Trying to safely connect my RV to house.

[CodyR]

Hi,
I have an motorhome (i call it the "bus") with 3.27kw of solar on it and an additional 1.962kw when the ground panels are deployed for a total of 5.232kw. When we travel it works great. The problem is all the solar just sit there with my batts fully charged doing nothing when I'm home. I'd like to power the house off the bus. So, what's the easiest way to do this? I assume the 120v bus inverter that's not designed to be attached to a grid wont work. If i get a grid tied inverter can i back feed a double pull breaker and just have a transfer switch on the bus to feed the inverter. I already have charge controllers on the bus. Are their any cheaper options that don't have the mppt built in and can just be fed 46-56 volts dc from the bus charge controllers? I would use most of the power during the day so there wouldnt be much back feeding to the grid. I understand if i don't have a bi directional meter and net metering set up i wont get credit for any extra, but will they have any problem or bill me more because i might back feed a little? I'd rather not do the whole permit thing which i think would be required to get net metering.
Thanks,
Cody

 

[chrisski]

Not many people have made this work.

but will they have any problem or bill me more because i might back feed a little? I'd rather not do the whole permit thing which i think would be required to get net metering.

They’d have a huge problem with this. You have to permit if you want to back feed. Most likely need to permit no matter what unless you are real isolated.

A 5 kW system will feed quite a bit back to the grid.

The easiest thing to do would be install some loads on a critical loads system and have a 30 amp or 50 amp generator that lug and plug in the RV and just have your RV run that.

I looked at something like that and with my higher wattage loads I use solar for, all are 240 volts and there was not enough demand on the 120 volt loads to make any difference.

I have a 3 kW inverter on the RV which honestly would power a single 20 amp 120 volt circuit. I could run some 120 volt kitchen appliances, but that’s only a couple kWh a day.

Would be useful if I was still level 1 charging my Tesla at 120 volts 12 amps, until I did anything more than drive to work for 25 miles. That 25 mile drive takes 13-18 hours to recharge at Level 1.

Honestly, I think it would be easier to live in the RV at the house than hook it up to provide power.

If you’re going to put a decent All in One, might as well get panels to go with it.

Edit: don’t know any cheap inverter chargers that backfeed to grid. There’s plenty of inverter/chargers that run off batteries that can work with your charge controller and hook to the grid. Mine is an Outback Radian and would work.

 

[DIYrich]

Connect the rv battery to the house battery. The rv will charge them both.

 

[CodyR]

Connect the rv battery to the house battery. The rv will charge them both.

I don't think you understand. The house is a real house with power from the grid. I'm not talking about the "house batt" on the bus. The goal is to save on my electric bill.

 

[CodyR]

Not many people have made this work.

They’d have a huge problem with this. You have to permit if you want to back feed. Most likely need to permit no matter what unless you are real isolated.

A 5 kW system will feed quite a bit back to the grid.

The easiest thing to do would be install some loads on a critical loads system and have a 30 amp or 50 amp generator that lug and plug in the RV and just have your RV run that.

I looked at something like that and with my higher wattage loads I use solar for, all are 240 volts and there was not enough demand on the 120 volt loads to make any difference.

I have a 3 kW inverter on the RV which honestly would power a single 20 amp 120 volt circuit. I could run some 120 volt kitchen appliances, but that’s only a couple kWh a day.

Would be useful if I was still level 1 charging my Tesla at 120 volts 12 amps, until I did anything more than drive to work for 25 miles. That 25 mile drive takes 13-18 hours to recharge at Level 1.

Honestly, I think it would be easier to live in the RV at the house than hook it up to provide power.

If you’re going to put a decent All in One, might as well get panels to go with it.

Edit: don’t know any cheap inverter chargers that backfeed to grid. There’s plenty of inverter/chargers that run off batteries that can work with your charge controller and hook to the grid. Mine is an Outback Radian and would work.

