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Windows 01-06-2011 09:56 AM

dimming light on new circuit
 
We recently upgraded to a 200 amp breaker box and got a new overhead service wire from the street. We are slowly replacing all the knob & tube and redesigning the circuits room by room as we renovate our house. One of the bedrooms has been completely rewired and is on its own 15amp arc fault breaker. (The work was done with permits and inspections.) Here is my question: the coffee maker is definitely on a different circuit (knob and tube), yet when its heater element cycles on and off, the bedroom (romex) lights dim a little bit. Is that to be expected? It seems to me like there should be sufficient current to run both easily, but then again I am just learning about electricity. Thanks for any insights.

AllanJ 01-06-2011 11:20 AM

You will need electricians' experience.

Measure the voltage at various places inside your main panel as the coffee maker switches on and off.

Including both the big lugs where the service wires come in and the service wires themselves.

We cannot rule out minor deficiencies in the power company pole transformer that cause noticeable voltage changes with not so large changes in current draw.

But we do want to check for possible loose connections between sub components in the panel.

Ideally you want to measure voltage at terminals just before and after the meter except you may not open up that box.

dmxtothemax 01-06-2011 03:51 PM

How much does the load change the supplied voltage ?
A small change is ok !
But if it is significant, then a current limit is in action.
You can start by working backwards from the light.
Measure at all connections,
If you find a spot where the reduction is a lot less,
or non existant, then you have an indication were the problem lies.
But if you get to the supply lines and it is still there, then the
problem lies with the electrical supplier.

Quote:

Originally Posted by Windows (Post 563963)
We recently upgraded to a 200 amp breaker box and got a new overhead service wire from the street. We are slowly replacing all the knob & tube and redesigning the circuits room by room as we renovate our house. One of the bedrooms has been completely rewired and is on its own 15amp arc fault breaker. (The work was done with permits and inspections.) Here is my question: the coffee maker is definitely on a different circuit (knob and tube), yet when its heater element cycles on and off, the bedroom (romex) lights dim a little bit. Is that to be expected? It seems to me like there should be sufficient current to run both easily, but then again I am just learning about electricity. Thanks for any insights.


rditz 01-06-2011 03:57 PM

dimming light
 
when you are moving circuits, make sure you are balancing them across both poles.

if you have an electrician friend, he will have a clamping meter that you can put on either of the incoming feeds. read the current on each leg. turn on and off different circuits and see if it is balanced.

rod

Windows 01-07-2011 12:06 PM

Quote:

Originally Posted by rditz (Post 564215)
when you are moving circuits, make sure you are balancing them across both poles.

if you have an electrician friend, he will have a clamping meter that you can put on either of the incoming feeds. read the current on each leg. turn on and off different circuits and see if it is balanced.

rod

The circuits are no where near balanced. When we installed the new breaker box we had an electrician transfer the circuits from the fuse box and he didn't spend a lot of time evening them out because rewiring is in the near future. Consequently, we have a couple of breakers virtually running the whole house (minus major appliances) and others with only one receptacle. Can this imbalance be responsible for the light dimming?

oberkc 01-07-2011 12:50 PM

I have been amazed at the various forums threads on the value (or lack thereof) in the balancing of the demand on your electrical legs. Regardless, I have trouble believing that this would, by itself, cause a drop in voltage caused by demand surge.

rditz 01-07-2011 01:16 PM

i don't profess to be an electrician, but it does stand to reason that you want to balance the poles for an even draw across each.

what is the value of having a draw of 70a/30a for example.

there are two things that are obvious to me with the original post... 1) the coffee maker is on the same pole as the bedroom lights. 2) the coffee maker is drawing enough load when the heater element comes on to dim the lights enough to be noticed.

by balancing the loads across the two poles, you are can effectively arrange higher draw items evenly so that two or more high draw loads are not switching on and off accummulatively causing a larger single spike than if they were balanced.

just my thoughts on it...


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