Solar Diverter for water heating in NZ? Would appreciate your experiences.

Forums › Home Workshop DIY › Solar Diverter for water heating in NZ? Would appreciate your experiences.

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cthombor

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#3155202 3-Nov-2023 05:51

tweake:

tdgeek:

Can you expand on that?

Ive got solar HW, and being nerdy/geeky I have an intimate knowledge how my system works, and I manage it accordingly. Not disparaging your post at all, just keen to hear more

sorry not a whole lot. i never went into details on the systems. even mates one was a long time ago. afaik the problem they mentioned was boiling the water in summer due to the solar. so its kept small to avoid that and they used wetback in the winter. most likely it would have been low pressure system. we used to boil our wetback so i know how much fun that is. the company i spoke to said they used things like outdoor swimming pool or even house water tank, to dump the hot water into to stop the hot water cylinder from overheating.

the idea of the PV is you can use a simple thermostat to turn it on/off. (except dc is problematic). if you want to work well in winter put bigger panels in as in summer the thermostat just turns it off. a waste of generation it may be.

cost wise i have no idea.

On-grid folks I know shifted off their solar HW and onto PV HW when they couldn't figure out how to get the solar HW system running quietly enough during summer. It was on a roof just above the master bedroom; burbling during summer afternoons was loud enough to be *really* annoying to the one who worked night shifts. A bog-standard electric HWC runs very quietly; but (as I posted when resuscitating this thread) the iBoost+ has a noisy fan so you'd definitely want to have that positioned where its fan-noise won't disturb anyone's daytime sleep. Alternatively you could contact Paladin NZ. as its principal has assured us (in this thread) that they're still in business.

Personally I'd be very cautious about a DC PV HWC system, unless it was designed by someone who really knows what they're doing. DC arcs are pretty dangerous -- they don't self-quench like AC ones... as Nicola Tesla had pointed out more than 100 years ago, when duking it out with Thomas Edison regarding the relative merits of AC v DC distribution. Well nowadays there's a resurgence of interest in DC-coupled PV systems (and I'd be keen to get one, someday, when they're productised into a DC slow-charger for my BEV that'll make efficient use of my household's wimpy PV array), and DC microgrids are now in the pilot-stage (see e.g. https://pcmp.springeropen.com/articles/10.1186/s41601-020-00157-9) but I personally wouldn't want to rely on my own (or some cowboy's) DC circuit-breaker offering anything more than a "security theatre" level of assurance against DC arcing in my home!

And... if perchance you're a DC/AC geek who hasn't seen the

Nikola Tesla vs Thomas Edison. Epic Rap Battles of History

you're in for a treat ;-) https://www.youtube.com/watch?v=gJ1Mz7kGVf0

tdgeek

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#3155222 3-Nov-2023 08:39

cthombor:

On-grid folks I know shifted off their solar HW and onto PV HW when they couldn't figure out how to get the solar HW system running quietly enough during summer. It was on a roof just above the master bedroom; burbling during summer afternoons was loud enough to be *really* annoying to the one who worked night shifts.

Never seen that at our house. Tubes on the roof, almost literally above me as I WFH. HWC is 4 metres from my desk, the pump is there. I used to hear it hum if its quiet here. Barely a hum. It started to rattle so I got it replaced, now I never hear it. The system, Apricus, was installed 2011

cthombor

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#3155354 3-Nov-2023 12:17

tdgeek:

cthombor:

On-grid folks I know shifted off their solar HW and onto PV HW when they couldn't figure out how to get the solar HW system running quietly enough during summer. It was on a roof just above the master bedroom; burbling during summer afternoons was loud enough to be *really* annoying to the one who worked night shifts.

Never seen that at our house. Tubes on the roof, almost literally above me as I WFH. HWC is 4 metres from my desk, the pump is there. I used to hear it hum if its quiet here. Barely a hum. It started to rattle so I got it replaced, now I never hear it. The system, Apricus, was installed 2011

Indeed, I'm sure it's possible to have a solar HW system that isn't noisy, and maybe it's even "easy" if you live somewhere that doesn't get as much sun as in the Northland. Dunno when the noisy system was installed, or whether it was designed & installed competently; but when its noise became intolerable it made more sense to divert some PV energy to a HWC, than to engage someone to diagnose & repair the noisy solar HW system. (https://www.solarhotwatercanberra.com.au/system-banging-sounds/)

A solar HW system won't last forever, maybe 20 years before some major servicing is required, but that's cheaper than replacing the inverter in a PV system (now expected to last about 14 years, see https://www.dnv.com/Publications/pv-inverter-useful-life-considerations-144365). I think many of the older inverters are crapping out within 10 years.

Ge0rge

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#3157443 8-Nov-2023 22:26

@Terciops:

I have the main switchboard and mains entry for my property in a workshop around 30m away from the house, where the hot water cylinder is. There is solar PV generated on the workshop roof, thus meaning there is quite a distance between the HWC and somewhere that import / export can be measured.

There is an original ripple control feed going from the main switch board across to the house that, while the ripple control system has been removed from the main board, still powers the HWC - so the element could easily be turned on and off from the workshop, but that would then have the issue of not being able to monitor the HWC temp.

I'm very keen to get something like the Paladin, but I'm not sure I can see how it would work in its current build with my property.

Your thoughts would be greatly appreciated.

Terciops

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#3157461 9-Nov-2023 07:09

2 or 3 years ago, with your setup (remote HWC from mains / solar measurement - but a dedicated mains feed to it) my answer would have been, not possible. At least for any sort of 'intelligent', temperature monitoring diversion / water temp control.

However that is why our LoRa remote infrastructure was developed. Mercifully that is now complete and working well.

Your situation fits perfectly with the remote temperature link as in the diagram above. This is now a mature and well proven solution and the only caveat is that the temperature transmitted at the tank needs a regular mains supply, apart from the feed from Paladin to the element, to power a USB adaptor - which provides the 5V to the transmitter. My original, and not yet abandoned - just delayed - intention was to use a battery and some form of induction charger (from the HW element power) to keep that battery charged. But that turned out to be rather optimistic given the duty cycle and power use of the temperature transmitter relative to say a 18650 battery. I will get there one of these days when I have time :) In the interim though, the USB adaptor has proven 100% reliable and is probably the best answer.

The additional benefit would be that you will have a remote monitor (also USB powered) to put in the house (actually you can have as many monitors as you like), that shows Paladin performance details by mirroring the actual Paladin screen - and more.

All this LoRa stuff is made to order as it is quite fiddly, requiring 3D printed cases etc - as we are not scaled for any sort of bulk activity on these extras. So there would be a few weeks lead time.

There are all manner of add-ons and variations that are viable using Paladin's data and LoRa broadcast. A good place to start looking at this is the Paladin FB page :

https://www.facebook.com/groups/1108024512629017

If you want more details : PALADIN.NZ

or contact me by PM directly.

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