Thanks for info. I may just run my window ac and gaming PC in the house off a heavy duty extension cord but my wife doesn't want a cord running up the side of the house lol.

 

[justinm001]

Victron inverters allow this. You can buy a simple Victron device that connects to your houses breaker panel using CTs and it'll monitor the house power. Basically it monitors how much power is coming into the house and pump that much into the panel so it doesn't use the grid.

Not sure if you need dual inverters for split phase house power or if you can do just 1 leg 120v. I guess technically you have a 120v sub panel and just have it power that stuff.

I was planning on doing this and bought the meter and everything but moved to a place that doesn't allow RVs so the RV is in storage running 100% off solar. I have about the same amount of solar as you just over 5kw. It sits in outdoor storage Nice and cool with a dehumidifier running 24/7

Also Victron has prioritize solar over grid so you can plug the RV into the house and it'll estimate how much solar you get so won't charge batteries if it thinks it'll get enough solar. Basically keeping the batteries at 80% or whatever. Then if leaving for a trip there's a charge to 100 option.

 

[MiSh]

Thanks for info. I may just run my window ac and gaming PC in the house off a heavy duty extension cord but my wife doesn't want a cord running up the side of the house lol.

They make junction boxes for what you propose. Plug RV cord into box outside, then connect inside power cord. Not sure the exact name though. Something like a "thru-the-wall" box. Makes for a much cleaner look than a cord running into a window.

 

[DIYrich]

I don't think you understand. The house is a real house with power from the grid. I'm not talking about the "house batt" on the bus. The goal is to save on my electric bill.

If you have solar on the house, then you can charge its battery from the rv. You will need a grid interactive inverter to use the power from the rv.

Or you could move circuits to a sub panel where you can switch from grid and rv. Same as a generator sub panel, where the rv is the generator.

 

[HighDesertOffgrid]

A "ground mount on Michellin tires" is not UL certified.
Sorry, couldn't help myself.

 

[Recovering EE]

Not many people have made this work.

They’d have a huge problem with this. You have to permit if you want to back feed. Most likely need to permit no matter what unless you are real isolated.

A 5 kW system will feed quite a bit back to the grid.

The easiest thing to do would be install some loads on a critical loads system and have a 30 amp or 50 amp generator that lug and plug in the RV and just have your RV run that.

I looked at something like that and with my higher wattage loads I use solar for, all are 240 volts and there was not enough demand on the 120 volt loads to make any difference.

I have a 3 kW inverter on the RV which honestly would power a single 20 amp 120 volt circuit. I could run some 120 volt kitchen appliances, but that’s only a couple kWh a day.

Would be useful if I was still level 1 charging my Tesla at 120 volts 12 amps, until I did anything more than drive to work for 25 miles. That 25 mile drive takes 13-18 hours to recharge at Level 1.

Honestly, I think it would be easier to live in the RV at the house than hook it up to provide power.

If you’re going to put a decent All in One, might as well get panels to go with it.

Edit: don’t know any cheap inverter chargers that backfeed to grid. There’s plenty of inverter/chargers that run off batteries that can work with your charge controller and hook to the grid. Mine is an Outback Radian and would work.

"Would be useful if I was still level 1 charging my Tesla at 120 volts 12 amps, until I did anything more than drive to work for 25 miles. That 25 mile drive takes 13-18 hours to recharge at Level 1."

120V at 12A yields 1.4kW. 15Hrs at 1.4kW yields 21kWh.

Your Tesla needs 21kWh to go 25 miles? What are you towing?!?

 

[chrisski]

I think I was exaggerating the hours. Driving does “cost me” 367 Wh per mile from the battery to inverter to Tesla. 6 - 8 hours.

"Would be useful if I was still level 1 charging my Tesla at 120 volts 12 amps, until I did anything more than drive to work for 25 miles. That 25 mile drive takes 13-18 hours to recharge at Level 1."

120V at 12A yields 1.4kW. 15Hrs at 1.4kW yields 21kWh.

