# Preventing breaking of fuse wire very frequently [closed]

we have two geysers 3kWh each. When we turn on both the geysers, the fuse wire breaks. This happen s quite often and in the same scenario. How to prevent this from happening keeping both the geysers on.

Edit: Here I am talking about electrical geysers use to heat water and not naturally occurring geysers.

• What country are the geysers in? Do you know what the local electrical wiring 'code' is? For example, in the UK, wiring outlets are 13A (roughly 3kW) on a shared 30A 'ring-main'. What is the wiring you are using? The answer is likely the one given by @pipe, but a bit more information would enable us to be clearer. Commented Jan 12, 2016 at 4:33
• What's a "geyser" that needs to be plugged in? The ones I know are naturally occurring and power from geothermal energy. Why do you want artificial ones? Commented Jan 12, 2016 at 11:59
• @olin I was a bit wrong. A geyser seems to be an on-demand hot water boiler. Just a heating element. Commented Jan 12, 2016 at 12:18
• 'Geyser' is an old-ish UK-ish term for a water heater. It may be an on-demand 'tankless' type or could be the normal large insulated tank - the term covers both, although usually if the tankless type is being referred to this would be specified somehow. Commented Jan 12, 2016 at 12:42

Your basic problem is you're trying to cram 20 pounds of stuff into a 10 pound bag.

Most likely you are overloading the circuit. 3 kW is a lot of power already, and 6 kW is beyond what typical ordinary "wall outlet" circuits can do. At this power, I'll assume you are using 240 V. (6 kW)/(240 V) = 25 A. Is whatever power feed you are running these "geyser" (whatever that is) things from rated for 25 A? Probably not.

Do you really need these geyser things on, especially at the same time? If you really do, then the best solution is to give each one its own circuit wired directly back to the breaker panel. This is, of course, assuming the power feed is capable of the overall power. For example, if you have 100 A service at 240 V, then both geysers on together will use up 1/4 of the power available to you.

You need to pull a second set of cable/wires, and by wires I mean both neutral and live. Then install the second circuit braker/fuse. Do not increase the size of fuse as Whiskeyjack suggests you to do. The fuse is to protect wires/cables, it shall be placed at every node where the cross section of the wire is reduced - this is normally done in the fuse box where a supply cable comes in with a large cross section and then it is redistributed to loads with smaller cross sections.

You didn't mention your country, as there are tables of cross sections and fuses for EU we have 10A @ 1.5mm2, 16A @ 2.5mm2, 25A @ 4mm2, 35A @ 6mm2, for US you have AWG tables. So don't change your fuse, increase the cross sections.

A lot of devices have an inrush current that is higher than the steady-state current. If this is the case, you can avoid it by turning them on in sequence. Many large setups require this, for example huge arrays of hard disk drives.

If the fuse still breaks, then you have a problem you can not easily overcome. Your required load is simply too high for the installation capacity, and if you upgrade the fuse, you probably break the law, but most importantly, you create a fire hazard. You can try to connect these devices to different outlets. If that is not possible, you have to have an electrician upgrade your cabling.

• A geyser is more or less just a resistor, which also doesn't become so hot that it changes it resistance. Therefore they don't really have a higher inrush current. So I think that's not the problem. Commented Jan 12, 2016 at 10:31
• We are using the similar approach of turning them on in sequence in order to prevent the fuse not to break. Commented Jan 13, 2016 at 3:52

One solution might be - installing a fuse with slightly higher current rating than what you are currently using.

Reason behind your problem seems to be a fuse having a current limit almost equal to what your devices are consuming. You should keep in mind that the rated power output is for rated voltage (110V or 220V). However voltage keeps fluctuating.

Just for an example, let's consider a 3000 watts geyser rated for 220V. Resistance = VxV/P = 16.13 ohms Current at 220V = 13.636 A

Now, the household voltage can go up to 250V in some cases. Current in that case will be 15.5 A

If you have a 15A fuse installed for the above scenario, it might blow during high voltage period but will continue to work when normal voltage is being received.

Also, fuses have a tolerance. They are not very precise. See this answer for more info.

A fuse is a sacrificial device. That means,it does it's job and die ( fuse's tiny wire break ). Fuse's job it to prevent High Current to flow in the circuit and hence allow user to operate their devices safely and protect the device itself. Because wire may burn in High Current. (and What not, you may accidentally touch it. )

Most Common reason for breaking Fuse Wire ?

' Short circuits, overloading, mismatched loads, or device failure are the prime reasons for excessive current. '