My Greenish Power Project and Updating a Few Grid Cords

[Burnin Since 1991]

I presume 20 kWh per day, not a max of 20 kW.
That, imo, will never be done with dinky solar panels.

I have 20 panels of 360 W, so 7.2 kW. Half facing East, half facing West on a rather low slope roof. Some trees affect generation after 3 pm in summers.

I produce, on average 17 kWh per day. 35 on high days, and zero on snow days. Total yearly production divided by 365 is 17 kWh .

You are farther north, have more cloudy days, but can orient your panels better.
I think you'd need at least 8kW to get 20 kWh on average (i.e. more in summer and much less in winter).
That's 40 200 W panels...!

yes, per day. Dang that's a lot of panels! I'm thinking we use too much electricity!

I do have fairly clear sun on sunny days with minimal shading. I don't want to cover my house with solar panels either. Well, I guess we will see where this goes!

Would you start with a big solar generator and build on it or home brew your own DIY setup? I'm really crunched for space. I'm not sure I can squeeze a DIY setup into my utility room or not. It's pretty tight in there already.

 

[stoveliker]

It depends on the goal.
If you want to end with whole home off grid,.do it right from the start. Finagling small diy parts is going to be orders of magnitude more expensive than biting the bullet for one big system.

But I think you should not do that given your time horizon.
Get a few panels and (<5) batteries for the essentials, and call it a day.
You wont make your money back anyhow with such small parts. But it gives peace of mind.akd that's worth something.

So peace of mind by having your essentials taken care off piecewise, and then spend any other money reducing power usage and increasing insulation and air sealing.

 

[Burnin Since 1991]

Solar may still be viable in mass. Look up balcony solar basically it’s a plug system that can be sized up to 1500w.

I meant to respond to you about "balcony solar" I think it's interesting. Unfortunately, it's only been approved in one state in the US. It's Utah. Good for them, not good for me. I will keep my ear to the ground on balcony solar though. Thanks for that idea!

 

[Burnin Since 1991]

It depends on the goal.
If you want to end with whole home off grid,.do it right from the start. Finagling small diy parts is going to be orders of magnitude more expensive than biting the bullet for one big system.

But I think you should not do that given your time horizon.
Get a few panels and (<5) batteries for the essentials, and call it a day.
You wont make your money back anyhow with such small parts. But it gives peace of mind.akd that's worth something.

So peace of mind by having your essentials taken care off piecewise, and then spend any other money reducing power usage and increasing insulation and air sealing.

You're right. Sometimes I get off on these tangents . I inherited a little bit of OCD from my mom. One thing I do still need to get figured out is how to route my starlink cable and the three solar panel wires from outside into the family room. I have room behind my tv where it won't be visible. I have a 3 foot knee wall around the family room as it was built into the slope of my backyard. I want to do something that will allow me to add and remove wires without making a mess. I will also run the wires out the side so that they can be hidden behind the vinyl siding. It's also where the new firewood racks will be set up so it's a good spot for the wires.

 

[bogieb]

An update and a couple of questions.


I tested the 50w solar panel for three days. Unfortunately, only one day had any sun and during the peak hours roughly of 10-3pm., the panel was pulling 45-55w. Not too shabby for a dinky panel propped up against my fence on the side of my house. The other days were both cloudy, but the panel was still pulling 5 watts or so, which didn't really do to much, needless to say.

I'm trying to understand solar panels plugged into solar generators. Maybe it's the all in one feature of the solar generators where they combine the solar charge controller, batteries and inverter.

If I have a sol/gen with an xt60 solar panel input and the max input is 200w and 50v does that mean the solar panel must be within those parameters or just that is the max they will use?

I decided to move on to the next phase of testing. I got a 200w 24v bifacial solar panel. It's still in the box, since it snowed last night. The panel is within the specs of the sol/gen.

What if... hahaha I really dislike that hypothetical questions, but here goes. What if I connected a 350w 24 or 48v panel. Would the sol/gen max out at 200 or so watts? The voltage would still be under the listed 50v.

My thoughts are that the wattage would be capped at some point but going over the voltage would be harmful to the sol/gen?

Is a 48v solar panel too close to the 50v max of the sol/gen.

