Adding a Tariff meter

[brian5]

I am adding a tariff meter for solar. I have a couple of questions:
1. Best way to tap the incoming line at the existing meter?
2. Does the utility supply still land on the top of the new meter socket?
3. On the PV disconnect to the tariff meter, does the PV feed land on the line or load side of the disconnect?

 

[Carultch]

I am adding a tariff meter for solar. I have a couple of questions:
1. Best way to tap the incoming line at the existing meter?
2. Does the utility supply still land on the top of the new meter socket?
3. On the PV disconnect to the tariff meter, does the PV feed land on the line or load side of the disconnect?

1. Utilities commonly do not allow any foreign connectors in a socket dedicated to their meter, such as insulation pierceing connectors or Polaris tap connectors. If the meter socket is equipped for two wires to terminate the way the manufacturer sells it, which is common for 320A meter sockets, then it is OK to use an otherwise-vacant terminal to connect your system. But if you need to use any connector that is not sold as an accessory to the meter socket, you should plan on making that connection either in a separate enclosure, or in a different enclosure such as your main panelboard.

2. You'll need to check with the utility on what their standard is, for this. The most common answer in my area is yes. This means the sign convention is consumption is positive, and production is negative, just as it is for a service meter that is only for loads. For a customer-owned meter that doesn't concern the utility by contrast, like a Locus meter, your monitoring platform would specify the convention, and it is most common to wire it so production is positive.

3. The "hinge" of the disconnect blades should be oriented toward the inverter. This way the blades and fuses if applicable, are de-energized in the open position. The part of the circuit that doesn't get de-energized by that particular switch, should land on its line-side terminals. Heavy-duty disconnects have plastic shields that guard against accidental contact to the still-energized terminals on the line size. Make sure this is called out clearly on your drawing, so it doesn't get overlooked. I find it helpful to rotate the schematic drawing of the unit so it matches the up/down orientation it has in reality, and articulate the wiring to its top and bottom. That way, the wiring orientation is deliberate and obvious.

I will also add that utilities typically have a standard about the sequence of the meter socket and service disconnect. Factors that affect the answer, are the nominal voltage, and whether the meter is self-contained or uses a CT cabinet. The terms are hot sequence and cold sequence. Hot sequence means the meter socket remains "hot" after the main service disconnect is opened. Cold-sequence means the customer can open their main service disconnect, and de-energize the meter.

 

[kwired]

If the supply is a overhead drop I'd probably just make a second riser and connect directly to the drop conductors just like the normal service does.

if underground supply probably use a splice box or aux gutter or whatever POCO will approve of similar design.

Add: 2 gang meter socket would work great also.

 

[Carultch]

If the supply is a overhead drop I'd probably just make a second riser and connect directly to the drop conductors just like the normal service does.

if underground supply probably use a splice box or aux gutter or whatever POCO will approve of similar design.

Add: 2 gang meter socket would work great also.

The OP will need to determine and advise, whether this system is intended to be a behind-the-meter interconnection, or a stand-alone service. In a behind-the-meter interconnection, you would only have the one service to the customer, that would serve both the on-site loads and be configured as a net meter or bidirectional meter to accommodate the source that backfeeds it. A stand-alone service by contrast, would mean there are separate utility services on the same property, separate service meters, such that one is dedicated to the on-site loads, and the other service is dedicated to the PV source.

The OP's diagram shows a behind-the-meter interconnection, with the tariff meter and PV system on the load-side of the service meter. It also shows cold-sequence metering for the service, that should be confirmed with the utility standards. Cold-sequence metering is rare on single phase 120/240V services.

 

[kwired]

The OP's diagram shows a behind-the-meter interconnection, with the tariff meter and PV system on the load-side of the service meter. It also shows cold-sequence metering for the service, that should be confirmed with the utility standards. Cold-sequence metering is rare on single phase 120/240V services.

I see no disconnects on the POCO side of metering in his diagram.

All I see is a supply conductor that splits to two meters then disconnects. One connects to the PV equipment one connects to customer loads/distribution.

Is basically no different than having two meters for different rates or something of that nature except energy is moving opposite direction in the one meter.

I think his question was how to make that tap to go to the two meters. I think there are many ways it can be done and be NEC compliant.

