Author Topic: Just bought a powerjack 15000, modding.  (Read 3421 times)

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Offline Fionn

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Re: Just bought a powerjack 15000, modding.
« Reply #60 on: January 12, 2017, 03:25:52 AM »
1. As has already been stated, your RCD won't work without the neutral to earth connection, you should reinstate it, ideally at your main distribution board has has been suggested.

2. Your idea of paralleling the individual 12V blocks is incorrect and contrary to the way that all commercial systems are configured and operated, for good reason.
As you have wired it, you can't check individiual cell or block voltages in isolation. You won't find out you have a bad pack until it has killed those in parallel with it and by then it could have obliterated the whole bank. You should reconfigure it to form parallel series strings ASAP.

3. The powerjack has 2 fuses on both the charger input and AC output side. They are 20mm x 5mm ones but I'm not sure of the rating. They are behind the black screw off caps.

Offline welshman

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Re: Just bought a powerjack 15000, modding.
« Reply #61 on: January 16, 2017, 03:24:29 PM »
1. As has already been stated, your RCD won't work without the neutral to earth connection, you should reinstate it, ideally at your main distribution board has has been suggested.

2. Your idea of paralleling the individual 12V blocks is incorrect and contrary to the way that all commercial systems are configured and operated, for good reason.
As you have wired it, you can't check individiual cell or block voltages in isolation. You won't find out you have a bad pack until it has killed those in parallel with it and by then it could have obliterated the whole bank. You should reconfigure it to form parallel series strings ASAP.

3. The powerjack has 2 fuses on both the charger input and AC output side. They are 20mm x 5mm ones but I'm not sure of the rating. They are behind the black screw off caps.

1) this is an isolation transformer, not only would bonding the earth to neutral make touching earth and live dangerous it would also blow up the fets as many have learned the hard way. plus the reason the rcd's wont work, is because the electrical fault condition they detect doesn't occur in the first place.

2) i know that industry practice is not to bond the batteries like this due to the fear of dead cell's, but each battery has a hydrometer and the status of the battery bank is monitored so cell death would be easily spotted. what this method does give as a bonus once that fear has been eliminated is the equalisation of all charge and discharge paths from one end of the bank to the other, improving the battery banks charecteristics.

3) I'm not sure what your mentioning of the fuses are about, i've already replaced them with din rail mcb's.

the system has been working for some time now flawlessly with 9kw+ loads and switching between charge and inverter several times a day without even switching off inverter.

this powerjack with the modifications i have made is powering a whole site flawlessly. washing machines, tumble dryers, double 3kw immersions, kettle. just like being attached to the mains. with a generator coming on and as necessary to keep the batteries from being cycled.

powerjack is an excellent product at an amazing price!

Offline frackers

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Re: Just bought a powerjack 15000, modding.
« Reply #62 on: January 16, 2017, 06:50:48 PM »
1) this is an isolation transformer, not only would bonding the earth to neutral make touching earth and live dangerous it would also blow up the fets as many have learned the hard way. plus the reason the rcd's wont work, is because the electrical fault condition they detect doesn't occur in the first place.

I can't help thinking you still "don't get it" about earth bonding.

The secondary of the transformer (i.e. the mains output) is floating and not connected to anything associated with the FETs, the battery or anything else, these are connected to the primary side of the transformer - no electrical connection between primary and secondary whatsoever (only a magnet connection to pass the power through).

For the RCD to operate it must be a part of a complete circuit and one side of that circuit is ground.

I you think a schematic would help I'll knock one up to help explain further.


Robin Down Under (or are you Up Over!)

Offline lighthunter

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Re: Just bought a powerjack 15000, modding.
« Reply #63 on: January 16, 2017, 09:55:08 PM »
This is first I have read this thread. Wow, great stuff good thinking guys!! I'm very impressed. Welshman you are one smart fellow. I like challenging ideas that have been in use and understanding thy whys rather than just accepting them as the "right way".

The bird on the wire concept is a great analogy ;D yet the raccoons and squirrels don't fare quite so well  ::) Darn grounds anyway!!

I really cant take sides on this as i see where Frackers is coming from also. I would like to take opportunity to mention one possibility that hasnt been discussed. There is another variable power supply in the sky connected to your home circuit; and you can't isolate its permanent earth ground connection. LIGHTNING, I'm only guessing but i think its the number 1 reason for our earth bonding practices. Lets face it, if direct lightning gets on the hot or neutral  conductors, many appliances will just cease to exist. I suspect an earth bonded home will have a better chance of not starting on fire in such an event. Lightning will find a path one way or another and the neutral - earth bond makes it easier and less destructive for it to do so.