I have refocused my power goal. I'm still working on the other goals of this phase of the project. I like what I have for the start of this project. I'm going to take my home off grid a room at a time. First, partially and then I will build out. Will I be able to run 24/7/365? Probably not. Will I ever do the whole house? Maybe? Maybe not. All of what I have purchased with regards to solar and power backups/ sol-gens etc. can be re-purposed as needed.

Most if not all of my family room is on a sub panel. I have two out buildings that are in the main box, but I can move them to the sub panel. They are mostly storage for my tools and projects that I am working on. I'm working to replace the 4' fluorescent lights with LED and the only other power is used for my portable radio and to charge my dewalt batteries during the other three seasons that don't get snow.

I'm in the process of determining the overall needs to do this. I want to make this a scalable DIY project. I feel like I need to come up with a solution that will be gradually put in place without replacing a lot of items. I want to try to only expand.

I'm looking at both DIY, buy separate controllers, batteries, inverters and so on vs an expandable sol/gen based system using expansion batteries.

I know it's impossible to really know what is going to work. I know that my high end of usage in Jan and Feb is 48-66kw average per day.

During the summer we use about 17kw average per day. 30-50kw per day in the winter is just for heating. Heating and air conditioning are a separate project and at this point I'm not going to include them in my calculations. I'm going to increase my daily number to 20kw.

Is there a percentage fudge factor to add? I don't want to over build by too much.

Adding different rooms will be less of a challenge. We have two spare bedrooms that only see lights and the one bedroom an outlet for charging my dewalt batteries, which is like an hour or two once a month in the winter. The rest of the time they are charged out in the shed.

The main bedroom has a ceiling fan with lights , a table lamp, tv, ac and a power strip for charging my wife's iphone.

The living room only has two lights and another power strip for charging our phones.

I will save the majority of the kitchen for down the road. I do recognize that I will need to build a system that ultimately will support 220v. I'm not sure if I understand if that is something I need to account from the beginning or if it can be added along the way?

Thanks for reading and as always, your input is invaluable!

@bogieb I sent you a DM.

"max input is 200w and 50v"

Volts are pushed to the generator from the panels. So, the max volts (VOC) you can use wtihout damaging the station is 50VOC (actually below that because during cold weather, the panels will produce more VOC - testing is done at 73-75*F).

Watts are pulled by the station. You could get a 500w panel (within the VOC), and it won't affect the station in any manner - BUT, the station will only use a max of 200w from the panel.

Having inverters with such a small amount of wattage input is pretty limiting since this area of the world doesn't get many perfect sun hours per day, even during summer.

 

[Burnin Since 1991]

"max input is 200w and 50v"

Volts are pushed to the generator from the panels. So, the max volts (VOC) you can use wtihout damaging the station is 50VOC (actually below that because during cold weather, the panels will produce more VOC - testing is done at 73-75*F).

Watts are pulled by the station. You could get a 500w panel (within the VOC), and it won't affect the station in any manner - BUT, the station will only use a max of 200w from the panel.

Having inverters with such a small amount of wattage input is pretty limiting since this area of the world doesn't get many perfect sun hours per day, even during summer.

It's a small power station 800w 512wh. I have two of them and will ultimately re-purpose them for the shed most likely. At least during the summer or like you did with the seed mat and box.

And thanks, your explanation helped me to understand. When I was younger I was interested in becoming an electrician. Some of the theories, I couldn't wrap my brain around.

How far under the max VOC should I allow for the winter increase?

The panel I bought from amazon is a 200w, 28voc and will be fine for now. It's bifacial so the true output should be decent on good days.

 

[woodgeek]

@Burnin Since 1991 you are describing a hobby project, not a way to save real money on electricity..

You asked about the solar controller.... the info is in the specs of the power-bank thingy you bought, but it is likely that the input POWER is capped to the spec. If you put a bigger panel on it (below max voltage) it will merely sip a smaller current than the panel can supply. But you should read the info. If the specs say that damage may occur of too high a voltage or too high a power panel is attached... respect that.

As I said, i built a hobby system years ago, with a separate charge controller, LFP battery, panel and inverter. The all in one systems didn't exist when I built mine. After 15 years, I figure I net about $1-2/kWh, about 10X what grid power cost me. And the amount of power I get in the spring/summer is about 3X what I get in the winter.

Now you can CERTAINLY do much better money-wise that I did (bigger systems would be better), but you have to think about scale. A few panels and a portable battery bank is going to struggle seasonally. Like in winter when its grey out for a couple weeks.

