J
JS
- Jan 1, 1970
- 0
I just installed a new circuit in my house. Being a bit paranoid, I stress
tested it; and didn't like the results.
The circuit is 50' long, in #12. The transformer for the house is about
300' away, with #1 aluminum wire. (well, it is #1 from the meter to the box,
I don't know what it is from the transformer to the meter; hopefully it is
bigger.)
Voltage on the new circuit is 120.6v when nothing is running.
When I plug in a shopvac, it draws 6.0a, and the voltage drops to 118.4v
When I plug in a toaster, it draws 12.0a, and the voltage drops to 115.6v
When I plug both in, they draw 17.5a, and the voltage drops to 113.4v.
So, I have a 7.2v drop on 17.5a. I tried another circuit (one I didn't
wire), and got similar results.
According to tables, I have a 3.3v drop on the circuit, and a 2.2v drop (or
less) on the service entrance.
What could the other 1.7v be?
People on alt.home.repair didn't know, and suggested here.
One guy said that a shopvac is an inductive load, and doesn't simply add to
the toaster; but I vaguely remember from the EE courses I took 30 years ago
that impedance tends to sum to less than the straight total; not more. Is
that right?
Other people suggested that I must have a bad connection, but it would have
to be a similar bad connection on two circuits; and I can't see a bad
connection giving a consistant 1.7v drop.
Any ideas? thanks
tested it; and didn't like the results.
The circuit is 50' long, in #12. The transformer for the house is about
300' away, with #1 aluminum wire. (well, it is #1 from the meter to the box,
I don't know what it is from the transformer to the meter; hopefully it is
bigger.)
Voltage on the new circuit is 120.6v when nothing is running.
When I plug in a shopvac, it draws 6.0a, and the voltage drops to 118.4v
When I plug in a toaster, it draws 12.0a, and the voltage drops to 115.6v
When I plug both in, they draw 17.5a, and the voltage drops to 113.4v.
So, I have a 7.2v drop on 17.5a. I tried another circuit (one I didn't
wire), and got similar results.
According to tables, I have a 3.3v drop on the circuit, and a 2.2v drop (or
less) on the service entrance.
What could the other 1.7v be?
People on alt.home.repair didn't know, and suggested here.
One guy said that a shopvac is an inductive load, and doesn't simply add to
the toaster; but I vaguely remember from the EE courses I took 30 years ago
that impedance tends to sum to less than the straight total; not more. Is
that right?
Other people suggested that I must have a bad connection, but it would have
to be a similar bad connection on two circuits; and I can't see a bad
connection giving a consistant 1.7v drop.
Any ideas? thanks