I have an ancient outbuilding with its own power meter and an ancient fuse style main panel (60A). The only reason it is there is to power the jet pump for an auxiliary well. In addition to the pump, there are two incandescent light fixtures (almost never used), and one quad receptacle box next to the main panel connected with 12-2. Setup is unchanged in the last ten years except for new wire from street to meter provided by the power co. after a tree took out the old wire about two years ago.
Today I plugged a 75′ 10-2 extension into the outlet, plugged my trusty DW compound miter into that and tried to cut wood. Saw ran slow- real slow- and basically wouldn’t work. I moved the same cord to an exterior outlet from the house, and it ran as good as always.
Voltmeter says there is 240 coming into the meter, and 120 at the outlet. At the end of the extension, it reads about the same, telling me (I think) that I got volts but not amps. Any thoughts on why I’m not getting full power and what to look at next?
Replies
Bad connection somewhere. Could be anywhere from the pole to the saw.
Most likely the neutral connection is mucked up. The 240V pump doesn't care whether there's a neutral or not, but your saw does. When you measure the voltage without the saw running you get 120V because there's a POOR connection, but still a connection. Turn on the saw, though, and the voltage dives towards zero (and the voltage on the other leg of the 240V line climbs upward a similar amount).
Of course, it could just be a bad connection in the quad outlet wiring, but my guess is that the neutral didn't get reconnected properly when the overhead line was replaced.
>my guess is that the neutral didn't get reconnected properly when the overhead line was replaced<How do I test for that? One of those plug-in polarity checker things shows wiring is correct: all lights are where they should be.I always thought that testing amperage under load took a special instrument. Can I do this with my multimeter?=====Zippy=====
Put your voltmeter across the 240V line and then try the saw (or other large load, like an electric space heater). The voltmeter should show a reasonably steady value -- dropping a volt or two. Next, put the voltmeter between one leg and the neutral AT THE PANEL. Try the saw. If you see the voltage drop substantially (5 or more volts) OR RISE SUBSTANTIALLY then it's probably a bad neutral connection, Switch the voltmeter to the other leg and try again -- if the voltage dropped on the first leg it should rise on the second and vice-versa. (Note, measure the voltage after the initial startup surge, not during the surge.)
The mark of the immature man is that he wants to die nobly for a cause, while the mark of a mature man is that he wants to live humbly for one. --Wilhelm Stekel
Okay, under load (space heater) volts go down to about 90. In the main box, I get 90 between hot and neutral on one leg, and 150 on the other leg. Repeating the same check on the incoming line yields the same results between each of the hots and the neutral.This looks out of my league, but is my next call is to the power company or an electrician?=====Zippy=====
Call the power company. They are free. It's either a bad neutral connection on the overhead line or in the metersocket.
Power company.More often it is the POCO as their connections are out in the weather.But with an installation as old as your and the fact that they preplaced the drop there is a better chance that it is in the connections at the meter base or main panel or even a corroded neutral in the SE cable.But I would still start at with the POCO. It could be that they did not get a good crimp in the first place..
William the Geezer, the sequel to Billy the Kid - Shoe
A better late than never followup: I called the power company who verified it was a bad neutral on their side of the meter. They traced it back to the pole at the street (about 250 feet, all new wire from the last time they were out). It turns out the power lines that run down the highway are on one side of the road and the pole that feeds my pumphouse is on the other side. The only chunk of bad wire left was what crosses the road- and they replaced that. Supervisor said that piece of wire looked like it had been there since the 1950's, and had an obviously broken neutral. Everything seems good now.Thanks to all for steering me in the right direction!=====Zippy=====
Also, If you have a very old meter box with probably an old service entry cable running out of the top of the box....check for a leak where the cable enters the top of the meter box. That is a very common place for problems on old services.
The seal around the cable leaks and water runs down into the meter box and corrodes the neutral connection.
If you suspect that, then contact the power company to pull the meter and look inside the box.
How does the Jet pump run? Are the incandescent lights working with the expected brightness? If they both work then the problem is between the panel ,12/2, line and receptacle box. Might be a weak connection there.
Good point about the neatral line. If your saw is a three prong.
Do you have a grounding rod connected to the 60 A panel?
Edited 12/18/2008 5:07 pm ET by hammer
"Good point about the neatral line. If your saw is a three prong.Do you have a grounding rod connected to the 60 A panel?"Ground, both the grounding electrode systems (ground rod and conductors) or the equipment grounding conductor (what the 3 pin connects to) have absolutely nothing to do with this kind of problem..
William the Geezer, the sequel to Billy the Kid - Shoe
FWIW, it appears to be properly grounded to a copper rod driven into the ground.=====Zippy=====
To test this you need a voltmeter and a load.The lights might be enough. Turn them on and measure the voltage from each hot to neutral at the fuse panel. They should be within 1-2 volts of each other.If that does not show a the problem then get a large load and hook it on the extension cord and the receptacle that you had problems with before.Don't use a anything with a motor.Use some 500 watt work light or a space heater or something like that.Then repeat the measure right where the power comes in. If that is OK then keep meausre it on the other side of the fuse to the neutral bus, if the same then meausre it at the receptacle.You should find some place where the voltage is much less..
William the Geezer, the sequel to Billy the Kid - Shoe
>Don't use a anything with a motor.Use some 500 watt work light or a space heater or something like that.<
Ok, just out of my own curiosity, why not a motor? I can see how the 500w lights would act like a constant reisistance but why not a motor?
Concern that the motor will burn out.It will work fine of the testing, but if the motor never gets up to speed it can draw a lot of current.And it may cause the fuses to blow while testing and that just confuses things more..
William the Geezer, the sequel to Billy the Kid - Shoe
Gotcha. thanks
Pump runs fine. Lights seem about as bright as I'd expect.=====Zippy=====
What Dan said.
I would first check the neutral between the panel and receptacle. If that's solid, then the panel to meter. If that's solid then it's time to get the utility co. involved.
BTW, loose neutrals can be a dangerous issue, although you're fortunate in that there are a very small number of devices connected to this service. I wouldn't be plugging in any more 120V loads until this is fixed.
Scott.
>I would first check the neutral between the panel and receptacle. If that's solid, then the panel to meter.<I admit to being confused. How do I check the neutral?=====Zippy=====
Bill's given you the correct diagnostic procedure.However, a visual inspection may suffice at first. The neutral is a normally the white conductor. Switch off the main disconnect. Get yourself a "Volt Tick" detector, which can save your life, and make sure that all conductors are cold. Now open up each box and look for flaky splices or loose lug screws. Anything flaky should be replaced with fresh wire nuts. Tighten all screws so that conductors are making good contact. Look for corrosion, clean if necessary, and fix the source of said corrosion.Now power everything up. If problems persist, then follow Bill's procedure....or call an electrician, which might be the best thing anyway if you're unclear about which conductor is the neutral.Best wishes,Scott.
Try plugging in the saw without the extension cord. If the motor is still sluggish, you need to read the plug with an ammeter. You will need a minimum of 15A.
A ground rod only protects against lightning strikes and line surges from the transformer.
You really have to check the voltage under load if you are looking for a loose connection. A dozen ohms in the connection won't show up at all if the only load is a meter, digital, an old analog one or even a wiggy, but you will not be running your saw at much more than half power.
Try a different extension cord .... or, after using your cord for a bit, check the cord near the plugs for hot spots. Bending the wire can improve / worsen the connections there.