I have been using a solarmax water pump for many years, which was eventually stolen. It was pumping from a borehole that was far from the house, so I can't see what is going on there. The model I had was an OB which is a positive displacement pump (i.e. little pistons inside) running from 2x100W panels. The pump needs to do about a 70m head, and this pump usually produced around 2000l per day. I see now you get solar centrifugal pumps which are cheaper than the positive displacement ones, has anyone had any experience with them?

What I liked about the solarmax is that it is a local product and I had it serviced a few times when it filled up with silt. Most other pumps seem to be Chinese imports and I would be concerned about spares etc.

The other problem is the theft issue. To stop the pump being pulled out of the hole, I am going to cast a concrete box that I can pick up with the tractor and put over the top of the hole. For the panels I'll have to build some sort of rebar cage that can't be sawn through with a hacksaw (which is the tool of choice or panel theives around here).

6 hours ago, DeepBass9 said:

has anyone had any experience with them?

I have a bit.

I have used a pump that has a built in controller (MPPT) that is very convenient literally panel two wires onto pump. Although external controllers are available.

I think it has for dry borehole protection built in as well, which I gather from my own experience, not from documentation.

I 've bought 4 so far, only two have been installed. I use a Alibaba and I can vouch the company and the quality of the products.  Not all the pumps are installed yet, as my travel plans to SA are on hold at the moment.

All the centrifugal pumps came with a spare impeller. I also bought a solar transfer pump and a pool pump, these haven't been installed yet either, but from their heft, I feel they are quality items.

One issue I found was that I bought a 70m head pump but on the slightest drawn down ( it is a very poor seepage hole) the pump would stop pumping. It would just pump for a couple of hours each morning. I replaced it with a 90m head pump and it seems to pump for longer, but then I think the dry hole protection kicks in.  I suppose the head it isn't far off 70m head to start with. I installed a cheap water meter and a non-return valve and just tapped into the water supply from the tanks. So this pump actually pumps into the bottom of the tanks. This also means the head increases as the tank fills from the bottom.

Please keep in mind that the 70m pump was something like 200W'ish and the 90m pump was something like 300W'ish. Off course you can get bigger, but I wanted to see first. I have now got a 500W  ( If I remember right), to got into another stronger borehole, but again not yet installed. At this size these are just 3" in diameter. It is a fairly small package to import.

The transfer pump is small (300W'ish), but without checking I think the pool pump is over 1 kW. The pool pump isn't small, it came in a wooden crate.

I had someone check the meter recently and the installed pump is still merrily pumping away, since it was installed last August.

I am happy so far, fit an forget. I get about 400l a day, which I think is about all that that hole can deliver. I think the pump is probably capable of double that on a normal day on a better hole.

I initially repurposed two of my older panels from those days when panels were only 200W each. 

Interestingly, when I was trying to find out why the pump wasn't working all day and experimenting, I installed a further 2x200W in parallel to check the difference. There was no discernible difference in daily delivery between four panels or two. I was going to take the two extra panels down, until one overcast morning I saw the pump pumping away. It wouldn't pump when it was overcast with two panels, so I left the things as is. So between what the borehole can deliver and the weather I can count on 400l a day, every day.

Edited June 26, 20206 yr by phil.g00

I am just checking my Alibaba transactions:

It seems I bought a 80m and 100m head pump not 70 and 90 as i wrote above.

 3SES1.5/80-D24/210  & SOLAR PUMP 3SES1.5/100-D24/300

80m 24V 210W  USD 135 & 100m 24V 300W USD 147 resp.

Shipping was around half as much again. I cant remember if I paid customs.

While I am checking for those that are interested:

The other pumps I bought, not yet installed are:

SOLAR PUMP 3SES1.8/110-D48/500 at USD 160

solar booster pump MTSQB2.2-35-24-250 with controller at USD 181

solar swimming pool pump MTSP31-19-72-1200 with controller at USD 357

The catalog of the company I bought from can be found at:

https://kairuijidian.en.alibaba.com/?spm=a2756.trade-order-list.0.0.663176e9Knd8KB&tracelog=from_orderlist_company

I dealt with Amy Guan on Alibaba and it was a smooth transaction with fast and tracked shipping to Ireland. My records show I received the orders within the same week as ordering, on one occasion within 3 days.

