Hooking up Inverter output to shore power receptacles

Denny16

This message is copied from another discussion…
Denny 16 wrote on reply to a question about connecting an inverter to an existing 120VAC power receptacle by splitting the receptacle into two circuits by removing the receptacle jumper that connects the two outlets together.  A common practice in houses, where one outlet may be switched and the other always hot.

My reply to a previous question regarding electrical code standards being applied to RVs:
Doug, the two circuits are both 120VAC, just from separate sources.  As long as the box is large enough to pull both cables into, and with the receptacle split and both sources are fuse or circuit breaker protected, it may not be an issue, as long as the Inverter is normally off, and only used when shore,power is disconnected.  Travel trailers do not conform to most electrical codes to start with (nor are they required to), with their 120 VAC wiring setups, and exposed surface wire pulls.
 Cheers   

Denny16

@kottum replied:
 Denny16, a power source from shore power and another power source from an inverter, then wired into the same electrical box is a safety issue and an electrical accident waiting to happen.  Even though the receptacle is modified to split the two different power sources.

Yes they are both 120VAC, but they are not in phase with one another, a receptacle in disguise.  Who would expect this if not aware of it?

If someone who is not aware of this modification was to work on this receptacle, or a device plugged into it, then shuts off one power source, he probably would not know the other side of the receptacle is still hot.  Dangerous.  

I am familiar with residential electrical codes but have no expertise in travel trailer electrical requirements.  I do have 30 years experience as an aircraft electrician; aircraft are not required to follow residential electrical codes either.  But as an electrician of any type, I can't imagine modifying an electrical system so that it may be a hazard to the user or technician who services it.

Isn't it better to put in another electrical box, one for shore power and a new one for inverter power, and take the extra measure of labeling each.  Not that hard to do, you're running another circuit anyway, just a matter of cutting in another box.
Doug

Denny16

@kottum and @AnOldUR

I split this discussion (by coping and pasting last two posts) from the previous discussion.  

Cheers 

Denny16

AnOldUR replied:

kottum said:

Who would expect this if not aware of it?

Labeling the single receptacle, as you suggested for doing with separate boxes, would answer this question. If there are any regulations against the practice of splitting an RV outlet I was not able to find them.

Denny16

@AnOldUR @kottum

In reply to both of your comments:
Doug, you have a very good point.  If both the inverter were left on whilst the trailer was connected to shore power, this could be an issue if some one went to work,on the box after disconnecting shore power or turning the circuit breaker off, and thinking the circuit was not powered.  The inverter side of the receptacle is still hot.  You raised a very good point.

AnOldUR, Labeling the two outlets would help…
But to solve both issues, I think a better solution is to have a transfer switch to switch the receptacle between shore power and the inverter.  This is how residential units are connected to a generator or battery/inverter power backup system.
 Cheers 

Tabaz

My inverter is located in the small cabinet under the refrigerator.  A direct line was run from it to the new outlet on the left.  In hindsight, I should have used a different color for the new outlet.

elbolillo

AnOldUR said:

@Denny16 a transfer switch would be the better choice, but I still have to look into the application. What have others done? Have you connected the inverter into the system before the EMS? If so, how does the WFCO work? Would it be attempting to charge the battery with inverter power sourced from that battery? Time for some research.

Admittedly, splitting the outlets was a lazy way to install my inverter but hopefully minimally dangerous.

I installed a transfer switch on my 2021 Tab 320. I separated the converter to it's own breaker so that I can leave it off while not on shore power. If I am on shore power then I have the option to turn on the breaker for the converter to charge the battery. With this setup, I can run anything in the unit with the inverter.

Yoshi_TAB

Hi,

I'm in the process of installing two lithium batteries along with an inverter in a TAB 320.  I'm on the fence of installing a transfer switch.  In the long run, it seems easier, then all outlets all ready.  It's a bit of a space issue..they are not that small.  Couple of questions:

1.  If you are plugged into shore power, does the transfer switch automatically select shore power over inverter?  Or do you have to make sure the inverter is powered off?  (I realize it's always good to have inverter off when not using it since it does use some battery power when just idle..so I've read)

2.  Seems like most inverters are for when you have a generator.  Do you just wire the inverter into the spot labeled for generator on transfer switch?

3.  I noticed about a $$60-70 difference between the GoPower and WFCO transfer switches.   What makes one more expensive?  Does it do anything different or just "better quality"?  The WFCO is much smaller than the GoPower making it more attractive for smaller locations.  

