Staying safe

[SquirrellCook]

Here we go as I prepare myself for being crucified!
Someone is lying! Either the chap in the video or the person responsible for the specs.
He says that the inverter gets it's reference timing from the incoming supply. Spec sheet says supply can be horrible but the output will be clean.
It's simple to have a pickup coil driving an amplifier to act as an oscillator to manage some power transistors. Wave form in matches wave form out.
If the output is clean it must have a timing device.
Just imagine a manky old generator with a well worn governor, rpm going up and down. Input voltage doing the same and the multiplus copying it!
Also with no RCD's if the supply is reversed the Multiplus's supply would be reversed too?
But remember it has a neutral grounding relay. It would never be allowed to ground live? Or would neutral be 0 volts and live be -240 volts? Is that possible?
Does the Multiplus complain if the supply is reversed. But then if you have a RCD in front of it that should trip?
The power assist is the puzzle. Unless it rectifies the external mains and then chops it up. Then puts it back together as clean Mains. Easy to do.
That is until you remember that the bigger units can be grid tied for in-feeding. So then you'd have to be able to match the supply.

Circuit diagram required

 

[wildebus]

Well, The chap in the video is, I think, the chap who owns the company, so likely to be the authority.

The way I understand if, if you have EHU in (mains, generator, whatever) it will match that in voltage and waveform - and it has to do that in order to keep in sync. for power ASSISTANCE, the AC is the controlling medium so must be replicated.
so manky mains in - yes, manky mains out I think (the VE Config program lets you specify just what degree of mankiness is permitted before it throws its hands up in disgust).

In Inverter mode, the unit creates the voltage level (and you specify that in the VE Config program) and it creates the Frequency (which again you specify) and Sine Waveform - and THIS, in inverter mode, is meant to be as good or cleaner than the grid sinewave.

I don't believe the Multiplus is designed to be a tool to clean up poor quality mains.

 

[SquirrellCook]

I don't believe the Multiplus is designed to be a tool to clean up poor quality mains.

It's a shame as the box of tricks must have most of what it needs in it.
I believe there is a strong connection with Fronius. I've been using their welding kit for the past 20 years and they are masters of power manipulation. Stupidly expensive though.

 

[wildebus]

Got all my wiring back together (and of course, made some further tweaks!) and was able to do some Multiplus Testing with Reverse Polarity....

(I can switch polarity and also turn the supply to the MP off very easily - see photo below)

My Tester has, like others, a light combo that tells me I have a good Earth, Live and Neutral ("Correct"), and another that tells me that Live and Neutral are swapped ("L&N Rev").

• EHU in; EHU-only Socket shows "Correct"; Flicked switch to reverse Polarity, Socket shows "L&N Rev" - so all good so far
• Breaker on to provide power to MP, set to "on"; Socket from MP shows same as above - "Correct", then "L&N Rev" when I Reverse Polarity.
• Multiplus set to 'Inverter only' - Tester shows "Correct" regardless of EHU Polarity - just as you would expect as it doesn't care about mains in that mode (mains in is actually disconnected internally)

So pretty much all as expected ... Inverter in standalone mode, the L&N are correct; with EHU input active it follows the EHU.

I did one other test which I think is interesting ...
I put the Multiplus into the nomal 'On' mode and flicked the input MCB on, then off, then on.
With the Incoming polarity right, the tester showed "Correct" at all times and there didn't seem to be any switchover pause between EHU to Inverter and back to EHU (so UPS-style operation though I didn't check this with any device)
I did the same thing, but this time with the input EHU polarity swapped. This time the Tester switched from "L&N Rev" to "Correct" as soon as the EHU input to the MP went when I tripped the Breaker, and then back to "L&N Rev" as soon as I put the Breaker back on.
So again as you would expect in fact, but again the Multiplus didn't seem to have any gaps in providing power despite the need to switch L&N over each time.
Pretty Good

 

[SquirrellCook]

So are you saying that the multiplus followed the polarity of the EHU without any problems?

