Need Help configuring for residential

[mtymous]

Bottom Line Up Front: In a rental, Property Manager is cool with some upgrades but not a full-blown solar upgrade. He's paying for a 200a panel upgrade and whole new panel etc. I'd like to buy an EG4 18k pv & EG4 PowerPro to power whatever I can from a transfer switch. Can you help me find/build a solution I can have wired in as a transfer switch that would only power the circuits in the transfer switch and still leave large appliances (Oven, Stove, HVAC) grid tied?


I'm in a rental property and the property owner doesn't want to put in solar permanently. He's ok with me having ground mount and things that aren't mounted to the house itself to power batteries etc. He has already agreed and found an electrician to install 200a service to the house (currently on 100a) and will be fully upgrading the panel and all breakers. I thought it might be as easy as having him install a 10 circuit transfer switch for a "generator" and having the other loads (HVAC, Oven, Stove, all the 220v loads) remain on the main panel and on the grid. This would let me run all of the 110v loads on an 18k pv and PowerPro setup, but if needed, I could switch the transfer switch back over to the grid and simply run them on grid if the batteries died etc. Of course that would be a manual process and I'd have to do my own power monitoring.

I'm trying to avoid having to sign up for a solar plan with with SoCal Edison and just run 10 or so circuits independent of the grid with the transfer switch in "generator" mode and still be able to switch back. I'm not an expert on this stuff just yet, so will a transfer switch still allow back-feeding to the grid or the main panel in any situation if it's all switched to "gen"? Will I need to get a main breaker lockout for generator mode if I have a separate 10 circuit TS? What about my meter? Is there a chance the TS in GEN mode would somehow still backfeed the meter?

Thanks for any help here. Not trying to pull the wool over on the power company or anything here. I just want to be able to design a system that will function this way and get it to the electrician before he goes to pull permits etc.

Thanks!

 

[chrisski]

Bottom Line Up Front: In a rental, Property Manager is cool with some upgrades but not a full-blown solar upgrade. He's paying for a 200a panel upgrade and whole new panel etc. I'd like to buy an EG4 18k pv & EG4 PowerPro to power whatever I can from a transfer switch. Can you help me find/build a solution I can have wired in as a transfer switch that would only power the circuits in the transfer switch and still leave large appliances (Oven, Stove, HVAC) grid tied?

I see no practical way to get this project done for a rental. pretending this is a free install, how much do you think your electric bill is a year?

What you’re asking for is a critical loads panel, another panel on the side of the house that will have what you run off solar. However, by taking the big loads off it, the 18k may be underutilized. I would be shocked if your 18k EG4 could not be setup for a critical loads panel.

Critical loads planning is pretty important so that the loads can be powered from the solar inverter and batteries. I did not find this easy for me, and even with what I thought was meticulous planning, I found a couple of extra items on there I did not expect, like the 15 amp kitchen circuit powered a couple of other rooms and the higher wattage dishasher. The critical loads panel ought to be limited to the kW the inverter can produce.

You can sell power back to the grid, but that is a grid tied system that your owner is against.

80% of my electricity comes from these large loads. I have 2 X AC units that draw 4.5 kW and 5.5 kW watts when powered up, and an EV charger that can charge at 11 kW. My 8 kW inverter has the smaller AC hooked to the critical loads panel, and any excess electricity is pushed back to the grid of which the power company still allows me to power my loads with my own generated electricity before it is sold back to them at 1/3 rd the cost I pay per kWh.

It seems with no permanent install, this really takes out the hope of a critical load panel, and also takes out the hope of a grid tied sell back option. Even if this was acceptable to you, I do not see any practical way this could be built without any permanent modifications to the structure.

 

[mtymous]

Thanks for the feedback, Chris. Really appreciate it.

I should have clarified, the home owner is ok with me paying for a permitted and professionally installed critical loads panel that could be powered by a generator etc (or in this case, hopefully the 18k). The homeowner and I work together well and hes very practical about these things so long as its a viable and useful upgrade to the house.

My electric bill is over $225 a month on average and I dont even have Air Conditioning. Ha. I actually use less than 20kWh a day on average, but the price of electricity here is insane

For better or worse, I live in SoCal and I dont have Central AC. The other large loads (Dishwasher, Oven, Stove, Clothes Dryer, HVAC Blower) can remain on the main panel since I hardly use them and they dont make sense as "critical loads" to me if the grid goes down. Ive mapped every other circuit in the house (every plug and switch) and tested the loads at idle and at normal load so I have those set.

