Hi guys,

Please help me to size a system for the following? Size of the inverter and the batteries, recommended brands for both.

A potable water supply system on a farm, to several residential dwellings. Needs to be convertible for adding solar in the future  purpose for now is to be loadshedding bulletproof.

One of 1kW jockey pump runs continually to keep the system pressurized. When someone opens a tap, the jockey pump may supply sufficient pressure. When another tap opens the pressure drops and a 3kW pump starts up to feed the system. When more taps open, a next 3kW pump starts up. Two pumps will not start up simultaneously, but all can end up running simultaneously. As and when water user taps close and the pressure rises, the 3kW pumps drop out one by one, and the 1kW pump is left running permanently.

Two scenarios then; all as above explained and the other one leaves out the one 3kW pump from the system entirely.

Is this system currently metered? If so, then you can look up monthly figures and we can get a rough average per day. With what's been given so far we can see the maximum load, but we can't see the average load per day or per hour.

This system has been running for years and now needs to to be converted for loadshedding. I’m not concerned about costing, but rather inverter sizing. Constant load on the pumps are relatively easy to assume. What I need to understand is what to size the inverter for the 3kW pump startup. Assuming only the 1kW jockey pump and one 3kW supply pump, an 8kW inverter should be fine. To spec the battery is also ok. But, will it handle the startup inrush currents?

3 hours ago, Cory said:

This system has been running for years and now needs to to be converted for loadshedding. I’m not concerned about costing, but rather inverter sizing. Constant load on the pumps are relatively easy to assume. What I need to understand is what to size the inverter for the 3kW pump startup. Assuming only the 1kW jockey pump and one 3kW supply pump, an 8kW inverter should be fine. To spec the battery is also ok. But, will it handle the startup inrush currents?

Are these pumps single phase? A 3kW is not kind to any form of supply for a few seconds. 

9 hours ago, Scorp007 said:

Are these pumps single phase? A 3kW is not kind to any form of supply for a few seconds. 

Three phase. It’s running a few years already so I assume it’s old’ish. 

16 hours ago, Cory said:

Three phase. It’s running a few years already so I assume it’s old’ish. 

I would think the 3ph 12kW Sunsynk will be fine. I am not sure if you can get a smaller than 12kW inverter from Sunsynk.