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I have one rig which keeps blowing fuse every other month. Load is around 1550 wattage(12.5A). I am using 20A socket. Two PSU together 1850 is being used in the rig. 10 cards of mixed 570 and 580.

Any suggestions?

Is the fuse blowing when the rig starts (for example, after power outage) or in normal use?

What kind of fuse you have, is it automatic circuit breaker or old type one-time-use fuse?

It is happening while rig is on for several days. The fuse is old style one time use.

Can you plug into a different 20a socket and see? There may be a flaw somewhere in your loop/spur and its warming up over time - doesn't sound great.

have you checked logs or anything to see if a mining program is restarting causing a power surge on warmed up household cables?

Good point.
I will also bring down load by 2A to see if that stays good

use a good fuse :) Legrand and Siemens are the best

There are several reasons what could be:

1. Your fuse is bad quality, or it is wrong rating
2. There was a power outage, or several power outages at short time. Current surge at both PSU powerups exceed the current rating and blows the fuse.
3. Load is more than what you think
4. Your PSU is going bad.

For point 1. It is possible your fuses are bad rating. Verify that it really is 20A fuse.
For point 2. When you power on the PSUs, especially 2 of them at the same time, there is massive current surge (2-5x more than rated) for very short period of time. In my opinion this is the most likely reason for your issues, that there was outage of power and then it blew up. Check if your fuse has a SNAIL marking on it (slow-blowing fuse, or delayed action fuse, what ever is the name, there will be a snail or letter T (timed) or letter L (lag) next to 20A rating)
3. Maybe your rigs lose some power optimizations after some time and run the cards overvolted. Very unlikely considering you would need more than 2.2KW of load to blow the fuse.
4. Very unlikely considering you experience this every few months

Have you checked the wiring for faulty connections and ratings? (ex. 12gauge+ wires for 20A) The most obvious signs are thin-looking wires in the circuit or bunch of "rat-tail" connections; if there's a problem, the wire or the connections will heat up and will "pop" your fuse.
If you're not qualified to do so, call for a professional electrician to do the job.

There's no other reasons for this other than faulty wiring since it's happening too often to be caused by a bad fuse, otherwise, frequent power outage.

Depending on your load, the size of the fuse used is no problem. If the fuse is always burned, it may be a problem with the fuse quality, or the circuit cable is aging, the temperature rises, and the current will increase. You need to check the line.

I am not expert in it. However how can a lower quality wire burn the fuse. Every time I noticed that fuse was burned badly. Why the "wire or the connection will heat up" will cause "pop the fuse". Can you please explain?
Thanks a lot for your help.

Low quality or even wrong type of wires and connections can have a lot of resistance mainly because of the current that flows in it had exceeded the limit.
When it happens, the wires will heat up and will cause the fuse to break because it is designed to "pop" before a circuit overload happens.

Since you're not an expert and there's certainly a problem, I suggest you to seek a professional to check-up your wiring.

The fuse you are using might not be capable of taking so much power. Change it and get a better quality fuse. The kind of wiring done can be another factor causing the fuse burn. Change the fuse first, then if the problem persists, you can check the wiring and circuit connections. Once you do this I believe there will be a difference.

One more tip. Check the temperature of your fuses. If they are hot, just use a fan to blow fresh air to them. Helps alot.

Got the same problem with constantly turning off fuses. Since I cool them, I never had any trouble again.

I noticed that when I had multiple appliances on (heater, oven, computer, mining rig, tv etc) then the fuse would sometimes trip.

My guess is that your system is overloaded. Does it happen at the same time? For example, in the afternoon when you're home using appliances? That would be a pretty good indicator.

I live in an apartment, so the bad/cheap fuse situation is probably common for your typical inner city apartment. If you rent, you could get your landlord to arrange an electrician to come check it out - that's what I did, they replaced it and now everything is working fine.

It is normal for electrical chains. You have to have double reserve of the power. When electrical equipment is switching on there appear impulse electricity for few ms. It is the reason of blowing of your fuse.

As correctly noted above, you can install a better fuse. If the problem remains after this, then you will not be able to do without a professional electrician who will strengthen your electrical wiring. Electricity is an area where strict professionalism is needed.

Well, my impression is that maybe you have the wrong wiring behind that 20A socket. If I'm not mistaken, for 20A in one phase you need at least 4mm wire.
2,5mm2 wire should be used to máx 16A but some people like to play with theoretical values and use it to 20A, causing excessive heating on the wiring...
It is still strange because the fuse should break by excess power, not wiring temp... but worth checking

The problem may be that you are using two PSU. Even exactly the same type PSUs have  slightly different internal resistance , resulting in their incresing  distort (caused by temperature) and the current increase in the power supply circuit. Practice taught me to always use the single PSU for rig.

Slowly moving to a single PSU rig. When I started I went for 850W PSU and therefore had to double them in a rig. Currently, I am planning to just lower usage to below 10A for the socket and see if that helps.

When the copper wire heats up (maybe you have it), the resistance increases and the current decreases. Thus, heating the wires can not lead to a blown fuse. If the fuse heats up with these wires, or the fuse socket has poor contact (which causes heating at high current), and the current is close to tripping, then the fuse may trip.
You should be powered by quality power wires, to use a good fuse socket and the fuse 1.5-2 times of load. If the load is 15 A, the fuse is at least 22.5 A.

Quick question...
Are you tripping a breaker or blowing a fuse?
What is your total electrical service? 100amps, 200amps?

You really, really want to make sure you don't start a fire. AND right now your box is giving you warning signs.

I have a old style bussman fuse that blows off. It is 100ams with 4X15 and 2 X 20Ams. One of the 20 Ams I was using with total load of 12.5 Amps. I have reduced it to 11Amps and will possibly bring it down to under 10Amps

You should have been fine, but because you are not and keep blowing a fuse, it makes me wonder what else is going on.
Time to use a multimeter and test the flow or call a electrician. 

Agree. The fuse blew 2 times in last 6 months. I will contact if it happens again. I will reduce the load further to below 10A this month.

If you have a short somewhere, it could cause a fire. Watch the temp of your wires - use a Laser Infrared Thermometer - they are cheap on Amazon.

do you have a kill-a-watt meter? some can show high watt and save if even when fuse blows

10 cards  can pull over 2000 watts + mobo + cpu + ram etc

amd cards go into power runaway and all  of them shift to full power.

 I have seen this on more then one occasion. almost always with windows

if this happens  and you are at 110 volts

2200/1100 = 20 amps and pop

that fuse can do 15 amps 24/7

try running 7 cards and my guess  it never happens again.

Or try smos and set cards lower.
smos is better then windows with wattage runaway issues

Split the mining gear across different circuits to avoid single socket overload. Also try using a UPS to regulate the power and avoid surges which often blows the fuses

And have you tried changing the fuse to find out if it would work out. You may have an old type electrical (which is mostly the best) but change it and try another brand may be it could help. Also don't forget to protect it from power fluctuations... For example, where I am, electricity can go off and come back at anytime risking your electricals.

Agree with you running 7. Currently I am using EthOS and with 9 cards. Will move some of the cards to other rigs.
Thanks

Ah I see if you are in the USA then yes your wall socket is rated for 110 volts (usually).

In most other countries it is 220 to 240, so your fuse is probably correctly blowing because you're overloading it if you have a nine card rig.

Agree with this the fuse might be overloaded that is why it always blowing. The solution you should do if you want to fix this issue replace a new and better fuse with higher wattage because if you put a fuse which is low wattage limit than the rigs required it will always blow so upgrade your fuse for higher wattage limit.