Water Heater Wiring Inquiry!

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Old 01-07-20, 10:50 AM
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Water Heater Wiring Inquiry!

Hey gang,

This isnít strictly a DIY question - I have a professional coming in today to do the work - but before I went forward with it, I wanted to ask what you think.

My girlfriend and I moved into a place a couple of years ago with a 26 year old electric water heater. In our first month of living here, we blew a fuse on its 30amp old-timey screw-in fuse circuit. Our first thought was that the heater went kaput so we had someone in to take a look at it and they said that they could replace it with a newer unit but it would probably blow the fuse again so they advised us to get a breaker installed first.

Well, cut to yesterday and I wake up with a puddle of water next to our heater in the laundry room. Itís *really* dead this time but we still havenít had anyone in to switch is to a breaker. Since our heater is a rental, we called the company and they sent out a technician to look at it. He says itís dead and heíll put in a new one but, considering the electrical issues we had last time, I decided to look at the fuse box before he came and saw that we have a 30amp circuit hooked to a 12 gauge wire for the water heater. I looked it up online and everywhere Iíve read said that this is a no-no. When I brought it up to the technician today, he said itís totally fine because the new water heaters have a lower max amperage than our current one so both the fuse box and wire are fine.

My question is, are we in danger if he hooks us up to that circuit? If the fuse goes again and we lose hot water, Iím happy to finally call in an electrician and have the breaker put in, but whatís the situation with the wire?

Thanks in advance for any help and advice you can give me - itís very much-appreciated!
 
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Old 01-07-20, 11:02 AM
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What size is the water heater? Most standard 40/50gal water heaters do require a 30A fuse/breaker and 10ga wire. But there are some smaller 20/30gal ones that require only 20A (and a 12ga wire).

Assuming you do have a larger one, it does require 10ga wire. There's nothing inherently wrong with fuses, you could keep the 30A fuse and upgrade the wiring.
Or you need to downgrade the fuse to 20A to keep the 12ga wire - and use a smaller water heater.

I agree with your assessment - I would not keep the 30A fuse on 12ga wire. That's against code and definitely a fire hazard.
 
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Old 01-07-20, 11:10 AM
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Our current heater is a 38.5L, 3000 watts with a max amp of 18.75. Like I said, the current heater has been on that circuit since 1994 without any major problems and the technician said these new units only pull like 14 AMPS (not sure if heís bringing us a 3700-3800 watt heater or a 4500. I looked up the specs for the 4500 and it says the max amp is 18.75, same as we have now, but Iíd prefer to go with a lower one if he gives us the option.) Iím hoping to get an electrician in to change that panel within the next week or two regardless, but Iím just curious about how safe itíll be until he gets here.

Again, thank you so much for your knowledge and advice - Iím a total newcomer with this kind of stuff!
 
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Old 01-07-20, 01:58 PM
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Your water will take longer to heat with the smaller elements.
 
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Old 01-07-20, 04:11 PM
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Okay, an update.

The service guys came and swapped out my old unit with a new one rated at the same (3000W) wattage. Everything Iím reading online says that this unit would be totally safe on a 20amp circuit with a 12 gauge wire but that doesnít change the fact that itís still wired into a 30 amp, 12 gauge circuit. If the heater will never conceivably rise above 20 amps of usage, should it be safe to be wired that way or am
I still in danger from that wire?

Thanks again for your help!
 
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Old 01-07-20, 04:26 PM
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Chqange the fuse or breaker to 20 amps while leaving the wiring as-is.
 
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Old 01-07-20, 05:44 PM
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Under normal use it will be fine. However breakers are there for faults not normal usage. If your heater was to fault ,heating element short to ground for example, then 30 amps could flow on the #12 wire and melt it.
 
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Old 01-07-20, 06:55 PM
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I agree. Easy fix. Change the fuses to 20 amp (assuming there is two for a 240-volt circuit) Also buy a couple of extras to have on hand. Fuses are just as safe as circuit breakers.
 
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Old 01-08-20, 08:03 AM
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Thanks so much for your help, you guys. The heater is run from a 30 amp screw in fuse breaker, with two outlets for fuses inside it. Both fuses that are in there are currently 20amp. When I saw this yesterday, I freaked out a little because I thought that brought us to a collective 40 amps on a 30 amp circuit but the water heater guy said itís totally fine, and that it actually means I could put two 30 amp fuses in there but since weíre never gonna touch that amperage, two 20 amp fuses are totally fine. Like I said, I know absolutely nothing about this stuff but is this guy right?
 
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Old 01-08-20, 10:20 AM
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Two 20 amp fuses in the holder is fine. Your #12 wire is protected properly.
 
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Old 01-08-20, 10:27 AM
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The guy is right in the sense that, here, two 20 amp fuses do not equal one 40 amp fuse.

But I dispute him regarding putting in two 30 amp fuses. While two 30 amp fuses here allow 30 amps, not 60 amps, I still maintain that 30 is too much.

Intrinsically, one fuse protects one of the two current carrying wires (think positive if you must) and the other fuse protects the other wire (think negative if you must). If just one of the fuses, either one, blows, the electricity flow, which requires both wires, is interrupted.

If there was only one fuse, only one of the two preceding wires would be protected. Both are live (hot). If a defect occurred causing a live wire or part inside the device (water heater) to touch the body or frame or other "grounded" part, the fuse will blow. Current could continue to flow on the other wire to ground without a fuse, and possibly reaching high enough amperage to overheat things and start a fire.
 
 

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