The mulitplus disconnects it's ground relay on sensing external mains. This makes sense, or the casing could/would go live.
When in inverter mode the ground relay closes combining neutral and ground.

I've been trying to find some sense on RCD's. It seems the common view is that they still work with reversed supply. Current may still flow, but I don't think it offers any protection.

Anita want's me to make a test board to explore the behaviour of RCD's. I do hope I don't find it shocking! Or suffer a flash of inspiration.

 

[wildebus]

So are you saying that the multiplus followed the polarity of the EHU without any problems?

The mulitplus disconnects it's ground relay on sensing external mains. This makes sense, or the casing could/would go live.
When in inverter mode the ground relay closes combining neutral and ground.

I've been trying to find some sense on RCD's. It seems the common view is that they still work with reversed supply. Current may still flow, but I don't think it offers any protection.

Anita want's me to make a test board to explore the behaviour of RCD's. I do hope I don't find it shocking! Or suffer a flash of inspiration.

Doing a "real world" test of an RCD can be scary. Only done that once and dont really want to repeat!

Yes, that ground relay option is a check option in the VE Config when setting up the Multiplus. Default is checked and I see no reason to remove that!

Ref "So are you saying that the multiplus followed the polarity of the EHU without any problems?" ...

Part 1 - In the words of the song 'Yes, we have no correction, we have no correction in mains'.
Part 2 - Well, it depends what you mean without problems? I don't think it ADDs to any problems that the Reversed Polarity gives, but I think there is a little quirk which it is important to know about (going to go out shortly and check if what I think happened does actually happen before revealing more).

 

[wildebus]

OK.
Done the test and the quirk I was thinking of does not seem to be there in fact.

Yesterday I wanted to check what happens when the Power Assist (where there is more demand than the EHU can provide) comes on. So I set the current limit low and put the hob on - but it seemed the Current limit was ignored? but a few minutes later it came into play. I was curious to know if the current limit worked by detecting using the Live and Earth say (be weird if it did I think?) and if the polarity was reversed it wasn't able to apply the limit as it couldn't detect it?
Or could it be that in Passthru mode, the polarity just carries on, but the inverter cannot actually provide power in a reversed L&N way, so Power Assist won't work when the input is wrong?
I was changing around so many things out of curiosity that I needed to repeat the test in a more controlled way today to confirm or otherwise....

With the polarity correct, I put the Multiplus into a 4A EHU limit (so no more than around 960W) and put the kettle on (Induction hob with a nominal 2000W output).

As you can see, the AC Load 1762W and the Hookup is providing some power, the battery is providing some power (and the Solar is doing a bit as well in fact).

I then repeated the test ... Removed power to MP, reversed Polarity and then reset the MCB so the MP had mains power again.
The Tester shows the "L&N Rev" condition as expected. Then put the kettle on again .... The Power Assist came on again with the identical Grid value of 856W.
So Power Assist is NOT dependant on correct L &N Polarity. I also kept an eye on the Tester and the condition remained as "L&N Rev" with or without Power Assist.
Then I removed EHU power whilst the hob was on and after a couple of seconds there was a loud click from the MP (internal Mains Relay opening I think after removal of power) and the Tester switched from "L&N Rev" to "Correct" without any apparent loss of output (the hob stayed on at the same setting afterwards).

All in all, behaving in a perfect manner I would say


Finally, I thought I would end with an RCD Test
So I took my shoes and socks off, stood in a bucket of water, licked the socket and ... Well, as it was a bit cold, so decided to use the "RCD Test" button on the tester instead
Worked as it should, tripping the RCD on the MP Output
I didn't try it with the EHU live as I didn't want to risk ending up tripping the house RCD instead of either of the two In-Van RCDs (the problem with multiple RCDs in series), and because the MP always has the polarity correct when there is no EHU, it didn't check the RCD operation in a reversed polarity condition.