You've really got three options:

Option A: Build a system like you've described, and move some of your loads onto it (like the fridge, some lights, wifi, etc). When the system is 'down' or depleted, switch those back to the grid and wait for the sun to return. I am doing the 'small' version of this, just for fun and to have a little backup power to charge phones and stuff in a power outage.

Option B: Build an 'off-grid' house. Build a LARGE solar array and battery bank,, controller and inverter (perhaps as separate units to be integrated) and move everything possible OFF of electric (space Heat and HW, might look at a propane or super efficient DC fridge). Use a backup genny to refill the battery bank as needed (mostly in the winter). Ofc genny power on gas or propane costs MORE than grid power. Overall, power this way is still a multiple of grid power costs, bc of the costs of the batteries. But off-grid is feasible.

Option C: Get a conventional grid-tied, oversized, solar install, take the tax breaks. This will cost 5 figures up front, but be fully automatic. The system will sell excess power to the grid, and buy power from the grid when needed (at a price lower than a backup genny), and you can in principle reach 'net zero'. where the excess you sell in the summer is equal to the shortage you buy in the winter.

Option D: Do C first. Then add a grid-tied battery bank (or two) that is big enough to cover your daily needs then some. This will cost another 5 figures up front also, but be fully automatic. Like in C you can get to Net Zero, but you the batteries pay for themselves selling power during peak demand periods to the utility. They also provide good backup in case of an outage.

Only Option C/D really have the potential to save you money in the long run IMO. It completely depends on the 'deal' you get from your utility and state. Regarding tax rebates and what the electricity buy/sell price. Those rates can be renegotiated later, making the deal less appealing.

Its like backup power. You can buy a little portable genny and run your fridge, a big wheeled genny that can power you house (mostly) or a $$$ fully automatic system (with a service contract) so you don't even know there was a power outage. Choices.

My fun project is to have an EV (with a 75 kWh battery included in the price, 75X larger than your current setup) and a $200 2000W inverter that can run my house during an outage. For days. No gas. No noise. Inside the garage. And I buy all my power cheap from the utility. I think that is a great backup solution for the price.

Have fun.

 

[Burnin Since 1991]

There are lots of options. Other considerations are that we are looking for a place in the southern half of NH with some acreage. Not sure if that will ever happen. Not sure I want to uproot and move somewhere else. My current location is far from ideal. No garage or basement on a slab. But it is home. And has been for the last 37 years. So, in keeping with that, I don't want to make many permanent changes that will affect selling the house, if we decide to do that. I think "Hobby/ spend money on not paying for electricity. at $.35 a kwh it doesn't take a lot to save some money.

 

[Burnin Since 1991]

Its like backup power. You can buy a little portable genny and run your fridge, a big wheeled genny that can power you house (mostly) or a $$$ fully automatic system (with a service contract) so you don't even know there was a power outage. Choices.

I have a nice Duro Max 4400/3300 genny. I don't have a plug to connect it to the panel, but we have plenty of extension cords. I am adding a connection to the breaker box and a lock out to my list of things to do in the spring. I looked into the whole house auto start/switch system. The costs are more than I care to spend. I'm looking at an inverter generator and I'm going to build an enclosure for it to keep it out of the elements.

 

[bogieb]

It's a small power station 800w 512wh. I have two of them and will ultimately re-purpose them for the shed most likely. At least during the summer or like you did with the seed mat and box.

And thanks, your explanation helped me to understand. When I was younger I was interested in becoming an electrician. Some of the theories, I couldn't wrap my brain around.

How far under the max VOC should I allow for the winter increase?

The panel I bought from amazon is a 200w, 28voc and will be fine for now. It's bifacial so the true output should be decent on good days.

That is about as much as I understand electrically, so don't expect me to provide any more knowledgeable questions LOL. I also know that volts are pulled and the panel needs to be capable of supplying the minimum amps needed by the station.

Sooo, the VoC allowance is one of those things I just know you need. But I can't figure out for you. It appears as if it is dependent on the Temperature Coefficient of the panel. I did some Googling, and found some links to calculators. Please note that I have not used any of these calculator because my circumstances mean I either parallel panels or have 2 solar inputs on stations.

Footprint hero

Solar helpers

And then I found this general rule of thumb at a DIY forum

May I suggest that you play around with the stations that you already have before deciding to go further? That will help give you an understanding of what capabilities and performances are important to you for potential expansion. You may find that it isn't for you. You may find that going to a more expensive power station is more appropriate for your goals and needs (or maybe not - everyone is different).