 

 

 

 

 

 

Howdy

How far is the borehole from your main AC power? We are pretty rural, and have had all our isolated solar borehole installations stolen repeatedly. Eventually i changed over to AC pumps (Hurricane Pumps) powered by long AC cables from our house for 2 reasons: 1) the pumps are easy to procure and cheap(R2000) as opposed to the Solarmax units and 2) Its easier to look after your panels if they're on the roof of your house:)

The pumps are secured 2 ways: either burying the head under a pile of soil, or cutting slots into the baseplate and then welding the baseplate to the headpipe at the slots.

No matter how we secured the panels, if the site was isolated, the guys would spend ages breaking the protection down, and it was better to spend the money on a 220V cable run.

Good luck whatever you do!

1 hour ago, Ian said:

Good luck whatever you do!

Yes, it is horses for courses, I don't think the OP has ESKOM, on the one hand on the other hand he may have excess self-generated AC at some time in the day.

I have ESKOM, but it is erratic at best and load-shedding comes on top of that. A recent bill mix-up during lock-down, resulted in a summary disconnection of supply and a two day wait for re-connection. Something about one ESKOM billing system doesn't talk to another billing system. It seems that ESKOM is less and less customer orientated, and becoming more dictatorial even as they outsource their incompetence. I'll happily admit that one of my  motivations is working towards ditching ESKOM entirely, and I put a value on the pleasure of doing without as much AC.

Right now, I use AC pumps on level switches for the bulk of my water. An AC pump would overpower the seepage hole, dry hole protection would be an extra expense and level detection would be an issue because of the distance from the tanks. I suppose some sort of rudimentary timer would suffice though. 

Another of the reasons, I am making these PV islands is that they are independent of the dictated AC-coupled capacity, very simple and don't require batteries. The 500W pump (yet to be installed), will be going down a hole with an existing AC pump. The AC pump can top up via level detection. I haven't decided how i want this to work exactly yet. Maybe something like every third night?

These pumps are small wattages and the MPPT is in the pump so for example the PV voltage can be up to just under twice the required pump voltage. So a for example the current is not 300W/24 W = 12.5A but could be down to say 300W/38V = 7.9A.  Cable losses are to the square of the current so this means longer cabling is cheaper, all things being equal.

Nearby roofs are not a problem for me, and theft is not a severe issue. I am thinking about another installation where theft may be an issue. I may experiment with a single panel on a single pole up high and see if the hardship of getting at a single panel outweighs the rewards if a thief's mind. I may include a little solar fencer somewhere in the mix.

I also have a theory that AC pumps (due to the inherent earthing of the neutral) are more prone to lightning damage as well. I am in the Drakensberg, so this is a consideration as well.

As you say though, everyone's circumstances are different, so I am just putting my info and my motivations out there.

 

 

Edited June 26, 20206 yr by phil.g00

On 2020/06/26 at 10:54 PM, Ian said:

Howdy

How far is the borehole from your main AC power? We are pretty rural, and have had all our isolated solar borehole installations stolen repeatedly. Eventually i changed over to AC pumps (Hurricane Pumps) powered by long AC cables from our house for 2 reasons: 1) the pumps are easy to procure and cheap(R2000) as opposed to the Solarmax units and 2) Its easier to look after your panels if they're on the roof of your house:)

The pumps are secured 2 ways: either burying the head under a pile of soil, or cutting slots into the baseplate and then welding the baseplate to the headpipe at the slots.

No matter how we secured the panels, if the site was isolated, the guys would spend ages breaking the protection down, and it was better to spend the money on a 220V cable run.

Good luck whatever you do!

The borehole is about 800m away and I can't see it as it is below a rise. Initially  I had AC pump there (like 10 years ago), but those cables were stolen and the cost for that length of 3 phase cable is prohibitive. The solarmax pump has been working for at least 10 years,even though the panels were stolen periodically, but the last theft was the pump as well.

I have 2 boreholes, one at the house is on a weak hole that I run from a normal AC pump. The remote one is a strong hole. Actually the water is only about 10m down the hole, but there is 50m + head to get it up to the house and into the tank.

Potentially I would like to put a bigger pump there to use for irrigation as well, but I'm not sure if the investment is worthwhile if the installation get stolen.

Phil, I was getting about 2000l a day from 200W panels at 70m head, so 400l a day seems a bit low, but if the dry hole protection is limiting it then that is understandable.

On 2020/06/27 at 12:28 AM, phil.g00 said:

 

Right now, I use AC pumps on level switches for the bulk of my water. An AC pump would overpower the seepage hole, dry hole protection would be an extra expense and level detection would be an issue because of the distance from the tanks. I suppose some sort of rudimentary timer would suffice though. 