I do recall around 25 years ago I just moved into a new flat and the RCD kept tripping when I was using one socket. Can't recall the exact details, but the problem was with an extension lead that had the L & N reversed and whenever I plugged in something (can't remember what), the RCD-type device tripped, but when I plugged in somewhere else in the flat, no problem, so without knowing any real details (was back in 1995 after all!), the RCDs, at least of that time, didn't like reversal (I think the designs - and names - of these things keep changing. I used to carry a ELCB in my toolkit around that time for example)

 

[SquirrellCook]

Finally, I thought I would end with an RCD Test
So I took my shoes and socks off, stood in a bucket of water, licked the socket and ..

Please children don't try this at home

 

[SquirrellCook]

At a previous works building I was being electrocuted on a regular basis.
The house on the site was powered from the same meter as me.
The house was not earthed nor was my building.
The house electric cooker developed a fault and made the earth live.
Hence me getting jolts.
When I showed them they had full mains voltage between the sink and the cooker it made them angry.
They were more concerned about the cost of the cooker.
No RCD's tripped!

 

[SquirrellCook]

Thank you so much for your efforts Dave, I'm sure you had better things to do than explore my silly questions.

 

[wildebus]

Thank you so much for your efforts Dave, I'm sure you had better things to do than explore my silly questions.

All useful stuff The more you know about your systems, the better you can exploit them in a SAFE way

I'll be checking the RCD operation on a reversed L&N hookup the next time I plug in the Generator

 

[wildebus]

Well, decided (unintentionally!) to test RCD in my Shed.

RCD in Shed CU tripped. RCD in House CU also Tripped.
Not much point in having Shed RCD really.

 

[SquirrellCook]

Just remember electricity travels a little slower than the speed of light. So the closer you are to the rcd, the quicker you’re disconnected.

 

[makaveli7]

Hi @wildebus

I hope you are alright . I am not sure if you remember but you kindly helped answer my question regarding your water heater setup last year. so thank you once again.

Since this topic is about the Multiplus wiring I hope you wont mind sheding some light and again please excuse my thread hijacking style

School holidays are here, ease of lockdown so the Misus is giving me a hard time to go away somewhere.

I have recently aquired a Multiplus 12/3000 to replace my existing modified wave inverter, I have been reading all day but I cannot get my head around it yet. (RCD and MCB types and where they should be placed before or after). I want to do it correctly. do you have any schematic I can follow? I was hoping to follow greg virgoes control box video but with the Multiplus I think I have to go a different route, (Still haven't finished Victron wiring unlimited). with regards to reverse polarity I have a tester lying around so I will always test before connecting to shore and have a reversed lead to fix the polarity issue. Space is at premuim in the control box . lol.

- I have few RCDs (type AC) and MCB (type B) lying around so I was hoping to use them however in the victron forum some advised to use RCD (type A) as it can handle pulsating DC. what do you advise?

Time is runing out and I would like to set off monday or tuesday. I would like to take the multiplus and this new blender to enjoy smoothies and soups on the road

I have this crazy idea to just buy an extention lead( picture attached) with built in RCD and hard wire it to the multiplus. What do you think? even just as a temp solution to save on the time until I am ready to build a proper consumer unit. I dont see my self having more than 3 sockets (220v fridge, heater, and a socket). I am not planning to connect to shore just yet. just to use the multiplus as inverter.

 

[Squiffy]

This has all been very interesting, but it has always been my understanding that the test button on an Rcd will only work if mains is supplied to it without the mains supply the trip coil inside the Rcd will not generate any current that will cause the trip mechanism to function, when mains are applied and the test button is depressed it basically shorts the live feed to neutral and earth the trip coil then builds up current which then trips the extra mechanical spring mechanism and so shuts off the power supply. It's my understanding then that if regardless of where your power supply is coming from to the Rcd switch if live and the button actuates when pressed you and your van are protected regardless of whether the van is earthed or not. So that is my view on investigating years ago as to how exactly an Rcd works.After all is said and done all the test button is doing is replicating a fault within the van So in a nutshell if your button trip's the unit your 97% safe as that is the recommended percentage of units that will work correctly when a fault develops. Phil

There might of course be an argument that a generator would not have a return earth but my test button still cuts of the power with my generator running so there must be an imbalance even with a generator ( Wether my Honda has some sort of leak cct incorporated I don't know, all I do know is when test is activated the power shuts down)

 

[wildebus]

Hi @wildebus

I hope you are alright . I am not sure if you remember but you kindly helped answer my question regarding your water heater setup last year. so thank you once again.

