UPS Electric question?

Contact a local qualified professional electrician to do an inspection on your system and then follow the recommendations.  If this is a fuse box as you state  plan on replacing it with a circuit breaker system.

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That will not help. If you draw too much power from one circuit, it will overload the fuse.

The UPS will maintain the power to say your computer until you replace the fuse, but that does nothing to address the original problem.

The fuses are blowing because they are protecting you from yourself.

the fuse is doing it's job, it is not eating fuses, need to find out the reason

If your fuse box eats fuses you need to get an electrician to look at it, and probably your house in general. Basically, are you trying to run too much power for the input available? A UPS is designed to keep a computer going for a few minutes while you save your files. It cannot power big users of electricity such as heaters and fridges. Your description of power use does nor seem to be excessive for domestic use in modern times, so there is possibly something wrong with the system.

Most portable UPS's can't handle the current needed for a space heater. But here you go, 1500w heater, 400 watt fridge, 250 watt computer, 2150 watts, https://amzn.to/2lH3lZD , $679.

The current for driving your space heater is likely the cause of blowing fuses anyway, and even if you just put your computer on a UPS would be counterproductive, actually putting higher load on the fuse due to charging, rectifying, and inverting processes. Some UPS's even have a maintenance cycle that stops charging until 5 to 10% of capacity is used, then it draws more power than just the outgoing load to recover.

Particularly scary is if you're in a house with fuses it is old, likely the wiring insulation has decayed, and you are putting so much current on those old worn out wires that you are blowing fuses! Everything wears out (second law of thermal dynamics). Abusing something makes it wear out faster. If you keep using the heater buy a couple of these too https://amzn.to/2lEUiZi , $6 smoke detectors.

I don't think you understand what a UPS does. You're blowing fuses because you're using more power than the fuses can handle. You can't plug all that into a UPS anyway. Do that, and you'll probably fry a $200(or more) UPS instead of a $5 fuse. If you want to stop blowing fuses than plug some of that stuff in on a different circuit. I'd start with the heater since it draws the most power.

space heater is causing overload. UPS won't help. put space heater on different circuit -- try the one in the kitchen

NO, backup power WILL NOT address overloading circuits.

If you still have fuses, it is likely your electrical system is VERY old and was never designed to handle the load you are demanding.

You need and electrician to inspect the wiring to recommend how to proceed.

You are running too many things on the same circuit. Try other outlets to separate them.

I used to trip the circuit breaker when I ran the microwave and toaster. I just moved the toaster.

I do not see how a UPS would help.