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a couple of electical questions

K

kd2777

Golden Member
I live in an older house and when the old fuse box was replaced 12-15 years ago for a breaker box it was only replaced with a 100 amp box. Now when our microwave comes on every light in the house dims.My computer and washing machine are on the same circuit, which causes the same problem when the washer comes on. Well I want to get an electrician to come and change our box out for a 200 amp box and run two new lines one to my computer and one to the microwave. Here are my questions:

-does anyone know how much something like this would cost
-how big of a circuit should I get for the microwave (1200 watt)
-how big of a circuit should I get for my computer

For the outlet that I would have run to the computer, I would like to have a four outlet plug put in. That way I can plug in any peripherals I would need down the road. I currently have 2 19" CRTs attached to my computer, but am going to get a third 21" CRT (I have been holding off until I get the power issue worked out). The other specs on my computer would probably make it in the higher end of computers, so I assume it needs a lot of juice. I also run a second computer in my office sometimes when my brother-in-law brings his over and we play online games together.

If anyone has any suggestions, or can think of anything I left out that would be important to know let me know.

Thanks

kd
 
I am rusty with this stuff but I believe W=VxA

You do not need 200 amps for a microwave and computer. Not even close; unless you live in a factory and have some heavy machines running on that breaker.

Talk to your local Electrician about it.
 
I am sure the microwave and the computer don't need 200 amps, but what I was saying is to take out my current 100 amp box and replace it with a 200 amp box, that way I can run my curent 100 amp stuff plus my two new circuits (ie 20 amp and 30 amp) an still have a few open spaces for when I add an outdoor building or what ever down the road.

I don't think you have to have anything extravagant to have a 200 amp service box, my parents and my brother both have one, but they both have newer houses and they came with it. I guess 200 amps is the standard now days.

kd
 
Sounds like the screws might need tightening. If they get loose, which they do, stuff like that starts happening. And 10-15 years sounds like the right time frame.
 
I had a place in Chicago that I had 200amp service dropped into. It cost about $2000. The electrical contractor had to pull permits and all kinds of crazy stuff.

Sounds like you could probably get away with just putting in a bigger breaker box, and setting up the circuit runs more intelligently (don't put CPU and washing machine on the same circuit, etc.).


 
From what I understand (very little), the 120V lines are typically 15A or 20A. You use 20A breakers for things like microwave, garbage disposal, refrigerator, washer, bathrooms, etc. You use 15A breakers for everything else.

Your house sounds to me like too many things are pulling off the same electrical lines. Your computer and washing machine should NOT be on the same circuit. The washing machine should have its own circuit.

IMO, a normal 15A breaker would not have a problem running 5 computers at the same time. Computers don't pull a ton of power - even high-end ones.

If you shut off power to your house, and then test it to make sure your wiring is done correctly, you shouldn't have a problem modifying your own fuse box. If your washing machine and computer are hooked on the same circuit that is spliced into the breaker using separate lines, you could just add a breaker to the box and seperate them.

 
you might try doing a load shed by running new lines(circuits) to the high current appliances and removing them from the existing light circuits. The upgraded service only helps if new heavy load lines are run to accommodate the high current appliances. What ever you do follow all local codes and/or hire an electrical contractor to do a proper load shed/ballance.
 
P = I * V

So, power of the microwave is 1200 watts. Voltage is 120V. So it draws 10 amps while operating.

However, it will draw more (maybe signifigantly) when it is first powered on, kind of a surge going into it, which is where your dimming comes from. Having a larger breaker box will not fix this . . . if the 100amp limit on your box was your problem, you would have the main breaker tripping, which is not happening.

If its really a big deal, get a seperate box for the microwave and washer/dryer.
 
Also to consider -- if you're house was designed around a 100A service, the power feed into the house is likely rated for only slightly more than 100A. So if you want to upgrade to 200A, you'll most likely need to replace the power feed into the house, which, depending on the construction of the feed, could be significant $$.
 
