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ACREL 10R meter confusion

ScottishBadger

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Nov 19, 2022
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Hi folks, after some info on the display LED's on the front of an Acrel 10R meter.
I am not convinced the CT clamp has been fitted the right way round, as I have found conflicting info on the internet - some say arrow to grid, another website specifically says arrow to grid if used as a PV meter, arrow away from grid if used as a grid meter. I can't find any clear info on any ACREL literature....
What does the "-" LED indicate, the chinese instructions with the meter are not clear, can anyone tell me if the "-" is indicating power to grid or power coming in from the grid, as again I am finding conflicting info.....!

Here's the issue I'm presently trying to resolve. I've other issues as well, but I'll concentrate on this one for the time being, please refer to the attached schematic.

I've been having problems with a Solis RAI charger & Fox-ESS LV5200 battery combination since installed. The installer is useless, to say the least.....
The RAI is programmed - correctly - to charge the battery from grid power between 00:31 and 04:29, which it does. But, roughly 5 minutes later at around 04:35, it then starts to charge once more even though nothing is set to charge. At this point, it draws power from my other storage system (Puredrive Purestore II AC) which has also been charging from the grid at the same times, continuing to draw power from the Purestore until the Fox battery is fully charged. There is no interconnection or communication between the two systems (RAI and Puredrive).

The Purestore is installed within the house close to the domestic power consumer unit and works correctly with no issues and has done since installation over 18 months ago. We have two solar inverters in parallel, each with their own panel arrays, these are located in a workshop some 30metres from the house. The RAI unit and Fox-ESS battery are also in the workshop, the PV CT Clamp for the RAI being fitted around the combined output from the two circuit breakers for the two inverters (see schematic). The RAI mains grid connection is to the consumer unit (breaker panel) within the workshop, from where it can feed back to the house. The Acrel meter is on the incoming grid power feed into the house and connected to the RAI unit via a 30meter Cat-5 cable. The solar PV clamp is correctly fitted and there is no solar at that time of the morning to "trigger" the RAI into charging, so I do not understand why it starts charging again outwith its programmed times?

My limited knowledge suggests the RAI should only charge the batteries under the following conditions:-
a. When programmed to charge from grid,
b. When house demands are met and surplus solar is available (PV CT indicating power coming from solar, Grid CT indicating output to grid)

This leads me to think there could be an issue with the signal from the Acrel meter.......
 

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With AC current I don't see how the CT can be directional. It would know how much but not know if you are drawing from the utility or not.
 
I'm not an electrical engineer, but I can assure you these current clamps are used worldwide on solar systems and do indeed give directional readings. I don't know how, but they do. I'm sure someone with far superior knowledge to myself will explain.....
 
DC is simple. Voltage stays positive, current is negative or positive.

AC is harder because the voltage an current reverse 100 or 120 time a second.

So what the inverter and CT does is to use the Voltage direction as a reference. When Voltage and Current are both positive or both negative you are drawing from the supply. When Voltage is positive and Current is negative (and the other way around), you are supplying to the grid.
That is simplifying things a lot, but it's the basic idea.
 
400bird, thanks for that. Yes, that was what I reckoned from that same Chinese manual, but then I read a post from UMSKI on this thread here -
in which it is suggested that a negative on the ACREL display is an import of power not an export, which has left me confused.
Plus, there's this:-
 

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That depends on which way you view positive vs negative.
It's somewhat arbitrary. Is power flowing into the house negative? Or is power flow from house to grid negative?
You'd need to check the inverter manual to see which way they have interpreted it, as the inverter is what need to know current direction.
 
And therein lies the issue. The inverter only displays the info received from the ACREL meter, so if the CT clamp on the grid line is the wrong way round, the inverter will display the wrong way round - and think power is flowing the opposite way to what it actually is.....
 
