Help with grid-interactive EG4 18k config

[DaBeaver]

I’m in the process of building a new house, doing everything myself except the framing. Got the concrete basement walls up and need to start thinking about how I’m going to set up the electrical panel.

Constraints:
1. Will need at least a 300A Panel for an electric tankless water heater.

2. Want the house to be backed up by the 18K except for two (big) loads. Those are (1) the tankless water heater and (2) the EV charger (both these loads will be in the garage close to the panel).

I’m considering a 300A or 400A panel with a 200A sub panel that runs the house and is backed up by the 18k. Or two independent panels, one of which is 300A and is not backed up, both these options seem cludgy, I suspect there’s a better config but not sure what it is.

The solar array will be ~14kW.

 

[pvgirl]

Common setup for 320/400 amp service is 2 200 amp panels fed of the same meter, instead of larger panels which are often very expensive.

One option is to have one 200 amp panel that is powered by the 18kpv, which has all the loads the will be backed up. The second 200 amp panel will be for the large loads that are not getting backed up.

 

[SignatureSolarJames]

This would be possible with the use of the CTs in the main panel

 

[DaBeaver]

Common setup for 320/400 amp service is 2 200 amp panels fed of the same meter, instead of larger panels which are often very expensive.

One option is to have one 200 amp panel that is powered by the 18kpv, which has all the loads the will be backed up. The second 200 amp panel will be for the large loads that are not getting backed up.

This would be the obvious thing to do if I didn’t need a 300A+ panel for the tankless electric water heater, or maybe I’m missing something. Also any advice on the cheapest way to get module-level shutdown?

 

[SignatureSolarJames]

This would be the obvious thing to do if I didn’t need a 300A+ panel for the tankless electric water heater, or maybe I’m missing something. Also any advice on the cheapest way to get module-level shutdown?

Tigo 2 panel RSD

Tigo TS4-A-2F Rapid Shutdown | Dual Module | 15A, 1000W, 1500VUL/1000VIEC | MC4, 2.2M Cable

Signature Solar provides solar panels, off-grid solar systems, grid-tie, and hybrid systems. Quality solar inverters, bifacial solar panels, complete solar kits, solar batteries. Featuring brands such as EG4 Electronics with their solar battery, LifePower4 and EG4 LLifePower4 and EG4 LL

signaturesolar.com

 

[Quattrohead]

tankless electric water heater

Could a hybrid water heater work for you ?

 

[DaBeaver]

Tigo 2 panel RSD

Tigo TS4-A-2F Rapid Shutdown | Dual Module | 15A, 1000W, 1500VUL/1000VIEC | MC4, 2.2M Cable

Signature Solar provides solar panels, off-grid solar systems, grid-tie, and hybrid systems. Quality solar inverters, bifacial solar panels, complete solar kits, solar batteries. Featuring brands such as EG4 Electronics with their solar battery, LifePower4 and EG4 LLifePower4 and EG4 LL

signaturesolar.com

Thanks James, ordered 40x Canadian solar 390W panels from sig solar today, will be ordering the inverter and batteries eventually too
Edit: was wondering why I couldn’t use the cheaper $30 ones for a bit before realizing the 2F units can each isolate two modules

 

[DaBeaver]

Could a hybrid water heater work for you ?

Never heard of it, link? Part of the reason for tankless is to save space

 

[Zapper77]

This would be possible with the use of the CTs in the main panel

I 2nd this.

 

[Zapper77]

Never heard of it, link? Part of the reason for tankless is to save space

Hybrid use a heat pump mounted on top of the water heater as the heat source.

 

[Zapper77]

They are not known for saving space. ?

 

[DaBeaver]

I 2nd this.

Could you expand on this a bit, CT = Current Transformer? Maybe I’ll downgrade my electric tankless water heater so I can get away with 2x 200A panels…

 

[Zapper77]

Could you expand on this a bit, CT = Current Transformer? Maybe I’ll downgrade my electric tankless water heater so I can get away with 2x 200A panels…

Using CTs on your main feed will allow the 18Kpv to provide maximum power towards all connected loads. I'll draw a quick napkin diagram.

 

[DaBeaver]

Wow, thanks! So CTs let you go straight from the meter to large loads?
Edit: Or are the CTs sensors to make sure I’m not back feeding the grid?
Edit again: should have put in OP, I have 1:1 net metering

 

[Zapper77]

Wow, thanks! So CTs let you go straight from the meter to large loads?
Edit: Or are the CTs sensors to make sure I’m not back feeding the grid?
Edit again: should have put in OP, I have 1:1 net metering

CTs are sensors that monitor flow of electric, they allow the 18Kpv to push power up stream.

Since you have 1:1 metering it doesn't matter assuming all excess solar is sent to the grid and returned at zero cost.

Some of us have crappy tarifs for excess solar and we still have to pay full price.
example: receive 5 cents per kWh that is fed to the grid and charged 15 cent when used....for a net loss of 10 cents.

 

[1201]

Electric and tankless don't go together, so I've heard

 

[pvgirl]

This would be the obvious thing to do if I didn’t need a 300A+ panel for the tankless electric water heater, or maybe I’m missing something.

For residential installs the 320/400 amp service is typically installed with 2 separate 200amp main panels fed by one meter, and loads are distributed across these 2 panels and because there are 2 separate 200 amp panels the total load can be up to the 320 amp maximum.

In your particular case you could have the circuits for the tank less water heater and the EV changer, along with any other loads that don't need backup in one of the main 200 amp panels. The other 200 amp panel, will be fed thru the 18kpv, and will contain the loads you want backed up. The CTs are used, if desired, to limit power be sent to the grid from your solar and batteries, but still use your solar or battery for loads on non backed up panel, the one with the water heater and ev charger, when the grid is available. The CTs will be placed close to the meter and around the wires feeding both the inverter, and the other 200 amp panel.

 

[pvgirl]

Electric and tankless don't go together, so I've heard

The big disadvantage is they require a large demand of electricity when they are running, especially in climates with cold water, which could mean needing a larger electric service, for customers with TOU rates paying big money for hot water during peak rates, and being very hard run off an inverter or generator. In addition to the requirement of all tankless water heaters requiring an annual flush.

 

[Quattrohead]

I assume by now you have found out that a hybrid water heater is basically a freezer turned inside out, it sucks heat from its surroundings and puts it into the water and returns cold air to the surroundings. They are about 18 inches taller than a regular tank and seem to use 600 to 1,000 w of energy to run.
The disadvantage is they do not work that well in a very cold environment and are slower, so you might want to upgrade to an 80 gallon.
They do also have regular heating elements built in that they will use as a last resort.

 

[DaBeaver]

So I’ve called these “heat pump hot water heaters” and did look into them, they’d be my second choice. I’m aware of the pros and cons of tankless electric and since I don’t have TOU and also pay 6.8c/kWh and also have 1:1 net metering and also want to save space I’m pretty set on the tankless electric.