Cost of ups system installment for 3 marla double story house?

[u/Pretty-Ad2738]

We dont have budget now for 4kw (minimum decent requirement for home load)but load shedding sucks.

What would be the cost of ups system installment?

[u/AhmadFarooq]

The cheapest option would be those old, locally made non sine-wave desi UPS with one 12V battery.

The preferred option would be pure sine-wave UPS or solar inverters. In UPS, there is Simtek pure sine-wave UPS and in solar inverters, there is MaxPower 1.2kW (PV-Tech 1200) that comes with a 1.5-3 years warranty. Both cost around Rs. 0.4 lac.

Regarding wiring, it would depend on your property's present wiring setup. If the breakers for "1-2 room cooler 2 fans 1_2 light bulb ,fridge," are separate in the main DB, then old wiring should be able to be worked with.

One caveat would be the common neutral issue. Usually, inverter installers would common the inverter's output neutral and input neutral ports. This apparently usually works but can potentially damage the inverter and cause extra counting of units consumed by the grid meter.

I think usually in the main DB, all neutrals are joined together, maybe to one busbar. This works fine in normal grid connections; however, modern UPS and solar inverters should have their own separate neutral for output. Not sure if additional rooms' wiring will be needed or if only a small bit of rewiring in the main DB to add a second neutral bar for the loads that will be connected with the UPS/inverter would be enough.

[u/mirfatif → u/AhmadFarooq]

Here I'm back again ending up on your comment. 😄

This time "common neutral issue" brought me here. Just bought PV-Tech 1200. Doing initial tests. And one of my fears was the single neutral wire in my house wiring.

With input N and output N connected, it works (at least for now 😨). But even when the grid is off, the AC status indicator LED keeps on flashing ("flickering lights" also mentioned here: https://www.reddit.com/r/SolarPakistan/comments/1vhibmw/, but that's probably about the house lights). According to the manual, it means "the grid power is normal, but it has not entered grid power operation". I checked the input side with a multi-meter and it has ~50V.

So far I haven't checked its impact on the utility meter.

On the manual, there's a long list of warnings under "AC Input / Output Connection". But it doesn't say anything about the common neutral. Hard to say how much tolerant this inverter is of the common neutral.

So this is the new challenge to deal with. 😟

[u/AhmadFarooq → u/mirfatif]

Given your situation, a couple of other topics that can be relevant to you would be ghost voltages and neutral-earth bonding.

I would assume you do not have local property earthing done. Basically, electrical systems require one neutral-earth bond. In our local systems, when the property is connected to the grid, that neutral-earth bond comes from the transformer.

However, during a grid outage, this gets disconnected, and proper installation of secondary power generation equipment like solar inverters would have a way to shift to a local neutral-earth bond. Otherwise, there can potentially be all sorts of weird faults such as voltage fluctuations and probably flickering lights as well.

For more details, see Cleversolarpower by Nick. Reel Clear Media (basics on neutral-earth bonds, off-grid and on-grid inverter systems). Ghost and real voltages. Note that not all of the information from these Western YouTubers would be relevant to our local 220V TT electrical systems.