I’m still fighting the lighting problem I posted about a few days ago, but now have some more info. I would really appreciate any insight anyone can offer.
Since the installed system uses four 12 volt bulbs that are 20 watts each. I duplicated that setup on a test board. With all four bulbs installed and connected to the transformer, all bulbs light at full brightness when I test at my house. BUT, when I return to the scene of the crime where the transformer is normally plugged in, they glow dimly. That location has it’s own service and the lighting transformer is the only thing connected to it. I measured voltage using a digital VOM and got 120v. So, it would appear that eventhough I’m seeing 120 volts there, it’s incapable of providing enough amperage to light the lights. What else can I check?
Replies
Hello,
Have you used the VOM to measure the resistance of the lighting string? From your earlier post it sounds like there there is a soft short in the wiring and the transformer is getting loaded down. My suggestion would be to disconect all the bulbs and check the resistance, it should be high (open).
Also, are all bulbs glowing at the same dimness?
Nate
I've eliminated the in-ground wiring from the picture by putting all the bulbs on a test board. I'm using the same test board at home and at the location where the lights are installed. And yes, they all glow at the same dimness. The transformer is plugged in, not hard wired.
Sorry for starting a new thread, I know what you mean, but old threads seem to get lost in the sauce....
Gotcha,
In that case, I'd go with Bill's suggestion regarding measuring the voltage with the transformer plugged in at the site. A bad conection in the 120V service would measure out fine without load, but droop when the lights are connected.
Good luck,
Nate
Thanks, that'll be my escapade for tomorrow. We've had issues with this service in the past, but it's usually been low voltage, not low current. It's always a fun ride trying to get the electric company to troubleshoot these problems. If I'm lucky, the problem is in the breaker panel. More news tomorrow.... Thanks again...
OK, here's the latest. At the breaker panel at the problematic location, with no load, I measure 248 volts across the two hot legs and 124 volts from each hot leg to neutral. So far, so good, right? When I add the load, the leg the load is on drops to 63 volts and the other leg goes to 185 volts. If I move the circuit to the other leg, that leg goes to 63v and the opposite leg goes to 185v. In other words the voltage drop follows the load and the opposite leg increases to 185v. I didn't find any loose connections, but tightenend everything anyway. All of these measurements were made in the breaker panel on both the bus and leads that come in to the main breaker. I didn't get into the meter. This is getting interesting now. Any thoughts?
"Any thoughts?"Yep.You have a bad neutral connection.Most likely it is the POCO's problem so call them..
William the Geezer, the sequel to Billy the Kid - Shoe
Bill’s right on the money. The Neutral connection is not well connected to the power company's transformer and they need to fix it. <!----><!----><!---->
At the pole, the high voltage is stepped down by a center tapped transformer to create a 240V feed. The center tap is connected to the neutral so that you also get two 120V feeds 180 degrees out of phase with each other.<!----><!---->
With a single load, all the current passes through the neutral. If the neutral has a poor connection, then the 240V gets split into the unequal voltages you are seeing. So in your case, the end taps of the transformer are stable at 248V, but due to the resistance in the neutral leg, the load from your lighting transformer is causing a voltage drop across the neutral and dropping the voltage. This is showing up as a shift in the voltages on the two phases. In houses with this problem, the lights on one phase get brighter when a large load (fridge, electrical range) turns on on the other.<!----><!---->
Not that you should do this but... Since the neutral only carries the difference in load currents, the problem could be reduced by adding another lighting transformer to the other phase and putting two bulbs on each (if the loads are the same then the voltages will balance). <!----><!---->
Good sleuthing!<!----><!---->
Nate
Yes, the classical bad neutral connection. If there is an outside disconnect panel next to the meter that you can get into, repeat your measurements there. If you get the same oddness call the electric co.
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
Thanks to the help from you folks, my problem is now fixed. The guy from the power company was pretty impressed with my troubleshooting and the fact that I had isolated the problem for him. Little did he know I have a bevy of experts behind me! He also indicated that they take bad neutrals pretty seriously and the problem was corrected the next day. Thanks for all the great advice!
Thank you for coming back with the outcome.
Too often all this troubleshooting ends with no ending report.A Great Place for Information, Comraderie, and a Sucker Punch.
Remodeling Contractor just outside the Glass City.
http://www.quittintime.com/
Maybe that's because we electrocute so many first time posters.
God is REAL, unless explicitly declared INTEGER
I guess I didn't give that one a thought.
Man, and we didn't even have the brains to send flowers.A Great Place for Information, Comraderie, and a Sucker Punch.
Remodeling Contractor just outside the Glass City.
http://www.quittintime.com/
Actually I think that we get a good amount of feed back.Specially on the electrical problems.I have seen many other forums where the response is very, very little.Don't even know if they got back to read the message..
William the Geezer, the sequel to Billy the Kid - Shoe
Can't agree Bill.
at least on the good amount.A Great Place for Information, Comraderie, and a Sucker Punch.
Remodeling Contractor just outside the Glass City.
http://www.quittintime.com/
Quick,
Old threads don't get lost when you bring them back up with a post. Folks that were reading along with them b/4 might have further input and will recognize them.
Best of luck with your finding the problem.A Great Place for Information, Comraderie, and a Sucker Punch.
Remodeling Contractor just outside the Glass City.
http://www.quittintime.com/
You really should have kept this in the original thread-alot of background info is there.
Is the transformer plugged in at the original power source or direct wired?
A Great Place for Information, Comraderie, and a Sucker Punch.
Remodeling Contractor just outside the Glass City.
http://www.quittintime.com/
Did you measure that 120 v UNDER LOAD.
With the transformer connected and the lights connected meaure the 120 on the input terminals of the transfomer. If that is not possible measure the voltage at the receptacle, again with everything connected and ON.
William the Geezer, the sequel to Billy the Kid - Shoe
I haven't seen your related thread so may be missing out on a lot. One thing I had thought of, which may not be all that obvious: Is it possible you measured the brightness in your home with the shades pulled and at the alternate sight outside under full sunshine so your eyes were making the adjustment? Please ignore if ......
I hate 12v exterior lights.... nearly burned my house down with the cheap transformers they use.
Save yourself..... throw it away now.
Are you getting 120V WHILE THE LIGHTS ARE LIT? When you measure the secondary voltage WHILE THE LIGHTS ARE LIT, is it pretty close to 12V?