RV AC electrical 110/220 crossing hots

[nutnspecial]

So i've been working on my rv circa 1990.

I've upgraded and moved 12v batt bank to weatherized location and added a new 110v 40a charger with switch to turn off when on inverter power.

Repaired 4.5kw 220v generator. This gives two hot 110 legs to a 50a panel containing all 110 breakers. The genny will just be for high draw tools and emergency batt bank recharge.

There is a 'shore' connection which uses a common 110v extension cord and adapting plug to split the 110 supply hot to both rv panel legs.
Again, nothing in the rv runs on 220v, it's just a common 50a 220v main panel.

Upon installing the 110v inverter, I am planning a point of introduction for it and 110v shore power near the genny feeder to 50a 220v main.

Obviously, feeding only one leg will not work as only half the breakers will energize.
I would prefer to elliminate the adapter plug and use a receptacle to plug inverter or shore power into, but doing so would require tieing into the main 50a and thus the two genny 110v legs together.

I know you can't combine both 110 legs being fed from grid power without special equipment or you get fireworks,
but I know I can split a single 110 across both panel legs to supply all breakers,
so can the genny run without detriment to itself while it's legs are crossed for the inverter/shore power receptacle?

Any form of additional switches or breakers are over complicating things, but I'm wondering if running the genny with legs crossed will hurt it?

Spoiler: prelim conclusion spoiler

I ran about 2000w on genny for awhile yesterday with both legs tied, and no issues or overheating of the jumper. Without any additional info I would test more extensively making sure to pull 2kw from each leg in the panel, but will there be long term ill effects, or are the two 110v legs of genny much more closely phased than grid power???

Thanks!

 

[nutnspecial]

Parallel hots is more accurate?
My fears are not that this is a dumb question, but nobody has a clue wtf I'm talking about.

I found an article on rewiring a 220v generator head (paralleling coils) to gain full load capacity from each 110 leg. Not sure if that will help or hinder when tieing the legs together anyway for a 110 input (inverter or shore) to power bothi legs in the panel, or even if there will be any difference doing one or the other?

My search terms may be off, I'm not finding the answers on up on the web.

 

[marty]

I say don't do it. Don't let hots touch. If someone connects camper to grid power there will be sparks.

 

[nutnspecial]

Thanks for the input. Absolutely right, 220v grid power can't have it's two 110's crossed.

That aside (there is no danger of someone plugging into 220 while the genny/inverter/110shore ((which would have the crossed hots to feed 110 across both legs into 220v main rv breaker)) is connected as input) what about having the two 110 legs of genny crossed, a necessary evil for the introduction point of inverter or shore 110?

I can make a video if question is too grey

 

[marty]

Think about this. Generator is running. Extension cord to shore power is connected to camper. There has to be a switch, [automatic or manual] to prevent male prongs of extension cord from being live. Wondering if your camper has this switch? Suspect this switch might also do what you are thinking as to enabling 110V shore power extension cord to power both legs of breaker box. Sorry that I don't know more about campers.

Do you have a wiring diagram for your camper? Camper manufacturer might mail you one for free.

 

[nutnspecial]

Thanks for the input! I think it's called a transfer switch. No don't have or want one. It's an old rv I got for cheap.
I'll try to make a very short video to explain what's going on, because that part should be a non-issue.

 

[markz]

I remember something I just cant think of whats its called.

I will draw you a little something something to get the brain juices flowing.

I am lazy and do not feel like going through my 1st year papers. Key is for equal currents, otherwise its not good.

 

[nutnspecial]

That must be over my head (pic) *crazy eyes* but thankyou.

Everything is always using the same neutral no matter what, so I'm not sure what you mean. From what I understand it's the different phases of alternating current that dislike coming in contact (grid), but the genny didn't seem to mind even tho it should be putting out very similar 220v ac.

 

[markz]

This may or may not help you.
[youtube]k6VFFXGyb3M[/youtube]

 

[nutnspecial]

Thanks much! It's some of the basics. I'm doing in reverse -gen is 220/240 and tieing to that with another optional 110 source, so effectively crossing it's legs.
Guy didn't mention, but another reason to leave his main off, is it would be nasty for grid to come back on and energize the cord that thimbles into 110, which is what I'm doing, except instead of grid 240, mine would genny 240 when occasionally run, and the genny didn't seem to mind crossed hots.