POCO's tend to have some their own rules they want followed so best to check with them as well.

 

[jaggedben]

Add: 2 gang meter socket would work great also.

That's a potentially good idea, but will only work if the PV meter is configured to work that direction or if someone is okay with it being inserted upside down. Every dedicated PV meter I ever installed had the PV connected to the top terminals, to measure PV production positively in the 'forward' direction.

 

[kwired]

That's a potentially good idea, but will only work if the PV meter is configured to work that direction or if someone is okay with it being inserted upside down. Every dedicated PV meter I ever installed had the PV connected to the top terminals, to measure PV production positively in the 'forward' direction.

Didn't think of that. Would work just fine to find the difference each billing period like they do with regular services those meters are bidirectional in recording, but division of weights and measures or whoever oversees this probably is who would discourage a normally decreasing meter reading vs an increasing reading each cycle.

Electronic meters used today possibly are easy to program to record to increase value in either direction.

Upgraded service at a school once and with it quite a bit of other work. One day not long after switching to new service I noticed POCO guys were back and had the transformer and meter can open. (CT's in transformer and meter on side of transformer) After talking to them they mentioned after first billing reading they discovered the metering was subtractive instead of additive and they had metering configured wrong. No big deal on figuring what was used just had to figure the opposite way from usual, but they were there to make it go the right direction.

 

[Carultch]

I see no disconnects on the POCO side of metering in his diagram.

All I see is a supply conductor that splits to two meters then disconnects. One connects to the PV equipment one connects to customer loads/distribution.

Ok, I misread it. I thought the part labeled "customer distribution" was the POCO's service.

You are correct. This is the diagram of a hot-sequence metered site that has two services.

Every dedicated PV meter I ever installed had the PV connected to the top terminals, to measure PV production positively in the 'forward' direction.

From what I've seen, that's usually the case for customer-owned meters that don't concern the utility, rather than utility service meters. Standards in your area may be different.

 

[brian5]

The drawing I attached in the initial post is how the Utility wants the connection. The Service is underground and existing. My main concern currently is how to legally tap the incoming service. I was thinking that since it will be well below the 10' tap rule I can just use a mechanical tap such as the Burndy wsplit bolt or a bolt on tap Burndy BIPC4/06 in the meter can?

 

[kwired]

The drawing I attached in the initial post is how the Utility wants the connection. The Service is underground and existing. My main concern currently is how to legally tap the incoming service. I was thinking that since it will be well below the 10' tap rule I can just use a mechanical tap such as the Burndy wsplit bolt or a bolt on tap Burndy BIPC4/06 in the meter can?

10 and 25 foot tap rules are for feeder taps.

there is no such rules for service conductors.

 

[jaggedben]

Neither do the tap rules say what type of connector you can use.

You can use any proper electrical connector that's intended for the voltage and wire type and size. Personally I like Polaris type terminal blocks but use whatever you prefer that meets requirements.

 

[kwired]

Neither do the tap rules say what type of connector you can use.

You can use any proper electrical connector that's intended for the voltage and wire type and size. Personally I like Polaris type terminal blocks but use whatever you prefer that meets requirements.

Changes are coming and eventually those methods of making the tap will need to be listed for use on the supply side of the service disconnecting means. 2020 NEC requires terminal blocks to be listed (requirement was moved to 230 that was previously in section for aux gutters/wireways) and a date, Jan 1, 2023 I believe added to give time for manufacturers of other devices to comply with required markings, so things like a Polaris tap may or may not be allowed after then depending if they are listed and have required markings.

 

[Carultch]

The drawing I attached in the initial post is how the Utility wants the connection. The Service is underground and existing. My main concern currently is how to legally tap the incoming service. I was thinking that since it will be well below the 10' tap rule I can just use a mechanical tap such as the Burndy wsplit bolt or a bolt on tap Burndy BIPC4/06 in the meter can?

That would be an example of what I meant by "foreign connectors" in the meter socket. There would be no code issue with doing that in the socket of a customer-owned meter that doesn't concern the utility, but the service meter socket is "their turf", so to speak. Expect that you likely would have to use a separate enclosure for taps on the line side of both meters, unless the utility approves otherwise. Your utility may also specify their own mechanics of constructing the new service.