 

Smaller pumps work better on holes with a low yield, they pull down the water table slower, and so don't switch on and off due to low water level so often.

I think having the controller and everything built into the pump is preferable, as it one less thing to steal. And also using as big a panel as possible, so it is as unwieldy to transport as possible, so 400W panels instead of small 100W panels.

To cover the hole I am thinking of a rebar steel box, cast in concrete, but with a loop on the top so I can lift it with the bobbejaan stert on the tractor to move out of the way, so it can weigh up to a tonne or so. *Hopefully* that will be impervious to people creeping around at night with hand tools.

At a stage I had panels on a high pole, but that was sawn off with a hacksaw and brought down. I suppose another option there would be to use a larger diameter pole and fill it with concrete to defeat the hacksaw. I could even concrete the cable inside the pole. So my most recent plan with panels was to just put them on the ground in the long grass so they weren't visible. The trade off was the cost of time, steel and construction against the price of 2 x 100W panels.

Edited June 29, 20206 yr by DeepBass9

For poles have used pipes filled with concrete with a steel fence post dropped inside it before now. Rebar offcuts would be an improvement on that again.

A railway track is uncut-table as well if you can get one.

On 2020/06/29 at 9:59 AM, DeepBass9 said:

The borehole is about 800m away and I can't see it as it is below a rise. Initially  I had AC pump there (like 10 years ago), but those cables were stolen and the cost for that length of 3 phase cable is prohibitive. The solarmax pump has been working for at least 10 years,even though the panels were stolen periodically, but the last theft was the pump as well.

I have 2 boreholes, one at the house is on a weak hole that I run from a normal AC pump. The remote one is a strong hole. Actually the water is only about 10m down the hole, but there is 50m + head to get it up to the house and into the tank.

Potentially I would like to put a bigger pump there to use for irrigation as well, but I'm not sure if the investment is worthwhile if the installation get stolen.

Phil, I was getting about 2000l a day from 200W panels at 70m head, so 400l a day seems a bit low, but if the dry hole protection is limiting it then that is understandable.

Just a FYI : You can achieve that head with a .5kW single phase AC pump, that can be driven by 800m of 2.5mm surfix, with a <10% cable power loss.

That's 2k for the pump and 8k for the cable.

Not sure how that compares to other options?

Similar cost I think, maybe a bit cheaper. Can you just have surfix running through the veld? It will need to be buried in conduit as well surely?

Legalities aside, I wouldn't bother with conduit. I know a place that must have 3km of surfex without conduit buried for over 20 years.  The only issue has been hitting it when laying some more.

I suppose the decision might be influenced by if you are going to dig the trench anyway for the pipe. 

The pipe exists already. I've stopped burying pipes actually. For small pipes the cost of labour to bury them is the same as the pipe, but try and find a leak in a buried pipe! I just run the pipes along fencelines so you can find them easily and tap off from wherever.

Its a bit of a conundrum. If I want to do some more irrigation I will either need to get a solar pump and panels, or get an AC pump, 800m of surfix and more panels to upgrade my solar system.

So if the panels are out of the equation, then it is AC pump and 800m of surfix, or a solar pump. and that works out just about the same. If pump thieves discover the cable running to the pump they will steal as much of that as they can, which is the same cost as the panels for the pump.

So I think I will take my chances with solar, and just try and make it theft proof.

Edited June 30, 20206 yr by DeepBass9

I'd like to see a photo of what you come up with, like I say I have this project in my future as well.

Rabid dogs and a machine gun should so the trick. 🙂

Getting back one of my original questions, how do centrifugal perform relative to positive displacement pumps at a high head. My solarmax used to trickle water, but it did it all day at 70m head. If you look at the performance curves for centrifugal they seem to drop off quite quickly with increasing head.

Positive displacement pumps are not limited by head. Subsequently, if the pipe gets blocked they'll pump until something else gives. A centrifugal pump works on a curve, the trick is to match your pump to your head so that you're still getting a pretty decent volume. Let's say that you are trying to get a rectangle with the most area under the curve. That is why it is important to look at centrifugal pumps curves before deciding on a particular pump.

Edited June 30, 20206 yr by phil.g00

What I had on my PD pump was a pressure release valve, which is actually essential if you have frost so it can release the pressure if it pumps against a frozen pipe. Its just a bit down in the borehole so the water goes back down the hole it it opens, and it doesn't freeze.

