220V dryer sparked on startup (3 wire) What to test?

Page 13 of 16  
On Tuesday, November 19, 2013 8:32:46 AM UTC-5, Stormin Mormon wrote:

Perhaps. I just thought of another way to make krw's day. It's a little complicated and clearly over his pay grade. His position is that with split-phase service, there is only one phase present, that you can't say the two hot legs are 180 deg out of phase, etc, because it originates from only one phase of the primary distribution. Well, then what about open delta? Open delta allows a utility to provide 3 phase service for lighter loads using just TWO transformers, instead of 3. It saves the cost of an additional transformer. One transformer is connected to each of TWO primary high voltage lines. So, they have connections to only 2 primary phases, yet they deliver 3 phase power. According to krw's standards, that should be called 2 phase, because it only uses two of the transmission's 3 phases. Yet it's called 3 phase, there are 3 phases that you can see on a scope and just like the 240V/120V service it's done with transformers.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 11/19/13 8:53 AM, snipped-for-privacy@optonline.net wrote:

Another thing a bit odd is the corner ground delta used by some of the local utilities for irrigation well hookups. 3ø, 480 vac, 100 hp or less in my area. The meter sockets look like single phase meter sockets. The utilities usually bring four wires into the sockets. Two of them go to the grounded center pole. One of those two will have the green/white stripe on it.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Sunday, November 17, 2013 8:28:53 PM UTC-5, Danny D'Amico wrote:

Yes. If you graph each hot vs the neutral, you will have two 120V sine waves that differ 180 deg in phase.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

The two wires are the same phase and that each in reference to the neutral show 180 degrees out of cycle. Both are on the same phase.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Wow. Amazing. "180 degrees out of cycle" = "same phase"????
Try "180 degrees out of cycle" = *out of* phase.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Monday, November 18, 2013 9:50:53 PM UTC-5, Doug Miller wrote:

Good luck explaining that to krw. According to him, the only proper term apparently is "opposite". What a precise engineering term...... I've even given him references to an IEEE paper delivered at a conference of power engineers that specifically addresses the point. But he just ignores it all.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 11/16/2013 10:34 AM, snipped-for-privacy@attt.bizz wrote:

If the angle between the phases was anything other than 180, would you call it 2 phase? If so, why this oddity?
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Sat, 16 Nov 2013 14:54:22 -0600, sam E

Probably. Not sure what your question is, but 2-phase, where the two are 90 degrees apart is interesting in that any phase relationship and any number of phases can be generated with simple transformers and a (very small) bit of trigonometry. It's quite useful but exceedingly rare.
Two phases generated 180 degrees from each other make no sense at all. It's no more efficient (less, actually) than single-phase and much less efficient than three-phase. There are all sorts of other alternatives, as well. Six-phase is somewhat interesting at times but it's not as efficient as three phase. There's a reason the world uses three.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Saturday, November 16, 2013 6:12:14 PM UTC-5, snipped-for-privacy@attt.bizz wrote:

I believe his question is the same one I have, which is why you insist on referring to a 180 deg phase difference between two AC waveforms only as "opposite" and deny that it is also correct that they differ by 180 degrees in phase. 180 deg is just one possible relationship between two waveforms, where one is the opposite of the other. And that is what you have at the dryer connection.
but 2-phase, where the two

Except of course to run the dryer, because regardless of whatever you want to call it, there are two hots going to that dryer that differ in phase by 180 deg. If you were in an EE physics, or math course and they presented you with a voltage vs time graph of two waveforms that you would get from an oscilloscope hooked up to:
Hot 1 to neutral and Hot 2 to neutral
And they asked, what is the phase relationship of these two voltage waveforms, what would your answer be?
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 11/15/2013 7:58 PM, snipped-for-privacy@attt.bizz wrote:

I've been trying to figure if the cold wire of a three wire dryer is a neutral or ground. I'd thought it was a ground, but some folks on the list and on the web thought it's a neutral.
--
.
Christopher A. Young
Learn about Jesus
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Sat, 16 Nov 2013 06:31:21 -0500, Stormin Mormon

It *is* a ground. It's connected to the case of the appliance. Would you connect a neutral to the case?
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Sat, 16 Nov 2013 11:35:17 -0500, snipped-for-privacy@attt.bizz wrote:

It's also connected to the ground bus inside the box, not the neutral bus. Uninsulated, too.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 11/16/2013 10:38 AM, snipped-for-privacy@attt.bizz wrote:

The NEC previously allowed the *neutral* for ranges and dryers to also be used as the ground. It is not allowed now for new circuits, but is explicitly grandfathered for old circuits that were compliant when installed.

