MPPSolar PIP5048

Feenster

Looking for a bit of help.
I bought a PIP4048 from MPPSolar many years ago and bought a new PIP5048 just recently.
I live off-grid and have a generator for back up.

Recently I replaced the PIP4048 with the new PIP5048.

The PIP5048 started up fine. However, when I started to turn on the breakers (we call them MCBs over here in Ireland) on the fuse board for the house many of them kept tripping. Occasionally the RCD (residual current device) would also trip. For example, when I turned on the breaker for the kitchen as soon as the 'fridge turned on the breaker fell. At first it was only the circuits with a 'fridge or freezer or small motor that tripped. Then, on another circuit, someone in the house turned on a small laptop and a trip occurred on that circuit.

I know most people here are from North America and therefore use different terminology for circuit breakers, etc.
Over here, in Ireland, each circuit, in a fuse board, has its own breaker - we call them MCBs or miniature circuit breakers. It trips if there is an overload or short circuit.
If the circuit is for sockets (I think you call them 'outlets') it has the added protection of an RCD or residual current device. I think its known as a GFCI in North America. An RCD will switch off the supply of electricity when electricity leaking to earth is detected at harmful levels.
I have 7 socket circuits, each with its own MCB, protected by one RCD.

On the advice of MPPSolar (after waiting for a reply for a long time) I replaced two of the MCBs. I took out 20A breakers and put in 32A ones.
I put back in the PIP5048. Unlike my first attempt, the MCBs didn't trip at all. However, the RCD did.

On each circuit as soon as an electrical appliance started the RCD tripped. I tried a 100W coffee grinder. RCD tripped. I tried something without a motor - a 700W toaster - RCD tripped. The only thing that appears to work on the RCD controlled circuits is a table lamp (5W).

On one of the circuits there is a small pump. Even when the pump is on standby but not actually running the RCD trips.

The RCD is a Hager 63A 2 pole RCD 30mA (type A).

This never happened with the PIP4048. I had to put the PIP4048 back in again as I couldn't function with the 5048.







I recently checked for continuity, using a multimeter, in the PIP4048 between neutral and ground and found that there is. I live offgrid. There also appears to be continuity in the PIP5048. However, there is something new in the 5048 manual that isn't in the 4048 manual:


This seems like it is referring to the neutral ground bond? The default setting is that it is disabled. Yet, there is continuity between N-G regardless of whether this is enabled or not.

Photowhit

I don't understand the nomenclature, perhaps someone more 'worldly' could figure it out.

What might be happening is one has an auto sensing neutral ground bonding, while the other either is always bonded or not bonded. This would likely show continuity when not energized. If you disconnect the inverter does your wiring show a bond between the neutral and ground?

It's common for some to have autosensing for use in Recreational vehicles. 

I'll bet Bill will understand this and may be typing a reply now...

RCinFLA

Make sure the battery charge current is setup on inverter to avoid too much AC input current.

RCD (GFI's) will trip if there is not balanced current on hot and neutral wire.  You can have 10 amps flowing through RCD breaker and if there is as little as a few mA's of difference in the hot and neutral 10 amp current the breaker will open.  This only applies to current on output side of RCD.  Many inverters put small AC bypass capacitors from AC input and output terminals to inverter case to suppress EMI RF interference from digital switching noise within inverter.  This can create a small amount of leakage current to ground that causes RCD to trip.

If breaker has arc fault interrupt, they are different animal.  They use high frequency noise from an arcing connection, and some do not like HF noise created by high frequency switching inverters.

Make sure your inverter ground is connected to utility ground and the neutral is grounded at the input source, typically in main electrical panel.

Many of the Chinese HF inverters have a relay that connects its neutral internally to inverter case ground when there is no AC input, which would be the typical situation for an off-grid system.  When the inverter sees AC input applied, its relay opens the internal neutral to ground connection turning over neutral to ground bonding responsibility to external AC input source.  

This can create a problem on a grid tied system as when AC input breaker is opened the inverter's internal neutral, which is also likely connected to your main panel neutral via the AC input wiring, will be duplicate ground by inverter.  If the inverter has a permanent neutral to ground internal bonding and there is an RCD breaker feeding AC input of inverter it will not like this duplicate neutral grounding by inverter.

