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Borehole pump on Victron solar system


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Hi All,

I'm looking to invest in a solar system with the primary aim of getting some independence from the grid. We have a borehole and the plan is to run that off the inverter to cater for scenarios where the municipal power and water supply have both failed. Will a hybrid inverter be able to handle the startup load of a 1800W borehole pump? Or are there better options for that? I understand that the regulations around the grid tie in will limit us to a 3KVA inverter on our 60A supply and I'm planning for the following Victron setup running ESS:

Victron Multiplus II 3000VA - 2400W continuous (peak 5500W)
2 x Pylontech US2000B - 2400W continuous discharge (peak 9600W)
SmartSolar MPPT 150/100
2kWp Solar Array
Venus GX

Thanks!

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Hi Dan,

Welcome.

A 3kva Multiplus II will run a 1800w borehole pump, it is the startup current that you mention that needs to be confirmed that it would be within the inverters limits.

@plonkster  @phil.g00 @The Bulldog what say you guys?

You also get solar pumps dedicated for water pumping IF the setup needs to power additional equipment, unless the pump is on for a very specific time?

The 150/100, it is a big MPPT, on 48v can take a lot of paneling so in that you are covered for a lot of expansion. 🙂 

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Is there a particular reason for having such a large pump? Is it running irrigation or something? It is more suitable for a solar system to have a smaller pump running for longer, than a large pump running for a short period of time. You will also use less power as a large pump creates a large cone of drawdown around the borehole because of the volume of water extracted. A smaller capacity pump doesn't pull the water table down so quickly so you will pump from a shallower depth.  

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I concur with @DeepBass9, your application is important as to your choice of pump.

The delivery capability and your volume requirement are also factors.

You can get a lot of water with a small pump if it works all day with a far simpler ( read less expensive) set up.

Also there are pumps that just hook straight to the panels with the MPPt built in.

Edited by phil.g00
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3 minutes ago, DeepBass9 said:

This is what happens, the faster you pump, the deeper the cone, and the permeability of the rock controls how quickly it will recharge.

Well blow me down. Baie dankie.

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Thanks all for the replies 😀

14 minutes ago, DeepBass9 said:

Is there a particular reason for having such a large pump

The pump runs the irrigation system and we use it to top up a JoJo for a backup water supply. I'm not concerned about the irrigation during a power failure, but we may need the pump for the JoJo. I'm trying to figure out if that is feasible and if so, is the 3KVA Multiplus a good choice? Or should I just disregard that as an option?

4 minutes ago, phil.g00 said:

You can get a lot of water with a small pump if it works all day with a far simpler ( read less expensive) set up

Long term sounds like the better solution would be a low power solar pump that empties to a storage tank and then run things from that. That would involve changes on irrigation system which I would have preferred to avoid.

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Dedicated solar pumps are very expensive, for the amount of water  they deliver. It is much cheaper to buy a small 220V borehole pump, which your inverter will drive with no problems at all. You can even put both pumps down the same hole and run the small one from the inverter and the big one from the grid when necessary. In that way you also have a spare pump, so if one pump breaks your can run the other.

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3 minutes ago, DeepBass9 said:

You can even put both pumps down the same hole and run the small one from the inverter and the big one from the grid when necessary

Thanks, I would never have thought that would even be an option.

I'd still like to figure out if running the existing pump off the inverter is even an option. Is it possible to damage the inverter / batteries testing a load like that, or would the pump just struggle to start / everything shuts down?

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19 minutes ago, Dan said:

I'd still like to figure out if running the existing pump off the inverter is even an option. Is it possible to damage the inverter / batteries testing a load like that, or would the pump just struggle to start / everything shuts down?

The Victron equipment won't be damaged. It can take up to double the rating for a second or so, before "BEEEEEEEP. Click! Silience."

So the trick is to find the pumps startup current, and IF the inverter can handle it, probably with no other loads on it, then no problem.

BUT we are missing a point here. IF you are off-grid, THEN it is an issue.

IF you are grid tied then it matters not. Eskom will take the punch, inverter just adding all the panels can give, to offset the Eskom draw and save you some money to boot.

And if there is a power failure, then the pump is not on the dedicated always on circuits, so no problem as I said.

The smaller pump as DB suggested, that can be on the always on circuit.

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Yes, it's important to know the max head required, from the water table up to the top of the water tank. All pumps have performance curves of litres per hour vs head.

For a crude pump test on your borehole do the following: Don't pump at all for as long as you can, then measure the water depth (just a piece of string with a weight, you will feel when it is submerged). Then pump for an hour, and measure again, pump another hour and then measure again. You will then get an idea of how many litres come out of the hole, for a given water table drop. And then when you have stopped pumping, measure again every hour until the water table has hopefully settled back to where it started. 

So empirically you will get an idea of what is going on underground. Typically you will get a quick drop as the water in the borehole is pumped out, then it should reach an equilibrium where the the inflow and the pumped water are similar. 

Edited by DeepBass9
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Thanks @DeepBass9@phil.g00 for the suggestions, I'll probably test it out on the inverter to start with, but it makes sense to switch to the low power pump long term to make use of all that solar during the day.

50 minutes ago, The Terrible Triplett said:

And if there is a power failure, then the pump is not on the dedicated always on circuits, so no problem as I said.

