Microcare PV geyser controller (and discussion)

Hi Guys
The Microcare solar geyser controller uses PV panels to heat the water instead of EV tube or flat plate technology. The advantage is that no plumbing is needed. Connect up to your existing geyser and start saving money from day one.

Buy the controller and connect your panels. Alternatively you can buy the kit which includes 3 x 275W HV Panels, Controller, Wi-Fi & Thermistor
WhatsApp me on 0733222089 for prices

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Does the controller use an inverter to increase the PV voltage?

From reading the description in the datasheet, it looks like this is basically a grid-tied inverter that limits it’s output to the geyser load.

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Grid-tied inverters don’t work during load-shedding though ( as per the ad).

Ah, I missed that. I guess that it is a “grid-tied” inverter that can work without a grid. In this situation it is actually not that difficult - your load is resistive, so you only ever have to run in current mode. Essentially, the case where the grid is off is exactly the same control algorithm as when it is on.

Grid tie inverters are expensive items!
These systems have a simple changeover from solar PV to a mains backup.
The question is how do they get the PV power transferred to a 220V element…

Have you looked up the price of this device?

I’ve tried more than once to get info (specifically technical) on these offerings but haven’t been too successful. I’m familiar with the Geyserwise Dual since this impressed me and I have one installed. However these other solar PV water heaters that use the existing mains element are a black box…
Check out this: https://www.4x4community.co.za/forum/showthread.php/349830-Geyserwise-vs-Geyserworx

If I had to guess, it probably has a simple boost converter, and since you can do MPPT with a boost converter as well, I would guess that’s what they did. It’s essentially an MPPT (like their existing range) that just goes the other way.

Anyway, that would be MY guess.

The panels probably has a Vmp around 45V, so this runs at 135V ish, at probably 10A or so, so maybe 1.4kW. You can then literally just run the converter for max power, there is not enough juice there to blow a standard geyser element.

1.4kW over 5 hours average peak sunshine, that’s 7kWh, which in my experience will heat around 120 to 150 liters of water. Standing loss not accounted for, so probably around 100 liters. In my house that won’t zero the bill… but it will halve it :slight_smile:

Yeah, it’s quite funny you trying to get someone else’s post removed for recommending a heatpump. :face_with_hand_over_mouth:

The most likely explanation is that this is essentially a micro-inverter with modified firmware and an anti-islanding relay.

From what I understand it is a micro-inverter.

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@Solarphile Thanks for the feedback.
I trust that all advertising is good so it’s ok to discuss the issue?
I’ve always had a phobia about inverters and attempting to step up a voltage to a higher voltage. This is based on conclusions that I’ve drawn without sound reasoning. :thinking:
What I would like is to do the comparison between the direct DC heater like mine and one of these inverter versions. I think a shootout like this would be interesting…
It’s fairly easy to do: If I had to go to the other site I would simply take my system with the dual element. On a clear day around midday would be ideal…

I think the dual version with the DC+AC element only allows up to 900W on the DC?
This one does up to 2kW, and does not require a special element.

Granted. But comparing apples with apples (i.e. the same PV panels for the test) we’ll be able to see what the comparative kW is between the two.
PS: I’ll take my BMV 700 to check the DC power…

If the DC-element is just straight coupled to the PV panels (no MPP-tracking), the high-voltage inverter model is going to win.

If the DC-element does have MPP-tracking, I think they will break even, as both will get the max energy minus the 3% or so lost in the converter.

Power is power in the end… :slight_smile:

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Indeed it does!
But the proof of the pudding will be in the measurement…

In that case it becomes a shootout between the two converters. I mean, if everything else is exactly the same (which they probably won’t be), or if you account for it somehow (which will be necessary).

What is unclear to me in this case is whether the higher-voltage one actually runs AC. @_a_a_a ? You know?

I heard somewhere that AC might in fact be the better option for the life of the tank. Not sure exactly, but I do know where electrical current flows, it creates am EMF field around the conductors and that can interact with corrosion of metal in the area. When you constantly swap the polarity that doesn’t happen.

The ceramic DC elements probably doesn’t have this problem. The coiled-up resistive heaters will be more susceptible. At least I would expect that to be the case.

Also, where inductive loads are concerned, the total impedance is actually R + X (where X is relative to the frequency), which means the device has a higher impedance when driven by AC. Garden irrigation 24V valves are like that. 24VAC is perfect, 24VDC will blow them up in the long run. But geyser elements are just about completely resistive, so not a factor here.

I have no idea, all of my comments are speculation. I must admit, from the image above it does not look like there are any inductors or space for inductors (although the image is unclear), so I might be way off the mark… Possibly it rectifies the incoming AC and just gives out DC to the element.

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If the same thermostat is to be relied on it will be an AC output.
Maybe a different frequency, maybe a modified sine wave, but it will be AC if the thermostat is expected to break the current.

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I actually suspect it is DC output but they make sure that the thermostat actually does not do the switching. The manual specifies to set the physical thermostat to maximum temp and then on the controller the “DC temp” is to be set 5° C lower than this.

Youtube video with better views of controller (and can hear the relays clicking when switching).

Btw @mmaritz maybe good idea to split the discussion out from the advert?

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