Pa's Wiring Conundrum (Longest Ever)

[George Stolz]

My dad bought a new table-saw from Harbor Freight, put it in his barn, turned it on and the fluorescents in his barn went into strobe mode. The next time I came by he asked me to took me out there to look at the situation and solve it.

Study the following diagram and discuss:

The plot consists of a 190x-built brick house with a 100A service. I could not inspect the terminations behind the meter socket (sealed), or the terminations at the drip loops at the top of the mast.

There is a conduit running underground from the service to the detached garage. The conduit enters the garage, enters a small 2-space panelboard with two 15A branch circuits for the lighting and receptacles in the garage. Conduit leaves this panel and crosses the ceiling, drops down the other side, exits the garage and runs underground to the barn.

In the barn there is a panel with four breakers. One for the loft, one for the main floor lights, and two for general purpose receptacles.

The saw's nameplate says "120V 22A" and the owner's manual calls for a 20A circuit. It has a standard 15A plug configuration. At startup, the saw draws 70A, and settles down to 5.5A running under no physical load.

Now, to my questions:

• Would it be compliant to install a dedicated 20A circuit for the saw?
• Why does the voltage increase in the kitchen receptacle when the saw starts up? Is this indicative of a resistive service neutral, or is this normal due to the capacitance of the neutral conductor?
• Why is there 2.2A flowing on the GEC's, even though the neutral current is seemingly correct for the loads measured on the phases? In my mind, the neutral should either be 4 or 8 amps: If 2.2 amps are coming into my service from neighboring services, then the neutral should be 8A. If the neutral current from my house is flowing into the GES (because of a resistive neutral), then the neutral current should be 4A.

I plan to install a new 60A feeder to the barn (directly), and install a new 3R panelboard to comply with 110.26 (the existing one is over a workbench with a toolbox screwed down in front of it). I intend to rewire the main floor to get rid of the extension-cord permanent wiring of the lights. That's for starters.

Thanks in advance for all replies, and sorry for it being so long.

Edit to add: The voltage at the saw receptacle when the saw starts drops to 90V. The lights are on the opposite phase and still flicker. I am uncertain of the voltages at the barn before/during the saw startup. (Another disclaimer would be that I wrote down these voltages after I got home, not when I was taking the readings. I also did not verify phases of each testing point, but made assumptions based on the readings as to which phase a testing point was on.)

 

[don_resqcapt19]

The increase in voltage on the opposite line along with realitively high current on the grounding electrode conductor under normal conditions indiciates a service neutral problem. Note my comment on the GEC current assumes that there is not a metal underground water pipe system that is common to other buildings in the area.
Don

 

[karl riley]

George, it certainly sounds like resistance on the service neutral. You have to be able to get behind the meter to check its terminations. I just came from a job where the hidden neutral terminations were corroded and causing 10 amps to flow out the water pipe.

Karl

 

[karl riley]

Don, we posted simultaneously. Two minds or one?
Karl

 

[George Stolz]

Thanks for the replies, guys.

For the moment, let's assume that there is an interconnected metal water piping electrode among services.

How could the 2.2 amps on the GES be accounted for and still show a reasonably balanced neutral?

Also curious about opinions on the branch circuit for the saw, as well.

Thanks again.

 

[TOMWELDS]

With that bad neutral, be extra careful while doing any work on the waterpipe ground..ouch!

 

[winnie]

I guess from the description of 'barn' I am assuming a rural location with _long_ service conductors. In this case, the voltage readings may not be caused by a _bad_ neutral, but simply a long high resistance neutral.

For the current on the EGC, I'd be tempted to chop power at the mains and see if there is _still_ current on the EGC; you have multiple detached structures with grounding electrodes, and I would not be surprised if there were current flowing 'in' on electrode and 'out' the other.

For the saw, I'd see if the motor can be re-wired for 220V operation and install a 240V circuit.

-Jon

 

[George Stolz]

Thanks, Jon.

I guess from the description of 'barn' I am assuming a rural location with _long_ service conductors. In this case, the voltage readings may not be caused by a _bad_ neutral, but simply a long high resistance neutral.