4.  I'm a bit fuzzy  on the above note..what happens if you don't seperate the converter to it's own breaker?

Thank you

Horigan

My boat just has a label next to the shore power receptacle; "Ensure the inverter is turned off before applying shore power".  You can do the same approach on an RV if you have AC outlets connected to both an inverter and shore power.

@Yoshi_TAB
Inverters are intended to provide AC power from the house battery.  An alternative would be to use a generator plugged into the shore power receptacle to provide AC power.

elbolillo

Yoshi_TAB said:

Hi,

I'm in the process of installing two lithium batteries along with an inverter in a TAB 320.  I'm on the fence of installing a transfer switch.  In the long run, it seems easier, then all outlets all ready.  It's a bit of a space issue..they are not that small.  Couple of questions:

1.  If you are plugged into shore power, does the transfer switch automatically select shore power over inverter?  Or do you have to make sure the inverter is powered off?  (I realize it's always good to have inverter off when not using it since it does use some battery power when just idle..so I've read)

2.  Seems like most inverters are for when you have a generator.  Do you just wire the inverter into the spot labeled for generator on transfer switch?

3.  I noticed about a $$60-70 difference between the GoPower and WFCO transfer switches.   What makes one more expensive?  Does it do anything different or just "better quality"?  The WFCO is much smaller than the GoPower making it more attractive for smaller locations.  

4.  I'm a bit fuzzy  on the above note..what happens if you don't seperate the converter to it's own breaker?

Thank you

I used the TS-30. Here is a diagram of what the connections would be. Ignore the connections for a charger as this does not apply to you. What I did was install a double breaker, 20amp/15amp where the microwave outlet breaker was. Connect the microwave outlet to the 20amp side and then the converter to the 15 amp side. Keep the converter breaker off when not connected to shore power and you want to use the inverter.

kottum

Murphy's Law: Anything that can go wrong, will go wrong.

Electrical systems are deadly if set up so the above law may apply. Legal implications may also apply. Don't take a chance.

Although it has been posted otherwise, I think our Tab RV's come under the National Electrical Code, section 551.  Use this as your guide to install electrical wiring, rather than internet forum advice (yes I know, I'm giving internet forum advice, and I'am no expert, but please know there are better sources of information).

Doug

Yoshi_TAB

Hi @kottum,

I was going to direct message you, but your profile is private. I agree with everything you say and value your input as I do with everyones on this forum who take their personal time to answer questions.  

I total agree with your comment about electrical systems.  I come from the chemical manufacturing industry and it was all about risk of what can go wrong and when, identifying those risks and mitigating them.    Like electricity, those risks often result in deadly consequences.  I saw over my career many things you would not think people would do, but they did, with some getting badly hurt.

Anyways, IMHO, folks that respond (at least in this particular forum) seem to stay in their swim lane and have a good knowledge of what they are saying.  But in the end, as you are implying, it's up to all of us to do our due diliegance with all the answers provided.

I did take a look at NEC 551 and it does cover  electrical conductors and equipment (but not  low voltage DC )  installed in recreational vehicles .

Best wishes...

Yoshi_TAB

Hi, Here's the link. Free Access - NFPA 70: National Electrical Code  You have to sign up.   I did not spend a lot of time looking it but I don't recall if it has any thing about split outlets.  It does have some specific requirments, but much of it references back to other parts of the NEC. 

 I did not nor did the other poster say that split outlets are specifically not allowed (I have no idea).  I don't want to speak for him, but I believe he was saying it may not be a good practice.  I can see if one was doing a hazard analysis or risk assessment that it would recommend that you not do it and install dedicated separate outlets.  Labeling is what they call an adminstrative control.  It relies on a person to do the right thing.  People can fail to follow signage.  It happens all the time.  I believe what the poster was saying, a better fail proof control  is to have seperate outlets.  Yes, in the end, you still count on someone to turn the power off (but that is a whole different topic )

Again, I'm not saying splits outlets is incorrect or wrong.  I don't want to get into a debate about that.   I'm actually still on the fence to do it myself or install a transfer switch.

Best wishes.

Yoshi_TAB

Hi, 

 Maybe a EE or electrician could chime in.

