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Mecer Axpert Parallel - Back to Utility


shcronje
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Hi All,

If the Axpert inverters are set to SBU (setting 1) and OSO (setting 16) and the Inverters switch over to utility during the evening because of setting 12 and a high load. If the load drops and If you force the utility to not be available it jumps back to battery. If you enable utility again it goes back to utility, should it not stay on battery because the voltage is above setting 12 or is it because the batteries have not been charged back to the voltage in setting 13?

Thanks,

Shaun

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Yes you have it right. If a high load causes voltage to drop below setting 12 the inverter will be powered by utility until the voltage recovers and exceeds setting 13. Thus a high load could cause the Axpert to go to grid prematurely. I would be circumspect about allowing a high load like that in the first place. Yes lead acids can take the punch but it is not good for them. In fact it is not good for any battery there are those which are more tolerant of high loads. If you are worried you could have grid charging of 2A or 10A but essentially one has solar to save electricity and to my mind grid charging should not be the norm. I have no problem grid charging when the weather is poor or there has been an accidental deep discharge - no problem. I also have no problem when the batteries are for power cuts and one is never sure when you are going to need the batteries next and in that instance I would want them charged as soon as possible.  

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Thanks for the feedback. I prefer not to charge the batteries using the gird and will stay on solar charging for now. I currently have 12 270-320w panels and 4 200Ah batteries which will last me the night at around 50% DOD if no real high load was put on the system. My biggest load is the geyser. I have the geyser on it own solar and using Geyserwise to manage when the geyser will use grid or battery. The load happens when the geyser needs a 'top-up' around late afternoon if the geyser was used often during the day and solar was not able to warm the geyser enough, and mostly in the morning before we shower. Is it wise to let the geyser run on solar/battery when required(I only have two cycles in 24 hours for warming the geyser)? When the load is too high and the voltage drops it does switch back to utility.

Thanks,

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6 minutes ago, shcronje said:

Is it wise to let the geyser run on solar/battery when required ...

For me, on batteries, that answer is: "Over. My. Dead. Body." :D

Why? In cities, Eskom is cheaper than batteries so it fails my 'test' in that I can never justify the "WANT" on geyser on batteries.

EV tubes and Eskom switched off is the way we went years ago, in Cpt to boot, with winter issues. If there is no hot water, you did not plan to manually switch on said geyser. 

We also change the shower times. All shower either evenings or mornings, that all can get hot water, heated by the sun.

Today it is shower faster and less and save water. Now THAT is a motto for SA and not just in Cpt.

Cpt was just the warning for the rest - like Eskom power failures when we where  the first affected as a city, whilst the rest scoffed, till it hit Jhb. ;-)

Today we are forced to shower even more wisely. So we have a oversupply of sun heated got water.

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12 minutes ago, The Terrible Triplett said:

Today it is shower faster and less and save water. Now THAT is a motto for SA and not just in Cpt.

It was amazing how we almost didn't notice, as in our lifestyle was very minimally impacted when my geyser burst three weeks ago. I had the plumber block it off for me, so the house had cold water. Then we had that long weekend with worker's day on the Tuesday, so no hot water for over a week.

The reality before that: Because it takes a really long time for hot water to reach the main bathroom, we were already using a mechanism of filling the bath an inch from the hot tap, and then using a kettle (or two) of boiling water to get the temperature up the rest of the way (and then putting both kids and dad through said inch of water, before someone shouts at me for filling(gasp!) a bath(gasp!) with water(shoch horror!)).

When we lost the hot water, we simply switched to using a MiniGeza in a bucket. I already had one from the previous geyser burst incident.

When you use so little water already, you almost don't need a geyser. In fact, I'm starting to wonder if the right thing to do might not be to fit little 10-liter water heaters where hot water is needed and getting rid of that horrible big tank.

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3 minutes ago, plonkster said:

When you use so little water already, you almost don't need a geyser.

Amen Brother! Now you are talking some serious savings and all that.

Us, being all grownups, our baths have not been used in years.

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Thanks, valuable information and I think we rethink how we use the geyser. I'm using the ICC software to monitor. I'm going to use the battery setting to set the Time for Control to change over to Eskom before the geyser kicks in in the late afternoon and switch back to batteries later at night. Unfortunately on ICC I can only set it once and would have liked to switch back to Eskom early in the morning for a second time before the geyser kicks in for the second cycle.

I guess the one option is to set the Axpert voltage setting 12 to a higher number then Eskom will have to kick in (because of the voltage drop) and once the geyser starts early in the morning if the house was running on batteries for most of the night? Second option is to set Geyserwise not to warm the geyser in the morning and let the sun warm the geyser for the day. Third option is disconnecting the geyser from the inverters and only to Eskom The reason I kept it one the inverters is because I have 2 5kva inverters which has captivity to run my whole house.

I like the MiniGeza (and the first time I seen it) for warming water in a bucket, but it still uses 2000w which will a be a high load on batteries.

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7 hours ago, shcronje said:

I like the MiniGeza

That thing is a lifesaver! Back in 2011 with an 18 month old in the house we lost hot water... around 4PM I remembered that I had seen this thing at the hardware store and promptly got in my car and bought it.

The bad news is that it seems to have burned out on the last morning it was called upon, the day my geyser was replaced. I'm not sure what happened, but it sure saved me on many occasions. For example, the geyser is shared between the main house and the flat. I had a female tenant that would regularly finish off all 150 liters of water.

I'm getting another one really soon. They should sell them in kits with two stop-ends and a pipe-cutter. Geyser-emergency-kit :-)

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8 hours ago, shcronje said:

Third option is disconnecting the geyser from the inverters and only to Eskom.