On a system tied with AC input to utility panel it is better to allow the main panel to always be the sole responsible neutral-ground bonding point.  This requires you defeat the inverter's internal neutral-ground bonding relay function.  Sometimes the inverter has a jumper wire to allow you to do this. Some require you remove an internal PCB to inverter case hold down screw to disconnect the relay neutral-case ground connection. 

Feenster

Photowhit said:

What might be happening is one has an auto sensing neutral ground bonding, while the other either is always bonded or not bonded. This would likely show continuity when not energized. If you disconnect the inverter does your wiring show a bond between the neutral and ground?

The inverter/charger causing the problem, the PIP5048, is sitting on its box and isn't energised. There is continuity between G-N. But what is setting 38 for? The PIP5048 is in default mode at the moment.

Feenster

RCinFLA said:

Make sure the battery charge current is setup on inverter to avoid too much AC input current.

I haven't tried to use the PIP5048 with an AC input current as of yet. The older PIP4048 prefers the default current of 30A. I did change it one or twice to 40A but the charge would keep dropping to 0. I use a generator for ac input.

Feenster

RCinFLA said:

Make sure your inverter ground is connected to utility ground and the neutral is grounded at the input source, typically in main electrical panel.

Many of the Chinese HF inverters have a relay that connects its neutral internally to inverter case ground when there is no AC input, which would be the typical situation for an off-grid system.  When the inverter sees AC input applied, its relay opens the internal neutral to ground connection turning over neutral to ground bonding responsibility to external AC input source.  

This can create a problem on a grid tied system as when AC input breaker is opened the inverter's internal neutral, which is also likely connected to your main panel neutral via the AC input wiring, will be duplicate ground by inverter.  If the inverter has a permanent neutral to ground internal bonding and there is an RCD breaker feeding AC input of inverter it will not like this duplicate neutral grounding by inverter.

On a system tied with AC input to utility panel it is better to allow the main panel to always be the sole responsible neutral-ground bonding point.  This requires you defeat the inverter's internal neutral-ground bonding relay function.  Sometimes the inverter has a jumper wire to allow you to do this. Some require you remove an internal PCB to inverter case hold down screw to disconnect the relay neutral-case ground connection.

Because this is an offgrid setup there is no grid power coming it or connections. Neutral-Ground bonding occurs in the inverter (there is continuity between G-N). From what I have read there should only be one G-N bond. There is an earth rod as can be seen from my diagram.

I haven't tried the PIP5048 yet with an ac input. The PIP4048 always worked fine from the generator. The neutral on the generator is tied to the chassis of the generator and the generator is earthed.

The PIP4048 has been working well for 7 years. I haven't changed anything and yet the PIP5048 keeps causing the RCD to trip.

So, RCinFLA, where do you think I should go from here? Thanks.

Photowhit

Feenster said:

Photowhit said:

 If you disconnect the inverter does your wiring show a bond between the neutral and ground?

The inverter/charger causing the problem, the PIP5048, is sitting on its box and isn't energised. There is continuity between G-N. But what is setting 38 for? The PIP5048 is in default mode at the moment.

I'm not familiar with setting 38, but when I asked this question, I was referring to your home wiring. I have a Prosine 1800 running my home for a while when I had to move from my old cabin. It had a sensing neutral ground bond as it was designed for RV and boats. By knowing if your home wiring had a bond it would help understand the situation. Okay perhaps the 38 is the one you posted I don't understand. In the past most home inverters did NOT have a neutral ground bond. The neutral ground bond was made in the mains breaker box.

Since these all-in-ones largely eliminate the need for breaker box I suspect most would be auto-sensing to make the bond in the inverter. Perhaps that is what the '38' info is trying to say. I honestly don't understand the signal to the grounding box info in the '38' clip.

Feenster

I honestly don't understand the signal to the grounding box info in the '38' clip.

I don't get it either. Whether its enabled or not I find that there is continuity between N-G. I had expected that when it was disabled the bond would have been broken.

RCinFLA

The setting 38 looks like they incorporated what I was talking about in relay controlled neutral-ground bonding.  They put it under user firmware selectable control versus the old way requiring invading inverter internals to make wire jumper changes.

