Another Question for an Electrician

[dudleydocker]

I have a 60 year old house that was upgraded to 100 amp service before we bought it 14 years ago. Since then I have replaced virtually all of the wiring (all runs conduit) and all of the outlets, switches and fixtures. I have also added breakers to split up the kitchen into multiple circuits, ease the load on the original 8 breakers, and dedicated breakers for things like the sump pump, back up sump, and computer power feed

My dilemma is that I still see a slight dimming in the lights when a major appliance like the washing machine kicks in. It even affects my monitor which is run through an APC 650 Pro UPS. I even put the washing machine on it's own breaker and it still affects the other runs.

All wiring is 12 or 14 guage, good connections at all wire nuts (twisted then capped) then taped.

What am I chasing down here?

I've already checked the voltage coming in with a multimeter, and the SmartUPS software that my UPC runs shows a range from 109-123v.


And now that you mention it (saw another thread) we do go through a lot of light bulbs, but it seems ot be limited to the heavy use fixtures.

Thanks.

 

[Armitage]

Try putting splitting your loads across the two 120V branches that feed your panel. Should just mean moving some brekers.
I had that problem in my garage subpanel ... all the breakers were on the same branch, so when I kicked on some high draw machine, the lights would flicker to the point that the flourescents would "unstart". Moved the outlet circuits to the other branch and all is well.

Also, make sure you have a good ground.

 

[dudleydocker]

Yeah, I forgot to mention that I need to extend the ground all the way to where the copper wire comes up out of the basement floor. Right now it's just clamped on a copper water pipe by the box, a good 50 feet from the main water feed.

So just rearrainging the breakers should help? Other than the washing machine, I've seen the dishwasher cause this, and maybe the garage door opener. So try to isolate the high-draw items AWAY (on the other side) from lights?

Thanks.

 

[sharkeeper]

Electric motors will draw LRA for a brief moment until the shaft speed is close to synchronus RPM. Tungsten lamps have extremely low filament impedence when cold and have an extremely high inrush current when started as well. How long is your run to your pole? What AWG is the run or UF it's underground? The dimming will be noticed even through your UPS since the UPS doesn't include voltage regulation.

Cheers!

 

[Armitage]

Originally posted by: dudleydocker
Yeah, I forgot to mention that I need to extend the ground all the way to where the copper wire comes up out of the basement floor. Right now it's just clamped on a copper water pipe by the box, a good 50 feet from the main water feed.

A copper water pipe should be a pretty good ground, but it the ground wire should connect closer to where the pipe comes out of the ground. Also make sure any non-metallic breaks in the water line (water filters, etc.) are jumpered across.

So just rearrainging the breakers should help? Other than the washing machine, I've seen the dishwasher cause this, and maybe the garage door opener. So try to isolate the high-draw items AWAY (on the other side) from lights?

Thanks.

Yea, it should probably help.
200A service would help more
Sometimes there is nothing to be done on your side though. If you're on the end of the line, you'll see alot of fluctuations. I still have that problem, although upgrading to 200A service helped.

 

[dudleydocker]

The more I'm thinking about this, I believe it's the manner of how I arrainged (or lack thereof ) the breakers as I've added them.

The service feed is above ground, approx. a 110' run. I don't know what gauge it is. The entire electrical grid is OLD. We're in the middle of a block of approx. 300 houses in our section. Again, it's all post WW II or older.

200 AMP service is an idea. I need a new meter box outside as well. It's my understanding that everything is mine up to where the line feed connects to the outside meter, correct?

Thanks for the replies.

 

[dudleydocker]

anybody else?

 

[Ornery]

I sure liked ergeorge's idea. Why not stick the circuits with motor loads on one branch, and the lights, computer(s) and other electronics on the other. Sounds like you've done the hard part already. Nice going!

 

[dudleydocker]

Guess what I will be doing this weekend?

 

[Armitage]

Originally posted by: dudleydocker
Guess what I will be doing this weekend?

Let us know how it goes!
and hey...
Be careful out there!

 

[przero]

Make sure all connections (esp. power feed lines) are tight. Check the condition of the Buss bar in the panel box. Do you have a main circuit breaker ?

 

[db]

Hmm, I could swear I read a thread exactly like this last month....

