Electrical Engineering - Phenomenon Noticed after converting Apt. outlets to screw connectors

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Phenomenon Noticed after converting Apt. outlets to screw connectors

ChrisCoaster

2008-01-30, 8:25 pm

I have the following voltmeter:

http://www.radioshack.com/product/i...rentPage=search

A while ago, I posted a thread about the effect of converting "back-
stab" household receptacles to their side-screws, or upgrading to
pressure-plate backwired outlets.

I now have three years of data indicating that my consumption(in
average daily kilowatt hours) has not fluctuated much from IE: January
2005>Jan 2006>Jan 2007, etc. The biggest factor in my bills is the
baseboard heat, the fridge, and the AC units in summer. Not to
mention that CL&P's generation rate is now twice what it was three
Januarys prior! In addition, I'm slowly converting higher wattage
75-100W bulbs(kitchen, entry way) to 15-20W(75W equiv) fluorescents.

The phenomenon mentioned in the Subject header is simple: Pre-
conversion, I was getting 121-122VAC readings on the radioshack
multimeter. Currently, after converting all non-switched receptacles
to side-screw or back-wire, I'm now getting readings between
124-125VAC!!

Is that safe? The meter always did read a little hot(a fresh out of
the sleeve AA battery would read 1.58 > 1.61 on the multimeter).
Should I purchase a second multimeter and see if it returns lower/
different readings? Still, the voltage readings at the outlets are
2-3VAC higher than before all this converting went on, so I know my
TVs/Stereos/Appliances are getting the most voltage they can in this
apartment.

Your comments on the multimeter or the outlets are welcome.

-ChrisCoaster

Palindrome

2008-01-30, 8:25 pm

ChrisCoaster wrote:
> I have the following voltmeter:
>
> http://www.radioshack.com/product/i...rentPage=search
>
> A while ago, I posted a thread about the effect of converting "back-
> stab" household receptacles to their side-screws, or upgrading to
> pressure-plate backwired outlets.
>
> I now have three years of data indicating that my consumption(in
> average daily kilowatt hours) has not fluctuated much from IE: January
> 2005>Jan 2006>Jan 2007, etc. The biggest factor in my bills is the
> baseboard heat, the fridge, and the AC units in summer. Not to
> mention that CL&P's generation rate is now twice what it was three
> Januarys prior! In addition, I'm slowly converting higher wattage
> 75-100W bulbs(kitchen, entry way) to 15-20W(75W equiv) fluorescents.
>
> The phenomenon mentioned in the Subject header is simple: Pre-
> conversion, I was getting 121-122VAC readings on the radioshack
> multimeter. Currently, after converting all non-switched receptacles
> to side-screw or back-wire, I'm now getting readings between
> 124-125VAC!!
>
> Is that safe? The meter always did read a little hot(a fresh out of
> the sleeve AA battery would read 1.58 > 1.61 on the multimeter).
> Should I purchase a second multimeter and see if it returns lower/
> different readings? Still, the voltage readings at the outlets are
> 2-3VAC higher than before all this converting went on, so I know my
> TVs/Stereos/Appliances are getting the most voltage they can in this
> apartment.
>
> Your comments on the multimeter or the outlets are welcome.
>
That meter has an accuracy, when new, of +/- 1.5% of fsd +/- 5 on the
lsd, when on ac volts.

Assuming that you are using the 200v range, that is an accuracy worse
than +/- 3v. A true voltage of 123 volts could read anything from below
120v to over 126v - so worrying about any variations in measurement
within that range are pretty pointless, with this meter.

Buying a different meter is pretty pointless too, unless you buy one
which has a certified accuracy better than the variations that you are
trying to measure.

Don't worry about it - the voltage coming out of your sockets seems
fine. Worry about something more important - like if you will actually
be able to afford to use electricity in twenty years time....

--
Sue

Dave Martindale

2008-01-30, 9:25 pm

ChrisCoaster <ckozicki@snet.net> writes:

>The phenomenon mentioned in the Subject header is simple: Pre-
>conversion, I was getting 121-122VAC readings on the radioshack
>multimeter. Currently, after converting all non-switched receptacles
>to side-screw or back-wire, I'm now getting readings between
>124-125VAC!!

Is this with the outlet loaded by a substantial load? Or with the meter
and nothing else plugged into the outlet?

Any resistance caused by a backstab receptacle is going to be far less
than the internal resistance of the meter. So unloaded outlet
measurements are basically just measuring voltage at your service panel.
These may be higher than they were before simply because you have
reduced your lighting load over that time, so there's less voltage drop
across your feeder wires. It's also possible that your neighbours have
reduced their power consumption, so there's less voltage drop in the
transfomer that feeds all of you, or in the wires that feed the
transformer. Or maybe your neighbourhood is drawing *more* current and
someone changed a transformer tap at your substation. There's no way
for you to determine which of these affected your voltage. (Well, you
could swapp all your CFLs for incandescents again and see if the voltage
drops).

On the other hand, if you are measuring outlet voltage under load, the
better connection between wire and receptacle might account for a couple
of volts difference in loaded voltage. Probably not.

>Is that safe? The meter always did read a little hot(a fresh out of
>the sleeve AA battery would read 1.58 > 1.61 on the multimeter).
>Should I purchase a second multimeter and see if it returns lower/
>different readings? Still, the voltage readings at the outlets are
>2-3VAC higher than before all this converting went on, so I know my
>TVs/Stereos/Appliances are getting the most voltage they can in this
>apartment.

125 V is perfectly safe. Everything in your household should tolerate
a 10% error above or below 120 V, at least.

And fresh alkaline batteries *are* more than 1.5 V, so this doesn't
indicate that your meter is inaccurate. Even if it is, the error is
likely different between AC and DC mode, and different between 2 V and
200 V scales.

Dave

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