 

[markz]

Yes you need my diagram, just reverse it. So on the open end is your 220, then you have 3 points (two 110's)
I tried looking through my modules but its in my computer test printouts. Should have balanced loads on both 110's.
The middle is the common neutral I believe.



Found it, its called a 3 wire Edison Circuit. I knew it had some weird name, I just could not pinpoint it. I dont know if you can buy a product that does it for you, or you build it yourself. Basically every house has 240 coming into it, then they split it. This should give you a good start for google purposes anyway. All my school work papers are just calculating amperages, balancing loads, and what would happen if neutral wire opened.

gen is 220/240 and tieing to that with another optional 110 source, so effectively crossing it's legs.

Yeah I dont quite know what you mean, I thought maybe you wanted 110 out of 220/240, but it seems to me you have a 220/240 gen and want an additional 110 tied into the 220/240. Which is beyond anything I have ever studied or read about. I can visualize something, its a great guess though, the only reason I can see for this setup is for "LOADS", having the tradition 220/240 edison 3 wire to get your two 110's, but then adding another 110 doesnt make electrical sense to me, but I know little to nothing. Its the return feed of electrons, makes everything unbalanced.
Your best bet is to find an electrician forum, or electrical forum, I've posted a few in random forums.

https://www.wisc-online.com/learn/career-clusters/stem/ace3703/the-edison-wire-system
http://www.electriciantalk.com/f2/three-wire-edison-circuits-having-trouble-understanding-school-104754/
https://i.imgur.com/haNSVwC.jpg
[youtube]-NzW5CU7UzE[/youtube]

 

[nutnspecial]

I am thinking balancing comes into play when trying to derive 220 from two separate 110 circuits already breakered and wired with receptacles.

If the source (gen) doesn't have issue, tieing it's hots might actually automatically balance panel draw from gen coils. Normally you would get only half gen capacity from each set (red or black) of [strike]receptacles[/strike] breakers because each is powered by a separate coil.

I saw something to parallel the coils in the genny, but think just tieing the two 110 outputs (in order to add 110 shore and 110 inverter) might be fine

View attachment jumpr.bmp

I shoulda started with the picture. Worth a thousand words- are they all 'STUPID!" ? :lol:

 

[markz]

A even more detailed picture would be helpful, with arrows for current flow.
Draw in the house, the RV, where the gen is (house or RV), where the outlets are etc etc etc.

The inverter is from the RV battery, output of inverter is 110?
The one below that is house 110 outlet?
Whats shore power? house outlet? RV park/camping outlet?
Your RV panel says 240, but you state the RV only runs on 110.



Your setup would achieve 440/480V, unless two additional 3 wire edison is used (Right hand side) then you'd have on the output, 2 neutral wires.
However the phases would be wrong, and balanced loads. In theory it might work, practicality I doubt it.

 

[marty]

Markz,
That YouTube video of guy connecting generator to dryer receptacle is dangerous, and wrong for many reasons. Any time a extension cord has 2 male ends, something has gone very wrong with planning.

Got no idea about your drawings showing way more then I understand.

******I think it's called a transfer switch.******

Yep! That what I think is needed here.
Here is a random one I found when searching for [rv transfer switch]
http://www.trci.net/products/surge-guard-rv/transfer-switches/50a-plus-hardwire-rvc-ats

Are you planing on having auxiliary 12V batteries? Most RVs do. Solar can also feed these batteries. Here is a random drawing of how a inverter ties into this. Why is spell check telling me I spell inverter wrong?
http://www.xantrex.com/documents/Inverter-Chargers/RV-Series-GS/RVSeries_2012-2512-3012-GS_Owners_Manual%28975-0209-01-01_Rev-A%29.pdf

Note the battery isolator, you need to buy that if RV don't already have one. Boat or RV shops are good sources for equipment. Why is spell check telling me I spell isolator wrong?

 

[nutnspecial]

Thanks guys. I don't know how you're getting 480 markz power sources would parallel with the possibility of feedback- not be series'd? I can rule out feedback by just not plugging into shore power when running genny or inverter. Why would one do that anyway? Your guesses are correct on shore and inverter. The panel is standard 220v. It uses a 220v main, and could use 220v circuits, but it never did or will. Direction of flow is all to the panel.

