The wiring at my friend’s apartment is shabby, and using the microwave in the kitchen tends to trip the breaker every other time. It’s pretty much guaranteed to happeen if the microwave is on and somebody turns on some other high-draw device (such as the Insinkerator), but even the microwave by itself (at less than full power to boot) will do it on occasion.
To make things worse, the circuit is shared not only between all the kitchen appliances but by the entire apartment AND the apartment next door.
My question is: Would an Uninterruptible Power Supply (UPS), such as the kind they make for computers, do anything for this situation? I’m wondering if it might smooth out the microwave’s power draw by resorting to its battery at critical times, but I don’t know enough about electricity to find out for myself.
Your logic about the UPS drawing on its battery for peak loads seems right, but the UPS is itself a big peak load when it is trying to charge its battery. If it starts with a charged battery, then even though it is less than 100% efficient it might do enough load leveling to help.
But, a microwave probably draws 5 or so amps. If the circuit is that badly misdesigned and misused, trying to put this bandaid on it feels a little weird. Of course, if this is one of the only options…
UPS most frequently only use the battery during a loss of electrical mains. there are some power conditioning units but more expensive than the common UPS.
in the USA the current electrical code says the microwave should have its own 20A circuit. recent ones on high power will eat a whole 15A circuit.
you need to exercise power discipline. don’t use a 2nd large appliance at the same time. don’t use microwave on high, it will do everything just slower.
That first statement is really your whole problem.
Current code requires a separate circuit for kitchen counter appliances, as johnpost said. And it can’t even be shared with other appliances or rooms in the same residence – much less another apartment next door!
You don’t say where you are, but I’d wonder if the wiring you describe meets code anywhere in the USA – even grandfather-in wiring would need to meet some minimum standards. Check with your city building inspection department. And consider moving. This is a fire waiting to happen, and only the circuit breaker doing its job is preventing a fire!
P.S.
That’s not relevant. Most microwaves actually work at full power all the time. If you set the control at 50% power, it actually just runs at full power for half the time, and off for half the time. Like on for half a second, then off for half a second. So the power used when the magnetron is turned on is still the full wattage rating. So setting the controls at lower power won’t help in this situation. All you can do is not turn on other appliances on the same circuit when it’s running. (And you can’t do anything about appliances your next-door neighbor has on.)
The friend lives in San Francisco, CA. He’s renting. Is this something that the landlord should be responsible for? Can I look up the building code somewhere, show it to the landlord and realistically expect her to fix it?
This, of course, would be the ideal solution. But I heard that rewiring may be prohibitively expensive and the building MAY be grandfathered in.
How could I go about finding out for sure?
How do I know how many amps it draws? I know the breaker’s on a 15-amp circuit.
My microwave oven is built-in and has a sticker just inside the door listing the electrical specs, including the amperage. On a free-standing one, the specs might be on the back.
Your friend should be aware that if the wiring is that shabby, and he makes a stink about it, the housing authorities might decide that it’s too unsafe to live in and he’d be forced to move quickly. On the other hand, I would not want to live somewhere with wiring that bad. I’d be too worried about the possibility of an electrical fire. The best thing is to find somewhere else to live, although I realize that San Francisco is an expensive place to do that.
Check the power level / wattage/ amperage of your current microwave.
A new, smaller less powerful one would probably cost less than either a UPS or fixing the wiring, and might be just enough of a reduction to solve the problem.
Even IF that works, in the interest of safety you should make a it a point to never run two high powered things if the wiring is that wonky.
As for the wiring…yeah get a good smoke detector at least
Yeah, I told my friend all of this but his answer inevitably came down to “I can’t afford it”, whether that’s a new microwave, a new apartment, or even a smoke detector. So I found him (what looks to be) an enterprise-grade UPS from a university recycling dump. It might save the day or it might jumpstart Armageddon; I’m not too eager to find out. I’m going to find him a detector and extinguisher in the meantime, but I really hope there’s something to be done about the wiring…
I’m going to research more on my own when I get back, but if any of ya are already familiar with the code, any guidance would be appreciated
Replace ALL regular bulbs in place with flourescents, that will save on the electric bill, the AC, and also might be just enough to bring the peak load down to a tolerable level.