My home has earth bonded to neutral and it also has a steel roof. One precious evening I was enjoying peaceful sleep when I bounced a foot straight up out of bed! I dont know but i suspect the lightning hit the roof. Ive been near lightning before but that was nothing short of an explosion!! There were two breakers tripped and no appliances hurt. Just one of many possible ways that could have turned out.

Frackers, yes our US split phase 120/240 is a nightmare on a good day and is even worse when a neutral connection has trouble which unbalances the center tap placing overvoltage on some appliances and under on others. >:(  I envy you guys with 240 consistent. I do like 60hz better though.

Great discussion, great thread!
LH

Offline mab

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Re: Just bought a powerjack 15000, modding.
« Reply #64 on: January 17, 2017, 04:02:21 PM »
have to agree with frackers on the earth bonding issue.

According to BS7671 wiring regs, if you're using a small portable generator for a single appliance then it's better to have a 'floating' output as you then need two faults to create a hazardous condition (not too likely with a single appliance) and as a portable generator is seldom grounded effectively, bonding N-E is of limited use.

If you're using a generator/inverter to supply multiple appliances - say an entire house - then the probability of two faults is very much higher and a N-E bond is the safest option.

The problem with floating output on a multiple appiance system is that the 1st fault grounds one of the live conductors (live or neutral) and you don't know about it as nothing will trip. the second fault will develop one day connecting the other 'live' conductor to earth, but as both faults are downstream of the RCD it doesn't trip.

There is another issue with floating supply besides the RCD: lets suppose a fault develops on a high current circuit; say, your 50A  mcb protected 11kw shower for e.g. - live to gnd - effectively grounding the live wire and making the neutral 230v to gnd. As this is the first fault nothing's going to trip and you remain oblivious to the fault. Then what happen if a fault develops on the 6A lighting circuit neutral to ground? As neutral is now 230v to ground (due to the 1st fault) quite a lot of current is going to flow through your 6A lighting neutral - but your 6A MCB is in the live conductor not the neutral and therefore isn't going to protect the 6A cable - you'd better hope the 50A mcb trips before your lighting cable sets your house on fire! To put some numbers to that:- as lighting circuits often have resistances of 2 ohms (cold wire - it goes up a lot as the copper heats up) that gives us a fault current of 120amps; for a 50A 'B' curve mcb to BS60898, 120A should trip it in 50-100 seconds according to the chart - assuming the wire maintains it's 'cold' resistance - I think a 1.0mm2 lighting cable will be glowing in rather less time than that.

trust me - you should have a N-E bond. :) The original reason for the N-E bond was that the fuses/single pole switches should always be in the live conductor - and that can only be true if the other conductor is grounded.

Offline welshman

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Re: Just bought a powerjack 15000, modding.
« Reply #65 on: January 20, 2017, 04:45:51 AM »
have to agree with frackers on the earth bonding issue.

According to BS7671 wiring regs, if you're using a small portable generator for a single appliance then it's better to have a 'floating' output as you then need two faults to create a hazardous condition (not too likely with a single appliance) and as a portable generator is seldom grounded effectively, bonding N-E is of limited use.

If you're using a generator/inverter to supply multiple appliances - say an entire house - then the probability of two faults is very much higher and a N-E bond is the safest option.

The problem with floating output on a multiple appiance system is that the 1st fault grounds one of the live conductors (live or neutral) and you don't know about it as nothing will trip. the second fault will develop one day connecting the other 'live' conductor to earth, but as both faults are downstream of the RCD it doesn't trip.

There is another issue with floating supply besides the RCD: lets suppose a fault develops on a high current circuit; say, your 50A  mcb protected 11kw shower for e.g. - live to gnd - effectively grounding the live wire and making the neutral 230v to gnd. As this is the first fault nothing's going to trip and you remain oblivious to the fault. Then what happen if a fault develops on the 6A lighting circuit neutral to ground? As neutral is now 230v to ground (due to the 1st fault) quite a lot of current is going to flow through your 6A lighting neutral - but your 6A MCB is in the live conductor not the neutral and therefore isn't going to protect the 6A cable - you'd better hope the 50A mcb trips before your lighting cable sets your house on fire! To put some numbers to that:- as lighting circuits often have resistances of 2 ohms (cold wire - it goes up a lot as the copper heats up) that gives us a fault current of 120amps; for a 50A 'B' curve mcb to BS60898, 120A should trip it in 50-100 seconds according to the chart - assuming the wire maintains it's 'cold' resistance - I think a 1.0mm2 lighting cable will be glowing in rather less time than that.

trust me - you should have a N-E bond. :) The original reason for the N-E bond was that the fuses/single pole switches should always be in the live conductor - and that can only be true if the other conductor is grounded.

I see, so to make this system safe I need to remove the earth altogether. No earth to sockets or consumer units, just an earth point on the inverters mainboard earth connection for filtering.