The battery systems are isolated with something lowtech and antiquated, but functional. Not sure if it will throw charge to 'house' batteries when driving or not, will have to test. To top up vehicle battery (when parked for awhile) I just use a little jumper across the solenoid of the isolater.

That schematic is impressive, but way overcomplex imo. Lays down the basics very well tho. Mine will have a separate 110v battery charger and inverter, and also the solar charge controller, as well as ac inputs from genny, shore, and inverter, and I'm not convinced I will need all the fancy stuff like auto switching and secondary panels.

Just concerned at the moment with why the genny doesn't seem to mind running with it's two 110 legs tied together. Cant do that with grid power, and pretty sure u can't do anytime you are running 220v breakers in a panel. I suppose since my panel only has 110v circuits and the genny coils have some flexibility, it's ok. I will do more testing.

 

[marty]

Don't tie two 110V legs of 220V generator together. DON'T DO IT!

Diagram of DPDT transfer switch.

Wondering if you RV has something like this?

All batteries should charge when RV engine is running.

 

[nutnspecial]

DON'T DO IT!

But why? I can't figure what issue that would cause, if any.

I found a diagram to parallel the genny coils, which would make each leg capable of full 50a, but still need to tie the legs to deliver 110 from inverter or shore across the 220 main in the panel.

I can't see how a switch would work. Not a dpdt or 3pdt and so on. Do you think it would work to introduce 110 across both legs of a 220main?

 

[marty]

Switch also has a OFF position. OFF is for when power is coming from inverter.

 

[markz]

Nuts doesnt want to use a switch.

Any form of additional switches or breakers are over complicating things, but I'm wondering if running the genny with legs crossed will hurt it?

Use my last hand written diagram, and parallel where I got the angular lines. Inverter and Shore.
Then you'd have your 220 gen, and your two 110's. I can't see how the current would split coming back from the load(s) at the intersection.
It would be a ton of current on the top and bottom rails near the loads. But the loads get whatever they want.

 

[Alan B]

If the generator has two independent 120V coils it might not mind paralleling them (if the phasing is right). You can run an experiment to find out. Wire a 240V light bulb between the two 120V generator outputs. If the bulb lights up then you have 240V there and you have to reverse the phase of one coil before you could parallel them. When paralleling them they can either produce 120V in phase or they can produce 240V into a short, with resulting damage, depending on the phasing.

If there is any way that generator or inverter power can feed out of your RV into the park via the inlet wiring, then it is dangerous and illegal. You may be responsible for damages or injury to the park or any other campers. DO NOT DEPEND on manual actions like unplugging unless they are fail-safe and CANNOT result in a dangerous situation.

It might be safer to set it up so the RV AC input plugs into the generator, or into shore power, or into the inverter. That way the one plug becomes the transfer safety switch. This could be a 240V plug so the generator would not have to be rewired. An adapter to the park power would be used, and the inverter output would be wired to both 120V circuits in the 240 socket for that source. No double male cables should be used, they are not safe.

The RV Inverter and generator may contain transfer switches, in which case cascading the power through them in the right order should work. That still requires sorting out the 120/240 issue that you are asking about.

You can simplify the system so far, making it any simpler becomes a safety hazard. There should be no way to plug things together that is dangerous. Safe wiring is not necessarily simple. Here we have a system with multiple power sources. That takes it out of the simple domain.

There are subtle things in the electrical code that are not simple to implement. For example the power source needs to connect neutral to ground. When the power source changes from the park to the generator to the inverter this neutral to ground tie should move between the units. When a generator or inverter is not the power source it is not allowed for a neutral to ground tie to exist there. It just isn't simple, but those are the safety requirements. A good inverter or generator transfer switch will have a grounding relay and logic to implement this. You can also implement it with the source plug mentioned earlier. Failing to follow this can result in floating neutral or other hazards.

Good luck in your project and stay safe. If you don't understand these systems and requirements then a suitable electrician should be engaged to keep you and others safe. Not all electricians will have the requisite experience with systems of this type.