Since this topic is about the Multiplus wiring I hope you wont mind sheding some light and again please excuse my thread hijacking style

School holidays are here, ease of lockdown so the Misus is giving me a hard time to go away somewhere.

I have recently aquired a Multiplus 12/3000 to replace my existing modified wave inverter, I have been reading all day but I cannot get my head around it yet. (RCD and MCB types and where they should be placed before or after). I want to do it correctly. do you have any schematic I can follow? I was hoping to follow greg virgoes control box video but with the Multiplus I think I have to go a different route, (Still haven't finished Victron wiring unlimited). with regards to reverse polarity I have a tester lying around so I will always test before connecting to shore and have a reversed lead to fix the polarity issue. Space is at premuim in the control box . lol.

- I have few RCDs (type AC) and MCB (type B) lying around so I was hoping to use them however in the victron forum some advised to use RCD (type A) as it can handle pulsating DC. what do you advise?

Time is runing out and I would like to set off monday or tuesday. I would like to take the multiplus and this new blender to enjoy smoothies and soups on the road

I have this crazy idea to just buy an extention lead( picture attached) with built in RCD and hard wire it to the multiplus. What do you think? even just as a temp solution to save on the time until I am ready to build a proper consumer unit. I dont see my self having more than 3 sockets (220v fridge, heater, and a socket). I am not planning to connect to shore just yet. just to use the multiplus as inverter.

We are talking 240V AC now and that can be dangerous stuff so I am going to caveat this reply with the statement "The following is not advice, but opinion" and you need to make your own decision on how to procede.

You said "I have recently aquired a Multiplus 12/3000 to replace my existing modified wave inverter, I have been reading all day but I cannot get my head around it yet. (RCD and MCB types and where they should be placed before or after). I want to do it correctly. do you have any schematic I can follow?"

I think a good starting point might actually be to look at how the Victron EasyPlus Inverter/Charger is setup. I say this as the EasyPlus is a Multiplus with an integral Consumer Unit pre-wired, and it is a reasonable assumption to make that Victron would wire the breakers in a way they would generally recommend for a Multiplus.
The way the EasyPlus is setup is that the AC output goes to an RCD, and then that RCD goes to the various MCBs for the circuits.
The Easyplus uses a standard Dual-Pole MCB for the input where you might think an RCD would be better - I can think of pros and cons for both, but I'd likely follow the Victron example on the basis they have the science and R&D facilities behind their decision.


You said "I was hoping to follow greg virgoes control box video"

It might depend on which iteration of Gregs setup you looked at? I know he changed the setup a couple of times (which got confusing for some folk emulating him as they found their setup was suddenly 'flawed'. I remember speaking to a chap at a show a couple of years ago in just this situation). I loved Gregs work and attention to detail when it came to his van building generally but TBH I was not a great fan of his electrics setup in a few ways


You said "I have few RCDs (type AC) and MCB (type B) lying around so I was hoping to use them however in the victron forum some advised to use RCD (type A) as it can handle pulsating DC. what do you advise?"

Not sure why you would want/need an RCD on a AC circuit that can handle 'pulsating DC'?
As far as I am aware the different types of MCB - A, B, C (or D) - are basically the same except for the way they deal with the amount and duration of over-current.
This is a good summary of the differences between the different types - https://mechatrofice.com/electrical/difference-between-class-b-c-d-type-mcb - and the kind of devices and installations likely to be used for each.
Generally you see B and C Breakers I think. Don't know if I have ever seen a Type A and from the summary of the link above I don't think you would want to use one in a typical environment? Going back to the comment about the EasyPlus, all the breakers pre-fitted in that by Victron are Type C. Type B is what you see in the usual house installation.


