Powering house from idle bus?

[semipro]

Originally Posted by ermracing

I think we'll just wire in a separate panel to be fed from the bus and plug in a few things to use the 'free' power, even when the grid is up. This system would not connect to the grid in any way, just to keep it simple.

This would seem to be the simplest and safest solution.

[semipro]

Originally Posted by roach711

Here's the 30amp transfer switch we installed. I ran a cable from it out to the garage so I can hook up the generator but a mobile solar array would be equally simple to hook up to. You'd need to come up with a safe way to run an extension cord from the bus to the garage power inlet (no hot male connectors!).

Your genny or solar array powers the transfer switch so there's no chance of back feeding the grid.

If you go this route though it seems like you can use the public utility grid or bus PV but not both at the same time correct?

For my future use I'm looking for a solution where my bus PV can augment the grid (with net metering) or provide backup power during grid outages.

[Dirtdoctor]

My farm is off grid- I store power in 2 - 48 volt forklift batteries. I will install a drop cord from the solar panels on the bus to feed I to the power house (tough shed) where my outback power inverter system is located. I’m behind schedule due to the flooding in 2017 we had - but I will ensure that both systems are compatible. Cheers.

[semipro]

From the research I've done, to use your bus as backup power where anti-islanding is automatic (to protect linemen ("linepersons"?) it seems you have to use a device that detects when the grid goes down and then use it to disconnect your system from the grid using a contactor (between your house and grid at the service connection).

Relay: The only one I could find, about $500
https://www.victronenergy.com/upload...lutions-EN.pdf

Contactor: something like this at about $200 (I didn't check the specs to see if the above relay was compatible): https://www.ebay.com/itm/Cutler-Hamm...wAAOSwg5FcQewe

[rffffffff]

I haven’t researched this at all yet, but you face a phase problem if you have two separate sources of AC at the same time. The AC waveform is a sine wave, and if the solar inverter wave goes up while the grid wave goes down you have issues. I’m assuming you would need a grid tie-able inverter on the bus in order to hook into house power unless you were isolated... if you just have a normal inverter like I have the idea of merging AC into AC seems like a really bad plan.

[semipro]

I believe you are correct. A grid-tied inverter does the phasing needed to align the sine waves and frequency which does vary from 60 Hz some.

[Rivetboy]

Originally Posted by BlackJohn

" We currently backfeed the main house panel from our generator (non-bus related) and simply kill the main, street side, breaker when the grid goes down."


...but you are livening up the neutral on the grid side. That can kill a lineman not expecting it.


John

OK, I will bite, How are you "livening" up the neutral? The main is open so there is no potential on A or B phase being backfed into the grid and at the service the neutral and ground are bonded together and also bonded to earth ground. The difference of neutral and ground is 0. Unless, you are talking difference of potential of grounds and I do not believe that you are.
Joe

[BlackJohn]

Originally Posted by Rivetboy

OK, I will bite, How are you "livening" up the neutral? The main is open so there is no potential on A or B phase being backfed into the grid and at the service the neutral and ground are bonded together and also bonded to earth ground. The difference of neutral and ground is 0. Unless, you are talking difference of potential of grounds and I do not believe that you are.
Joe

Fair question but I do not get how you are powering up the circuits you want to be hot from the source you have.


If you are tying into the house panel branch circuit wiring say, on certain breakers...then the neutrals for those circuits are tied into the main neutral block of the house panel.


That is in no way connected to the main buss bars but loads the neutral bar when on auxiliary power.



That is why I asked for pics to get some idea how it is wired. i could tell in a glance of the setup but just guessing how you did things.


So, if using the neutrals of those circuits you liven up and the main neutral bar, therein lies the problem, back feeding the grid neutral.



Make sense now?


My questions for you are precautionary because if that wasn't inspected and passed there could be major legal and insurance implications, issues etc if stuff happens. Don't mean to alarm you but a heads up.



John

[ermracing]

We backfeed the panel through a 30a 220 breaker from our generator (un-related to the bus issue). Both are off when there is grid power. When the grid goes down I flip the 200a main breaker off as well as all the other breakers in the panel, crank up the generator then flip the 30amp breaker on. I then selectively turn on breakers to the house based on what we need, and what the generator can power.

[Mudhutwarrior]

Run solar panels and battery bank with an inverter. Have a wind genny I can raise when needed. Installed a heavy duty 400a alternator also. When power goes down I can easily power the house from the bus. I use a 100' 8/3 sj cord though its overkill because my house load during a power failure rarely exceeds 35a. Issue for high gauge on cord is to compensate for voltage drop under load. I just kill the mains and power the house when needed. No wind and no sun I can just idle the diesel and charge the battery bank. Have run 11 days like that previously with no issues and never drew down the bank past 60%.

[ermracing]

Originally Posted by Mudhutwarrior

Run solar panels and battery bank with an inverter. Have a wind genny I can raise when needed. Installed a heavy duty 400a alternator also. When power goes down I can easily power the house from the bus. I use a 100' 8/3 sj cord though its overkill because my house load during a power failure rarely exceeds 35a. Issue for high gauge on cord is to compensate for voltage drop under load. I just kill the mains and power the house when needed. No wind and no sun I can just idle the diesel and charge the battery bank. Have run 11 days like that previously with no issues and never drew down the bank past 60%.

Thanks for the details on your setup. We have a 100' 10g extension cord which I think is good for 20a. How big is your battery bank?

[Rivetboy]

So you are backfeeding ground essentially. I think I understand what you are saying if there is no ground on the aux genset the neutral will be hot after the load but it is still bonded to earth at the service regardless if the ground is floating on the aux genset.Where is the difference of potential? Anyhow, Lineman and Electricians these days are required to be using dated and tested gloves, face sheilds with arc/blast protection, Nomex and cotton clothing and insulated boots. Cheers! Joe

[Mudhutwarrior]

Originally Posted by ermracing

Thanks for the details on your setup. We have a 100' 10g extension cord which I think is good for 20a. How big is your battery bank?

I run eight golf cart batteries. In a cost benefit sense it works best for me.
If your running 10ga. I would suggest the best connectors for it. biggest issues I have run into is the connections. They will suffer burn offs easily from high resistance. Use the best quality connectors and receptacles.
Hospital grade work best but I got real lucky and found surplus pin and sleeve connectors. They are the cats arse but expensive as all get out.
If you just use off the shelf check them regularly and have spares. If one shows heating replace both the receptacle and plug at the same time. If one is damaged they both are.