If I had to place a bet, I would say it is not in any code violation for the following reason.  The design of the outlet (when you break the tab) allows for  power to the single outlet to come from two different circuit branches or breakers.  I don't see how that is any different being powered half by shore power and 1/2 by the inverter.  

I  apologize if I'm the one who implied  a code violation.  That is not what I meant  by my examples.  To me, there is a difference between best practices and code violation.  Like I said, I've  also been thinking about doing it that way.

I think labeling is fine , but I see how having seperate outlets or using a transfer switch could be one step better (depending on one's personal view).

Happy TAB New Year...

kottum

If a residential electrical code does not specifically indicate a violation, the residential electrical inspector still has the option of disqualifying the installation if he decides it is unsafe.

With RV systems, we have no electrical inspector requirement that I know of, some people just flying without a compass.  My judgement with this is to ask myself, does this violate Murphy's Law?. "If something can go wrong, it will".

Two instances of something going wrong here come to mind.

One is having a two completely separate power supplies feeding a single (split) receptacle, and the factory installed power supply disconnected by a technician or future owner who is not aware of the split receptacle.  He may turn off the factory installed power supply, leaving the other half of the receptacle possibly hot.

The other concern is inside this one electrical box are two 120V,  60 cycle sources of power, most probably out of phase with one another.  At any moment, there may be 240 volts difference between them.  If you somehow get between these two parts of the receptacle, or between two different faulty items powered by them, that could be a lethal dose.  And with two different circuit breakers powering the two sides, how much current will it take to trip the breaker to protect you?

I've worked as an aircraft electrician and as a residential/commercial electrician.  I would never install something with this potential for doing harm.  Dangerous practice is not always covered by electrical codes, or "I've seen others do it".

Good practice I believe, would be to properly install a transfer relay, so any of the electrical systems in the trailer would never be supplied by two different power supplies at the same time.  Be aware that RV transfer relays are not bullet-proof, they will prevent two sources of power at he same time, but have a history of failure to make the transfer.  I've had one fail on our Airstream.

Doug

Yoshi_TAB

elbolillo said:

I used the TS-30. Here is a diagram of what the connections would be. Ignore the connections for a charger as this does not apply to you. What I did was install a double breaker, 20amp/15amp where the microwave outlet breaker was. Connect the microwave outlet to the 20amp side and then the converter to the 15 amp side. Keep the converter breaker off when not connected to shore power and you want to use the inverter.

Hi, @elbolillo

I've been looking more at this wiring diagram and the TS-30 transfer switch.  When you say to ignore the connections for the charger, maybe I'm not clear, but isn't that connection designed to do what we are talking about, disconnect the battery charger power when using the inverter?  If the converter charger was connected, when there is shore power, the  N.O. contacts close at the shore power and  at the charger, sending shore power to the charger.  When on inverter power, the N.O. contacts stay open up at both shore power and the charger, not allowing any power to be sent that way.  That would be one advantage of this brand over another, having that built in.

Thank you,

tomtek

     I might be late to this conversation.  I highly recommend the transfer switch .

     I went the Transfer switch route and wired almost exactly like the diagram above for the TS-30.  I used DIN rail mounted breakers for over current protection and a small inline automotive style fuse for current protection of the transfer relay coil itself.  

     I also moved the Alde 120v power to the Shore power side through a DIN breaker to prevent it from being used with inverter.  Basically you end up with Shore power only circuits that you don't want to run off inverter like the Charger and Alde then you have the inverter side with powers all the rest of the 120V circuits.  

     When Shore power is connected the Transfer switch energizes and Shore power is connected to all circuits.  Remove Shore power and the inverter connects to all the circuits minus the ones that are on the Shore power side only. 

   All works awesome and I don't have to worry about what is on or off when plugging in.  I feel the Transfer switch is the only true safe solution.   

     My biggest issue with the split outlet is if 2 things are plugged in at the same time one in inverter outlet and one in any other outlet that have a Hot Chassis which is many devices with 2 pronged plugs then there will be an out of phase high voltage(240 v) situation between the 2 outlets if plugged into Shore power.   It will cycle between zero and 240 volts differential because the Inverter and Shore power would not be in phase and cycle locked with each other.  Sometimes it's more than Electrical Code to provide safety.

This 240 volt possibility seems like enough to not go that route.

elbolillo

Yoshi_TAB said:

elbolillo said:

I used the TS-30. Here is a diagram of what the connections would be. Ignore the connections for a charger as this does not apply to you. What I did was install a double breaker, 20amp/15amp where the microwave outlet breaker was. Connect the microwave outlet to the 20amp side and then the converter to the 15 amp side. Keep the converter breaker off when not connected to shore power and you want to use the inverter.

