Connecting Neutral & Ground from Generator to Home

[ePowerBank]

I feel all alone on this one having a very unusual generator plug basically without neutral.
Apparently this company designed in something not on any of today's generators - a NEMA 10-50 (on the parallel outlet box).

As I understand, this should be 2 hots and a ground. If that's the case, is there supposed to be a Neutral connection to the generator(s)?

These are 2 new generators for backup power that will be connected to main panel via an interlock, where ground & neutral are bonded.
I get polarity between parallel ground lead and parallel center plug - suggesting the NEMA 10-50 outlet has ground and not common.
I get no polarity between parallel kit's white lead and any of holes on parallel outlet box (?).
I get no polarity between generator control panel's ground & neutral plugs - suggesting it's floating neutral setup.

I thought this is basic stuff, however, when I double generators other day I SMOKED 2 power strips!
Subsequently I bypassed cord #1 (below) and the outlet box and instead connected cord #2 directly into one of the gensets "while" joining the two gensets via the parallel cables - passed initial test (HVAC & Micro etc). Problem is there's only 30A plug directly from geni control panel instead of the 50A on the parallel box, although I'm using a 50A homemade cord.

Thinking this through causes me to think - how can AC return to it's source if Neutral isn't connected?

 

[ePowerBank]

Correction to above - I should have said "I get continuity" not "polarity".... opps!

 

[TheJeremy]

Split phase

 

[newbostonconst]

What country are you in? Are the Generators for the EU?

I don't see this working without an "autotransformer"... People are using these the Growatts without a neutral.

Sounds like these generators are inverter type because of the parallel cables?

What are you measuring between ground and each leg(both X and Y in your diagram)?

 

[ePowerBank]

Thanks for the insights - although I know basics of electricity this is my first backup generator + the dual part.
I'm in US and below are links for, yes, Inverter Generators along with the parallel kit.
I plan to follow up with some readings tomorrow as suggested - thank you.

https://www.northerntool.com/shop/tools/product_200788693_200788693

https://www.northerntool.com/shop/tools/product_200832956_200832956

I think what I'm hearing here is this may be a case to create split phase with autotransformer, but is that only for 240v "parallel" case?

The generator inverters include 240v when single setup - key reason I purchased them (circled below). And they do measure 120v X to Neutral or Y to Neutral. I checked with Northerntool (Generator supplier) and they said it's OK to connect gensets together with parallel kit and use the 240v 30A plug directly from generator (again circled below) - I just won't benefit the 50A parallel plug (box below). I was successful I think running this way (direct from one of two generators) - see below readings for X & Y leg (tested HVAC fan and microwave, at different times). Got it up to about 3000W - but need some balancing as it shows below on the Wh.


Again, goal is to hook up two gensets with cord #1 above to parallel 50A box - to go full load.
When I initially connected whole set to 50A box (cord #1 & cord #2) I fried (smoked) two power strips -

Next step: get some data as suggested (THANKS!)
Measurements will be made with Interlock - shutting off Main and connecting Cord #2 to panel, and no load.

Note home ground (panel) are gensets ground system in this case - where Main Panel ground-neutral are bonded.

 

[ePowerBank]

Follow up here to suggestion from @newbostonconst (various voltages).
See below & attached for the full report / detail.

So it seems these are normal readings?
I did round to 120 or 240, maybe I shouldn't have?

Pkit is the Parallel Kit with box. In the 2nd case I used the Pkit to parallel (link) the 2 Gensets, however, connected to house inlet vea Cord #2 only, directly to the Gen Control panel (30A), not the 50A box. I suppose I'm fine to do this if less than 30A.

 

[newbostonconst]

Read what you wrote thoroughly, nicely written....

I would connect one plug at a time and measure voltage at the terminals of the plug as you go along. Seems like you are sending 240 to the terminal strip to smoke it. Checking voltage between each voltage terminal, between each voltage terminal and ground, between each voltage terminal and neutral, and between the neutral and ground. If a wire were wrong you could get higher then 240 vac.

I also think in the back of my mind what would happen if the generators aren't syncing up and are giving you anywhere between 240 and 480 VAC. Or they are only syncing when under load.

I would also check for a difference in voltage between the frames/engine blocks of the two units while they are running. I think the parallel cable would tie them together.