4th Option. Geyser on solar during the day via inverter ... connected on one side (other side is Eskom) changeover switch.

Best of both worlds.

I do that with my lights. During a power failure - it is batteries - otherwise Eskom as even with lights it Eskom is cheaper. :-)
Note: IF you do this, make the electrician understand LIVE and NEUTRAL, not just live. Happened to me, electrician swapped the live only, blew the dinges out of a few things. Earth in the above, I have NO idea where it goes with a geyser for it is a must.

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10 minutes ago, The Terrible Triplett said:

Earth in the above, I have NO idea where it goes with a geyser for it is a must. 

That's always an interesting topic. One way is that all earths are tied together. I don't even think you have much of an option, since most transfer switches don't switch the earth, probably for good reason too. The Multiplus doesn't (I've had it open, they are just tied together between in and out), and the Axpert also doesn't (it doesn't even switch both sides on the inverter side at least on some models).

The only possible issue with that is in a typical TN-S setup where your earth connector is a separate conductor running back to the transformer where it is earthed. A broken cable would not only leave you without power (which the inverter would take over of course) but also without an earth. The alternative is usually not allowed though. Some would add another ground on the premises, sometimes called a PME (protective multiple earth) setup, but this allows multiple paths, ground loops and all that, and is usually not allowed.

Edited by plonkster
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10 hours ago, The Terrible Triplett said:

4th Option. Geyser on solar during the day via inverter ... connected on one side (other side is Eskom) changeover switch.

Best of both worlds.

I have a Kwikot geyser that originally had a spiraled element. I had a stainless steel plate modified and it now can take two universal elements. One element is powered by a phase of our generator (when it is on) and one element is powered by my inverter using excess solar energy. This could give one the flexibility without switches etc. 

W.r.t. the earth Mike Holt's mantra "The earth is an alternate pathway for stray current back to source" give you a clue what to do with the earth. If it is powered by the inverter the earth pathway must be to inverter. If the geyser is powered by grid earth pathway to your neutral earth bond. 

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I'm thinking to switch between grid and batteries twice within 24 hours to cater for certain loads. Is it advisable to send commands to the inverters to switch (I know it's a controlled switch) multiple times a day and could there be long term damage to appliances, tv's etc. as do notice a switch from solar/battery to grid does makes my tv turn of and on again?

Thanks,

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7 hours ago, shcronje said:

I'm thinking to switch between grid and batteries twice within 24 hours to cater for certain loads. Is it advisable to send commands to the inverters to switch (I know it's a controlled switch) multiple times a day and could there be long term damage to appliances, tv's etc. as do notice a switch from solar/battery to grid does makes my tv turn of and on again?

Thanks,

Hi Shaun

If your switching is causing problems with PCs and TVs try and set Program 3 to UPS. Your change over time is 10ms. I live on a farm and have to have Program 3 set to APL as the power from my gennie is too unstable but the 20ms change over is not picked up by PCs TV etc. I do notice a flicker in the lights.

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On 2018/05/23 at 6:02 PM, shcronje said:

Is it wise to let the geyser run on solar/battery when required

I have my solar hot water booster (I guess you'd call that the geyser element) connected to mains power. Here, mains power is quite reliable, so that may make a difference.

The logic is that if there isn't enough sun to heat the hot water, there probably isn't any spare energy in the energy system battery, which is charged from the same sun or lack thereof.

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  • 2 months later...
On 2018/05/23 at 10:02 AM, shcronje said:

Is it wise to let the geyser run on solar/battery when required

(I only have two cycles in 24 hours for warming the geyser)? When the load is too high and the voltage drops it does switch back to utility.

Thanks,

I run my geyser off solar and I use a geyserwise controller to control the time & temperature. It kicks in at 13:00 and takes about 3 and half hours to heat from say 35 to 65, then it just keeps the water heated till we bath later at night. 

You can use a contactor, connected to the dry outputs on your inverter to switch off the geyser when running on batteries. 

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Is your geyser permanently connected to utility or do you switch off from solar at 13:00? I also have a geyserwise running but my whole house runs through the 2 inverters so if geyserwise switches power on to the geyser it can use solar/inverter.

Do you have some more information on how to use a contactor and connect it to the geyser and inverter?

Thanks,

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Late to the conversation, but your config does sound similar to my previous setup @shcronje.

With reference to the Geyser: I have a Geyserwise Max, and solar tubes and even in winter almost never need to use power. Even the pump that moves the water has it's own small battery and 50W PV panel. That said, I have a direct MANUAL bypass on the geyser for when we need -> Direct from Utility, not via Invertor, and connected DIRECTLY to the element. This is on a Stove style 30A switch with a neon light that indicates on. Since our element is a 4kW rather than the standard 2kW, there is no way we could run this through the Invertor. The only reason I didn't switch on the incoming side of the Geyserwise is that it would keep tripping the Earth Leakage. The biggest negative of this approach is that if someone forgets to turn the manual switch off..,

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On 2018/08/02 at 6:29 PM, shcronje said:

Is your geyser permanently connected to utility or do you switch off from solar at 13:00? I also have a geyserwise running but my whole house runs through the 2 inverters so if geyserwise switches power on to the geyser it can use solar/inverter.

Do you have some more information on how to use a contactor and connect it to the geyser and inverter?

Thanks,

Most of our house is permanently run off solar energy, including the geyser. So I don't have a contactor connected to it. 

A contactor, is basically a relay, so it can switch the geyser off (if connected to the dry contacts) when you run off batteries and it gets a bit low. Use a double pole contactor to switch both Live and Neutral. For safety, wire it to the NO poles. 

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