NetNews Usenet Archive 1992 #31/NN_1992_31.iso/spool/misc/consumer/house/16211

Text File | 1993-01-01 | 3.0 KB | 67 lines

Newsgroups: misc.consumers.house
Path: sparky!uunet!psinntp!panix!jeffj
From: [e-mail] (Jeff Jonas)
Subject: Re: "balancing" a power panel
Message-ID: <[e-mail]>
Date: Thu, 31 Dec 1992 08:38:29 GMT
References: <[e-mail]>
Organization: Jeff's House of Electronic Parts
Lines: 56

In article <[e-mail]> [e-mail]
    (Fred Christiansen) writes:
>What does "balancing" a power panel mean?  Why is it necessary?  How
>is it typically accomplished?  Yes, I know I can ask my electrician,
>but the Net often has many gems of wisdom which I would not get from
>a non-talkative tradesman.  Thx.

I'll try to make this brief but informative.
The usual electrical power you draw from an outlet is a single sine
wave that's 120 volts on the average (using a root-mean-square average
thus the "volts AC - RMS" on voltmeters).

Since sine waves go to zero twice per cycle, there are 120 times
a second that there is no voltage on the line (the U.S. is 60 Hertz).
This is inefficient for the transmission of electrical power,
so power lines tend to use polyphase / multiple phase transmission.
The 3 lines are 120 degrees out of phase to each other so there's
always a line carrying power at any given moment in time.

2 phases are delivered to your house.  If they're 120 degrees
out of phase, you get 208 volts across the lines.
If they're 180 degrees out of phase, you get 240 volts across
the lines.  This matters only if you have some non-120 volt circuits
for large appliances (such as electrical clothes dryers).

It's polite to the electric company to draw equally from both
sides of the line.  There are actually 3 lines going to your house:
the two "hot" wires and a neutral line.
You get 120 volts from either hot to the neutral.
If you draw the same amount of power from both hot wires,
there should be no current flowing through the neutral wire.
This makes for happy transformers and a happy electrical company.
Unbalance the load and you're drawing power from only one side of the
house's feed.  In the least, this is wasting the capacity
of the other hot wire that's less loaded.
In the worst case, you're placing your power demand on one output of
the transformer feeding your house instead of spreading it to
two outputs.  It's this stressing of the utility's equipment
that the electric company dislikes.
Since you share the transformer with your neighbors,
their loads and yours should balance out.

So - yes, you need to anticipate how much power you're going to draw
from the circuits and split them half and half.
Most breaker panels help by alternating the phases to alternate
breakers.  220v circuits simply have a double width breaker.

I hope I made this clearer.
I'd make an analogy if I could think of some well understood
case of something with 2 equal sources.
(like, you have 2 wells for water.  Take all your water from only
one and you'll start coming up dry, so it's in your best interest
to draw from both wells equally).

-- Jeffrey Jonas
[e-mail]