question

Mohamed Mamdouh Elkadragy avatar image
Mohamed Mamdouh Elkadragy asked

ACout 2 programming for Deferrable Load (water heater) control.

We are trying to get the ACout 2 relay work as a deferrable Load controller, the issue we are facing is that we need the following condition to happen in AND not OR logic to activate our water-heater so we can make sure that we are

1- Not affecting the batteries absorption cycle by sucking current from it during Absorbution, which will be the case if we use ONLY a voltage set point.

2- Create a very narrow operation window for the deveriable load to work in

Is there any possibility to make a programmable relay logic conditions in AND not OR?

Relay
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4 Answers
Mark avatar image
Mark answered ·

The short answer is NO.

Also;

- Remember that all conditions require an activation assistant and a deactivation assistant.

- Be careful with using load as an activation/deactivation condition because as soon as the dump load is activated the condition will probably be violated, although you may be able to get it to work with hysteresis.

But there are 2 'work-around's' that you could consider / try;

1- If you can reduce your activation conditions to only a few, then you could possibly setup a separate assistant to trigger a separate programmable relay for each condition - then physically wire each programmable relay together in SERIES to an AUX input.

Then use the AUX input state to control AC2 Out - all relays will need to be closed (AND condition) in order for the AUX input to activate AC2 Out.

2- Try to setup all conditions OPPOSITE and use it to trigger a programmable relay - then physically wire the programmable relay to an AUX input.

Then use the AUX input state to control AC2 Out - but trigger AC2 Out ON if the AUX input is open circuit (rather than closed circuit).

Because if ON is an OR condition, then OFF is inherently an AND condition.

As a simplified example - if you 'ACTUALLY' want AC2 Out ON when A) voltage is >54V AND B) SOC is >99% AND C) Power is <2000W, then you actually program the OPPOSITE logic, so ON when A) voltage is <54V OR B) SOC is <99% OR C) Power is >2000W.

Then you will have the correct AND / OR logic, but you just have the INVERT the final output from OFF to ON / ON to OFF.

You could also possibly do this using the same general reversed logic, but with an external relay that has both NO & NC contacts.

Also I have not properly tried this myself, so you will need to experiment yourself to see exactly what will work and the best way to do it.

Start simple and then add more!

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Thanks, Marc for the clarification, however, it is a bit complicated for implementation and its robustness is not guaranteed from my point of view. I wish there would be an option to select AND or OR conditions in the logic in the future from Victron, which would solve the problem easily.

We have found an easier solution which I will post as an answer, would be happy to see if you have comments on it.

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Mark avatar image Mark ♦♦ Mohamed Mamdouh Elkadragy ·

I was already thinking of possibly using the generator start/stop assistant if it contains all the conditions you want- sorry i should have probably said that.

But from memory I couldn't remember that you can make it control AC2 Out directly or inverse the operation directly.

I agree that it's better/cleaner if you can do it without any wires.

The key is to just setup everything in reverse and then just invert the final output.

With your 2nd programmable relay assistant, I don't think that you have anything to reset the low battery alarm condition or the AC1 available condition, so you probably need to add another assistant for this (or I think it may become 'stuck' if it's ever triggered).

Also, ON conditions should always have priority over OFF conditions, so I don't think that the 2nd programmable relay will actually work as you expect (depending on the generator start / stop assistant).

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Thanks, Mark, I have provided a detailed answer on the solution post.

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Dear Mark,

From your answer I see that regarding the assistants I need to take into account that:

1. ON rules have priority over OFF rules.

2. ON assistants with multiple variables are based on OR conditions

3. Off assistants with multiple variable are based on AND conditions

Is that correct?

How should I then solve the following setup?

-where I want in the evening to turn OFF AC out2 (warmwater etc) when there is no grid, sun is down (not charging) and SOC <75%.

-Then in the morning turn AC out2 ON again when it is charging again for 900 seconds and SOC >40%

This is what I not have, but I noticed yesterday that it did not turn off AC out2 in the evening when SOC dropped below 75%. (and then it was not charging for more than an hour)

summary-assistants-small.jpg

How should I reverse the rules to have it work like I decribed it?

To be complete I have added also the other rules, in case there might be any conflicts.

Thank you for any tips.

