Thinking of using Splitter Trough to avoid up-sizing main breaker panel

[2PVorNotToPV]

Is it a dumb idea to install an exterior splitter box / trough where a person can land the solar output so that you can avoid up-sizing the main breaker panel? This is for a grid connected system.

[Ampster]

Are you talking about a line-side or a load-side tap? There are a lot of workarounds depending on the code in your area. I used a wiring trough to add a subpanel that I derated so i did not exceed the buss capacity of my main panel. It is more about the calculations and less about the mechanical boxes and troughs.

[2PVorNotToPV]

Thks, Ampster.

In this case the wiring trough would be between the util meter and the main breaker panel.

Can you elaborate a bit on the "I used a wiring trough to add a subpanel that I derated so i did not exceed the buss capacity of my main panel." I don't see what you're doing with that.

[Ampster]

...........
Can you elaborate a bit on the "I used a wiring trough to add a subpanel that I derated so i did not exceed the buss capacity of my main panel." I don't see what you're doing with that.

I have a hybrid inverter which required a separate critical loads panel and my GT solar is connected to that sub panel as well as the hybrid inverter. The subpanel is rated at 100 Amps but is fed with a 70 Amp breaker. The sum of the breakers on my main panel do not exceed the capacity of the main panel busbar. Instead of conduits, I used wiring troughs to connect the panels so I had flexibility in moving circuits. The reference to the trough was just the mechanical method of connecting the panels, nothing magical.

[2PVorNotToPV]

Since this splitter trough will live it's life outdoors on the side of a house I want to make it at least a little challenging to gain access for safety. All I have for ideas so far is to swap the screws that come with the box cover for a type that has a tamper resistant drive. Any ideas ?

[Ampster]

What risks are you trying to manage? The only requirement is that it be waterproof.
Are you worried about someone stealing power?

[foo1bar]

Since this splitter trough will live it's life outdoors on the side of a house I want to make it at least a little challenging to gain access for safety. All I have for ideas so far is to swap the screws that come with the box cover for a type that has a tamper resistant drive. Any ideas ?

I would not bother with tamper resistant screws.

Is your main panel outside? I'm guessing it is. It is likely using screws with normal heads. And probably when you take off the metal panel that covers the breakers you have great big bus bars that can carry 100A or 200A (and probably a hell of a lot more for a fraction of a second if you were to do something stupid like drop a screwdriver across them.)

Even your meter probably doesn't have anything really tamper resistant - maybe a tamper-evident "padlock" that you could cut with a scissors or a wirecutter.
And that won't even have a breaker to trip nearby - you open that up and drop a screwdriver across those contacts and it'll be real nasty.

It's not clear what configuration you currently have - nor what you're looking to do for adding solar.

What amperage can your meter handle?
What amperage can the lines to your meter from the POCO handle?
What amperage is the main breaker in your main panel?
Are they two separate boxes (Sounds like they are)
How difficult would it be to replace your main panel?
How difficult would it be to make your current main panel be a sub panel, and insert a new panel that is now your "main panel" (and is sufficiently sized for solar)?
Have you read up about line side taps?
Do you think you would be comfortable having one?
Would your installation meet all the requirements for a line side tap (wire sizes?,wire length?)
Will you be doing that wiring yourself or hiring it out?
If hiring it out - can you find someone competent to do the work?
If doing it yourself, are you competent to do the work?

What I think you're describing as a "splitter trough" would be a junction box - a much larger junction box than the typical one used for light switches and outlets - but still a junction box that woulld contain your line side tap.

There's also "meter adapters" - that may work for your situation - I would look at them as well.

Personally I had a combination meter/main panel - and it was one that needed replacing anyhow because it was crappy federal pacific. So it's gone and replaced with one that worked for my solar install.

[2PVorNotToPV]

Here is what we are looking at:

Main breaker panel is indoors, rated 200 A and fairly full.
PoCo meter is located outside on the house wall and is rated 200 A.

Will be adding 10 kW dc this summer and will most likely add another 10 kW in a few years ( This is in a Northern local... long heating season that mostly uses heat pumps )
I am familiar with line side taps.
This will be hired out, but I enjoy wrapping the noodle around the options and trade-offs of things like this.

The utility in my area requires 2 separate meters in order to have net metering ( 1 for Util and 1 for NET ). So in this situation the conduit between the existing meter and the main breaker panel has to be cracked open in order to insert the second meter. Indeed, it is kinda in-efficient to use 2 meters when 1 bi-directional meter will do, but I don't have the gold so I don't make the rules.

Since the exterior works has to be "opened and adjusted" I though that the splitter trough could be one good option.

Thanks for mentioning the "meter adapters". I just had a glance at this. So you are referring to what some places call "meter interbase adapters" ?

[khanh dam]

sounds like more insulation would be better investment than another 10kw array. IMHO. also you better check the exact payback terms on the netmetering contract. Because every utility I have talked to that requries a 2 meter setup is actually a pay all buy all scam where they pay you 1/4 the value of what they charge you.