 

[dudleydocker]

Yes, the box has a main (100 AMP) breaker. I've never touched anything upstream of that, nor do I want to. I received an e-mail suggesting that I have the power utility come out and check the feed line to the house and also to double check the ground, so I think I will do that as well as re-order the breakers. I've identified all the things that have a initial hi amp draw, i.e. washing machine, and will isolate those on one side. See how it goes...

 

[Analog]

Originally posted by: dudleydocker
Yes, the box has a main (100 AMP) breaker. I've never touched anything upstream of that, nor do I want to. I received an e-mail suggesting that I have the power utility come out and check the feed line to the house and also to double check the ground, so I think I will do that as well as re-order the breakers. I've identified all the things that have a initial hi amp draw, i.e. washing machine, and will isolate those on one side. See how it goes...

probably not a grounding problem. Think about it, if your service transformer has sufficient impedance (or the wire size for your service feed from the transformer is long or is smaller gauge), then you'll get this "dimming" effect NO MATTER what your service is rated, at the panel. I.E. the service from the utility cannot supply enough current, thus causing the line voltage to sag to conform to Ohm's law.

Some questions to ponder: What is the KVA rating of your transformer? What is the length of service cable from the transformer to the panel? What gauge is it? What is your nominal line voltage (is it unusually low?)? How long a cable run is it from the panel to the motor? What gauge wire to the motor? What guage wire to the critical stuff you don't want to brown out? Can you fix any of this easily?

 

[dudleydocker]

<<"Some questions to ponder: What is the KVA rating of your transformer? What is the length of service cable from the transformer to the panel? What gauge is it? What is your nominal line voltage (is it unusually low?)? How long a cable run is it from the panel to the motor? What gauge wire to the motor? What guage wire to the critical stuff you don't want to brown out? Can you fix any of this easily?">>

Don't know what the transformer is rated (assuming you're talking about the on eon the utility pole).

My house is approx. 120' from the service connection (overhead) and the breaker box is in the basement directly under where it connects to the meter outside the house.

Gauge...dunno.

Voltages as reported by my APC UPS software are usually 120 and below. A few spikes now and then. Also a few significant drops...I've see 91-92 v on occasion.

Wiring from the breaker to the motor is 12 g and less than 5 feet in distance.

80% of the wiring is 14 g, some 12 g to the bigger stuff.

Fix easily? everything inside my house. From the panel on out, I'm not touching it!

 

[feralkid]

You could also use motor controllers to reduce the load when motorized appliances start up. Easy, though not dirt cheap.




<<80% of the wiring is 14 g, some 12 g to the bigger stuff.>> that's not so great, but for other reasons.

 

[dudleydocker]

<<80% of the wiring is 14 g, some 12 g to the bigger stuff.>>


<<" that's not so great, but for other reasons.">>


why is that?

 

[dudleydocker]

anybody else?

 

[amdskip]

Originally posted by: dudleydocker
<<80% of the wiring is 14 g, some 12 g to the bigger stuff.>> <<" that's not so great, but for other reasons.">> why is that?

Why isn't it so great?

 

[feralkid]

Originally posted by: dudleydocker
<<80% of the wiring is 14 g, some 12 g to the bigger stuff.>>


<<" that's not so great, but for other reasons.">>


why is that?

Well, it varies by location, but most local codes only allow it for 15 amp lighting circuits.

 

[Analog]

if you have a clamp-on ammeter, you could check the loads on each circuit without opening any wires.

 

[KMurphy]

The reason for dimming when starting induction motors is the voltage drop during motor acceleration from the sudden sharp increase in current draw. This is worsened by the fact the utility's transformer feeding your house is very near full load rating. Ask your neighbors fed from the same transformer if they have it bad too. Get the utility to look into upgrading the transformer or adding another transformer to ease the burden.

Another reason for dimming (voltage drop) is insufficient sized conductors running from the transformer to your main panel. This effect is not usually significant unless your conductors are way undersized. You probably want to get the utility involved though.

Besides Yellowfiero's comments, the other comments won't be helpful at all in reducing voltage drop. Your ups is a battery standby system, not a true online blipless transfer type. Once the voltage dips to a predetermined point for a predetermined period, the standy UPS transfers to battery backup.

 

[KMurphy]

Forgot to mention; if all your neighbors have bad dimming during motor starts, get them all to complain to the utility. They will listen.

 

[dudleydocker]

<<"This is worsened by the fact the utility's transformer feeding your house is very near full load rating.">>

How can you determine this?

 

[dudleydocker]

^^