It is in the middle of town; in 1908, I guess horses still hadn't been replaced, hence the barn. I was holding off on asking them to have the POCO check their connections (thinking there was more to it than I was seeing)- I will measure the overhead tonight and get back to you on the length. I'd guess about 100' - 125' of length.

For the current on the EGC, I'd be tempted to chop power at the mains and see if there is _still_ current on the EGC; you have multiple detached structures with grounding electrodes, and I would not be surprised if there were current flowing 'in' one electrode and 'out' the other.

I didn't think to check the current on the neutral of the existing feeder to the garage/barn at the service, so that could be correct. I will shut off the mains and see if the current is still there.

At the barn, the only grounding electrode is a single ground rod, as I hear it.

For the saw, I'd see if the motor can be re-wired for 220V operation and install a 240V circuit.

Not from the factory. That's what I was initially hoping for too. The odd thing is, it's just a sticker on the motor - it doesn't really look like a nameplate. I believe I saw "Made in China" on it, too.

 

[George Stolz]

Update: Some of my previous information wasn't correct. There is no current on the GEC - I accidentally had the EGC of the 10-3 feeder in the clamp at the same time I took the original readings. The neutrals and grounds are tied together in the barn, so the current was neutral current from there. That will be fixed when I replace the panel.

The distance of the overhead is pretty long: 371 feet. It actually runs down the alley and back again. Judging from the readings from a few nights ago, I would surmise that the voltage at the transformer was roughly 246V, given a phase at 122V at 22A.

I suspect the service neutral in the mast is bad, or a bad connection inside the meterbase. Does anyone think the overhead's distance would account for the seemingly impaired neutral? Given the lack of juice flowing out on the GEC (0.0), it leaves me with a little bit of doubt. I'd like some confirmation before I call in the POCO.

I feel kind of bad for not picking up heavier on the neutral thing sooner, they've already hand-dug half the trench for the new feeder. I re-learned an important aspect of troubleshooting again: Check everything yourself. My dad moved the breaker for the saw to "an opposite phase" to the lights, per my request. But the GE slimline panel uses two breakers per phase space, so he ended up putting the lights back onto the same phase.

When I saw it tonight, I put it onto the opposite phase, and the lights got brighter (128V) not dimmer (90V).

I still feel like replacing the feeder is still a sound course of action, because of the romex in the ground, complete with plumbing 90?s to enter the building. But I do feel like kind of a bonehead for not putting two and two together before they had the trench half dug.

 

[dlhoule]

The odd thing is, it's just a sticker on the motor - it doesn't really look like a nameplate. I believe I saw "Made in China" on it, too.

Does this saw have a UL label or any listing from a qualified listing agency? China and a few other places are putting counterfeit UL labels on a lot of equipment these days and many of them do not come close to meeting UL standards.

IMO you will solve the problem by doing what is planned. I am not very comfortable with the description of the saw though.

 

[dlhoule]

Pa's Wiring Conundrum (Longest Ever)

And I was wonering why you cared what went on in Pennsylvania!:lol:

 

[ceknight]

I am not very comfortable with the description of the saw though.

Yeah, in private communication with George I suggested that he be a good son and buy his father a real table saw.

 

[George Stolz]

I'm already giving him a hard time sleeping at the price tag for a new feeder (4/3 URD $97), a new panel ($90), romex (250' 12-2 $90). He can use that saw until it dies, IMO.

When I'm done, it shouldn't see less than 111V, if all goes to plan. So that crummy high-falutin' saw should last for years, hopefully.

Well, unless someone thinks that somehow the long overhead could cause a "open neutral-esque" fluctuation at the motor startup, then I will let them know they need to call the POCO to correct the mast.

Last call...

 

[al hildenbrand]

PoCo Secondary Length

PoCo Secondary Length

Good morning George,

I read this thread yesterday afternoon and have been mulling over the observations you've reported.

This is a problem, IMO, that is created on both sides of the Service Point. I agree with Karl :

George, it certainly sounds like resistance on the service neutral.

but from a slightly different angle than he went on to explain. Like Jon said :

the voltage readings may not be caused by a _bad_ neutral, but simply a long high resistance neutral.