It's highly unlikely you need a service change, unless you are in an all electric situation. My house only has a 60A service, but that's more than adequate as all appliances are gas. There is a forum here that can help you plan. I've gotten good answers from those folks.
 
i dont let someone talk you into getting a new panel... are there any free breaker spots on your current one? if so, all you will need to do or have done is run a new line for some of the stuff on the one thats getting overloaded. You likely have too much stuff on one circuit. Flip the breaker and see if it all turns off. If so, and there is space in your panel, you need a new breaker for the new line, some wire and some boxes. It could be a DIY thing if you know abit about electricity. Otherwise, get a electrician or a handiman to do it. If you use a handiman, you might want to get a permit so it can be inspected to make sure he did a good/safe job. Permits are a second opinion on the work. Its up to you
 
Yep ... what others said. 200A service upgrade will likely run $1500-$2000
But first I would try to run the new circuits you need off of the existing 100A service. You want a 20A line for the microwave, but 15A should be fine for anything any sane person is likely to do with a PC. But then again, if your pulling wire anyway, it's not that big a deal to pull 12gauge instead of 14.

If you still have issues, look at rearranging your panel a bit. If all the high draw stuff is running off of the same leg, try moving some of it over to the other side. I had that problem in my shop ... big tools would cause the flourecent lights to unstart & flicker badly. Moved those outlets to the other leg, and all is good.
 
Are you tripping breakers? or are the lights dimming a little bit?
Typically there are 2 legs of 120V w/ a Neutral and/or Ground in the breaker box. You may want to move some stuff around, to balance out the 2 legs. Simply adding another breaker isn't gonna do it. Most of the time a matter of finding other outlets to balance the load. There are too many variables, there could be old/inadequate wiring, long wire runs to the box, loose/corroded screws/lugs, or simly not enough power coming in off the pole. Depending on local code, if you upgrade the Mains Panel, you may have to replace the Meter, and Wiring coming into the house. Where are you at? Here in New England there is a LOT of really old wiring in these houses (including mine).
We have a 100Amp Service, and it is adequate. Electric Stove and AC in the summertime makes me a little nervous. The lights will quickly dim when the TV or AC first comes on.
Do you rent or own?? In our town, if you rent, and anyone other than the Landlord hires or does the work, the Tenant(s) are liable.

edit - others said what I said while I was replying!
 
I'm not an electrician, but an electrical engineer (3rd year). I can't tell you about running lines, but I can say that power isn't always volts times amps. It is in DC analysis, but when dealing AC devices, i.e anything you plug into a wall, especially those that have large motors, such as washing machines, or other inductive loads (I can't think of any device that has would swing the power factor towards capacitance) the amount of 'real' power you draw isn't what is being delivered.

http://en.wikipedia.org/wiki/Power_factor

Nonetheless, most microwaves are <1500W. They should fit just fine on normal 15A circuits. I would run 20A to the fridge, but I'd venture a guess that your washing machine is probably on 220V, not 110.
 
OK here is what I have. I have a 2.5 ton central air, forced air furnace (but it is gas), electric range/oven, electric dryer, washing machine, electric water heater, microwave, couple TVs, 75 gal and 50 gallon fish tanks, and the other usual stuff. I also have a pool so in the summer the pump for it runs.

I have never thrown the main breaker, but I have thrown numerous smaller breakers. When I talk about the lights dimming when the microwave comes on I don?t mean just flicker, I mean major dimming. Also if there is a fan running you will hear it literally slow down (~20-30%) When the washer kicks on, my monitors will flicker like they are degaussing. I have a very small physical box compared to others I have seen, and with what all I have hooked up I do not have anymore open spots.

I do own my house, but I have not checked into local ordinances yet. I mainly wanted to get some ideas before I talked to an electrician so I was up to speed and didn?t pay for a lot of stuff I didn?t need. I hope it is just a matter of reworking my existing circuits, but I am afraid it isn?t, because I don?t have any strong circuits in the whole house. There are only two plugs in the house that my wife can plug her hair dyer into with out flipping a breaker and they are on the same circuit. So I have just always figured I was under powered for the crap I have going at the same time. However if it does cost in the neighborhood of 2000 dollars to upgrade, I will more than likely just leave it the way it is and look into moving sooner rather than later. We have a 3 bedroom now and are in the talks of having a second child, so I would either have to give up my home ?office/computer room?, have the two children share a room, or what would more than likely happen is we would buy a bigger house sometime in the next couple of years. I just can?t see sinking 2 grand into a house and not being able to get it back if I sold it or rented it out.

Thanks for the help.

kd
 
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