I'm installing 68 modules as 4 strings of 17 with Enphase M215s. My 200 amp service panel does not have any more spaces. Do I need to upgrade my service panel or is there another way to add to the existing one? Line-side tap?
Comments
A supply side interconnection is an option if your utility and AHJ allows it, not all do. You can combine your strings in an AC combiner so you only need one breaker in the service panel. You could try interconnecting at a sub-panel. There are a number of ways to free up spaces in a panel that you can try. If those don't work you are going to have to change out the service panel. Good luck
You also need to look at the panel's main bus over capacity rating. I had a 150 amp panel and luckily the main bus had a capacity rating of 125%. This is located on the manufacturer spec sticker on the panel. Luckily the 30 amps I was adding to the bus did not exceed the over capacity. Otherwise I would have had to upgrade by service panel.
It is vitally important, that you have a load balance test and measurements performed on your panel.
Thermography scan as well.
Adding secondary power source, means that if you have an INTERCONNECTION agreement,
Which I am assuming that you do means that your Buss on your panel must be able to handle the possible short circuit fault that the system could produce.
The number of spaces alone within your panel is not enough information.
If you currently have an unbalanced load profile on your existing panel. that needs to be remedied, PRIO to bringing your inverters online.
In our systems we generally always recommend that the service panel and service entrance be upgraded.
Most of what you need to accomplish can be corrected by installing a Service/Meter socket that also has service rated circuit breakers, they can be purchased and installed and come in many different configurations. This by far is the single most efficient way to upgrade an existing service. your current service panel (inside) remains intact and you can generally use the existing service entrance cable. the mast, weatherhead and connecting clamps can generally be reused (not recommended) and new conductors will be installed into the mast or the underground service lateral.
Some splice the service entrance conductors, we refuse to do that.
NEC 705.12(A) and NEC 230.82(6) specifically permit the connection of an electric power source (ie. a utility interactive inverter) on the supply side of the service disconnecting means. You would need to combine the four 20A branch circuits in an AC combiner panel, as Marvin mentioned, and then tap onto the feeders from the meter using Polaris taps or insulation piercings. In order to perform the tap, you may need to intercept the feeders from the meter in a junction box of adequate size.
Upgrading the electrical panel should be your very last option. Before doing this you can also try having a new load calculation performed on your service to see if you can reduce the size of your main breaker. If it can be reduced to 150A you can probably change some of the existing single pole breakers in your service panel to miniature circuit breakers to make room for a new 80A breaker from the AC combiner panel at the opposite end of the utility feed. (On another note, many 200A electrical panels are actually rated at 225A, so you may be able to get by with reducing the main breaker to 175A. This would comply with NEC 705.12(D)(2).
The very first possibility is to change some of the breakers in the panel. That in turn depends on the manufacturer of the panel, and the quantity and type of breakers installed.
Then, it depends on how your utility meters your power and your PV Power contribution.
Please feel free to contact me for a free consultation as to the possibilities, I love sharing.
Charles Nelson, Master Electrician, Pooh Corner Electric
The main point is there are no stock answers. You must gather more information, then analyse it to begin to understand your possibilities.
Start with an overall picture of the existing Meter and Main Panel, including either the mast for an overhead service, or the Conduit feeding from an underground service.
Take very close-up pictures of the label(s) inside the cover of the Main Panel.
Then remove the inside cover, known as a dead front, and take pictures of the wiring interior to the panel.
You are looking for at least 10 pieces of information:
The Manufacturer of the Panel,
The nominal voltage of the installation,
The rating of the Bus Bars in the Panel,
The size of the Main disconnect, which could be a breaker in the Panel; or a separate Disconnect, utilizing either a breaker or fuses for limiting the Fault current available, as well as the Overload current trip point.
If there are fuses for the main disconnect; record the Alpha/numberic designation printed them. Typically five to seven digits,
If the main is a breaker, the overload rating size is typically on the handle, or immediately adjacent, e.g. 200, 175, or 150 (Amps). The Fault Current rating which is normally expressed as a number, e.g. 9000 or 10000 or 22000, folloed by some various accronyms containing the letters IC. That stands for interrupting current.
The size and insulation type of the conductors (wires) comprising the Service Entrance Feeders.
The type, rating, and utilization of each of the branch circuit breakers. If the Panel installation meets the National Electrical Code (NEC) - there will be a breaker label inside the panel designating the device(s) connected to each. If it is not labeled, you will need to investigate what is connected to each breaker and then produce a label to install in the Panel,
The type and size of the Meter Socket. Do not open the meter, just take a picture. Any experienced electrician can tell from that what the meter size is.
Then you need to inquire from your Utility as to their requirements for connecting a Distributed Generation System to their distribution grid. There is a probability that there will need to be a second meter installed.
As to performing a full load balance test/report, it is seldom necessary. Generally, a panel full of breakers is a sign that the installing electrician does/did not understand the NEC requirements. Many of those breakers will be found to have little if any load on them. Or intermittent loads such as the Disposal, Garage Door, Sump Pump, etc. that are required to have their own circuit and breaker.