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Matthias Lange - DE avatar image
Matthias Lange - DE answered ·

The heater is an AC-load right? So if AC IN ist available it should not interrupt the charging because the AC IN gets passthrough to AC OUT. What can happen is the Multi(?) will reduce the charging current to not extend the AC input limit.

You use to many conditions try to reduce it to a minimum.

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I believe with the solution proposed, all the too many conditions which are posted in the question are fulfilled and even we did test it as mentioned in the field, and it does work as needed so far.

Note: The reason behind the multi-conditions is mainly ensuring the battery storage maximum lifetime while maximizing the system techno-economic effectiveness by best utilization of the excess energy system can produce in SOME of the yearly days.


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Mohamed Mamdouh Elkadragy avatar image
Mohamed Mamdouh Elkadragy answered ·

Update: We have put together and tested this way to overcome this logic challenge. Which did work at last for our logic operating window, but it needed to go around the direct way using multi-assistance for creating this operation window for the water heater deferrable Load control

  • System setup
    • Offgrid for household (location Canada)
    • Using a hybrid battery system lead-acid + li-ion and
    • 48V DC Coupling
    • Deveriable load is water heater element (AC 120V)
    • SOC measurement using BMV 702
    • CCgx installed
    • Inverter Quattro 5000 120V

How it works

  • The Generator start-stop assistant + the ACout 2 programmable relay are used.
  • Generator start-stop assistant used to control ACout 2 (it has a higher logic order than the ACout 2 programmable relay)
    • Open relay to start generator: This reverse the logic of hour the relay operates ( to understand it simply replace any words says [START with STOP] and [STOP with START]
    • Conditions
      • Deveriable load will stop is load higher than 2000 W
      • and Deveriable load will start if load lower than 1000 W for 20 sec
      • Stop if DC voltage lower than 54:00 V for 20 sec
      • Stop if SOC lower than 100%
      • if the load turned off due to a lower voltage than 54:00 V for 20 sec, it will never be on again until the voltage goes to 56.7 for 3600 Sec (1hour) >> this way we ensure the best lifetime of the lead-acid batteries.
      • If the load is turned off, it will BE ABLE to come on again only after 900m of waiting time (which we need basing on our system structure for Hybrid battery behaviour)
  • The ACout 2 programmable relay
    • The function is to ensure that the load is turned off if the Genset is running and there is an ACinput on ACin1 for 60 sec
    • OR if there is a low-battery-pre-alarm for 10 sec
  • Final note: Make sure you use your own values and time waitings based on your system topology.

This solution we have tested for our off-grid system, and it does work as needed. We will keep monitoring it and update the solution if needed. If you have any comments/ remakes let us know, please.

@Victron energy: It would be appreciated if the logic programming can be updated in the next firmware versions to be more straight-forward allowing the user to select between AND / OR conditions and create customized programmable relay conditions.



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@Mark thanks for your comment on the previous answer, I want to grab your attention to the solution posted here as you mentioned it is much straight forward one.


Regarding your concern:

About the 2nd programmable relay, it actually does work very well based on field tests, and it never got STUCK in ON or OFF conditions.


It works as following: when Genset is available on ACin1 for min 60 sec, the deferrable load (water heater elements) turned off, and then the priority of the Genset start/stop assistance come in place with any condition of the programmed once to bring it on again.

So We do believe that we have created a solution for that, but it would be much better to have from Victron a more transparent programmable relay which advanced user can customize according to the application needs.

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@Guy Stewart (Victron Community Manager) I have seen some comments from your side regarding the same issue which supported the formulation of that solution.

If you have any comments from your side would be appreciated as well.

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kaffeetasse avatar image
kaffeetasse answered ·

Are there any news on this topic?
Will it be possible to set "AND" conditions in the future? I have the same problem as I want to connect my EV Charger to a programmable relay, but if the SOC is high enough, I also want to make sure that the AC loads are below a certain value, in order not to overload the inverter and have it immediately turn the Charger off again. Of course I don't want to turn it on every time my loads are below a certain value if there is no production. Also, time requirements are missing.


Initially I was planning on using the Generator Assistant in inverted logic, just as suggested above, was pleased to find out that there was a more flexible option with the programmable relay Assistant and assumed all the conditions added into the Assistant are connected in AND logic, since you can create OR logic by adding another instance of the Assistant anyways. Well, seems like I have to go back to the Generator Assistant, which provides more functionality in that instance, and also the option to add time requirements.

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