There are a number of limitations on using the neutral as both neutral and ground. One of them is the circuit has to originate in the service panel. The neutral and ground are bonded at the service. It has to originate on the neutral bus. In many panels the neutral and ground bus are the same. If there is a separate ground bus that only connected to the enclosure the wire can not be connected there.
Another limitation is uninsulated wires in romex can not be used.
From gfretwell in a recent post: "During WWII they jammed through an exception allowing the neutral to also be used as the ground to save copper. In the 1996 code cycle CMP 5 finally accepted Phil Simmon's assertion that the war was over and they should dump this exemption for new circuits. (existing can stay)"
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
<snip>

Not always. Older, or cheap, load centers used to do this, but the newer panels give a dedicated ground bus with a tapping screw to the panel case and an isolated grounded conductor bus.
In some instances, in meter-main/load center combos, the tapping screw may be allowed as the point at which the grounded conductor obtains its bond to ground, but it is preferred to do this in the meter section of all installations so that there is no messing things up via some moron coming in at a later time and thinking that it is all the same...
Why I hated residential work...
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 11/16/2013 1:47 PM, Nightcrawler® wrote:

(which is wrong)

It is common practice to use the same bus for both neutral and ground in a service panel. The bus is bonded to the enclosure (N-G bond), and the earthing electrode system connects to it.
Can also be done with a separate ground bar connected to the enclosure. (Neutrals can't connect to such a ground bar.)
The neutral bar in a service panel must be bonded to the enclosure/ground system.

Not obvious what you are saying.
The system N-G bond is at the service disconnect.
It is common for the neutral in a meter can to be connected to the can. That is done to "ground" the can.
Your post would be more clearer to most people if you used "neutral" instead of "grounded conductor".
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 11/16/2013 11:35 AM, snipped-for-privacy@attt.bizz wrote:

Oh, now I'm all confused.
--
.
Christopher A. Young
Learn about Jesus
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
wrote:

It is more of just what you want to call it. As most dryers use the 120 volts from one leg to power the control circuits and light , the third wire is acting as a neutral. At the same time it is connected to the frame of the dryer and is acting as a neutral. I am sure if you search the electrical code there will be some name for this wire.
On the 4 wire dryer wiring , you do have a seperate ground and neutral wire, but they both connect to the frame of the breaker box so in effect it is just one wire but they go to two differant places on the dryer. Outside the fact they may be differant sizes and color code differantly to meet the code it would not really mater which wire was hooked to the neutral or ground at the dryer as they both go to the same place in the breaker box.
Having a seperate ground wire for the dryer just gives an extra layer of protection.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Sat, 16 Nov 2013 12:05:12 -0500, Ralph Mowery wrote:

Well, that answers my question as to whether the neutral is carrying current.
Since there are 120v "things" on that dryer (e.g., the timer, the bulbs, etc.), there *must* be some current in that neutral (unless the loads are perfectly balanced).
So, in the case of my 3-wire dryer, the neutral is always carrying current, whereas a ground wire shouldn't normally be carrying current (because once you carry current, there is a chance that there will be resistance, and if there is resistance, you get a potential, whether you like it or not).
So, maybe, just maybe, my spark, is due to a high-resistance neutral? Geez. How do I check for a high-resistance neutral?
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Sat, 16 Nov 2013 20:18:17 +0000 (UTC), Danny D'Amico

Yes, though it's possible to balance the two, it would be quite expensive to perfectly do so under all conditions. The fourth wire is cheaper.

Sure.

It would have to be a very high resistance neutral to get a spark. Even if there is no neutral, the voltage on the common point (the neutral on the dryer) would be very close to ground. The imbalance is proportional to the ratio of the current in the heater and the timer. You would measure resistance with an ohm meter. ;-)
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Site Timeline

Related Threads

    HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.