# House Electrical Circuit: Leakage?

Discussion in 'Home Power and Microgeneration' started by (PeteCresswell), Jan 7, 2013.

1. ### (PeteCresswell)Guest

Recently installed a generator cutover switch
(http://tinyurl.com/a6e9fgn) which tells me how much each circuit
is drawing.

I have one circuit which, when I *think* everything is unplugged,
still draws 18 watts.

First thing that comes to mind is that the circuit is serving
something that I do not know about; but I am hard-pressed to find
it.

That seems to leave "Leakage".

Is there any such thing as an electrical leak in home wiring?

If so, typical causes? Location strategies?

2. ### Neon JohnGuest

There can be leakage but not the type you're thinking of. Romex has
capacitance between the hot and ground wire and to a lesser extent, to
the neutral. It is insulated with a high dielectric loss (PVC)
insulation. Thus, some small amount of real power dissipation will be
consumed per foot heating the cable even when there is no load. If
the runs are long that could amount to a few watts.

Do you have a doorbell transformer? It probably dissipated 4 or 5
watts just sitting there.

Is your furnace/heat pump on the circuit? If so, there's a control
transformer that also will consume a few watts unloaded.

Finally, the is the question of near-zero-indication accuracy of the
meter. I see from the specs that the input spec is 30 amps.
Presumably the current transducer is rated for at least 30 amps and
probably 50. 14 watts would be 14/120 volts = 0.116 amps. That is
0.116/50 = 0.233 percent of full scale on the transducer. That's not
figuring in the tolerance of the voltage transducer. The CT is likely
to be a 1 or maybe 0.5% part. So that 14 watt reading could be
literally nothing.

One way to check is to open all the breakers. What does the wattmeter
say? Now close in the breakers, one at a time and see what happens.
If the reading develops when you close a breaker then you know that
it's real. Remember that an indication that low is way outside the
tolerance of the metering element so it might be 1 watt or 20 watts or
??? If it really is 14 watts then that's enough power dissipation
that you should be able to find something warm to the touch on that
circuit.

John

John DeArmond
http://www.neon-john.com
http://www.fluxeon.com
Tellico Plains, Occupied TN

3. ### Jim WilkinsGuest

Doorbell or old Princess telephone transformer? It would likely be on
a junction box cover rather than plugged into an outlet.

4. ### Jim WilkinsGuest

That's a very good point, so I checked two connected 100' extension
cords with neon bulbs in their sockets on a P4460 KAWez. The readings
were 0.00A, 0.0W.
jsw

5. ### mikeGuest

Are we sure that the unit measures watts and not volt-amps?
Still 14 VA is a lot for a disconnected circuit.

Did you actually disconnect the wire? AKA "where does
the transfer switch get power?

Doorbell? Burglar Alarm? Garage door opener?
turn off the suspect breaker and see if they all still work.

You can break the circuit at any wall plate.
Half-interval search method should get you there in few tries.

6. ### danny bursteinGuest

[snip]

any motion detector lights? cable/sateliite tv box?

7. ### VaughnGuest

They stick doorbell transformers in the strangest places. I've been
living in this old house for 25 years and still haven't stumbled across
mine. Yet the doorbell works.

When that hidden transformer finally goes bad, I hope it's an open
primary and not shorted turns.

Vaughn

8. ### T. KeatingGuest

Each GFI(outlet or breaker) or Arc-fault breaker will consume a couple of watts per unit.
(tripped or active will make no difference.)

There is not very much you can do about it, since building code requires them for certain
locations.

Other leakage... Clocks on appliances, doorbell, transformer powering thermostat, power
line modules(x-10), etc..

9. ### Jim WilkinsGuest

Another good point. A single-outlet plug-in GFCI here draws 1.4W.
jsw

10. ### jGuest

Interesting. With a cost of electricity at just under \$.12 kWHr, it's ~
1\$/W or \$1.40 for that single GFCI. I have 5 of them, so \$7/yr.

How did you come up with the draw so quick?

(copy sent to OP by accident)

Jeff

11. ### Jim WilkinsGuest

I'll spare you a quick-draw joke.
http://www.p3international.com/products/p4460.html

12. ### (PeteCresswell)Guest

Per mike:
Bingo!

That circuit was one of the two circuits that power the transfer
switch.

Swapped it over to another circuit and the "leakage" went away.

Thanks!... I never would have thought of that.

13. ### Jim WilkinsGuest

No, the KAW doesn't measure the draw of the socket it's plugged into,
GFCI or standard. I plugged a stand-alone, plug-in GFCI into the KAW.

14. ### Pete C.Guest

Probably a doorbell transformer buried in the attic or similar.

15. ### gGuest

In my old house they fixed the transformer onto the service panel. You
cannot see it unless you take off the front cover...

//g