Offline Pete

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Re: Just bought a powerjack 15000, modding.
« Reply #66 on: January 21, 2017, 02:52:24 PM »
Welshman, what you are wanting to create is a floating voltage system, as mab pointed out, a floating system is reasonably safe as long as there are not many appliances connected to the circuit.
A simple example of what "mab" pointed out would be that the toaster gets an active to frame fault. No problem on a floating circuit, but then say the kettle has a bit of moisture on it and has leakage or a short from neutral to frame. Touching both of these at the same time would put you across the active and neutral.
Like the adage says, "one flash and youre ash"
To avoid problems on a floating system you would have to make sure that  all the switches were double pole. That is switching both the active and neutral.
In Australia this is a requirement for any installation that is supplied by an extension lead.
Really you may get away with the floating system, but I don't see why you want to reinvent the wheel.
What we have in Australia is a Multiple Earthed Neutral distribution system, which prevents the neutral voltage from rising above earth in the case of a fault.
It works very well and RCD's trip when a person gets connected in the wrong places. I can attest to their fantastic service, Once while working on an amplifier I turned it around to get to the bottom of the board to check voltages, accidentally touching the fuse on the amp. Zap, then nothing, the RCD tripped.
It seems to me that power supplies are set up by pretty smart people, I worked as an electrician and contractor for most of my working time and am happy to take their advice.
Pete

Offline mab

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Re: Just bought a powerjack 15000, modding.
« Reply #67 on: January 23, 2017, 05:33:59 PM »
Quote
I see, so to make this system safe I need to remove the earth altogether. No earth to sockets or consumer units, just an earth point on the inverters mainboard earth connection for filtering.

don't be daft!

Quote
I've also decided to leave neutral floating and not connected to earth. In my mind if between part of the circuit board where the powejack has  the "neutral" path and the appliance is damaged in someway where it is now an open circtui and it is bonded to earth then the current will be sent down the earth wire. If this path happens to be more conductive at the appliance to ground than all the way back to the grounding rod, there could be a situation where there is a high voltage on the negative/neutral and anyone touching an appliance metal casing in this situation could receive a shock.

Contrary to popular belief, electricity takes all paths back to its source, not just the path of least resistance.

It may well be fine bridging earth to neutral in the consumer unit/main panel on mains where it's unlike that the neutral will break to the grid. But when relying on a circuit board made in china to a questionable quality, I'm not going to take the risk of bridging earth to neutral, I'm far safer not doing so and using a RCBO with less then 30ma trip, which monitors earth leak and neutral / hot sync.

The generator in using has its own earthing rod. It also has its neutral bonded to earth. The inverter and the entire sites wiring are on a seperate earth rod to the generator.

I re-read that from your earlier post to try and get my head around your thinking, and I can't quite see what the powerjack pcb's have to do with it; In my house the PJ is just a box providing the AC supply, the N-E bond is downstream of the PJ and before the main RCD and consumer unit. If the PJ develops a fault I lose the AC but the house stays safe regardless of how the PJ fails.

The only thing I can see in your system where a n-e bond at the 'house' may be an issue is when running the generator through the PJ, because the generator has it's own n-e bond. You should only ever have one n-e bond.  In this case the loss of the neutral between the genny's n-e bond and the house n-e bond would push the house neutral (and earth) up to a hazardous potential relative to ground by pushing the neutral current through the rods -  so I'm guessing this is what you meant.

If that's the case, the better solution might be to bond the house earth and the genny earth together (I'd do that anyway) make the n-e link at the output of the PJ and remove the n-e link at the generator - although this assumes you aren't going to use the generator independently of the house. If you do want to use the generator at times when isolated from the house, you could use a changeover switch with a n-e bond on the local output at the generator, so that the generator only sees the n-e bond at the house OR the one local to the generator.

hope that makes sense.

Offline welshman

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Re: Just bought a powerjack 15000, modding.
« Reply #68 on: March 01, 2017, 08:17:34 AM »
After working flawlessly for some time , I've decided to bond the earth and the neutral at the mainboard of the PJ yesterday. Will see how it behaves, if the FETs blow etc. So far so good.

Offline Fionn

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Re: Just bought a powerjack 15000, modding.
« Reply #69 on: April 25, 2017, 05:00:19 PM »
Haven't been here in a while, just to recap on your earlier post.


The only way of getting a shock is by touching both the live and neutral at the same time.. which an RCD won't protect against anyway.
This is incorrect, in a normal neutral-earth bonded installation with RCD protection where someone touches live and neutral at the same time, current will flow to earth as well as from live to netural through the person's body.
To quote yourself, current takes every path available, not just the one of least resistance. This at least gives a chance that the RCD will protect the user assuming the fault current to earth exceeds 30mA - which is quite likely.

in a neutral earth bonded system you could touch the live and earth at the same time to get the same result so in this respect it's actually worse.
While I understand that you are saying that there is an increased number of fault scenarios, my earlier point stands and a servicable RCD will definitely trip in a live to earth fault.

