View Full Version : Should one pole on main breaker be warm?

December 12th, 2004, 01:05 AM
Let me start by saying I am a laymen when it comes to electrical work. So I am not sure if the breaker should be warm or not. It is not hot. I am asking if this condition is okay because last winter the main breaker and most of the other breakers in this panel were replaced. The previous main breaker had burned up. That is, the plastic around the connection to the subpanel's bus had actually burned away and began to arc (3 inch arcs actually). The subpanel was not replaced (landlord refused to replace it). Not knowing much about electricity I was concerned when I performed the yearly breaker test (on and off) and found that the bottom pole of the main breaker was warm to the touch.

This is a subpanel in the basement which is a Power-Kraft panel (I believe that was Montgomery Ward's brand).

Most of the breakers are GE.

The main breaker is a dual pole GE rated at 100 amps.

The hot water heater, water pump, and three electric baseboard heaters (approx. 5000 watts each) are the largest electrical devices on the panel. The water heater is a 4500 watt dual element (4500 watts each) and is wired into a dual pole 20 amp breaker in the subpanel. The water pump is a 240v, 70 amp, water pump with its own breaker box, but is wired to the subpanel where there is another breaker (dual pole 30 amp)for the water pump in the box.

Two of the heaters are on one bank and wired to a dual pole 20 amp breaker. The last heater is wired into its own dual pole 20 amp breaker.

The main breaker pole becomes warmest when both washing machine upstairs is run (I assume because both the water pump and water heater are energised, but I am not sure).

I would appreciate any input anyone might have on this.

Mabe I am just being paranoid.

December 12th, 2004, 08:01 AM
My opinion is that warm is okay, but hot is not. Depending on how the loads are arranged in the panel, there could be a little more load on the warm pole than the other pole. Does the lug or the wire on the warm pole seem discolored at all? If not, I don't think that there's any real cause for alarm. If I was coming over to your house to service this, I would double check that the lug is tight on the wire and take an amp draw reading of both poles of the main breaker to confirm that the warmer one has more current flowing to make it warmer.

December 12th, 2004, 10:48 AM
Warm is not good. Warm means you have a resistance creating heat. A switch is not supposed to have any resistance and create any heat.

A dimmer is a different type of switch and it does create heat.

December 12th, 2004, 10:58 AM
Warm is not good. Warm means you have a resistance creating heat. A switch is not supposed to have any resistance and create any heat.

A dimmer is a different type of switch and it does create heat.Joed, I think that you need to look at how a breaker functions. There is an actual 'heater' in the breaker to trip under overload conditions. There is also a magnetic trip to trip very fast during short circuit conditions.

The term is Thermal-Magnetic. This gives the inverse time characteristic for overloads and an almost instantaneous trip for short circuits.


December 12th, 2004, 11:11 AM
Warm is not good. Warm means you have a resistance creating heat. A switch is not supposed to have any resistance and create any heat.

A dimmer is a different type of switch and it does create heat.

I'm afraid I disagree on this matter. In accordance with UL489 testing procedures, a breaker's temperature may rise up to (but not over) the temperature rating of the lug (normally 75C or 167F) when the breaker is drawing it's full load rating. So, a warm breaker at 1/2 or 3/4 load is permissable. After all, the typical QO plug on breaker does have a bi-metal that depends on this thermal heating to operate the trip element. Walk into a large room full of panels in a factory or hotel and the room will be almost sweltering from all the heat given off from the breakers and associated wiring.

My wife has been drying laundry all morning with our electric clothes dryer that draws 27 amps. The QOB230 breaker is now quite warm.

December 12th, 2004, 04:10 PM
Hot is a hey you better take a close look at this breaker. Warm to touch is a hey I am pushing my limits on this breaker or I have a loose connection. Check for the loose connection first or a damaged breaker such as water damage.

Now warm or hot either one would make me look to see that I have all breakers in that panel listed for use with that certain panel. Reason is a noncompatible breaker may not make contact with the buss bar properly causing heat to travel to a nearby breaker or even all breakers and eventually ruin your panel and be a fire risk. Make sure you have the breakers in that panel that is listed for that panel. Don't allow a mixture of brands in a panel unless that odd brand breaker is listed as approved for use in that panel. Buss bars of different style and brands of panels come with different thickness of buss bar tabs that the breakers slide onto to make the connection.

Now if all is fine but the main breaker is warm then take look at each circuit breaker. Example you mentioned two washers running at same time. Move one heavier loaded breaker from the warm pole of that main to be carried from the other lighter load of that panel. Kind of like a minor adjustment of load balance. Most often the intermittent load of a home makes load balancing almost impossible because amount of load to each braeker changes almost by the minute when everyone is home. However if you have one hot such as line one pulling heavier consistantly than line 2 of the same panel then move a branch circuit that is more heavily loaded found on that warm line to the other hot line and the main breaker should cool back down.

Hope this helps


December 14th, 2004, 09:06 PM
Thank you all for the input.
I removed the subpanel cover and inspected the main breaker. The plastic is not burned.

This house is not mine, so I cannot dismantle the subbox to inspect the breaker-to-bus contacts. What is visible of them looks okay, although the bottom pole of the main breaker is hard to see clearly.

With the subbox cover off, I noted that there is a buzz/hum comming from the breakers (not sure which of the top three it is, they are all dual pole).

There is no burning smell or the like (which happened for months the last time there was a problem with this subbox).

My concern is that my landlord refused to have this subpanel box replaced. I am looking for some advice on this before I speak to him. Also, the electrician who "fixed" the box last time replaced the burned up breakers with old spares he had (there are no new breakers in this box). So the condition of these breakers is questionable. The breakers are also of different brands, and I am not knowledgable enough to know which brands go with this subpanel and/or if any they installed are the wrong types.

As you can probably imagine, I would like to take the easy way out of this and move to another rental. But, like most people, I'm short on cash and this place is all I can afford right now.

I am considering hiring an electrician at my own expense, however I understand that if the subpanel needs to be replaced and rewired it could cost a bunch. Though it may be worth it to prevent a fire.

What do you gentlemen think?

December 16th, 2004, 08:57 PM
The electrician came out today. He found that the bus was indeed "arc welded". The bottom pole had a pit in it about 3/32nds of an inch deep (almost through the 1/8 inch thick bus bar). This gentlemen is a veteran electrician of 30+ years and was of the opinion that any heat generated on the main breaker is usually due to a bad connection and/or arcing.
Secondary breakers may just be due to the load on it (as most of you here probably already know :) ).
For those interested, the bottom pole had a loss of 395 watts and the top pole had a loss of 225 watts. Both of which, I learned, are unsafe.
The whole panel and all breakers are going to be replaced with all new components next week. A temp set up is currently in place (he moved the main to a pair of undamaged bus bars and placed the heater on the damaged bar. This is a bandaid that should last until the new parts arrive next week and the job can be completed.

I hope my little electrical adventure is of some help to others on this board who may find themselves in the same situation.
My thanks to all you gentlemen for your suggestions and advice.