[2PVorNotToPV]

Hey k.d.

Yeah, it's a bigger house, but it is R70 attic and R24 walls. All energy use in the house is 100% electric so before you know it you're using 20,000 kWh a year plus thinking about a potential electric car in the coming years.

In this area the Net Metering is only banking your sun juice. The utility does not pay you anything, but you can bank your surplus for up to a year which is handy for over producing in the summer and then tapping into your surplus during the winter. I don't see it as a scam. I see it as the utility being my battery. There definitely are less desirable net metering arrangements in other places.

[foo1bar]

The utility in my area requires 2 separate meters in order to have net metering ( 1 for Util and 1 for NET ). So in this situation the conduit between the existing meter and the main breaker panel has to be cracked open in order to insert the second meter. Indeed, it is kinda in-efficient to use 2 meters when 1 bi-directional meter will do,

I'm not clear on how what you're going to have for metering.
It could be a meter that connects back to the util - then AFTER that meter, it splits to consumption and production. And there's a meter to measure just production of solar.
OR
A split on the POCO side of the meters - one meter has only production, the other meter has only consumption.
(If the split is on the POCO side of the meters, I would expect those wires/connections will need to be in a box that has a tamper-evident seal.)

[2PVorNotToPV]

I know that what our local utility does with net metering is not super common, but maybe it is much more uncommon than I'm aware of.

Here is exactly how it's done here. The util line comes in from the street ( let's say it's overhead) and into the meter socket box. The digital meters being used here only "count" when juice flows from Line to Load. If there is flow in the opposite direction nothing happens ( there is no second number that the meter keeps track of and the existing count does not go down ). This meter is locally called the Utility meter. If you are going the net metering way then you need to add a second meter which is connected next in line with the existing meter. This second meter will be called the "Net Meter" and it is connected such that "line goes to load" and "load goes to line". Wired in this fashion the meter only "Counts" juice going back out to the street.

The set-up configuration that I'm considering for here is ... Util meter (existing) then Net meter (new) then splitter trough (new) then main breaker panel (existing). The PV will connect in at the splitter.

Clear as mud ?

[foo1bar]

I know that what our local utility does with net metering is not super common, but maybe it is much more uncommon than I'm aware of.

...
The set-up configuration that I'm considering for here is ... Util meter (existing) then Net meter (new) then splitter trough (new) then main breaker panel (existing). The PV will connect in at the splitter.

So - instead of a single bi-directional meter, they do a pair of uni-directional meters measuring the same set of wires.

That doesn't make a lot of sense.

Do they charge you extra for the second meter? Because if they don't, I would think a single bidirectional meter would be cheaper than two unidirectional ones.
Even if you have the bidirectional be digital (so can get each direction's numbers independently) - I would think it's cheaper.
(But maybe I just don't know the pricing of meters)
For that matter - are they already digital meters anyhow?
I know >10 years ago around here the POCOs were rolling out digital meters to everyone - so I would think that most of the country the utilities have at least been looking at it and making plans by now.

In any case - probably the wires from pole to the meter and from meter to 2nd meter need to be in something that'd be tamper evident.
And beyond that you can have the junction box with your line side tap that leads to your main panel and your solar breakers.

How long would the wires be for your tap?
How big would the wires be?
It seems likely that you would be able to do a line side tap.
Not sure it'd be any cheaper or easier than installing a new main panel outside next to your meters and having what's currently your main panel become a sub-panel.
Either way you need a new exterior breaker box. With a new main panel, you'd add the cost of a breaker to feed your inside panel. But that may be cheaper than the cost for a large exterior junction box, the taps to join the wires, and the labor to do that connection. Really, whichever the electrician is more comfortable with is probably going to be your cheaper option - because his time to double check that he has done everything right is extra money. An extra 2 hours of his time is probably going to cover any cost differential betwen the options. (An extra 4 hours because he has to come back for a 2nd inspection because of some minor issue he missed the first time definitely will)

[Ampster]

So - instead of a single bi-directional meter, they do a pair of uni-directional meters measuring the same set of wires.

......

I understood him to say one unidirectional meter in the usual spot and another unidirectional meter reversed and placed on just the solar feed. Different wires and devices measuring flows in different directions. I agree it is inefficient.

[2PVorNotToPV]

So - instead of a single bi-directional meter, they do a pair of uni-directional meters measuring the same set of wires.

That doesn't make a lot of sense.

Foo, you are correct. Over the years there has not been many net metering hook-ups, but the last couple of years PV is taking off in our area so hopefully the util will bring in bi-directional meters. Until that happens it is what it is.

In our snowy area outside breaker panels are basically unheard of. We save our shovelling muscles for the driveway.

The local util rolled out new digital meters a few years back ... might be close to 10 years back, but they are all uni-directional only.

You make lots of solid points, Foo. Our POCO does not charge for a second meter.

It's anyone's guess as to why the POCO has not made bidirectional meters available thus far. My 2 cents is that not bring in bidirectional meters is the path of least resistance (doing nothing).