 

[Burnin Since 1991]

That is about as much as I understand electrically, so don't expect me to provide any more knowledgeable questions LOL. I also know that volts are pulled and the panel needs to be capable of supplying the minimum amps needed by the station.

Sooo, the VoC allowance is one of those things I just know you need. But I can't figure out for you. It appears as if it is dependent on the Temperature Coefficient of the panel. I did some Googling, and found some links to calculators. Please note that I have not used any of these calculator because my circumstances mean I either parallel panels or have 2 solar inputs on stations.

Footprint hero

Solar helpers

And then I found this general rule of thumb at a DIY forum

View attachment 346516

May I suggest that you play around with the stations that you already have before deciding to go further? That will help give you an understanding of what capabilities and performances are important to you for potential expansion. You may find that it isn't for you. You may find that going to a more expensive power station is more appropriate for your goals and needs (or maybe not - everyone is different).

True all! I will check out the calculators. I have been doing some reading on that forum and also watching the you tube videos that the founder of the forum runs. I was just reading yesterday that 15% was a good cushion but now 20-25%

The Aferiy P280 2800w 2048wh is expandable to 10k I believe. The expansion batteries are reasonable priced. It's the main reason I bought it. Next step however is getting that 200w panel connected to the smaller 512w unit. Though clearly, there is no rush to get that done, with the weather we're having.

 

[Burnin Since 1991]

I'm confounded...

The Aferiy P280 has 2 XT90 solar ports, each rated to a max of 600 watts for 1200 total

The max voltage is 55 and a 15% overage protection get us to a max of 44v. Max amperage is 20a.

If I do that math, 44voc x 20a = 880w

if I do it the other way for totals, 1200w / 20a = 60v. I've only got 55 max volts.

If I understand this correctly for each leg (XT90) the max is 600w, 22voc and 10amps. That can't be right as that doesn't get anywhere near 600 watts on each XT90.

another way using their exact numbers 55v x 20a = 1100w still 100w short of the 1200 listed.

 

[bogieb]

I'm confounded...

The Aferiy P280 has 2 XT90 solar ports, each rated to a max of 600 watts for 1200 total

The max voltage is 55 and a 15% overage protection get us to a max of 44v. Max amperage is 20a.

If I do that math, 44voc x 20a = 880w

if I do it the other way for totals, 1200w / 20a = 60v. I've only got 55 max volts.

If I understand this correctly for each leg (XT90) the max is 600w, 22voc and 10amps. That can't be right as that doesn't get anywhere near 600 watts on each XT90.

another way using their exact numbers 55v x 20a = 1100w still 100w short of the 1200 listed.

Those specs are most likely for each input, not total. So, 600w, 55 voc (not accounting for cold) and 20a for each input. Unless, of course, the documentation specifies it differently.

That is the way Ecoflow does it anyway.

 

[Burnin Since 1991]

That would make more sense. Their documentation is a little lacking in clarification.

 

[woodgeek]

Remember that solar panels produce power on a curve. When the amps are zero, the voltage is a maximum. This is Open Circuit OC voltage, Voc. Also, if you short the panel out you can maximum amps, Imax, but zero voltage. Since power is current times amps, the power in BOTH of these cases is ZERO.

And wouldn't it be nice if you could get Imax and Voc at the SAME TIME, P = Voc*Imax? Nope, you can't. The power you get is a parabolic curve as a function of V_out, and zero at V_out = 0 and V_out = Voc.

Think of it kinda like the transmission on an engine. Poor power out at low RPM and max RPM. Your max horsepower is not determined by multiplying max torque by max RPM, bc you can't have both at the same time.

So the max power out of a solar panel will be when its Vout is LESS than Voc and Iout is less than Imax.

A good solar controller adjusts Iout until Vout gives maximum power. A maximum power point tracking controller. MPPT. The controller is an 'automatic CVT' for your panel.

The input port needs to have a max voltage in which won't be damaged by Voc, even if the operating voltage is well below that limit. Bc if the controller battery is 'full' it will set I_out to zero, and the voltage from the panel will jump to V_oc.

 

[Burnin Since 1991]

I've spent the last week or so studying up on solar power and reaffirming my electrical knowledge. That is when I wasn't moving massive piles of snow...etc. Looks like the worst of winter has passed. The snow is melting back and mud season is approaching.

