Off Grid Living / Camping > Utilities

Solar Water Transfer Pump

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rossw:

--- Quote from: OTG on August 20, 2018, 08:31:27 pm ---Jeez Ross, what did a positive displacement pump ever do to you!?  ;)

--- End quote ---

Apart from the obvious (letting me down!) ??    :)



--- Quote ---Though, a 400m run of 3 core is impressive ross, you must have a good trench shovel/back!   ;D

--- End quote ---

I ran a 40mm pipe (1 1/4"), plus conduit with 2 x 10mm power cables, a suitable earth and I think 3 x 2.5mm for controls if I ever wanted them later). Digging that trench in this terrain by hand wasn't happening!

OTG:
Well, I decided to go the bore pump route and picked up another 24V 210W solar screw pump - Item 32417332198 on aliexpress.com. You're a very persuasive bloke Oz!  ;D

As noted, this way I can use the existing panels (or panel - it's just 1 x 320W Jinko) and controller, plus I can swap parts on these pumps and now have a spare/backup controller to boot - easy!

The trick now is finding a way to switch between the two pumps...

I could be lazy and simply wire in two 3 Pole DC Breakers - but the cost of this ( 2 x 4pole or 1 x 6pole enclosure/breakers) quickly adds up, it's a bit messy, I don't really have the space for it, and with the better half running the pumps now and then I want it to be as simple as possible.

So after a bit of digging on the google machine I found this -
https://au.rs-online.com/web/p/non-fused-switch-disconnectors/3307792/
https://docs-apac.rs-online.com/webdocs/134b/0900766b8134ba75.pdf

A 3 Pole/3 Position rotary switch, rated for 10A @ 24V DC (210W Pump Motor @ 24V = 8.75A), I won't be switching under load so that shouldn't be an issue (will turn the controller on/of & flip the solar panel breaker on/off when switching pumps), it's IP65 surface mount, will fit nicely where the solar cable is currently coiled up (in the picture - I'm yet to run conduit with proper MC4's - I needed the water with the drought and all :) ), and it's $65 from RS Online. I'm just clarifying the contact sequence with RS to be sure it suits - I believe it'll be 1 x Open Common State & 2 x Closed States (per my scrappy drawing).

Whaddaya'll think - do the job? I'd be happy to hear any thoughts, suggestions or alternative switching ideas.

rossw:
Looks like a winner to me.

The "Contact sequence" in the PDF for that switch shows it as six discrete SPST contact pairs, with jumpers between two to make change-over contacts.

(Eg, in position 1, contacts 1-2 are joined, in position 2 contacts 3-4 are joined, and the jumper from 2-4 makes you a change-over with 1/2/3 where contact 1-2 is closed in position 1, and contact 2-3 is closed in position 2.

All switches are indicated off/open in the centre-off position, so this will do your application nicely.

It would also be easy to rewire it as a reversing switch for a 3-phase application - so a handy switch to have.

OTG:

--- Quote ---Looks like a winner to me.
--- End quote ---
I thought so too. And your contacts explanation makes sense and was a good help, thanks! Good point re 3-phase.

Funny story - When I mentioned clarifying with RS, I meant Eaton... after a brief chat with the sales guy, his advice was (paraphrasing) - I can't advise on a switch because your products/devices aren't Eaton and our switches haven't been tested with them... ??? After an awkward silence, I noted that Eaton don't make every kind of electrickery product/device and there's no way they have tested every possible mix of components either... to which he promptly replied (again paraphrasing) - I know, but that's what we've been told to say!  ???...  ::)... Anyways, after suggesting we ignore my specific devices for a moment and just focus on the circuit design/parameters, he did come up with some suggestions and agreed this switch was best.

In the end however, I ended up going the next model up - https://au.rs-online.com/web/p/non-fused-switch-disconnectors/3307809/

Bigger knockouts (M25 vs M20) bottom AND top (the 3G 2.5 power + level sensors cables would have struggled with M20 - plus I hate butchering enclosures, and I don't know how "butcherable" these are either), plus a higher amperage rating (handy if I ever get bigger pumps).

Now I just need it all to show up! I'll post an update after I've chucked it all together.

OTG:
Well, I got the switch in last weekend and it's now working a treat with the bore pump.

The screw pump for the tank also arrived and is fitted with another shroud ready to drop in the tank - I just need a few more conduit bits to run the power cable to the tank and then I can drop it in!

A few points about the switch:
 - the enclosure actually has those rubberised "knockouts" that you're supposed to break away (but not cut-out, for whatever reason). I've noticed this is increasingly prevalent on a lot of enclosures for some reason? To me, they seem an unnecessary weak-point and I'd personally prefer screwed or plain entries, but as they say... whatcha-gunna-do!?
- it had an additional rubberised hole @ centre bottom about 12mm round (intended for earth or other aux wires I think) which was actually quite handy as I ran the bore power cable through it (the centre black cable - the board sits right above the bore) and the bottom left corrugated conduit I'll run to the tank pump.
- finally the switch can only be mounted one way, which made the wiring messier than it could have been, but again... whatcha-gunna-do.

And a quick pointer on the screw pumps:

I've found that with both my screw pumps, there were a lot of metal shavings (some quite big chunks too) in behind the inlet screen/mesh. ??? It almost looks like the pumps are fully assembled BEFORE they mill the inlet openings in the SS casing because the screws themselves had shavings on them too!  So I'd recommend anybody else getting a screw pump from china, take the screen off and give it a good wipe/rinse out before you prematurely bugger the rubber screw.

Good old Chinese QA!  :P

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