You can ohm check AC input side and AC output side neutral-ground bonding (just avoid touching hot lines) for the various options. Depending on setting 38, it grounds neutral only when AC input is NOT present, or it never ground bonds neutral on other 38 setting which means you determine ground-neutral bonding on AC input side externally.,

1) When is input neutral ground bonded?
2) When is output ground bonded?
3) Is there always AC input to AC output neutral pass-through connection?  Do they break the AC input to AC out neutral connection when it does not detect AC input voltage applied.

The above conditions may change if there is AC input power vs not having AC input power in addition to setting 38 affecting how it reacts when AC input power is present.

Best solution is inverter always floats the neutral within the inverter and you control the neutral-ground bonding externally on AC input side.  This assumes there is straight through neutral connection between AC input neutral and AC output neutral.

It might be a good idea to get one of the plug in LED light outlet testers to verify there are no outlets with ground-neutral reversed, grounds missing, or neutral-hot reversed. 

Europe has some funky neutral-ground bonding schemes.  I believe now it is mostly bonded at user main breaker panel, with an external grounding stake, but old systems float it at main panel and ground bond neutral at the utility service pole/junction box. It can also depend on housing density (flats/attached dwelling vs separated houses)

Should likely start with regular breaker popping issue. 

Refrig can have a larger startup surge current if it is not left off for a minimum period of time, like 15-30 minutes.

Feenster

RCinFLA said:

Best solution is inverter always floats the neutral within the inverter and you control the neutral-ground bonding externally on AC input side.  This assumes there is straight through neutral connection between AC input neutral and AC output neutral.

I am still waiting to hear back from MPPSolar. My only concern with removing the n-g bond in the inverter itself is that it will invalidate the warranty. Never had any problems with tripping with the PIP4048 and the n-g bond is within the inverter. During the last few days I have been tidying up the wires around the inverter checking for problems. Nothing obvious.

Feenster

RCinFLA said:

Best solution is inverter always floats the neutral within the inverter and you control the neutral-ground bonding externally on AC input side.  This assumes there is straight through neutral connection between AC input neutral and AC output neutral

I have come back to read your comments a few times RCinFLA.

A lot of 'toing and froing' still going on between MPPSolar and myself - progress is slow.

On my existing inverter - the one that works, the PIP4048 - the neutral ground bond can be easily removed. Most people suggest putting it in the distribution panel, which is an easy thing to do.

My only ac input is from a generator. In fact I have 2 generators - a 6.5KVA diesel one and a 3.1KVA petrol one. I nearly always use the diesel. The problem is that it needs repairing. I set the petrol one going today and did some checks on things that I never checked before. The voltage between live and neutral is 240V, between live and earth is 120V and between neutral and earth is 120V. I wasn't expecting this. Effectively, there are 2 live wires?

So the question is:

(a) With the status quo, i.e., the n-g bond in the inverter.  When the generator provides the ac input to the inverter, a relay disconnects the n-g bond in the inverter. How is neutral-ground bonding achieved?

(b) With n-g bond removed from the inverter and placed in the distribution panel. When the generator provides the ac input the neutral (v earth of 120V on the generator) won't like being bonded to the earth in the panel. Am I right in saying this?

RCinFLA

If your generator is a portable model, best way is to run four wire cord with L1,L2,N, and Gnd which is connected to generator case.

Neutral-ground is at one point in junction box with a double pole breaker on generator L1,L2 lines which goes to inverter AC input.

No other neutral-ground connection from that point.  Neutral can go to inverter neutral.  Inverter output neutral goes to floating neutral in your breaker panel.  This assumes inverter neutral AC input to AC output always maintains straight through neutral connection.  Ground from generator junction box, which is connected to external ground stake, is connected to all metal cases in electrical system, junction box, inverter, breaker panel.

On output of inverter, breaker panel bus bar is floating (not grounded to breaker box case).  Neutral-ground bonding is done back at the generator junction box.

All grounds to metal boxes are done with separate appropriate gauge wire.  Metal conduit between electrical boxes are not allowed to be the only primary ground connection.  Conduit clamps have a way of loosening up versus time.

Feenster

Thanks for that RCinFLA. Sorry for taking so long to reply. Trying to fix the diesel generator, etc.