 

[nutnspecial]

Very cool thanks. I actually couldn't envision how a dpdt would work for it, but that would be perfect. Just need one good for genny amperage since I'd have to break those lines. A dp3t (or the actual transfer switch) would allow for 'off' or another separate source, but that defin isn't needed. Although a 'proper' transfer switch looks like 1-several hundred, looks like a dp relay would be around 30$, but it's not about the money it's the pita and kiss factor so markz is right. If not needed I don't want it. Hell I'm trying to heat with wood and compost my sh!t :lol: :lol:

In my first post under 'spoiler' I already tried with the legs crossed and it didn't seem to hurt anything, so I've been looking for technical reasons why not to do that, and have found none.

Exactly Markz, just like if the 110 ran between invert and shore in your drawing. At this point I'm pretty much just wondering if paralleling the gen coils too would help anything.

Thanks for taking an interest and for the time/help guys! I'll update to confirm/deny all of our suspicions on the workings.

This thing will shape up

:lol:

I just read your post Alan Thanks. You touch on good points. So if I didn't have a 240 bulb and I simply tied the two gen legs (output after coils) together, what should/would that do? Mine continued to output as before, but I didn't try to load the gen much over 1/2 capacity. I'm thinking it's okay because there are no 220 breakers, all are 110 cept the main for the panel. Possible to hurt coils if they're not paralleled? Hmmm, maybe they already are, because the trailer never had any 220v appliances, and without parallel coils each 110 leg can only carry 2.25kw (half) to it's set of breakers (parallel obvious best choice for 110 circuits in a 220 panel). . .

 

[Alan B]

If you paralleled the coils already and they didn't blow up then the phasing must be the same. Or one coil already blew out. That was a really dangerous experiment, to just parallel them without being certain. If each coil individually still works then they must be phased the same. You can't get 240 out of that generator that way. It is set up for a pair of 120 circuits, not 240.

 

[nutnspecial]

Gotcha thanks much!
I was kinda thinking that but wanted to attempt verification danger may have passed.

Nahhh it wasn't that bad. Precautions taken, and I learnt about crossing grid hots firsthand awhile ago.

So to confirm I should just check whether the two separate legs can test for 240/220. I'll do that before going further.

Thanks for all the input, although the floating neutral might also need visited by me. I'm not sure I understand that, if ground and neutral bars are residentially always tied nowadays, and (my borough at least) requires two independant grounds from that, how is that different than having extra chassis grounds and/or uncharged coils? I do understand the legality/danger with backfeeding voltage unmetered onto the grid tho- big no no

 

[nutnspecial]

So I've recieved a cheapish cobra inverter for install in an rv to give a little 110 from the battery bank without running a generator or connecting to grid (shore) power. (in my RV project)

Here it is http://www.amazon.com/Cobra-CPI1575-1500-Power-Inverter/dp/B00GMRH8AK/ref=sr_1_3?ie=UTF8&qid=1450456373&sr=8-3&keywords=cobra+1500w

It has a nice on/off, usb, and most importantly is already configured to show input voltage and output in watts.


Unfortunately the placement won't allow the benefit of this display unless I relocate it away from the inverter and batteries.

Hence my question. . . the display reminds me of a Cycle Analyst with it's 7 wires. It would appear they won't be asked to carry any more current than what the usb might draw, so I'm thinking of extending the cable and placing the whole display/switch inside.

Upon investigation, I noticed that the seventh wire is slightly thicker because it is actually the braided/twisted shielding of the wire bundle- it is also connected to pcb on both sides, besides another black wire assumably as ground. This would be a pita to duplicate, and wonder if this is even necessary as wire gets away from inverter. I can lengthen it, but to rebraid around the rest is out of the question.

My guess is it's only to keep signals clean from the electrical noice possibly generated inside the inverter anyay?

My other question is wire gauge. Seems the wires are heavier than necessary for mostly just sensing/display. I'd like to try running a 4 pair Cat wire as the extension which will be much thinner. Thinking it may only effect the usb charge port if anything. I could double up the 7th and 8th cat wire for any extra current needed on any of the original seven.

Comments welcome. Thanks!

 

[marty]

I'd like to try running a 4 pair Cat wire as the extension which will be much thinner.

Thinner gauge NO. Use the same gauge or thicker. How about 18/7 or 18/8 thermostat wire?

Shielding? I don't know?