 

[RCinFLA]

If it has a parallel kit is must be an inverter-generator. Most all U.S. split-phase inverter-generators have 120vac inverter modules. A large wattage inverter-generator that has 240vac capablity has two 120vac inverter modules connected in series and it may have a switch to allow them to run in parallel as 120vac for full generator rated wattage.

The NEMA 10-50 in parallel adaptor looks like neutral and ground is connected together in adaptor box. This should not be done for connection to house panel.

Inverter generators syncronize their output by whichever generator is started first becomes master for phase. Second generator, seeing AC on its inverter output will sync to already applied AC from other generator's phase. You will probably find in manual that parallel kit must be connected first before any generator is started. If both generators are running before you connect parallel kit they will be operating with independent phasing and sparks will fly when you plug in parallel kit.

The banana plugs just go to AC outlets in generator. Using the insulated banana plugs prevents live exposed prongs on a male to male 'suicide' parallel cord.

I would try to replace the NEMA 10-50 in adaptor box so you have a separated neutral and ground. A CR6369 or NEMA 14-50 for 50A 120/240vac would be a good choice,.

 

[ePowerBank]

Good trouble shooting points - peel the onion.
I realized this as I was randomly gathering the data...

 

[ePowerBank]

If it has a parallel kit is must be an inverter-generator. Most all U.S. split-phase inverter-generators have 120vac inverter modules. A large wattage inverter-generator that has 240vac capablity has two 120vac inverter modules connected in series and it may have a switch to allow them to run in parallel as 120vac for full generator rated wattage.

The NEMA 10-50 in parallel adaptor looks like neutral and ground is connected together in adaptor box. This should not be done for connection to house panel.

Inverter generators syncronize their output by whichever generator is started first becomes master for phase. Second generator, seeing AC on its inverter output will sync to already applied AC from other generator's phase. You will probably find in manual that parallel kit must be connected first before any generator is started. If both generators are running before you connect parallel kit they will be operating with independent phasing and sparks will fly when you plug in parallel kit.

The banana plugs just go to AC outlets in generator. Using the insulated banana plugs prevents live exposed prongs on a male to male 'suicide' parallel cord.

I would try to replace the NEMA 10-5 in adaptor box so you have a separated neutral and ground. A CR6369 receptacle for 50A 120/240vac would be a good choice,.

Disappointed with Northerntool's support - basically say hire an electrician.
I would think instructions had a better baseline - no instructions with parallel kit, and no mention of parallel in generator's main instruction either.

What generator instructions do say is to "start generator without loads connected". I get the loads shouldn't be applied when starting, but I'm thinking since this uses house ground system I should at least tie ground/neutral (or the the whole cord) connected - before starting (???)

Thank you to confirm, parallel cords should be connected - before starting. I'll be honest, I don't remember which I did first the day I fried the power strips. I do remember checking 120V & 240V though.

As @newbostonconst suggests, I can check voltages. Is there a way to confirm if generators are in sycn is what I wonder?

> Correct, these are inverter-generators:
https://www.northerntool.com/shop/tools/product_200788693_200788693
https://www.northerntool.com/shop/tools/product_200832956_200832956
> These generators include "120V/240V" or "120V only" switches
> The Parallel box only has continuity between Center (W) terminal and Ground banana plug, not the white (neutral?) plug.
> LOVE your idea of replacing the box - I'm just not to sure about this type of wiring, and why I just bought this. I see YT videos about making suicide plugs to link 2 gensets then just plugging supply into one or the other (scary). That's all I'm doing I think when I run supply cord directly from one of my generator panels while liking with the Northertool Parallel kit - my fall back that Northertool said was OK.

As my layout below shows, it just doesn't add up how neutral get's through the NEMA 10-50. Yes I have homemade cords, but I've checked the continuity over and over. Theory here is voltage is returning via ground, which I think is wrong?

 

[RCinFLA]

A 120/240v switch and parallelling gens adds another twist. Both parallel banana connections and 120/240v switch violate idiot proof design rules. It seems too easy to accidentially hit one of the 240/120v rocker switch when gens are running in parallel. Probably won't blow up but may have three 2250 watt inverters on one 120vac split phase leg and a single 2250 watt inverter on other 120vac leg.