A "heavy" load distributed amongst the whole house on the circuits which would be on that Critical Loads panel would be 2.8kW And a max "surge" (less than 5 minutes) would be no more than 7kW. And thats a VRRY heavy estimate.

 

[zanydroid]

This sounds like a terrible idea. I can be convinced otherwise with the financial numbers and Bill of Materials breakdown, and I’m disinclined to supply help beyond this point without seeing more of the project feasibility analysis and risk management

Before tax credit you will be out $9000 for the 18kpv and batteries. The solar panels plus mounting balance of system are probably at best at a floor of $1/W unless you scrounge up used panels.

Structurally compliant ground mounts are probably not that cheap, and if I was a property owner I would be worried about liability if panels get pulled out by uplift and blown around. California gets some crazy gusts at times.

Now, if you make the financials make sense to this point, then you have to factor in the contractor markup. The panel up is usually less than $4k up here in SF area, so that isn’t terrible, but you also don’t need it. Redoing circuits it in a transfer switch/Critical loads compatible way is the major value add from that electrical rewire, it would probably fit in that $4k.

Then that leaves the panels, and usually you can’t find someone to hire for cheap in California, the industry is geared towards turnkey. This is where it gets really sketchy.

Neither you nor the property owner can do electrical work as an owner builder since this is a rental property, which means all work has to be done by a licensed contractor. Or the majority of the system (including the ESS portion which California is highly opinionated on with respect to residential code due to the fire risk) needs to be done off the books.

OTOH you are forgoing interconnect which means you can do a lot more stuff off the books. And you can also pick cheaper equipment like 6000XP, which is $3500 less than 18kpv. 6000XP will likely never be eligible for code compliant install in CA.

(On the other other hand, I do not trust/permit my renters to DIY this level of alteration)

You can also consider 12kpv, which is somewhere in the middle. This is pending certification for code compliant install.

You can maybe consider PowerPro plus 6000XP with no solar and superpeak SCE plan (note you may not be allowed to enroll in it, check eligibility). And use that battery only setup to harvest the $.25 or so spread between peak and off peak. Solar panels have better ROI than batteries, but I’m not sold that you can pull off ground mounts safely and economically

 

[mtymous]

I appreciate the financial advice, but I'm not really concerned with the cost. This is an investment that will certainly pay for itself in savings over time and the peace of mind of having a battery and solar backup when the power goes out (10 times a year last 2 years). I already have 5kW of solar and 7.2kWh of off-grid power at the house that is all permitted and installed, so thats a non-factor (why I didnt include it in the original post). Ill be getting the 18k pv and PowerPro. This is again an investment for a buy once and grow into the system. I can/will take it with me when I move as well, furthering the ROI. If you dont want to help without seeing my business plan, RMP, and financial status, then thats ok.

Money isnt really the problem here. While I do appreciate the general concern for cost and potential ROI, I'd prefer to just look at the reasonable technical solutions and then make a financial call later.

 

[zanydroid]

OK, I can't help you with the ground mounts, and it would be a lot of salvaging work to pull them off.

A transfer switch/transfer panel by definition is supposed to allow two power sources (typically grid and generator) to be interlocked such that they can't operate in parallel with each other. Transfer switches and interlocks are pretty simple, and I would trust a UL-listed one of either kind to do the right thing.

The appropriate off-grid inverter or hybrid (and this is annoyingly complicated to verify, inverter companies are terrible at explaining which mode they operate in) can include an automatic transfer switch programmed to not allow grid and inverter to run in parallel. Some people don't trust these, and add an external manual or automatic transfer switch. The potential of messing it up is the large disadvantage of relying on the internal transfer switch, and I do not know of an easy, universal way to verify what it exactly does (whether from looking in documentation, certifications, or with commissioning test process that works for all equipment), that doesn't eventually rely on "word of mouth" (best case, it's from a higher level tech / owner of the company selling it to me). This is, as you might imagine, highly unprofessional and frustrating.

The advantage of the integrated transfer switch is that you can automatically switch back to grid / charge the batteries from grid.

Another approach is to use manual transfer switch + something like a chargeverter to keep the battery topped off. This is called double conversion and will add 15% overhead to any power you take from the grid.

 

[mtymous]

Thanks! I appreciate that. I figured a regular transfer switch and having the inverter run directly into it would be the easiest way, albeit a one-way street and cant really charge the batteries from the grid. I think the o ly solution for that would be to have a 30a plug out to the inverter or have it on its own circuit at the panel as well. Though, Im really not overly worried aboit charginf from the grid. That would sort of defeat what Im going for here and if I need to charge the batteries, I could switch the loads back to grid and let the solar fill the batteries. Take the grid $ hit either way