winding. The brown wire goes to the aux winding.

What readings did you measure?

Originally Posted by timebuilder

With today's four wire cord, you do NOT hook up the strap. They want NO connection between the neutral and the equipment grounding conductor*. The strap was only used when there were only three wires.

*In the dryer.

There IS a connection between the neutral and ground, but that ONLY happens at the service entrance panel.

Just to be 100% clear.

I ohmed the new motor right out of the box. The motor only has 3 leads, black, yellow and brown. I just checked from one lead to another. I checked the old motot the same way, with the motor leads off.

I guess there is a chance my meter was wrong, but I ohmed a different motor the same day because I wanted to compare numbers and it was about right. The only difference was the voltage. The old and new motor were 460 single phase. The compared motor was 208/240 single phase.

I knew somthing was up...

Originally Posted by SBKold

Thanks for the reply and explanation. My conclusion is then it is a backup conductor to the single grounding conductor we used in the past. Because depending on which conductor has the least resistance for the neutral currents it may be using either one.

With today's four wire cord, you do NOT hook up the strap. They want NO connection between the neutral and the equipment grounding conductor. The strap was only used when there were only three wires.

Originally Posted by timebuilder

The intention of that equipment jumper was to place the chassis of the dryer at the same potential as the "grounded conductor," which we routinely call the "neutral" conductor.

(Note: the NEC refers to the "hot" wires as the "ungrounded" conductors, the neutral as the "groundED conductor, and the ground wire as the "groundING conductor. They are working on changing the verbiage for most grounding conductors to BONDING conductors, since the purpose of an Equipment Grounding Conductor is to "bond" the metal parts to the panel via wires and conduit so that any short results in the overcurrent device being opened, which cuts off power to the offending appliance.)

Today, we use a separate conductor that is intended to carry NO current unless there is a fault, and that is the fourth wire. It eliminates the possibility that the cabinet can become energized due to neutral currents in the circuit. This raises the level of safety, which is what the code is all about.

Does that help?

Thanks for the reply and explanation. My conclusion is then it is a backup conductor to the single grounding conductor we used in the past. Because depending on which conductor has the least resistance for the neutral currents it may be using either one.

Originally Posted by timebuilder

I would have to see the method used. Perhaps that would explain it.

A three phase motor would have the same resistance for all windings. Are you perhaps talking about a three phase motor??

I agree, something is not right here. Either you have a 3 phase motor, your meter is not working properly, or your not ohming it out right. Was the motor completely disconnected and isolated when you took the readings?

Originally Posted by jarganda83

But the resistances were that way on the old and the new motor. The new motor runs within it's rating.

I would have to see the method used. Perhaps that would explain it.

A three phase motor would have the same resistance for all windings. Are you perhaps talking about a three phase motor??

Originally Posted by timebuilder

Yes. It is usually caused by a winding-to-winding short circuit.

But the resistances were that way on the old and the new motor. The new motor runs within it's rating.

Originally Posted by jarganda83

Has anyone ever ohmed out a single phase motor and got 3 similar resistances?

Yes. It is usually caused by a winding-to-winding short circuit.

Originally Posted by SBKold

At the dryer electrical connection there is a jumper from ground to neutral so what did this really accomplish?

The intention of that equipment jumper was to place the chassis of the dryer at the same potential as the "grounded conductor," which we routinely call the "neutral" conductor.

(Note: the NEC refers to the "hot" wires as the "ungrounded" conductors, the neutral as the "groundED conductor, and the ground wire as the "groundING conductor. They are working on changing the verbiage for most grounding conductors to BONDING conductors, since the purpose of an Equipment Grounding Conductor is to "bond" the metal parts to the panel via wires and conduit so that any short results in the overcurrent device being opened, which cuts off power to the offending appliance.)

Today, we use a separate conductor that is intended to carry NO current unless there is a fault, and that is the fourth wire. It eliminates the possibility that the cabinet can become energized due to neutral currents in the circuit. This raises the level of safety, which is what the code is all about.

Does that help?

Originally Posted by timebuilder

I caught myself using an incorrect term, so I want to correct it for all of you. My bad.

The jumper for bonding at the panel is the MAIN bonding jumper. The System bonding jumper is used where to have a transformer in a store (for example) where the service is 460v, and the transformer is there to supply power to the outlets, lighting, equipment, etc, that need 120v. In the transformer you have the SYSTEM bonding jumper, as it is a "separately derived system."

Timebuilder I have wondered this for some time now - about the seperate neutral 4 wire range and dryer cords.

I understand what you mean about not using ground as current path.

At the dryer electrical connection there is a jumper from ground to neutral so what did this really accomplish?

Originally Posted by jarganda83

How could a single phase motor ohm out all the same? The motor only uses 2 legs of power. L1 to common, L2 to run cap to run, other side of run cap to start.

???

Has anyone ever ohmed out a single phase motor and got 3 similar resistances?

Originally Posted by timebuilder

The problem would not be with the grounding stake or rod. The ground path begins at the panel with the system bonding jumper, which connects the ground bar to the cabinet and the neutral. This is the ONLY point in a system where the neutral and grounding conductors meet, so as to avoid what they call "objectionable current," that is, where current typically is flowing through the ground conductors. That current should ONLY flow during a fault. That's why they changed from three wire to four wire plugs for dryers, because we used to tie the ground (cabinet) to the neutral at the terminals in the back of the dryer. Now, only the cabinet connects to the fourth wire, and never carries current until something in the dryer shorts to the cabinet.

The grounding conductors carry fault current to the neutral at the panel, so as to assist the overcurrent device to open. The ground rod outside is there to take any lightning potential in the building wiring system to a low impedance earth ground, which only lightning uses as its sought potential. We can read voltage potential to ground because the building neutral and the utility transformer neutral (the center tap of the secondary) both tie to ground rods for lightning protection of the grid and structure.

I caught myself using an incorrect term, so I want to correct it for all of you. My bad.

The jumper for bonding at the panel is the MAIN bonding jumper. The System bonding jumper is used where to have a transformer in a store (for example) where the service is 460v, and the transformer is there to supply power to the outlets, lighting, equipment, etc, that need 120v. In the transformer you have the SYSTEM bonding jumper, as it is a "separately derived system."

You guys are absolutely right! When I got zapped I was repositioning the lid because I removed it to install the cc heater. The motor leads were still connected and the screws to the lid were not installed and the unit was supplied with power.... You guys are good.

I know your right because I checked voltage at the grille and at the cabinet. I was not showing any voltage at the cabinet because it is properly grounded.