power loss in half of house

[Greg1707]

I got a call where the house lost power in half of the circuits. Sounds familiar. First thing I checked to see if the electric dryer worked, no. Same thing with through the wall 240 volt AC units.
I checked panel and no power one side. The owner then turned the switch on a 240 volt wall heater and all the lights came back on.
I checked the panel and power on both sides. I turned off the wall heater and the lights went off again.
Turned wall heater on again and power on both sides.

Any ideas?

 

[GoldDigger]

Simple.
The POCO wire feeding one side of the 120/240 is open.
When you turn on a high power (low resistance) load it connects one bus to the other and feeds the 120V loads on that side in series with the heater.
As you add more load on that side the voltage will drop and the heater will begin to warm up.
If the incoming service wire is solidly connected at the panel call POCO.

 

[ptonsparky]

Classic symptom of a blown Main fuse on the old main/range panels.
I agree with GD. You could have a pole on the MB open but quick voltage checks should show that.

 

[templdl]

I got a call where the house lost power in half of the circuits. Sounds familiar. First thing I checked to see if the electric dryer worked, no. Same thing with through the wall 240 volt AC units.
I checked panel and no power one side. The owner then turned the switch on a 240 volt wall heater and all the lights came back on.
I checked the panel and power on both sides. I turned off the wall heater and the lights went off again.
Turned wall heater on again and power on both sides.

Any ideas?

Ah, so you checked the "power" at the main. Line or load side of the main or both? Is the main a breaker? Did you check the voltage from the line side to load side of the main? In doing so this would either zero in on the main of eliminate it as the issue.

 

[Dennis Alwon]

Greg you need to turn off the main or all the loads and check the power to ground or neutral. One phase is out and my experience has been that it is a power company issue over 95% of the time

 

[kwired]

One incoming line is lost - be it on utility side, malfunctioning pole in a main breaker, blown fuse, etc.

Let's say line B is the one lost, by turning on a 240 volt load - you send voltage from line A through the 240 volt load and back to the B bus. This puts the 240 volt load in series with all the 120 volt loads connected to B, depending on resistance of the 240 volt load and how much 120 volt load is being supplied from the B bus - you will see variation of the B voltage. Most 240 volt household loads will be low enough resistance to allow high enough voltage through that you may not easily notice something is not right.

However none of the 240 volt loads will ever see enough voltage to function properly and this will eventually be noticed.