Beginners Help

[Jsbgraphics]

I have just recently joined the forum and would like to run by the people in the know here what I'd like to do and get any help possible.

I have a generator interlock installed and a small 4,000 watt gas generator that supplies power in an emergency (just barely). I run basic necessities off of this when the power fails. Lights, receptacles, one chest freezer and regular Fridge and my well pump.

I can't justify buying a bigger gas generator with things going the way they are with gas etc.

I'd like to install some solar that would handle this load in an emergency, and potentially run these systems full time. Below is what I am looking at:

My plan is to purchase a Sungold Power All in one 48 volt inverter charger: https://sungoldpower.com/collection...-hybrid-solar-inverter-split-phase-120-240vac

and at least one 48 volt Lifepo4 200 AH battery.

I am a bit confused about calculating the correct number / type of panels and the best way to connect them for this system. I have 3 100 watt panels and use one to power a small 12 volt system in my shop. (tool battery charging and few 12 volt lights etc.

The ultimate goal is to install the all in one Inverter Charger, the battery bank, and a satisfactory PV array and then have my electrician tie it into something like a Reliance transfer switch so that I can run the above systems off the solar either during a power outage or as I said full time.

The Sungold unit can be grid tied etc. but I have no interest in that, this would be a strictly off grid system.

Just trying to wrap my head around the whole system and understand what I need to do and how to do it before investing.

 

[upnorthandpersonal]

The size of your solar array is determined by the size of the battery, location and usage patterns. A 48V 200Ah stores 9kWh. Let's assume you had a rainy week and you have an empty battery. To charge it fully, you need to generate 9kWh with your array. Assuming you live in a sunny place with about 4 to 5 sun-hours a day, you would need a 2kW array minimum to recharge the battery without any additional loads. This is also assuming you get the 2kW out from the panels during that entire 4 to 5 hour window, which is highly doubtful - so let's put the minimum at 3kW.

Now, if you also have loads to power during the time you're charging your battery, you will have to increase the array size even further. If you don't need to charge the battery in one day and have few loads (for example, that 9kWh represents two or three days of autonomy), you could do with less.

One thing a battery this size also allows you to do is optimize your generator use: you can use the generator to charge the battery instead of just having it sit there running and wasting power you don't use. For example if your generator is continuously generating 2kW but your loads are only 1kW, you waste 50% of the power it generates. If you can instead capture this in the battery, you can be much more efficient with your fuel.

 

[MichaelK]

What's the specs on your well-pump? Is it 120V or 240V? That most likely is going to be your single largest load. Everything EXCEPT the well pump most likely will require no more than 4-5kWh of power per day.

There are different ways to look at this. One way is to look at what can definately make you 5kWh of power each and every day, during the worst month of the year. So, maybe 1500-2000W of solar, from that viewpoint.

Another way is to determine what your single biggest load is and use 2X the amount of solar panels to feed that load. Let's say your biggest load is the well-pump, and consumes 1500W while running. A good amount of solar to run that load is 2X of 1500W, or 3000W of solar.

Well-pumps can be very hard to start, with what is called starting surge, or inrush, which with my pump is 4X the running wattage. With whichever inverter you chose, make sure that it can surge to at least 4X your pump's running wattage for at least 1 second. A lot of budget AiO units can surge to 200% for no more than 16 milliseconds, which is essentially no real surge at all.

For sizing your battery, a good rule of thumb is to size your battery to the size of your load. For a lead-acid battery, size it 8X the load. For a Li battery, size if 4X the load. Let's say your pump needs 1500W to run. Size a LA battery to 1500W X 8 = 12,000Wh of capacity. For a 48V battery, that works out to be 12,000/48V = 250Ah.

As UNP mentions, now that you know your battery size, you can size the solar to match it. A LA battery likes charging at 1/8th of C. 1/4C for Li. So, for a LA battery that's (250Ah/8) X 50Vcharging X 1.175fudgefactor = 1836W.

 

[Jsbgraphics]

Thanks for the reply’s. Yes, the well pump is 240v. I’m not sure what the specs are for the starting voltage of the pump, but what I do know is that I have a very small gas generator that supplies 4000w max surge and a 20 amp max load. It can handle the well pump even when running basic receptacles / fridge and freezer, but it does work hard at it.

I’m just in the planning stage, so I’m just trying to understand as much as possible so I can make educated decisions about equipment type and size.

