Resistance breaker to breaker


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Old 02-20-24, 04:15 PM
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Resistance breaker to breaker

Hi - I am trying to find the reason for a major jump in our electric bill and looking at wiring at the circuit breaker box as a possible culprit. I bought a electric power monitor and installed it and it said I have some issues to resolve. With the main panel open to install 18 small clamp meters, I turned off the main and all of the individual breakers. I then started measuring the resistance from breaker to breaker. Most of the readings were infinite. However, I have 5 single pole breakers which do not have infinite resistance between themselves. Is that normal?

For example, I put one multimeter lead on breaker 17 and one on 19 and the resistance is about 200 ohms. 19 to 21 - near 0 ohms. These are all 15 amp circuit breakers. Also 18 and 20 have the same problem. 17 to18 has 100 ohms, 17 to 19 = 200 ohms, 19 to 21 - close to 0 ohms. 17-20 about 100 ohms.

Not sure if this matters, but the odds number breakers are all on one side of the breaker box and the evens on the other. When the main breaker is on, the voltage from the odd to the even is 240 volts. Both branches are 120 volts to ground.

A similar question. We have a heat pump double pole breaker. When that breaker is off and the main is off, I get close to zero ohms. We also have a electric cook top with a double breaker, when that breaker is off, the resistance is about 200 ohms.

Are these correct readings?

The house was built in 1978. The box is Square D. None of the breakers are hot. We have found some faulty grounds (using the 3 light plug-in circuit tester) before and circuits and power to an outlet running through 2 breakers. The electrician fixed some. I am wondering if we have more. I am ready to call the electrician, but want to check here.
 
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Old 02-21-24, 04:30 AM
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If you have not disconnected the load wire from at least one of the 2 breakers, you could be reading load side resistance of the circuits, especially with 2 breakers powering one load that you mention. Does your electric meter run with the main breaker off or main breaker on and all circuit breakers off? Why are you looking at breaker to breaker resistance instead of using the power monitor measurements to troubleshoot?
 
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Old 02-21-24, 09:04 AM
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As you can probably tell, electricity is not a strong suit for me. But I thought any single pole breaker to any single pole breaker at the breaker box should have infinite resistance - aren't they supposed to be separate circuits? What is troubling to me was going across to the other hot leg - 240 volts. I certainly can take the load wire out of the circuit breakers and see if this makes a difference. My thinking is that this should not make a difference (The breaker should have infinite resistance to the bus bar). I certainly could be wrong.

I thought I would read the load side resistance if I went from the breaker wire to ground - for things without a switch. Is that incorrect?

The app for the clamp meters says that I have some of the clamps on the same circuit. It just warns me about that. I don't have any clamps on the same breaker - but I do have what I noted originally. This jogged my memory from when we last had an electrician in here. We had been doing some work and were throwing the breakers on one by one and noted that some lamps came on with either of two different circuit breakers. The electrician separated those circuits but we might have more. I will see it I can do the same thing again - trying multiple breakers to turn on the same lamp. The panel is reasonably labeled - I can try to do this much more completely.

The power monitors should still be able to help. The good news is the electrician is only a phone call away.

If it matters, we have solar panels - but they only feed the grid (net metering). If the power goes off, I cannot run the house on the solar panels. They are not even in the same circuit breaker box. With the main 200 amp fuse thrown (off), I have 0 volts everywhere in my circuit breaker box.
 
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Old 02-21-24, 03:24 PM
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Breakers typically alternate t op to bottom in an ABABA fashion. Breakers across from each other are on the same leg of the panel. Thus 1 and 2, 3 and 4 etc.
 
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Old 02-21-24, 03:45 PM
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Don't forget.... 120v circuits share a common neutral.
So if you measure from one breaker to another.... the circuit is tied common thru the neutral.

You aren't concerned with resistances unless you have a breaker tripping issue.
You've installed current donuts on all the circuits and now you can monitor their current.

240v devices connect to the panel with two pole breakers.
Both legs will be the same current.
You my be able to use one CT on one leg of a 240v circuit.
If it's a 120v based testing device.... you'd need to double the reading measured on one leg.
 
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Old 02-21-24, 04:17 PM
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What are you trying to accomplish by checking resistances? Tell us more about the house for example, start with your location. Do you have a basement or a slab. What type of heat and water heating do you have? Have you upgraded to LED lighting yet?
 
 

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