Should make sure both gens set to 240 vac and bananas are plugged into their corresponding color outlets along with ground lug connected to generator chassis.

I have doubts that the parallel kit box NEMA 10-50 ground is just connected to generator case ground (green wire). The NEMA 10-50 parallel kit box may have both the generator's neutral (white wire) and ground (green wire) connected to NEMA 10-50 ground pin. Check it with an ohmmeter or open up the parallel kit box and look.

If it does have neutral and ground connected in parallel kit box it will work, just not per code. Connect NEMA 10-50 ground/neutral to house neutral.

 

[newbostonconst]

If the generators aren't in sync you can get from 240 volts ac to up to double voltages at 480 vac I think....

 

[ePowerBank]

I have doubts that the parallel kit box NEMA 10-50 ground is just connected to generator case ground (green wire). The NEMA 10-50 parallel kit box may have both the generator's neutral (white wire) and ground (green wire) connected to NEMA 10-50 ground pin. Check it with an ohmmeter or open up the parallel kit box and look.

If it does have neutral and ground connected in parallel kit box it will work, just not per code. Connect NEMA 10-50 ground/netral to house neutral.

My thought is same as you about ground and neutral being tied in the parallel box and just checked (again) and no continuity there (must have checked 10 times in last 5 wks).
I also tried to opening box but can't - it's plastic snapped and sealed box - opening probably means wrecking the box.

As I understand, bonding ground and neutral should only happen in one place, otherwise known as Separately Derived System, and for my case is my house main panel. Acceptable way to ground generator I believe.

Apparently generators are sold 1 of 2 ways, either Bonded, or unbonded (floating neutral). I confirmed that mine are floating (no continuity between genset Ground and Neutral). I also plugged in the parallel kit and checked gen panel and no continuity Ground to Neutral when kit is plugged in.

So if I tie (jumper) receptacle end of my Cord #1 below, am I bonding in 2 places ???

 

[ePowerBank]

If the generators aren't in sync you can get from 240 volts ac to up to double voltages at 480 vac I think....

If I can repeat the event (fried powered strips) I'll feel much better that I know root cause.
Without connecting to my home I'll start generators, "then" connect the parallel kit (forced non-sync even?) and take some measurements.

THANKS FOR ALL THE SUGGESTIONS!

 

[ePowerBank]

A 120/240v switch and parallelling gens adds another twist. Both parallel banana connections and 120/240v switch violate idiot proof design rules. It seems too easy to accidentially hit one of the 240/120v rocker switch when gens are running in parallel. Probably won't blow up but may have three 2250 watt inverters on one 120vac split phase leg and a single 2250 watt inverter on other 120vac leg.

Should make sure both gens set to 240 vac and bananas are plugged into their corresponding color outlets along with ground lug connected to generator chassis.

I have doubts that the parallel kit box NEMA 10-50 ground is just connected to generator case ground (green wire). The NEMA 10-50 parallel kit box may have both the generator's neutral (white wire) and ground (green wire) connected to NEMA 10-50 ground pin. Check it with an ohmmeter or open up the parallel kit box and look.

If it does have neutral and ground connected in parallel kit box it will work, just not per code. Connect NEMA 10-50 ground/neutral to house neutral.

Reminder that my cords are home made - hardly anybody sells something for this one-of-a-kind product I guess I've purchased.

It's the only parallel 240 inverter generator I found - which hopefully offers options to run quiet, low/hi wattage, low fuel, ability to back feed both legs of my 240 panel etc,. They were backorder for almost 5 months! You must know better than I do if you're in FL.... In MI where I'm at we hardly see 1 tornado every 5 years, but past month been about 6 - and some of those were minutes away!

 

[newbostonconst]

I am in Michigan on the north side of ann arbor.....Let me know how it goes.

I eventually want a 240 inverter generator for backup if my solar/batteries can't keep up in winter... One of those would work nice if you want to get rid of one.

 

[ePowerBank]

Hey @newbostonconst, we're practically neighbors - I'm on south side of Rochester Hills.