Hi, @elbolillo

I've been looking more at this wiring diagram and the TS-30 transfer switch.  When you say to ignore the connections for the charger, maybe I'm not clear, but isn't that connection designed to do what we are talking about, disconnect the battery charger power when using the inverter?  If the converter charger was connected, when there is shore power, the  N.O. contacts close at the shore power and  at the charger, sending shore power to the charger.  When on inverter power, the N.O. contacts stay open up at both shore power and the charger, not allowing any power to be sent that way.  That would be one advantage of this brand over another, having that built in.

Thank you,

You wire the transfer switch to the WCFO panel via the AC panel. That will power the converter when connected to shore power. The converter is what charges your batteries. You will need to turn the breaker for the converter off when using the inverter. 

tomtek

elbolillo said:

You wire the transfer switch to the WCFO panel via the AC panel. That will power the converter when connected to shore power. The converter is what charges your batteries. You will need to turn the breaker for the converter off when using the inverter. 

I have my charger circuit of the converter and my Alde A/C wired to the Shore power side.   It only charges when plugged in.  I don't have anything yet on the breaker that was for the Charger.

I have the rest of the A/C circuits in the Converter wired to the transfer switch to go from Shore power to inverter power.

elbolillo

tomtek said:

elbolillo said:

You wire the transfer switch to the WCFO panel via the AC panel. That will power the converter when connected to shore power. The converter is what charges your batteries. You will need to turn the breaker for the converter off when using the inverter. 

I have my charger circuit of the converter and my Alde A/C wired to the Shore power side.   It only charges when plugged in.  I don't have anything yet on the breaker that was for the Charger.

I have the rest of the A/C circuits in the Converter wired to the transfer switch to go from Shore power to inverter power.

I wanted to have the option of running everything off the inverter, even the Air8. I put a new split breaker in (20/15amp) in place of the single breaker for the microwave outlet and then connected the converter to the 15amp side. In reality I hardly ever used the converter since it is not lithium specific. I used my solar to keep everything charged.

tomtek

elbolillo said:

I wanted to have the option of running everything off the inverter, even the Air8. I put a new split breaker in (20/15amp) in place of the single breaker for the microwave outlet and then connected the converter to the 15amp side. In reality I hardly ever used the converter since it is not lithium specific. I used my solar to keep everything charged.

We have ran the Air8 2 nights last summer on my Lithium Inverter setup.   Turned it on after sun went down and back off in the morning.  Worked fairly well but it won't go any more time than that unless you have a substantial amount of Solar Panels.   My 300 Watts of Solar wasn't able to come close to replenishing during the day.  

My Converter is the Progressive Dynamics 60 amp charge Lithium capable version.  

ckjs

tomtek said:

     ...  
     I also moved the Alde 120v power to the Shore power side through a DIN breaker to prevent it from being used with inverter.  Basically you end up with Shore power only circuits that you don't want to run off inverter like the Charger and Alde then you have the inverter side with powers all the rest of the 120V circuits. 

That’s a great idea. Did you mount a small DIN rail in a box? I looked around a little and didn’t find a small enough DIN enclosure to hold the breaker. What did you use, if I may ask?  ( well I guess I just did )

tomtek

ckjs said:

That’s a great idea. Did you mount a small DIN rail in a box? I looked around a little and didn’t find a small enough DIN enclosure to hold the breaker. What did you use, if I may ask?  ( well I guess I just did )

I didn't put it in a box I just screwed the DIN Rail to the wall next to where the Shore power comes through wall.  I mounted a grounding bar below it for the Shore power side.   On the DIN rail is a bus bar with a cover built in for the neutral and 2 mini DIN rail breakers.   One breaker for Alde and one for the PD Converter Charger.  

Here are the DIN products purchased I had the little short rail piece in a drawer.   The components all have decent protection from bare exposed circuits so I didn't feel the need to put it in a box.

https://www.amazon.com/gp/product/B00SFYWO02
https://www.amazon.com/gp/product/B08JJDZ667
https://www.amazon.com/gp/product/B09F5ZY3LM




Its a little messy I will clean it up when the temperature rises some

All seems to work very well happy with it and it didn't cost a whole lot.