400bird, you got me thinking!
So, I've just done some more investigating.
With the Puredrive (Victron) software confirming an import into the house from the grid of 710 Watts, I connected the Solis (ACREL) ct clamp as-per the instructions a few posts up, i.e. arrow away from grid. I then went up to the workshop, turned the Solis RAI charger back on and waited for it to boot... As soon as it booted up, it went straight to charge, thinking the value was an export not an import! I swapped the ct clamp back round (arrow towards grid) and the Solis stopped charging, so I guess that kind-of proves three things...
1, the arrow does indeed point to the grid, and
2, Accrel meter shows an import of power from the grid as a negative and an export as a positive!
3, Solis RAI is operating correctly in so much as it is seeing an export as available power to use for battery charging.

I still haven't found the cause of the original problem, the Solis continuing to charge the Fox battery after the charge time has ended.

I've turned the Solis back off for the time being, I'm gathering data on total power consumed from the grid at present to try and prove whether the second system (Solis and Fox) is actually saving me anything in terms of energy costs - I'm having my doubts!
 
400bird, thanks for that. Yes, that was what I reckoned from that same Chinese manual, but then I read a post from UMSKI on this thread here -
in which it is suggested that a negative on the ACREL display is an import of power not an export, which has left me confused.
Plus, there's this:-
Um, I didn't know which way around the Acrel showed positive or negative - I hadn't really deep dived into the Acrel display but it's useful to know that it correlates it seems and that the - indicator means a nett import - the Solis UI displays negative when charging and positive when discharging which would seem counter intuitive to me but then again I guess it's the point of reference e.g. taking from the grid or adding to it?!

I suspect what it happening to you is that once your Solis stops charging, it then 'sees' a nett export from the Fox unit powering the house which may be set up to err on the side of caution and export a tiny amount (or it's not that accurate) - the Solis has the PV CT but I'm not convinced this is accurate or effective as I know of other installs mentioned here that have multiple PV systems and don't use the PV CT so the Solis just looks for export. This problem then becomes a runaway as the Fox sees demand (the Solis wanting to charge) and happily supplies what it wants and as the Acrel see 'zero' going out or in, the Solis will just suck the power out of the Fox instead. I had a similar situation with my DHW diverter which was causing the Solis to discharge my batteries, however it's a DIY system so I was able to add in a fudge condition where the diversion is killed if there is any discharge of the battery - it's taken a bit of tweaking to account for different situations but I got there eventually!
 
Umski, I'm thinking that I need an "offset" on the figure being sent from the Acrel meter to the Solis charger, so it operates at a different "grid set-point" to the Puredrive AC system in the house. I've created a seperate post on this, but can't get any info. If the Solis was looking to achieve a steady-state of, say, 100W import at the grid meter, that would allow the Puredrive system to operate normally and discharge to feed the house loads without the FOX battery (Solis charger) pinching power from the Puredrive battery?
 
Umski, I'm thinking that I need an "offset" on the figure being sent from the Acrel meter to the Solis charger, so it operates at a different "grid set-point" to the Puredrive AC system in the house. I've created a seperate post on this, but can't get any info. If the Solis was looking to achieve a steady-state of, say, 100W import at the grid meter, that would allow the Puredrive system to operate normally and discharge to feed the house loads without the FOX battery (Solis charger) pinching power from the Puredrive battery?
Just posted in your other thread - I think it would solve it but I don't think the Acrel or Solis will allow it, if the Puredrive allows for a small import offset then the Solis could take up the remainder and work in parallel, though there is a small danger that the opposite then happens...
 
Yes, I can do it with the Puredrive quite easily, but I was hoping to leave it at zero offset as the "primary" system. The problem with the ACREL/Solis combination is the sheer lack of info other than the basic poor translation documents available online. There are a LOT of functions that the Solis manual simply says "engineer only" and doesn't actually tell you what they do...... I'm wishing I hadn't bought this Solis system, wishing I'd gone for a Victron unit instead as at least I know it's controllable, as that's what's inside the Puredrive! All this hassle because Puredrive can't/won't make their AC coupled system expandable......!
 
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