How much battery capacity are you running?
My goal is eventually have:
1. Active battery backup for sump pump - sump runs about every 30 sec's in heavy heavy rain, as long as I have power
2. Passive Inverter Generator whole house backup - manual
3. Passive battery whole house backup - manual

I'm OK for manual set up, since it's only needed if I'm at home.
For the Sump though I want it to be automatic, so thought is an inverter (4KW) / battery (5kwh) combination.
As I understand, I should have 8kw to 10kw generator to keep up with home load + battery charge (worst worst case), or double the KWH.
I'm in process of converting these 2 gensets to natural gas - got 1 converted so far.

I'm just trying to get plan to play out if I can confidently get the generator part going ?

I went with this open frame model thinking easier to convert to natural gas.
Northerntool has several other options also, and think availability is much better now vs earlier this year - I waited over 5 mo's.
My runner up was their 7500W model (Honda $5k copy), but I figure I actually have more capacity with my two for less $ and less weight (100# vs 300#).

Here's a side-by-side showing my two, where 2nd one has has natural gas + wheel kit + easy oil drain hose added (tri fuel now).
Between the 8ga cords and 3/4" (ID) gas QC lines I have, this feels like the monster cable package!

 

[ePowerBank]

Inverter generators syncronize their output by whichever generator is started first becomes master for phase. Second generator, seeing AC on its inverter output will sync to already applied AC from other generator's phase. You will probably find in manual that parallel kit must be connected first before any generator is started. If both generators are running before you connect parallel kit they will be operating with independent phasing and sparks will fly when you plug in parallel kit.

Update: I spoke with Northerntool yesterday about Parallel Kit connection.
They advised to start up both gensets first, then connect Parallel wires.

My confusion is this is opposite what you advised. Hope you don't mind my asking if you're perspective comes from a certain model / application? Just trying to be cautious. I checked a Wen & Champion manual and both agreed with your suggestion, connect first.

The person helping me also told me my generators were bonded, and I asked him to double check - when he got back on the phone he said sorry, they where floating neutral - so I do have some doubts. His training was that "all" cables should be unplugged while starting. I wonder if that's just for keeping loads out of the picture in start up.

Would it be crazy to run experiment (?) :
1 - start gensets, plug in parallel kit, measure voltage at NEMA 10-50R
2 - plug in parallel kit, start gensets, measure voltage at NEMA 10-50R

 

[ePowerBank]

Experiment complete :
1 - start gensets, then plug in parallel kit, measure voltage at NEMA 10-50R <240v L1toL2; 120v L1/L2toG>
2 - plug in parallel kit, then start gensets, measure voltage at NEMA 10-50R <240v L1toL2; 120v L1/L2toG>
>> I also checked frequency and duty cycle under each condition. Whish I had a scope as these are modified wave (THD supposedly < 2%).

No difference between 1 and 2 results, other than I was scared to try it. Back of my mind I was hoping for a failure though to understand what caused power strips to fry first time the other day (see post #1).
Difference may be that this test wasn't plugged into house system, just isolated test with an extension cord.

 

[Tecnodave]

Inverter generators syncronize their output by whichever generator is started first becomes master for phase. Second generator, seeing AC on its inverter output will sync to already applied AC from other generator's phase. You will probably find in manual that parallel kit must be connected first before any generator is started. If both generators are running before you connect parallel kit they will be operating with independent phasing and sparks will fly when you plug in parallel kit.

The banana plugs just go to AC outlets in generator. Using the insulated banana plugs prevents live exposed prongs on a male to

Exactly where did you discover this.......

In the ones that I have been into the generator is three phase AC variable frequency which is exactly what allows the generator to throttle up faster as more power is needed and reduce the throttle when less power is needed. This results in variable frequency at output of the generator, it varies from about 30 hz up to 400 hz, again three phase Then it is then rectified to DC. that is what appears ot the banana connectors......DC....The inverter in the generator takes this DC and inverts this into AC........The inverter in only one generator is used to provide the 60 hz. output

I have not torn into every inverter generator but the ones I have been into this is exactly how it was done.

I am way too curious on electricity to not dig into a variable speed generator that maintains constant 60 hz

Basic physics 3600 RPM 2 pole Generator ......60 hz...
Variable speed ......Variable frequency

It is not too hard to sync the inverters if both inverters are used but syncing two generators directly is not trivial, if one generator were to cough everything is knocked out of phase.....dead shorting each other out


Now you know how its done

Prove me wrong....