I picked a pretty bad time, weather wise to get interested in solar as we've had only 2 or 3 somewhat sunny days in the last 2 weeks.

I am the owner of a Reliance Pro/Tran 6 breaker generator transfer panel. I bought at least 5-7 years ago and I've only taken it out of the box to look at it. Initially, I was too intimidated to consider installing it, however after recently reading the directions, I realize my worries were unfounded and it's extremely easy to install. I've worked on breaker panels before, so I have some experience with this. I have replaced breakers and moved breakers and circuits.

A though occurred to me recently. I have a 100amp panel. I have a sub-panel that has 6 or 8 circuits in it. Only 3 or 4 circuits are in use in the sub panel.

My generator uses an L14-30 P/R (Plug / Receptacle) connector. An L-14-30R comes with the Pro/Tran and can be wired up inside my utility room as part of the Pro/Tran panel or outside, user/ installer discretion.

Most of the gasoline powered inverter generators come "RV Ready" and utilize the TT30 P/R connections. Many of the new Power Stations (battery BU, Solar gen's... not sure what to call them so I'm going with power station) come with the TT30 P/R connections for powering a 30amp RV connection. Most can't receive input power from anything other than a 120v electrical power cord or via solar panels. To recharge the power station with an inverter generator would require connecting via 120v power cord. They only supply 120v and not two phase 240v. Some of the newer power stations and inverter generators can either output 240v or can be inter-connected to supply 240v. If you run a 120v single phase plug (TT30P/R) into an electrical panel, only one leg of the panel is powered.

The Pro/Tran has the capability of being setup as all 120v, all 240v or a mixture of the two. Since the only 240 I would run in an outage would be nothing, I'm not considering 240v at this time.

I have identified the 6 circuits I want to power and most of it is essential lights, tv, internet, charging, fridge etc. We run a woodstove and can cook on several different grills etc.

I need to install a generator receptacle. I'm torn between a main lockout and a breaker for the receptacle (manually turning off all circuits and then turning on only the ones I want to run in the panel and pre-marked and designated on the panel -OR- the Pro/Tran, all wired up and can be switched to the generator circuit whether the power is on or off.

To make matters more confusing I want to install a power station (or a DIY built solar power/ battery backup/inverter) to provide 12v to 120v power in case of an outage. Again, powering only essential needs.

I'm doing some calculations, but if I had to guess, 3500 watts will do what I need to do in an emergency. My intent is to build this out as I go and it's not an all or nothing deal.

I see it as a backup for an outage where it can be charged by solar and if it gets below a certain threshold, the generator would charge the power station, while the power station continues to power the house

- OR -

Once the power station is low, the power station is disconnected from the electrical panel, the generator runs and powers the essentials, including 120v power to the power station to recharge it. Once it is charged, the generator would be shutdown and the power station would be reconnected to continue powering the panel.

I know there are Double Pole, Double Throw switches configured On-Off-On. One leg to the power station and one leg to the inverter generator. Is that doable?

-OR-

To minimalize the chance of having more than one power source should I run the panel lockout and put the generator to the top breaker and then connect the power station to the Pro/Tran?

Another option would be to connect the power station to the panel and the inverter generator to the power station only?

I want redundancy and safety.

Would an On Off On switch rated at 30amps and 120volts work as a switch between power sources?

https://www.amazon.com/gp/product/B0078S8KKO/

I know I threw out a lot of or's but If what I wrote is confusing please ask and I will do my best to clarify!

At this point all of the above is hypothetical as I haven't moved on any of it so far, other than what I already owned.

 

[gthomas785]

If this is for backup only, I would install the interlock in your main panel with a 30A breaker going to the backup sources. Rearrange all the critical loads breakers be on the same leg. From there you can have a SPDT switch to select battery or generator. All manually controlled. The solar would just charge the batteries.

If you want automatic backup it's also doable but gets much more expensive especially to accommodate all the different possible modes.

 

[Burnin Since 1991]

If this is for backup only, I would install the interlock in your main panel with a 30A breaker going to the backup sources. Rearrange all the critical loads breakers be on the same leg. From there you can have a SPDT switch to select battery or generator. All manually controlled. The solar would just charge the batteries.

If you want automatic backup it's also doable but gets much more expensive especially to accommodate all the different possible modes.