You said "I have this crazy idea to just buy an extention lead( picture attached) with built in RCD and hard wire it to the multiplus. What do you think?"

Can't see any reason why it wouldn't work and certainly would get you out the hole of having something in place and fairly safe in the next day of so.


You said "I dont see my self having more than 3 sockets (220v fridge, heater, and a socket). I am not planning to connect to shore just yet. just to use the multiplus as inverter."

If you mean Water Heater, then fine. If you mean Room/Space Heater, then don't connect that upto the Inverter (AC1) outlet of the Multiplus - you cannot run electric heating off a battery bank for any length of time unless you had an incredibly large bank! The best way to wire up a socket for a Space Heater (or any other kind of EHU-only load) on a Multiplus 12/3000 is to use the AC2 outlet. This is designed* as an EHU-only outlet and so goes dead when the EHU is not connected, but why you use this instead of simply bypassing the MultiPlus is that the MultiPlus will register the amount of load this outlet is pulling and using the Power Assist feature will ensure that you are not overloading the EHU supply. If you bypass the Multiplus it will not know there is a 2KW load or whatever already on the supply and happily run up the 2kW Water Heater off the supply - and that will overlead the supply and at the least trip the breaker on the EHU supply, but could do potentially worse.

*designed as an EHU-only outlet but it is possible to load an 'assistant' to have that work off the Inverter if a setup needs that to happen. generally best to keep as a straight EHU-only for most people IMO.



HTH

 

[makaveli7]

We are talking 240V AC now and that can be dangerous stuff so I am going to caveat this reply with the statement "The following is not advice, but opinion" and you need to make your own decision on how to procede.

You said "I have recently aquired a Multiplus 12/3000 to replace my existing modified wave inverter, I have been reading all day but I cannot get my head around it yet. (RCD and MCB types and where they should be placed before or after). I want to do it correctly. do you have any schematic I can follow?"

I think a good starting point might actually be to look at how the Victron EasyPlus Inverter/Charger is setup. I say this as the EasyPlus is a Multiplus with an integral Consumer Unit pre-wired, and it is a reasonable assumption to make that Victron would wire the breakers in a way they would generally recommend for a Multiplus.
The way the EasyPlus is setup is that the AC output goes to an RCD, and then that RCD goes to the various MCBs for the circuits.
The Easyplus uses a standard Dual-Pole MCB for the input where you might think an RCD would be better - I can think of pros and cons for both, but I'd likely follow the Victron example on the basis they have the science and R&D facilities behind their decision.


You said "I was hoping to follow greg virgoes control box video"

It might depend on which iteration of Gregs setup you looked at? I know he changed the setup a couple of times (which got confusing for some folk emulating him as they found their setup was suddenly 'flawed'. I remember speaking to a chap at a show a couple of years ago in just this situation). I loved Gregs work and attention to detail when it came to his van building generally but TBH I was not a great fan of his electrics setup in a few ways


You said "I have few RCDs (type AC) and MCB (type B) lying around so I was hoping to use them however in the victron forum some advised to use RCD (type A) as it can handle pulsating DC. what do you advise?"

Not sure why you would want/need an RCD on a AC circuit that can handle 'pulsating DC'?
As far as I am aware the different types of MCB - A, B, C (or D) - are basically the same except for the way they deal with the amount and duration of over-current.
This is a good summary of the differences between the different types - https://mechatrofice.com/electrical/difference-between-class-b-c-d-type-mcb - and the kind of devices and installations likely to be used for each.
Generally you see B and C Breakers I think. Don't know if I have ever seen a Type A and from the summary of the link above I don't think you would want to use one in a typical environment? Going back to the comment about the EasyPlus, all the breakers pre-fitted in that by Victron are Type C. Type B is what you see in the usual house installation.


You said "I have this crazy idea to just buy an extention lead( picture attached) with built in RCD and hard wire it to the multiplus. What do you think?"

Can't see any reason why it wouldn't work and certainly would get you out the hole of having something in place and fairly safe in the next day of so.