The distance to the PoCo transformer contributes a significant part to the voltage fluctuations that comes from the PoCo's own secondary wires and splices. Also, any preloading by the neighbors that are supplied by the same transformer will introduce voltage drop along the portion of the circuit that is shared with your Pa's saw current.

Given the house is inside the "old town", the return current on the neutral, once it hits your Pa's house main bonding jumper, is going to go in several directions, given the interconnected metal municipal water service (that I assume is present)

Reducing the voltage drop to the table saw by increasing the size of the conductors that you can change out will decrease the effects of the saw's 70 A start current, but the size increase won't remove the voltage fluctuation entirely.

If the PoCo has an old 50 or 75 kVA transformer on the pole, and the neighborhood has a history of new loads, such as central ACs, kitchen remodels, etc., you may well be able to sweet talk the PoCo engineers into setting a second transformer closer to the customers on the end of the old secondary, by complaining about the voltage drop that remains after your feeder upgrades.

 

[George Stolz]

Thanks, Al.

So, my first course of action would be to have the POCO check their connections, and perhaps replace the conductors in the mast (the overhead looks okay). Then, if I'm still experiencing the upswing on the opposite phase, then I should try sweet-talking a new transformer closer to the house, right?

The odd thing is, their conductors could easily be shorter. Their tap on the utility line is further away from the transformer than their lot is. Their overhead actually backtracks to get to their house, it is odd.

I'll go ahead and have them call the POCO now, to investigate their terminations.

Thanks for all the replies, I appreciate it.

Does this saw have a UL label or any listing from a qualified listing agency?

I'll take a picture of the saw next time I'm over there, and take some of the existing wiring, too. I'm not sure of the listing of the saw. Any other thoughts on that, by the way?

 

[dlhoule]

Originally Posted by dlhoule
Does this saw have a UL label or any listing from a qualified listing agency?

I'll take a picture of the saw next time I'm over there, and take some of the existing wiring, too. I'm not sure of the listing of the saw. Any other thoughts on that, by the way?

My only thought was that if it has no listing; wouln't it be improper to provide power for an unlisted piece of utilization equipment. Aw, forget it. If you and your father are aware of the potential hazards; technically all you are doing is providing power to the outlet. How he chooses to use the outlet is up to him.

 

[al hildenbrand]

Larry,

I'll just bet that this saw has some form of a NRTL approval on it.

The motor, 120 V 22 A on the "nameplate", with a NEMA15P cord cap, is in an interesting (to me) subgroup of machines.

The shop that the handyperson sets up in their basement, garage, or, in this case, barn, is rarely wired for the tools. Most of the time, the person is buying the tool with the most capability at the lowest price, and expects to "just plug it in". The tool advertising department will tailor the language of its ads, most of the time, to the non-electrical woodworker. This results in the marketing of machines with motors like this saw.

The home woodworker will never use this as a "continuous load" (per Art. 100), yet if a dense enough workpiece is cut with a dull enough blade on the end of enough circuit resistance, then the OCPD will trip before meaningful work can be done.

If I can't afford the wiring to support the new tool, then I surely can't afford to replace the tool with something perhaps better suited (such as a 120/240 or straight 240 V version of the tool), and then I have to redefine what I will accept as "meaningful work" to something slower.

IMO, the tool manufacturer takes advantage of how difficult the electrical circuit issues are, and markets to the confusion.

 

[al hildenbrand]

my first course of action would be to have the POCO check their connections, and perhaps replace the conductors in the mast (the overhead looks okay). Then, if I'm still experiencing the upswing on the opposite phase, then I should try sweet-talking a new transformer closer to the house, right?

I assume the feeder to the garage is going in, like you mentioned earlier. Get it in. Then get the PoCo into the sweet talking if appreciable voltage drop remains. Having the connections at the meter pan, etc., checked can be done anytime, IMO.

 

[George Stolz]

I assume the feeder to the garage is going in, like you mentioned earlier. Get it in. Then get the PoCo into the sweet talking if appreciable voltage drop remains. Having the connections at the meter pan, etc., checked can be done anytime, IMO.

So, you think the upswing on the opposite phase inside the house could be from the undersized feeder going out to the barn? I can't picture it.

 

[al hildenbrand]

Not from the barn feeder but, rather, the service grounded conductor & GES parallel path.