Also, a thorough reading of your past 12 months of Utility bills will provide substanial information as to usage totals, and patterns.
I know that is more than 10, and while comprehensive, it is not complete. There are other questions such as placement, grounding, and others that will need to be answered.
The available slots in the panel is not the issue. As was mentioned, tandem breakers could be used to free up space and that is typically the way it is done. The problem is that you can't feed 80 amps on the load side since the limit for a 200 amp panel is only 40 amps (assuming that the bus bar has the same rating as the main breaker).
That leaves a line side tap. The panel was never designed for this and and for that and several other reasons the local utility usually will not allow it. If they did, then you could add up 200 amps of solar since you would be coming in ahead of the main breaker.
Hope you don't have to replace your panel but manufactures like Seimens make solar ready panels with built in line side taps.
Many utilities allow you to add up to 90% of the service capacity. This means for a 200A service, you safely can tie in up to 180A of PV ahead of the main disconnecting means.
As mentioned earlier, an engineer can perform a new load calculation allowing the reduction of the main circuit breaker to 150A and allowing you to add an 80A breaker for the PV system in the electrical panel. You would only have a total of 230A of overcurrent devices feeding the 200A busbar and the NEC allows up to 240.
Comments
You can combine your strings in an AC combiner so you only need one breaker in the service panel. You could try interconnecting at a sub-panel. There are a number of ways to free up spaces in a panel that you can try. If those don't work you are going to have to change out the service panel.
Good luck
You also need to look at the panel's main bus over capacity rating. I had a 150 amp panel and luckily the main bus had a capacity rating of 125%. This is located on the manufacturer spec sticker on the panel. Luckily the 30 amps I was adding to the bus did not exceed the over capacity. Otherwise I would have had to upgrade by service panel.
If your panel is that full.
It is vitally important, that you have a load balance test and measurements performed on your panel.
Thermography scan as well.
Adding secondary power source, means that if you have an INTERCONNECTION agreement,
Which I am assuming that you do means that your Buss on your panel must be able to handle the possible short circuit fault that the system could produce.
The number of spaces alone within your panel is not enough information.
If you currently have an unbalanced load profile on your existing panel. that needs to be remedied, PRIO to bringing your inverters online.
In our systems we generally always recommend that the service panel and service entrance be upgraded.
Most of what you need to accomplish can be corrected by installing a Service/Meter socket that also has service rated circuit breakers, they can be purchased and installed and come in many different configurations. This by far is the single most efficient way to upgrade an existing service. your current service panel (inside) remains intact and you can generally use the existing service entrance cable. the mast, weatherhead and connecting clamps can generally be reused (not recommended) and new conductors will be installed into the mast or the underground service lateral.
Some splice the service entrance conductors, we refuse to do that.
NEC 705.12(A) and NEC 230.82(6) specifically permit the connection of an electric power source (ie. a utility interactive inverter) on the supply side of the service disconnecting means. You would need to combine the four 20A branch circuits in an AC combiner panel, as Marvin mentioned, and then tap onto the feeders from the meter using Polaris taps or insulation piercings. In order to perform the tap, you may need to intercept the feeders from the meter in a junction box of adequate size.
Upgrading the electrical panel should be your very last option. Before doing this you can also try having a new load calculation performed on your service to see if you can reduce the size of your main breaker. If it can be reduced to 150A you can probably change some of the existing single pole breakers in your service panel to miniature circuit breakers to make room for a new 80A breaker from the AC combiner panel at the opposite end of the utility feed. (On another note, many 200A electrical panels are actually rated at 225A, so you may be able to get by with reducing the main breaker to 175A. This would comply with NEC 705.12(D)(2).
I hope this helps.
Kimandy Lawrence
Director of Engineering
VB Engineering, Inc. www.vbengineering.com
G'Day,
As the stock answer said- it depends.
The very first possibility is to change some of the breakers in the panel. That in turn depends on the manufacturer of the panel, and the quantity and type of breakers installed.
Then, it depends on how your utility meters your power and your PV Power contribution.
Please feel free to contact me for a free consultation as to the possibilities, I love sharing.
Charles Nelson, Master Electrician, Pooh Corner Electric
ChuckL4RE@gmail.com
G'Day once more,
The main point is there are no stock answers. You must gather more information, then analyse it to begin to understand your possibilities.
I know that is more than 10, and while comprehensive, it is not complete. There are other questions such as placement, grounding, and others that will need to be answered.
The available slots in the panel is not the issue. As was mentioned, tandem breakers could be used to free up space and that is typically the way it is done. The problem is that you can't feed 80 amps on the load side since the limit for a 200 amp panel is only 40 amps (assuming that the bus bar has the same rating as the main breaker).
That leaves a line side tap. The panel was never designed for this and and for that and several other reasons the local utility usually will not allow it. If they did, then you could add up 200 amps of solar since you would be coming in ahead of the main breaker.
Hope you don't have to replace your panel but manufactures like Seimens make solar ready panels with built in line side taps.
Bob Scibelli
RBS Solar, rscibelli@gmail.com