You said "I dont see my self having more than 3 sockets (220v fridge, heater, and a socket). I am not planning to connect to shore just yet. just to use the multiplus as inverter."

If you mean Water Heater, then fine. If you mean Room/Space Heater, then don't connect that upto the Inverter (AC1) outlet of the Multiplus - you cannot run electric heating off a battery bank for any length of time unless you had an incredibly large bank! The best way to wire up a socket for a Space Heater (or any other kind of EHU-only load) on a Multiplus 12/3000 is to use the AC2 outlet. This is designed* as an EHU-only outlet and so goes dead when the EHU is not connected, but why you use this instead of simply bypassing the MultiPlus is that the MultiPlus will register the amount of load this outlet is pulling and using the Power Assist feature will ensure that you are not overloading the EHU supply. If you bypass the Multiplus it will not know there is a 2KW load or whatever already on the supply and happily run up the 2kW Water Heater off the supply - and that will overlead the supply and at the least trip the breaker on the EHU supply, but could do potentially worse.

*designed as an EHU-only outlet but it is possible to load an 'assistant' to have that work off the Inverter if a setup needs that to happen. generally best to keep as a straight EHU-only for most people IMO.



HTH

Hi @ wildebus. Thanks for the reply. I have been fiddling away trying to fit the multiplus in a rather tight spot. somehow it slpit trough my hand and I broke one of the LED bulbs. (gutted, really, but I think I should be alright as I wont be looking at the LED and will have it hooked to the PI running venus

- It is a good hint to follow the Easyplus wiring.

- Creg video: you are right his videos were handy. I am aware that he changed his electric set up and even took out some of the 240v stuff. I met him once in a campervan meetup. He is nice chap had a look at my van when I was still building it ( well the build will never end really, it is a fact .. lol). I also agree that some is his electric is not 100%. e.g. his battery parralel wiring is not balanced not balanced. but then again one can never really acheive 100% balanced draw unless lab conditions, all factors play into this, cable, crimp quality even batteries...

- Types of RCDs and MCBs: the one I have and the one common on household is type AC RCD, type B, A is the newer model and can handle pulasting DC as new electronic devices, LED TVs another chargers use DC and can trough some DC current back on the AC circuit, this current apparently affect the function of Type AC RCD and it wont trip if there is a fault, that is why all new instalation now have type A or B(more expensive) RCD. I am just reading about AFDD which might be a better route as it combine, mcb, rcd and can handle arc detection. MCBs come in B,C,D,K,Z there is no A type it was left out to not confuse it with AMPS (See I am doing a lot of reading... lol)

- I still remember your water heater setup it was a rather a breaktrough at the time with a timer and all. I since bought an EU version of the ariston 1200W, much easier on my old inverter then and it can hold hot water for hours. Never I had time to fit a time like yours. but now I have gone a diffirent route relying on the victron open source and software. I can turn on and off the multiplus using set of script and in the end I will acheive your same results. I can take reading of the water tempreature using a wireless thermostat and chose to turn the heater if condition are met (e.g. engine is runing, battery SOC, MPPT state... it is endless what you can do) but this is something I can elaborate more on another topic. once I have everything up and running

What are your plans are you travelling anywhere?

 

[wildebus]

A 1200W water heater would be preferable I think so that is good. I doubt I would have bothered with an on/off timer with a lower power heater - the idea of that was to not give the batteries so much of a continuous high hit of >200A

I have a new Motorhomer now so different setup - water heater is 800W and I have the supply to that controlled by a relay on the Cerbo GX so it will only come on when the battery SOC is greater than a defined value (80% I think I chose), but I have an physical switch same as in the van with the 2000W heater which lets me override entirely the SOC control.
But it lets me also if I choose, to instead override for 60 minutes (using a electronic countdown timer) and then go back to auto-control based on the SOC (handy if I want to get hot water via the element and I know I will be getting battery charging later from EHU or the B2B.

Sounds like you will have a very nice setup. You'll have to post a write-up up. Be very interested to see it

Will be heading away for some trips but not really staying away until August (vaccines taking effect and that kind of thing).