At this point I have my vision on emergency backup. I "intend" to keep building on this project but I'm going to at least lay the foundation with a third idea of not being too permanent, in case we decide to relocate.

I got stung pretty bad by the last snow storm. We have a house (jointly owned by the family, not me) but I'm the caretaker. We lost power on Monday and on Tuesday when Eversource announced we should have mostly everyone back online by Friday, I decided I better go down there. I made it to within 40 feet of the house and there was a tree down across the driveway I couldn't get around. I got stuck on the hill there till I was able to hand dig the truck out a little at a time and with help from my neighbor and a passing snow plow driver that did me a huge favor for a generous tip. We have a gas boiler and it needs electricity for the circulators and the ignitor. I re-wired the boiler and got it connected with a pig tail to a 2048wh power station that it ran off for about 16 hours. I shut it down to charge to the power station and shortly after that the power came back on on Thursday afternoon.

The pipes were good, nothing froze. The wifi and cable were out until the power came on, so I ran my cell phone in mobile hot spot mode and connected that way to the internet.

The rest of the story... I had a shovel but no snow blower. The driveway is at least 150 feet long and the walkways are a combined 100 feet. Way too much to hand shovel, though I did most of it over the four days I was there.

I had to bring shovels, a power station and a generator from home, 90 miles away. My home generator and snow blower are moving to the cape and I'm replacing them with new ones for home.

I will most likely duplicate the power station/ backup generator connection setup that I decide on for home. The only difference is a much roomier 200amp panel was just installed last summer at the cape house.

Thanks for your input! Sounds like a plan.

 

[Burnin Since 1991]

If this is for backup only, I would install the interlock in your main panel with a 30A breaker going to the backup sources. Rearrange all the critical loads breakers be on the same leg. From there you can have a SPDT switch to select battery or generator. All manually controlled. The solar would just charge the batteries.

If you want automatic backup it's also doable but gets much more expensive especially to accommodate all the different possible modes.

any recommendations on a switch?

 

[woodgeek]

I faced a very similar dilemmas when I was planning my backup.

What I wanted:
1) A system that was not 'weird' in a way that would need to be torn out when I sold the house, or I would need to explain if I had a tech come and do work on it.
2) The ability to run selected or ALL 120V loads in my house from a standalone 120V source (an EV with an 2 kW inverter in my case).
3) The ability to run a second high power EVSE if/when I needed one.

My 'elegant' solution was just to install a 14-50 Receptacle next to my breaker box, with suitable wiring (6AWG) to a 50A breaker. This is a 4-prong plug that contains BOTH hot legs, a Neutral and Ground.

No interlocks, no switches. Just a code NEMA 14-50 receptacle.

THEN, I made up two NEMA 14-50 plugs (wiring the back of the plug).

Plug ONE adapted the 240V input to the plug needed for a 240V portable EVSE. I could have gotten a 240V EVSE that went into the 14-50 directly, but I already had a 3kW 240V one that had a different plug.

Plug TWO is interesting. Technically it is a 'suicide cord' since it has two males. The 14-50 male, and a normal 120V plug male (with ground). Inside the plug the neutral is tied to the neutral. The ground is tied to the ground. And the 120V hot is tied to BOTH Hots in the 14-50 plug. I keep this plug with the inverter.

Normal operation, I can use Plug ONE to power an EVSE, and charge our second EV. Or any other load I need a lot of juice for, given that 14-50 is becoming the new standard for that.

Backup operation. I pull that regular EVSE plug out. I switch the main breaker to OFF. I padlock the main breaker in the OFF position (I bought a bracket attachment for this), and put the key in my pocket. I switch all the 240V breakers and a couple heavy 120V circuits to OFF. I then plug the suicide plug TWO into the 14-50. I start up my EV, hook up the 120V sine wave inverter, and run a heavy duty 12G 120V extension cord from the inverter to the suicide plug.

This way the inverter drives BOTH 120v legs, in phase. Sweet. If I 'forget' and leave a 240V load energized, it does not run... because it sees 0 volts across the two hots. In phase.

This setup is technically illegal, because I am supposed to have an interlock or interlock panel. My nod to this is padlocking the main OFF. This prevents another person from switching it to ON and energizing the grid (like a sleepy spouse, a curious neighbor or a first responder). I am also convinced that if I did try to energize the grid (if I still had a grid connection to the transformer) I would just pop the breaker on my inverter from overload.