A flourescent draws about a sixth the power for the same amount of light that regular bulb does. All those regular bulbs in there might add up to a significant load.
Heck, if you have the UPS, give that baby a try.
It might only work this way though. When you want to use the microwave, you disconnect the UPS from the “grid”. Use a surge protector/power strip with an on off switch so that you can easily connect/disconnect the UPS from the household grid.
A UPS isn’t going to help. It isn’t going to provide any extra amps to make up for the current draw of multiple appliances. When the breaker trips(which it still will) the appliances plugged into the USP will pull whatever the maximum amps that can out of the USP. A typical USP can’t provide what is needed and such activity will shorten the USP’s life.
If you have a computer or something that you are worried about losing power you can keep it running off the USP when the breaker trips.
I’m not a UPS expert, but my understanding is that they will “condition” the power only to the extent of controlling power ripples, transients, surges etc. As far as amperage draw tripping the breaker I don’t really see how they are going to help with this. The full amperage load is being passed through the UPS and will still trip the breaker as before, in fact it may trip it more easily now that you have the constant power load of the UPS charging circuit online in addition to everything else.
The UPS will kick on when the breaker is tripped and keep the microwave going, but it still requires a trip to reset the breaker, and everything not on the UPS will be power cycled. If I’m misunderstanding how a standard UPS operates please let me know.
Not quite. It WILL provide extra power if the UPS ISNT connected to the household current at the time its supplying power to the microwave. All that power is coming from its internal batteries.
The OP needs to see what power the UPS draws while charging its batteries and compare that to the microwave.
UPS’s really aren’t designed to be drawn down 2-4+ times a day as you would have to do make your scheme work. They are designed to be “on” a handful of times a year for the odd power outage. I think pushing them like you describe would kill the batteries fairly quickly.
True enough, but the OP has a BIG UPS, not a small one, which will/could make a major difference. And more importantly its something he HAS or can get DARN cheap.
Of course if its an old UPS, there is a good chance the batteries are already crapped out due to old age alone.
Ok, I got back and examined the UPS more closely. Heh, my mistake… it’s hardly an “enterprise-level” UPS; more like a crappy generic home version. It’s a paltry 500-watt thing that would take seven hours to charge for maybe two minutes of use with the microwave if I’m lucky. Even more so because I found it in a recycling stash and the batteries is probably years, if not decades, old.
It still turns on and blinks, at least, and I figured it might help if it could just cover moments of peak voltage draw, but if like astro said it doesn’t kick in unless power is cut completely, tha’s not going to happen.
So, plan C: Flywheel. Plus giant army of hamsters. I’ll report back
P.S. If I know the microwave is a 1200 watt device and runs off a 120V circuit, does that mean it’s drawing 10 amps (1200 watts = 120V * 10 A)?
ETA: Dammit. The hamsters ate all the food. Useless monsters.
His friend doesn’t even have the spare cash to buy a smoke detector. So buying a bunch of CFL bulbs is probably also outside his budget.
He’s not paying the electric bill, the landlord is. Since the circuits are shared between apartments, there can’t be separate meters, so the electricity is included as part of his rent. And a landlord who has apartments this bad isn’t going to reduce the rent just because they conserve electricity.
SF electrical code. (But this is just the SF modifications to the California & National Electrical code. What you want might not be in there.)
You might be able to get a quicker response by just calling the Housing Building Inspector: 415-558-6220. You could call them anonymously if you wanted.
Also, San Francisco has a fairly active Tenants Union: www.sftu.org/. They might be able to help. They offer drop-in counseling every day.
If everything else is outa his budget, getting his rent raised by the slumlord after paying out the wazzoo for electrical repairs is outa his budget too.
Or, mabye he will get really lucky and the place will get condemned, cause as we all know, moving is FREE !