Your Tesla needs 21kWh to go 25 miles? What are you towing?!?

This thread goes over some stats I got one night.

Thread 'Level 1Charging a Tesla Model 3 off grid'

Dec 3, 2022

I did level 1 charging with my Tesla model 3 with my solar setup, and these are the results:

4.33 miles / hour charged
322 wh/mile from the ac inverter
367 wh/mile from the Batteries to cover AC losses
AC draw from inverter while charging 1400 watts +/-2watts.
AC Draw from inverter before charging 0 watts

Drove 28.2 miles
AC 9.1 kWh used (This accounts for wattage from the inverter only, not DC to AC conversion loses)
DC 10.289 kWh used to cover AC to dc conversion losses. Turns out my inverter is 87% efficient
6.5 hours to charge

Idle Draw of Tesla when it plugged in for charging and...

• chrisski
• Replies: 17
• Forum: Off-grid Living Discussion

• 
• 

“4.33 miles / hour charged
322 wh/mile from the ac inverter
367 wh/mile from the Batteries to cover AC losses
AC draw from inverter while charging 1400 watts +/-2watts.
AC Draw from inverter before charging 0 watts”

 

[justinm001]

Not many people have made this work.

They’d have a huge problem with this. You have to permit if you want to back feed. Most likely need to permit no matter what unless you are real isolated.

A 5 kW system will feed quite a bit back to the grid.

The easiest thing to do would be install some loads on a critical loads system and have a 30 amp or 50 amp generator that lug and plug in the RV and just have your RV run that.

I looked at something like that and with my higher wattage loads I use solar for, all are 240 volts and there was not enough demand on the 120 volt loads to make any difference.

I have a 3 kW inverter on the RV which honestly would power a single 20 amp 120 volt circuit. I could run some 120 volt kitchen appliances, but that’s only a couple kWh a day.

Would be useful if I was still level 1 charging my Tesla at 120 volts 12 amps, until I did anything more than drive to work for 25 miles. That 25 mile drive takes 13-18 hours to recharge at Level 1.

Honestly, I think it would be easier to live in the RV at the house than hook it up to provide power.

If you’re going to put a decent All in One, might as well get panels to go with it.

Edit: don’t know any cheap inverter chargers that backfeed to grid. There’s plenty of inverter/chargers that run off batteries that can work with your charge controller and hook to the grid. Mine is an Outback Radian and would work.

You can get a 120v 30a adapter for Tesla charger and just set it to 2800w or whatever on the 3000w inverter. Get 24a instead of 12a.

You also don't want to backfeed into the grid, you want to offset the consumption. Backfeeding into the grid requires electric company approval and such. Not worth it for 5kw solar. At $.10/kwh and perfectly sunny days you're only gonna hope to get $75/month. Likely you use way more electricity than that

 

[45North]

Kinda gives V2H a whole new meaning. At least the timing is right - assuming the RV is sitting in the driveway all day, unlike an EV.

 

[chicagoandy]

I've been pondering with this idea myself.

1. I already have a Sol-Ark 15K running the whole house, which has documented support for AC coupling of additional PV.
2. In the RV I have Victron Multiplus 2, which should be more than happy to provide that AC.

I think this means I just plug the output of a Multiplus 2 directly into a nearby wall outlet.

It seems like an overall bad idea, but maybe not?

 

[justinm001]

I've been pondering with this idea myself.

1. I already have a Sol-Ark 15K running the whole house, which has documented support for AC coupling of additional PV.
2. In the RV I have Victron Multiplus 2, which should be more than happy to provide that AC.

I think this means I just plug the output of a Multiplus 2 directly into a nearby wall outlet.

It seems like an overall bad idea, but maybe not?

Victron has a network device that you connect to your house breaker panel and it'll backfeed power into the house to offset the load. Not sure how it works on 120v though. I bought it but have dual inverters in split phase but moved before it came so couldn't test it out.