There is one other factor. The normal problem with suicide cords is the hot prongs. That can't happen in my setup. If I plug in plug TWO while the grid power is on, I am connecting a 12G wire across the 240 V hots (!!). Needless to say... the 50A breaker would pop. So I don't do that.

Overall, I have used this system for close to a decade now, and its been perfect. All my 120V circuits run, and I go through the house and do things like unplug the microwave and a couple other loads. Takes me 10 minutes to set up or break down.

-----------------

For your situation: If you have a 240V genny, or expect to get a 240V rig in the future, put in the interlock box and wire in a 4 prong generator receptacle (actually a twist male plug in a socket) not a bogus 120V RV plug. Get an extension cord for your genny. I would not 'subpanel' and just make it able to run the whole thing, and load manage by switching breakers. Write out a list of which breaker to switch off when its NOT an emergency in the middle of the night, or if a spouse has to do it. This is conventional, safe, legal and future proof.

IF you want to run your house loads with a 120V source, consider making up an adapter to power the genny receptacle with both 120V hots in phase. This would then be like my system, but with a proper safety interlock.

 

[gthomas785]

I am also convinced that if I did try to energize the grid (if I still had a grid connection to the transformer) I would just pop the breaker on my inverter from overload

Have you tried to simulate this? It really depends on where the line is down. If no other houses are on the broken segment you can very easily put 13 kV back on the primary with a generator.
However, with your setup, I don't think you'd see anything on the primary due to both hots being the same voltage. You would similarly be powering any other houses that might happen to be on the secondary side of your transformer and probably saturating the secondary windings of the transformer with out of phase current. That should trip your generator breaker, but I wouldn't bet a lineman's life on it without some testing.

 

[woodgeek]

Have you tried to simulate this? It really depends on where the line is down. If no other houses are on the broken segment you can very easily put 13 kV back on the primary with a generator.
However, with your setup, I don't think you'd see anything on the primary due to both hots being the same voltage. You would similarly be powering any other houses that might happen to be on the secondary side of your transformer and probably saturating the secondary windings of the transformer with out of phase current. That should trip your generator breaker, but I wouldn't bet a lineman's life on it without some testing.

Needless to say, I am not trying to simulate this. But I agree that the in phase drive would not do much at the transformer, but that really depends on how its tapped off. which I won't claim to understand. But the 120V loads on the network WOULD load my inverter and pop the breaker.

The real danger is my aerial line is down, a workman doesn't hear a genny in my house, and gets shocked by 120V.

The risks are really all 'human factors'. Like I have a heart attack or an intruder, and a first responder comes to my house and flips the main breaker, etc. Thus, the padlock.

 

[Burnin Since 1991]

I faced a very similar dilemmas when I was planning my backup.

What I wanted:
1) A system that was not 'weird' in a way that would need to be torn out when I sold the house, or I would need to explain if I had a tech come and do work on it.
2) The ability to run selected or ALL 120V loads in my house from a standalone 120V source (an EV with an 2 kW inverter in my case).
3) The ability to run a second high power EVSE if/when I needed one.

My 'elegant' solution was just to install a 14-50 Receptacle next to my breaker box, with suitable wiring (6AWG) to a 50A breaker. This is a 4-prong plug that contains BOTH hot legs, a Neutral and Ground.

No interlocks, no switches. Just a code NEMA 14-50 receptacle.

THEN, I made up two NEMA 14-50 plugs (wiring the back of the plug).

Plug ONE adapted the 240V input to the plug needed for a 240V portable EVSE. I could have gotten a 240V EVSE that went into the 14-50 directly, but I already had a 3kW 240V one that had a different plug.

Plug TWO is interesting. Technically it is a 'suicide cord' since it has two males. The 14-50 male, and a normal 120V plug male (with ground). Inside the plug the neutral is tied to the neutral. The ground is tied to the ground. And the 120V hot is tied to BOTH Hots in the 14-50 plug. I keep this plug with the inverter.

Normal operation, I can use Plug ONE to power an EVSE, and charge our second EV. Or any other load I need a lot of juice for, given that 14-50 is becoming the new standard for that.

