# question regarding new specs on off-grid system



## MrsRaspberry (Sep 21, 2004)

Starting a new thread but want to continue what was discussed before.

Re-cap: We are building a new home and want to be off-grid. Our first round of estimates was way more than what we could afford, but we realized we had incorrectly over-estimated our usage and now think we can have a 3.8KW system that will meet our needs. (The contractor came up with a usage of 7.9KW based on incorrect information.) In an attempt to get closer to what we can spend at this time we cut out the high useage items and are also willing to curtail discretionary usage to keep us within our energy budget. 

However, we would like to install a 240vac well pump: 3.3amps rating with service factor of 3.9amps up to 300' depth. Some of the off-grid folks we have talked to around here have had trouble with other types of well pumps. (i.e. Like not having water pressure when they need it)

I have read quite a few posts and must confess that when it comes to the science behind electrical issues I have trouble following everything. So please excuse my ignorance, but is there anyway to keep costs down and still have a 240vac pump? Do we need two inverters or can we get by with one? 

We don't want to buy cheap and be sorry later but realze there might be some out of the box ideas that we can try to help us stay within our budget (energy and monetary) and still enable us to be completiely off-grid. 

You all have been so helpful before and thanks in advance for your comments.


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## wy_white_wolf (Oct 14, 2004)

If this is your only 240VAC load then it will add a big expense to the system.

You will either need 2 inverters that allow stacking or 1 inverter capable of supplying 240VAC. Most only supply 120VAC. The 1 inverter system will be wasteful when you only need 120VAC power. 

If you're really stuck on that well pump, I'd consider a cistern and 2nd pump to pressurize the house. Use a generator to run the pump to fill the cistern then a smaller DC pump or gravity feed to pressurize the house.

WWW


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## MattB4 (Jan 3, 2016)

How much water do you need? You might be able to get by with a low volume DC pump. If it is setup to pump to a large unpressurised holding tank you can than pump from that tank to a pressure system. Your well pump would pump during sunny periods. I suggest you do some searching at the solar power sites concerning DC pumps.


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## JeepHammer (May 12, 2015)

MrsRaspberry said:


> Starting a new thread but want to continue what was discussed before.
> 
> Re-cap: We are building a new home and want to be off-grid. Our first round of estimates was way more than what we could afford, but we realized we had incorrectly over-estimated our usage and now think we can have a 3.8KW system that will meet our needs. (The contractor came up with a usage of 7.9KW based on incorrect information.) In an attempt to get closer to what we can spend at this time we cut out the high useage items and are also willing to curtail discretionary usage to keep us within our energy budget.
> 
> ...


I 'Assume' you already have a breaker box in the home...
That is TWO 120 volt 'Hot' legs that combine for 240 Volt usage.

I did this very same thing, I simply got an inverter that produced in 240,
TWO 120 Volt 'Hot' legs, that combine for 240 volts when needed,
And your current breaker box does that automatically.

You simply feed the breaker box from the inverter instead of the grid,
Since the inverter is producing in EXACTLY what you were getting from the grid, it's a simple source to breaker box switch.

Panels/Batteries to Inverter, Inverter sends AC power to Breaker Box.
Nothing changes inside the home, only the SOURCE to the breaker box.

It's just not that complicated, although a lot of people try to make it more complicated than it has to be...

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Well pumps are designed to produce VOLUME, not 'Pressure'.

The pump puts water in a PRESSURE TANK, the tank maintains the pressure on the line to the house.


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## red-beard (Jan 10, 2016)

We build off-grid solar systems. 

A few things to consider: 

What do plan to run? Make everything you can non-electric. It will be cheaper in the long run, as capital costs on solar can add up quickly. 

110/220. There are inverters which produce either. If you don't have any 220 appliances, just go with 110. 

Map out your electric needs. Map out when things will run. Also, for pumps and Air Conditioning consider Variable Frequency Drives or Soft Starters. You may also want a generator to backup the solar. 

If you need more help, PM me. We build complete off-grid systems.


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