Also if we removed the earth altogether from the system and isolated the inverter so it wasn't earthed either and throwing away the rcd, that would ironically be the safest option. Birds don't get electrocuted sitting on the live wire as in this situation we have an isolation transformer we shouldnt get a shock either.

The only way something could go wrong is if another appliance shorted "neutral" to the same physical ground or casing you are in contact with and also touching the live wire.
You have correctly identified the flaw in this scheme. Without monitoring, the supposedly isolated system can become referenced to earth at any time and you will be unaware until there is a fault.
Just remember that the live could just as easily be referenced to earth as the neutral. Initially this won't cause an identifiable problem. However this could lead to the casing of your inverter (or any other connected appliance) assuming a potential of -230V if there was a neutral to case fault on any appliance (which is of course isolated) potentially delivering a fatal shock to anyone that comes in contact with it.

As far as i can tell the only reason the RCBO wont trip is because youre not getting a shock.
You are correct but you now have no way of testing your RCBO in your installation so you have no idea if it will work when you need it or not.

I have a gut feeling the entire electrics industry grounds neutral for voltage stability and pretends in some far fetched situation it provides safety.
I'm sure you're joking and can appreciate that international electrical specifications are drafted by well meaning educated professionals - pro bono in my country, in the interest of public safety.

Offline Fionn

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Re: Just bought a powerjack 15000, modding.
« Reply #70 on: April 25, 2017, 05:06:04 PM »
2) i know that industry practice is not to bond the batteries like this due to the fear of dead cell's, but each battery has a hydrometer and the status of the battery bank is monitored so cell death would be easily spotted. what this method does give as a bonus once that fear has been eliminated is the equalisation of all charge and discharge paths from one end of the bank to the other, improving the battery banks charecteristics.
It is possible that at some point you will develop a short in one of your cells - which could happen at any time, will just take a piece of plate material to drop off in an unfortunate position.
When this happens, that cell and all the other cells which are in parallel with it will discharge through it at high current.
If you're lucky, this will only mean that you destroy every block in that parallel string but it is far more likely that you will have a significant thermal event - fire and / or explosion when it happens.
If not, you will just kill all the other blocks in the pack from overcharge as your generator will likely kick in immediately and overcharge the surviving blocks.
It's possible that this may not happen within the lifetime of your installation, but you're certainly rolling the dice.

Offline rossw

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Re: Just bought a powerjack 15000, modding.
« Reply #71 on: April 25, 2017, 05:19:39 PM »

The only way of getting a shock is by touching both the live and neutral at the same time.. which an RCD won't protect against anyway.
This is incorrect, in a normal neutral-earth bonded installation with RCD protection where someone touches live and neutral at the same time, current will flow to earth as well as from live to netural through the person's body.

I hate to correct your "correction", but you are also in error under certain circumstances.

If you'd said that current "MAY flow to earth" and indicated that the RCD "MAY" trip, I'd have left it.
There are plenty of cases where there is insufficient out-of-balance current to trip an RCD, and I can testify to it myself.

Electrical Safety equipment certainly increases your chance of survival significantly, but it doesn't guarantee to save you in 100% of instances!

Offline Fionn

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Re: Just bought a powerjack 15000, modding.
« Reply #72 on: April 25, 2017, 05:43:20 PM »
I agree wholeheartedly Ross, the fault current to earth would still have to exceed 30mA of course, I was merely trying to illustrate that the standard approach at least has a chance of working in that fault scenario. Some current will certainly flow to earth however so I don't think "may" is appropriate, the only uncertainty is around the quantity.
An unmonitored distributed isolated system has a far greater chance of causing unintended death however.
This thread is rife with practices that should never be followed.

Offline Fionn

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Re: Just bought a powerjack 15000, modding.
« Reply #73 on: April 25, 2017, 06:13:35 PM »
Hang on, scratch that Ross, I fully qualified in my original post that the fault current would have to exceed 30mA - directly under the line you quoted.

Offline rossw

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Re: Just bought a powerjack 15000, modding.
« Reply #74 on: April 25, 2017, 06:29:29 PM »
Hang on, scratch that Ross, I fully qualified in my original post that the fault current would have to exceed 30mA - directly under the line you quoted.

And I contend that there are plenty of times when standing, working on something where there would NOT be any earth current if you got tangled up across active/neutral and that therefore the RCD would NOT operate.

My workshop floor for example, has large rubber mats - mainly to reduce foot and leg fatigue.
Over my many years working on stuff, I tend NOT to lean against or otherwise contact the metalwork of equipment, switchboard frames, equipment enclosures etc.
So tell me where the earth current would come from when I've got the covers off a "thing" and get myself across Active and Neutral??