Backup operation. I pull that regular EVSE plug out. I switch the main breaker to OFF. I padlock the main breaker in the OFF position (I bought a bracket attachment for this), and put the key in my pocket. I switch all the 240V breakers and a couple heavy 120V circuits to OFF. I then plug the suicide plug TWO into the 14-50. I start up my EV, hook up the 120V sine wave inverter, and run a heavy duty 12G 120V extension cord from the inverter to the suicide plug.

This way the inverter drives BOTH 120v legs, in phase. Sweet. If I 'forget' and leave a 240V load energized, it does not run... because it sees 0 volts across the two hots. In phase.

This setup is technically illegal, because I am supposed to have an interlock or interlock panel. My nod to this is padlocking the main OFF. This prevents another person from switching it to ON and energizing the grid (like a sleepy spouse, a curious neighbor or a first responder). I am also convinced that if I did try to energize the grid (if I still had a grid connection to the transformer) I would just pop the breaker on my inverter from overload.

There is one other factor. The normal problem with suicide cords is the hot prongs. That can't happen in my setup. If I plug in plug TWO while the grid power is on, I am connecting a 12G wire across the 240 V hots (!!). Needless to say... the 50A breaker would pop. So I don't do that.

Overall, I have used this system for close to a decade now, and its been perfect. All my 120V circuits run, and I go through the house and do things like unplug the microwave and a couple other loads. Takes me 10 minutes to set up or break down.

-----------------

For your situation: If you have a 240V genny, or expect to get a 240V rig in the future, put in the interlock box and wire in a 4 prong generator receptacle (actually a twist male plug in a socket) not a bogus 120V RV plug. Get an extension cord for your genny. I would not 'subpanel' and just make it able to run the whole thing, and load manage by switching breakers. Write out a list of which breaker to switch off when its NOT an emergency in the middle of the night, or if a spouse has to do it. This is conventional, safe, legal and future proof.

IF you want to run your house loads with a 120V source, consider making up an adapter to power the genny receptacle with both 120V hots in phase. This would then be like my system, but with a proper safety interlock.

My house is on a slab. No basement and no garage. I have a utility room or "closet". The access to the room is via an exterior door. The room contains Electrical, water, sewer and Natural Gas.

I do have a generator that runs 30amp 240v, via the L14-30R. All of the different plugs and receptacles and even the required cables, are available online. I can wire up any cable, any way I need. I had planned to install the L14-30R for the generator on the outside of the house. The generator has to run from the backyard. If I run it on the side of the house it makes too much noise, echoing off the house next door.

I understand the voltage drop from running the longer cord.

If I only have one L14-30R I can't connect to the Battery Power Station inside. I can wire up the TT-30 cable to a L14-30 plug and wire it to both phases to get both sides of the panel.

I may install the 50amp receptacles and breaker for future use. Need to think that one out. I only have a 100 amp panel. I could install the R's on a 30 amp breaker initially with tags that the breaker would need to be upgraded to 50 amp if used with a higher amp requirement.

Unfortunately I need to have two receptacles. One outside and one inside. Running cords in and out of the utility room door is just not feasible. The door faces East so if it's open, it's mostly out of the weather but when It's cold I heat the room to keep the pipes happy. I've already have had pipes freeze in there, with the door left open only a crack, in error.

I agree on the interlock and I need to take a closer look at the main panel and the sub panel to see how they're wired. The sub panel was installed when the last owner built the family room addition and I need to make sure he did it properly. I had the panels and the whole house inspected when we bought it and the electrical was pretty solid. They only found a couple of minor issues, which I corrected when we moved in.


My Main panel is 200 amps Murry Crouse Hinds. It has a 200amp hump back main breaker and an interlock kit is between $140 and $200. I have no idea why it would be so much.

So at this point... More thinking is needed

 

[stoveliker]

. I have no idea why it would be so much.

Liability insurance for the mfg.
Welcome to the world of safety equipment.
When things go wrong, they go wrong "bigly" and lawsuits appear.

 

[Burnin Since 1991]

Liability insurance for the mfg.
Welcome to the world of safety equipment.
When things go wrong, they go wrong "bigly" and lawsuits appear.

I looked around and see interlocks selling in the $20-$30 range. Since we're talking about a sliding piece of steel and 4 or 5 small nuts bolts, that price range seems reasonable. 10x that much seems a little unreasonable.

I just found a company selling the interlock for $69- Better than the others I found. Free shipping too.

And I believe earlier I stated I had a 100amp panel. Now that I understand it's a 200amp panel I might install the 50amp receptacles