On 2020/06/30 at 2:07 PM, Ian said:

Just a FYI : You can achieve that head with a .5kW single phase AC pump, that can be driven by 800m of 2.5mm surfix, with a <10% cable power loss.

Just a question, SANS regulation only allow for less than 5% volt drop, do you think 10% is wise? If you increase the cable size to be within specs, the cost will increase by quit a bit..  

Hi Jaco, what's the motivation behind the SANS regulation?  It might be in place to ensure best practice by contractors - but if you know what you're getting. then does it apply?  I'm an engineer,  (rf not electrical) - I can't see why it would pose any problem, but that's or each to assess.

There are quite few online cable loss calculators - very useful for doing the trade offs

Cheers

Ian

7 hours ago, Ian said:

Hi Jaco, what's the motivation behind the SANS regulation?  It might be in place to ensure best practice by contractors - but if you know what you're getting. then does it apply? 

Yes it does, that regulation was put in place for safety reasons and to prevent the cable from overheating (possible fire hazard) in the first place and protecting your end of line equipment against under voltage situation. If you ever need a COC for that installation and the Electrician knows his story, he will not issue the COC. 

7 hours ago, Ian said:

There are quite few online cable loss calculators - very useful for doing the trade offs

Sadly, knowing what the volt drop is does not change the regulation. 

 

7 hours ago, Ian said:

but that's or each to assess.

If it was this easy and everybody could decide for himself, i guarantee you the insurance company's will be very busy investigation electrical fires, and I can save a bunch on cable costs for my clients... looks like a win win for everybody... 

 

7 hours ago, Ian said:

I'm an engineer, 

Awesome, then you would perfectly understand that very clever engineers was the authors of these regulations and in the majority of the cases it was put into place with the safety of the public in mind. So I totally disagree with your statement "thats for each to assess". The risk has been assessed years ago and regulations put in place to mitigate that risk.  

Jaco, there's a saying that 'the law is an ass'   

Being an engineer, I'm always asking 'why' and trying to understand all the subtleties.

In the case of the above scenario, a 10% voltage drop would imply about 50W being dissipated over 800m of cable, much less than .1W/m. So as much of a fire hazard as gently rubbing the cable.

I wouldn't have any hesitation installing something like that, but then I'd be doing it for my own use anyway.  I'm also very grateful that I live remotely and off-grid - I can do what makes sense. But most people don't have that luxury. And if I were an installer, for sure I would be following the regulations. And trying to find the fine print that justifies the above scenario:)

Cheers!

Jaco, another thought...

Here is that SANS regulation in question:

5.2.2 Voltage drop 5.2.2.1 When all conductors of an a.c. installation are carrying their maximum estimated load, the difference in voltage (the voltage drop) between the point of supply and any point of outlet or terminals of fixed appliances shall not exceed 5 % of the standard voltage or of the declared phase-to-neutral voltage (see also 6.2.7). In the case where reticulation is part of the electrical installation after the point of supply, the 5 % voltage drop shall be calculated to include the reticulation part of the installation (for example, in the case of a housing scheme where further submetering with a further point of control is installed for individual consumers).

If the pump were supplied with 800m of cable attached, we wouldn't even be having this debate?   

The actual loss for the 2.5mm .5kW pump is about 6%, BTW. But my experience is that they draw a good bit more. Why I went with ~10%

 

 

 

45 minutes ago, Ian said:

there's a saying that 'the law is an ass'

 

Assumptions are being made as to why it is a regulation, as @Ian states heat dissipation would not seem to be the logical reason.

But then to go on to further assume if that first assumption is flawed there is no valid reason for the regulation is an equally flawed second assumption.

There is also a saying about the maternal qualities of assumptions.

 

 

One has to be pragmatic in these situations. It's all very well to be pedantic and say : this is the rule, and regardless of whether it makes sense (in this application), it must be followed. This discussion originates in part due to the issue a lot of folks experience: infrastructure theft.

in a perfect world, the solution would be a solar panel and solar pump combo. Maybe Rk20 of equipment installed out there at the borehole, and life goes on. But when that becomes a target, one has to start trading off options. Replace the setup with Rk5 worth of AC pump and AC cable. Or be compliant and use thicker cable, which now becomes a Rk15 solution, and a bigger target for thieves?  As I said above, if the pump was supplied with a 800m lead, the issue would be moot.

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