 

[MichaelK]

When I first bought my property years ago, the well-pump was powered with on old Onan 4000W generator. As the generator aged more the well-pump went from OK. to barely starting, to finally stalling the generator. I replaced the old generator with a 6000W one. So, I'd guestimate that you have a 1hp pump like what I have.

The best thing to do is get a clamp meter that can measure inrush current, and find out what the starting surge of your pump is. I recommend you get a "Uni-T 216C", which has worked well for me. Without any other information, I'd suggest you go with my starting inrush number, which is ~9100W.

Here is where you might want to make some serious choices. Getting an inverter that powers everything except the well-pump will be easy. Just about any inverter in the 4000-6000W range will power just about anything in your home.

If however you want to run the well-pump, that is also doable, but with a bigger inverter starting at 6000W on up. Pay close attention the the starting surge that your selection can handle. That is what will be critical. I have a Schneider XW+6848, that can surge to 12000W for 60 seconds. Less well-designed inverters might surge that high only for 16 milliseconds. 4500W of solar runs my well-pump from 8AM till 4PM.

 

[Jsbgraphics]

When I first bought my property years ago, the well-pump was powered with on old Onan 4000W generator. As the generator aged more the well-pump went from OK. to barely starting, to finally stalling the generator. I replaced the old generator with a 6000W one. So, I'd guestimate that you have a 1hp pump like what I have.

The best thing to do is get a clamp meter that can measure inrush current, and find out what the starting surge of your pump is. I recommend you get a "Uni-T 216C", which has worked well for me. Without any other information, I'd suggest you go with my starting inrush number, which is ~9100W.

Here is where you might want to make some serious choices. Getting an inverter that powers everything except the well-pump will be easy. Just about any inverter in the 4000-6000W range will power just about anything in your home.

If however you want to run the well-pump, that is also doable, but with a bigger inverter starting at 6000W on up. Pay close attention the the starting surge that your selection can handle. That is what will be critical. I have a Schneider XW+6848, that can surge to 12000W for 60 seconds. Less well-designed inverters might surge that high only for 16 milliseconds. 4500W of solar runs my well-pump from 8AM till 4PM.

Thanks MichaelK,

Elsewhere on the forum I found a discussion about the surge capacity of the Sungold unit the company states: “Dear customer, the overload capacity of TP6048 is 5sec, @>150% Load ; 10sec, @110%~150%,” but I haven’t found an actual wattage figure for the surge capacity. The specs on the EG4 6500 says a surge capacity of 13,000 watts for 5 sec. soooo, maybe it will start the pump maybe not. I’m almost sure it is a 1 hp pump. I just need to find the install invoice to get the info on the pump. Then I can look up the specs.

The other thing I’m thinking is just to go with the standard 6048 or the EG4 6500 and just run my 110 loads from it. That way I could reserve the full wattage of the generator for nothing but the well pump. Maybe not ideal, but it gets it done. It’s just my wife and me and our water and power usage is truly minimal. By this fall I’ll be set to burn wood for heat so not overly worried about the HVAC.

 

[12VoltInstalls]

That way I could reserve the full wattage of the generator for nothing but the well pump. Maybe not ideal, but it gets it done.

That would drive me nuts. Due to the intermittent and on-demand arrangement of virtually all deep well pumps supplying a residence I’d just cover the pump and only worry about the genny when batteries have gone low. Some stuff is worth planning a little convenience for especially in inclement weather.

 

[MichaelK]

Thanks MichaelK,

Elsewhere on the forum I found a discussion about the surge capacity of the Sungold unit the company states: “Dear customer, the overload capacity of TP6048 is 5sec, @>150% Load ; 10sec, @110%~150%,” but I haven’t found an actual wattage figure for the surge capacity. The specs on the EG4 6500 says a surge capacity of 13,000 watts for 5 sec. soooo, maybe it will start the pump maybe not. I’m almost sure it is a 1 hp pump. I just need to find the install invoice to get the info on the pump. Then I can look up the specs.

Since the Sungold is rated at 6000W, I'd assume that their 150% load means 9000W for up to 5 seconds? That's cutting it really close. What I can tell you is that my inverter says it can surge to 12,000W for up to 60 seconds, and I can tell you that is has never had one single problem starting 9100W. But, that's still 3kW of extra surge there.

I think the EG4 might be the better choice, but we really don't get to find out till you flip the ON switch? Good luck!!!