Introducing MongooseMan (and his installation)

Finally I get to contribute to this thread [image]

@JacoDeJongh & team finished my install yesterday, so I’m about 16 hours into being as off-grid as possible. I cannot recommend them more highly. Really great team, despite my house throwing many challenges at them.

3x Victron Multiplus 48 (one is a GX unit) (yes, it’s a lot, but we have a big property with a decent amount of usage, so I prefer a larger upfront outlay to avoid having to change things down the line)

21x 410W panels (15 facing NE, 6 facing NW, total of 7 strings of 3) (don’t get Jaco started on my roof, it was not a fun job for them)

4x US3000 Pylons

Batteries went down to 20% overnight, mainly because of the geyser. I’ll look at installing a timer and integrating it with Home Assistant.

7kWh of production so far today

Got it integrated fairly easily into Home Assistant using Modbus. That “Total Solar Saving” is a fun number to watch.

A few more pics:


Hi MongooseMan,

Your system looks great. Welcome to the club of happy clients of Jaco :vb-grin:


Looking good. Looking at those panels and their weird angles I can just imagine it was a fun project.

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The angles were the easy part. The roof is covered with asbestos slate tiles 400 x 700 mm and where the brackets must go, there is 4 layers of them. Ensuring that there will be no leaks in the future proved to be the most challenging part.

Contrary to popular belief (that you ought to immediately remove it completely), it is often much better to leave it alone. A roof replacement job often creates far more asbestos fibres that the drilling of a few holes. The important part is to always wet-drill to keep the dust down. Also, the asbestos in such materials are often of a very low percentage. At least… this is what I’ve been told.

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Welcome Mongoose, and well done Jaco.

I just have one titbit to share on this awesome install, to forestall any surprises.

Having seen a MPII derate due to ambient temp, having seen batt temps rise during the day, having had my system under a similar “see-through” roof, summer in CPT is a bastard!

I can see aircon dedicated to keeping the ambient temp controlled. :vb-cool2:

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Hi @MongooseMan, welcome to the forum!

I thought the same. The parts generate a fair bit of heat themselves so one needs to be careful.

@MongooseMan if it is the geysers running your batteries down, what works great for me is to run my geysers during the daytime using my timers, and then we just live with the warm water produced then. Haven’t run out of it yet! We do however had our 100l main bedroom geyser come on at 5am. For that time I turn on scheduled charging because I don’t want to punish the batteries, but you don’t need to.

Welcome @MongooseMan – looking great (if complicated and dangerous!)

Having a geyser in Home Assistant is pretty awesome and well recommended.

Yeah, just trying to work out the best way to get it done.
My geyser has a 3kW element, so that rules out a Sonoff without also doing a relay.

So I either have to go the relay option, or get a smaller element and use a Sonoff Pow or TH16.

Interesting, thanks.
I’ll see how it goes.

The only (minor) complaints so far are from my wife & mother-in-law about the very low pitched hum it produces at night when inverting a big load (the geyser last night). (The inverters are mounted on the other side of our bedroom wall so the low noise carries through the bricks).

Hopefully scheduling the geyser mitigates this, otherwise I’ll need to install some sound-proofing as well.

I am not to worried about this specific installation. Its in quite a big room, doors both sides thats normally open and creating a draft. Its also on a south facing wall and under a overhang of the roof.
My approach is very simple when installing, I normally wait for the system to tell me its not happy, and touch wood, I only had to add additional cooling (Extractor fan) on one of my installations in phalaborwa. A cupboard install gets one as a rule, but outside installations not so much.

Adding one in this case would also be relatively easy, hence I left it out to see what will happen in the summer. @MongooseMan is good with Home assistant and can easily add some logic to start an extractor if and when needed.


There’s a couple of guys online (at MyBroadband) looking at Solid State relays, but there’s concerns about them overheating.

You can do what I did and go the contactor route (Jaco installed it for me) - basically 30A contactor which is switched on by a Sonoff flashed with Tasmota.

The only unfortunate part is that you miss energy consumption.

I approx it by adding a template sensor in HA that says 4000W when the Sonoff is on and 0W when it is off – this is close enough for my estimates to at least see roughly how much kWh a month my geyser consumes. The thermostat is also very high – 75 degrees, so it doesn’t stop by itself (I stop it before it reaches that temperature).

An alternative is to use something like a Shelly EM (with a CT clamp) to measure current consumption indirectly.

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I’m a simple oke … got the basic Geyserwise controller installed, the one that has the time and manual on/off switch - for the wife to override - dropped the element to 2kw and set the times, done and dusted.

Geyser is outside the house, B+ rated, and keeps the temps blerrie well over 24h. Our kitchen was the bastard, so I changed the pipes and added a 4kw 50l geyser there, also for one shower. So I don’t bother with a timer there. Cents on the dollar to heat it.

The rules are:

  1. Cold kitchen water,
  2. Cold shower,
    … either and/or both will get a solar system removed so fast, your head will spin.

Once you have seen your data, even leave the 2kw element on as long as you have spare solar - me, I need 4 hours per day for 2 x 150l geysers … it works for us.

Over time one gets used to it … but as you say, if you don’t have geysers heating at night, either because of settings on the system like Keep charged, or Min SOC etc … then the system is as quiet as it can be.

SSRs need to be mounted to a heatsink for anything more than a few amps. On the inside they usually consist of a TRIAC switched by an opto-triac. That TRIAC will have an internal resistance and a thermal rating (junction to case) that have to be kept in mind.

I don’t like those SSRs. CBI does a nice, fat, WiFi relay; I’m pretty sure you’ve seen us discussing it over on MyBB. Issue is it can’t be Tasmotized.

Anyway, I bought a couple and will replace the Tuya boards with vanilla ESP12 modules. Hopefully I can get it to work, then you have a thumping 30A power monitored switch that can run nicely in HA. A project for this weekend methinks.

This is my geyser project:

Probably the single biggest gain in battery use.

I opted for a wired RS485/modbus connection, as I wanted guaranteed fast response from the geyser (to turn it off within the 10s overload window of the inverter, if load ever got too high).


My only 2 concerns - shading issues from string next to geyser.
Batteries likely insufficient given system size.

I’d address the batteries if possible, as this will cost the most if you abuse them with too high discharge.

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Well done!
I love those fisheye pictures. It always amazes me if you look at something and then want to relay it in a picture. It just never wants to fit.

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Shading only starts after 4 in the afternoon, by that time the production on the north facing array has already decreased quite a lot, and the shading only affects the one panel to the left of the geyser. The big north roof to the left of the picture could not be used as there is big trees just out of view to the left of the picture that would have caused serious shading in the winter.

System size was determined by daytime use (And Possible peaks) and not night time usage. Batteries bank was chosen on night time loads. Last night the batteries reached 40% so they are not being over worked. Because batteries are the most expensive and with Pylontechs you can always add should you need to, we decided on 4 to start with. Soon we will know if more is needed, and if so, that is what the space on the right of the battery fuses are for.

For now, those four Pylontechs will go a long way…