That's what I'm trying to figure out - can I put the pump on the essential circuit to provide us with a backup water supply in cases when the grid and water supply are both down. Edge case, but its happened to us 

41 minutes ago, The Terrible Triplett said:

IF you are grid tied then it matters not. Eskom will take the punch, inverter just adding all the panels can give, to offset the Eskom draw and save you some money to boot.

So will the Victron use the output from the PV and then just take the balance from the grid? Or will it switch the entire load the grid and the potential PV generation is lost if batteries are full?

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3 hours ago, The Terrible Triplett said:

Hi Dan,

Welcome.

A 3kva Multiplus II will run a 1800w borehole pump, it is the startup current that you mention that needs to be confirmed that it would be within the inverters limits.

@plonkster  @phil.g00 @The Bulldog what say you guys?

You also get solar pumps dedicated for water pumping IF the setup needs to power additional equipment, unless the pump is on for a very specific time?

The 150/100, it is a big MPPT, on 48v can take a lot of paneling so in that you are covered for a lot of expansion. 🙂 

Well, I am running a 1.5KW borehole pump, 1.5KW (max) pressure pump for irrigation and a 1KW (max) pressure pump for the house. The pressure pumps are "inverter" type pumps so they just use whatever power is needed to maintain pressure. Borehole is just over 100 meters and I pump an average of about 5KL-10KL per day in summer, much less in winter. I supply our estate with 12 houses total with water so that's why I pump a relatively high amount per day.

I set the system up so it only pumps from the borehole during the day and all runs off solar.

Yes you get a wide selection of DC pumps intended for direct connection to PV usually with a dedicated controller. But if you already are using PV for your house it does not make sense to go that route unless you have a good reason for this. If you already have a PV system - rather add a few panels, even add an inverter in parallel (since you can do that) - at least then the added "borehole" panels can be useful to you when you are not pumping water.

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55 minutes ago, Dan said:

That's what I'm trying to figure out - can I put the pump on the essential circuit to provide us with a backup water supply in cases when the grid and water supply are both down. Edge case, but its happened to us 

I would suggest essential circuit for the smaller pump, not the big one.

Or if it is dire need, and the startup does not trip, then plug the pump into the essentials circuit and pump what is needed, then switch off, switch back essential loads, assuming the combination exceeds 2.4kw. It is "make it work" scenario.

 

55 minutes ago, Dan said:

So will the Victron use the output from the PV and then just take the balance from the grid? Or will it switch the entire load the grid and the potential PV generation is lost if batteries are full?

Let me try and explain it so that it makes sense. 
Because "we" only use:
AC_in - Inverter connected to the main DB
AC_out1 - essential always on loads connected to inverter via either a separate DB or what what ...

Picture it that both Eskom and Inverter are supplying AC to the main DB.
Now picture the Victron kit pushing all the power it can draw from mainly the panels, IF there are AC loads on the main DB, to force a lower draw from Eskom.
If there are no loads or small loads on the main DB, the Victron kit will supply just enough to balance the draw from Eskom, to like 10-50w, depending on your setting.

Versus ...
IF one was to connect the main DB to AC_out2, THAT would have meant all passes via the inverter, which complicates things. So we don't do that.

Therein the need for the Carlo Gavazzi to measure all that goes into and out of the main DB, if AC_out2 is not used, so that it knows how much power it must push into the main DB.

Edited by Guest
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53 minutes ago, The Bulldog said:

Well, I am running a 1.5KW borehole pump, 1.5KW (max) pressure pump for irrigation and a 1KW (max) pressure pump for the house. The pressure pumps are "inverter" type pumps so they just use whatever power is needed to maintain pressure. Borehole is just over 100 meters and I pump an average of about 5KL-10KL per day in summer, much less in winter. I supply our estate with 12 houses total with water so that's why I pump a relatively high amount per day.

I set the system up so it only pumps from the borehole during the day and all runs off solar.

What setup do you have running that?

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13 minutes ago, The Terrible Triplett said:

Let me try and explain it so that it makes sense. 
Because "we" only use:
AC_in - Inverter connected to the main DB
AC_out1 - essential always on loads connected to inverter via either a separate DB or what what ...

Picture it that both Eskom and Inverter are supplying AC to the main DB.
Now picture the Victron kit pushing all the power it can draw from mainly the panels, IF there are AC loads on the main DB, to force a lower draw from Eskom.
If there are no loads or small load on the main DB, the Victron kit will supply enough to balance the draw from Eskom, to like 10-50w.

Versus ...
IF one was to connect the main DB to AC_out2, THAT would have meant all passes via the inverter, which complicates things. So we don't do that.

Therein the need for the Carlo Gavazzi to measure all that goes into and out of the main DB, if AC_out2 is not used, so that it knows how much power it must send to the main DB.

Understood, so the inverter feeds enough back into the main DB to reduce the usage, but not enough to push back into the grid. Why does using AC_out2 complicate things? It seems to be the intended purpose and removes the need for the Carlo Gavazzi. I assume that there are some practicalities I haven't thought off?

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14 minutes ago, Dan said:

Why does using AC_out2 complicate things?

It has to do with the max amps the inverter can handle in total. A house would required more than 50amps, therein the complication "we" avoid.

It if was a small house or a boat / ship, then the 50amps is spot on. But most homes have a 63amp breaker.

Carlo Gavazzi is wot, R1150 or some such AND you get to see all the data of the entire DB, which goes far towards proper planning for expansion, if need be, in the future.

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