I know dick about electrical systems. Please advise.
When Kim and I moved into our apartment last May we knew that living in an older building was going to have some idiosyncracies that we’d not experienced in the past. The primary one for us has been that, especially during the summer when we have the AC units cranking, we are replacing our fuses quite often.
Last night we came home to a dark apartment well beyond the reasonable hour of being able to run to the hardware store to buy fuses (we have the round plug style fuses and I wasn’t about to go out at 3AM only to discover that Harris Teeter didn’t carry them). So we slept in a sweltering apartment all night and I woke up at the buttcrack of dawn and drove to Lowe’s to get some fuses.
Up until this moment, I’ve been replacing “like with like” without really knowing if the previous tenants knew what the hell they were doing. The orange 20 amp fuses at the top go to the kitchen and run the fridge (and something else, I don’t know what) and the rest are 15 amp fuses. For some reason I didn’t think to read the plate on the left because A) it contained a diagram that makes no sense to me and B) it seemed too old to be relevant to my interests. So I continued to blissfully replace 15 amp fuses with 15 amp fuses (this time I bought the Heavy duty versions) and 20-amp fuses with 20 amp fuses. Well today Kim points out that that the diagram says “30 Amp. Main”. I don’t know if that means that the main circuit is 30 amps, if the diagram is poorly designed and “30 Amp” is a separate idea from “Main,” which is referring to the diagram itself (possibly meaning that all of these circuits are 30 amps and the sign is telling me what kind of fuses to use), or some other interpretation of the facts presented on this sign which was made in the age before litigation. There was one occasion where the maintenance guy replaced a 15 amp fuse with a 20 amp fuse and I wasn’t sure if that was just some kind of shady, cheapskate slumlord thing to do or if 20 amp fuses were a perfectly ok thing to use. I have since replaced that fuse for safety’s sake because I didn’t want to die in a fire.
I really hope Ozzy is the first one to respond to this post.
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I see your problem. The switch is off.
I think main signifies the main power source in the diagram. 30 amps may mean the most the whole system can handle at once. Though I am not sure what trips if you draw that much. In general things that go to outlets should be 15amp fuses. It would make sense that something heavy duty like a fridge would take 20. I would replace them with the same ones. It boils down to what your wiring can handle without melting and I am not in a position to comment on that.
Unfortunately for you, but fortunately for me, my old houses have been rewired and have breaker boxes, so I am almost as ignorant as you. I do know that replacing a fuse with higher amperage than it should be can cause a lot more problems than the inconvenience of have to replace an occasional fuse.
I will send this to my old man and and he’ll give you an answer today. He has been an electrician and actually taught electrician’s at the community college for 40 some years.
Hang tight.
Thanks dudes.
The problem lies in that there was no foresight into today’s modern appliances. Think about how many you own that were not even invented or were a luxury item back then. 30A max is really not that much. DO NOT increase the fuse size. Your wiring (depending on the gauge) will likely become the weak link and is a good way to burn your place down.
Compressors in your A/Cs and in your refrigerator create an in-rush of current on start-up. If they occur at the same time, it might be enough to max your box. Also, compressors that are on the fritz will have a tendency to draw excessive amperage, though their overloads are supposed to take care of that. There may be nameplate data on the equipment that will tell you RLA (running load amperage) and FLA (full load amperage). Other than that, your loads should be relatively minor when you are not there. Why it tripped while you were away can be any number of things though.
I was wondering if you were gonna chime in, Rob. Thanks man.
(in case you were all wondering: Rob’s an HVAC guy and one of my bass students)
So you interpret that 30 Amp. label as the max load?
30A is your max load. I was able to blow up the photo a bit better on a monitor at work (I have a crappy tablet PC). Anyway, you do appear to be cutting yourself short 10A. I’m assuming your top two fuses are for your main and could be 30A instead of 20A. Depends on the wire size coming to your panel. Then you would have 60A of utility across 4 loads assuming you are not using that much at once.
If you can hang tight until Tuesday evening, I can swing by after class and pull the cover off to verify the wiring. I’ll bring an amp clamp too so we can get an idea of what kind of loads you are pulling.
That’d be cool.. though the thought of seeing what the wiring actually looks like is probably not something I really want to see.
I am fairly positive the top left fuse goes to the circuit the fridge is on and the one on the right goes to the odd ball 250volt receptacle in the living room (which is right by the front window so I think it was intended for an AC unit, but we don’t have anything to plug into it).