"For replacement use" breakers
What does this mean exactly? If the old panels are not supposed to accept these then why do they make them?
I made a post a while back about my Murray LC112DS and found that the previous owner has put in a bunch of these tandems. I had a licensed electrician come in who also put one in. I need to add some circuits. I was thinking about removing all of the tandems and putting regular 1" back, and then putting a 60 amp sub-panel so I can run all 1" breakers.
mmmm....couple of questions come to mind before adding any NEW
circuits....( IE NEW loads )
* when you took your amp meter ....after turning on just about
everything in the house...for realistic loads . . .what were the total
current loads ?
* what amperage of service is currently tied to your home?
* when you reconcile the above two...make sure your load isnt
in the close neighborhood of 80% of your available service
* what are the realistically calculated new loads you want to add ?
If you arent popping breaKERS ALREADY...making sure the above is
SKILLFULLY CARRIED OUT WILL GO A LONG WAY TO PREVENTING
that very thing happening
Sorry I never replied to this.
We are no where near 100 amps running everything at once.
We have all gas appliances (heater, stove, dryer, water heater). The issue is remodeling and needing to add more circuits (same loads, just now on their own circuits).
When you are breaking up a circuit with lots of lights/receptacles into two or three circuits with fewer, you will not be tripping individual breakers more often. When you add more circuits and breakers, you won't be tripping those breakers but rather you could be tripping the main breaker if you use that much power.
Your system is technically not meeting code if you do a "load analysis" according to the rules of the National Electric Code (book) and the household wattage computed there exceeds your main panel capacity. There is a number for general lighting and plug-in small appliances, I think 3 watts per square foot. There are numbers for refrigerators, electric dryers, washing machines, air conditioners, etc.
This is not an issue about 100 amp service not being enough. It is plenty.
I am trying to figure out if it is legal to put tandems in the Murray, if not then I need a sub panel or new panel.
Let me just give an example. We come into the house with a box with possibly illegal tandems, and want to make changes to the bathroom. Any changes to bathroom require bathroom to be put on its own circuit. NOW we need to address all old, (possibly) code breaking tandems before we even think about finding a place to legally put the bathroom on its own circuit.
Can you double up on some circuits, freeing up some space for a full sized breaker? I don't know if the panel accepts tandems or not, but if not, then I would not use them. If you have two rooms on different circuits, maybe you could combine the receptacles on one breaker, and maybe some lights here or there. Or, if you don't want to do that, and you can't or don't want to change the panel, then maybe you could put a bus tap in and feed a 40 circuit MLO panel next to the old one. Then you'd have all the space you need.
The reason certain tandem breakers are 'for replacement use only' is because a normal tandem breaker has a rejection feature that allows it to be installed only in a panel that will accept tandems. This is usually accomplished by a notch in the bus extensions.
If you use all 'replacement' tandems, you could actually get 40 tandems in a 40 circuit panel, resulting is 80 circuits total, thus violating NEC 408.35. This section states that there can't be more than 42 circuits in a panel.
This section is deleted in the 2008 edition of the code.
My panel will not take the breakers with the rejection feature. However in old advertisements I find (as well as the "Direct replacement" for my 1983 panel), it says it will take up to 24 circuits (12 regular 1"). It is a Murray panel and Murray breakers. So this leaves me confused as to whether or not it is OK to use them... I had a licensed electrician come in before I started doing these things myself and he put one in but this does not say too much to me.
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