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TECHNICAL BRIEF
Designing Multi-Tenant and Multi-Home Developments with
Enphase Microinverters
Overview
Enphase Energy’s Microinverter system is the ideal solar electric solution for new home developments,
existing retrofit developments, and multi-tenant housing projects. Due to the flexibility in design that Enphase
Microinverters offer, they are particularly suited for these applications. This document discusses the design
considerations that are particular to using Enphase in applications with multiple Envoy™ Communication
Gateways installed on a common utility transformer, such as new home developments, multi-tenant projects,
and high density retrofit construction projects.
The Enphase system is unique from other systems because all of the wiring is 240VAC or 208VAC, which
can be installed by any competent electrician without additional special training. The microinverters convert
DC power to AC power with high efficiency. The system also enables module-level monitoring of the
production from the Enphase Enlighten™ website. The system is reliable and easy to install but requires a
few special considerations to ensure a successful project with robust communications between the
microinverters and the Envoy.
The purpose of this document is to give an overview of the design, installation, and commissioning
processes for homebuilders, developers, and integrators to use when installing Enphase in new and existing
communities.
General Considerations for All Applications
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Keys to Success
AC power distribution
Locating the Envoy
Commissioning multiple Envoys
Mounting the Envoy outdoors
Network configurations of the Envoy
Activating the system in Enlighten
Specific Applications Covered
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New home developments
Multiple homes on a common transformer
Typical multi-tenant buildings with distributed interconnection points
Multi-tenant buildings with a common point of interconnection
Multi-tenant projects with more than 500 microinverters
For commercial scale, multi-tenant systems that feed a single electric meter, best practices are detailed in a
separate document, Enphase Application Note: Commercial System Design for M215, available at:
www.enphaseenergy.com/support/downloads/
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September 24, 2012
Multi-Tenant/Multi-Home Design
Sample Electrical Schematic for a Typical Installation
Keys to Success
Observe the following key considerations to ensure project success. We will come back to these two
concepts throughout the document.
1. Install a dedicated Envoy receptacle on a dedicated branch circuit.
While not required, this will help to ensure robust Power Line Communications (PLC) between the
Envoy and the microinverters. This dedicated Envoy branch circuit should be wired directly from the
solar load center or at the load center that contains the microinverter output circuits.
2. Turn on each system individually and disable the Device Scan before commissioning another system
on the same utility transformer.
When multiple Envoys are located on a single utility transformer, take precautions to ensure that
each Envoy’s database is populated only with the microinverter serial numbers in that
communication domain. You can best do this by commissioning each Envoy and it’s associated
system separately. After commissioning each system, be sure to use the Envoy to Disable the
Device Scan before commissioning another system. (See the step-by-step procedure in
Commissioning Multiple Envoys on page 12 for more details.)
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Multi-Tenant/Multi-Home Design
AC Power Distribution
The AC wiring and components required for an Enphase system are readily available from hardware stores
and electrical supply houses. The microinverter output circuits will generally terminate in the resident service
panel, but for systems with multiple branch circuits, a solar subpanel can be used to combine the circuits
first. If a solar load center is used, it can be installed near the main service panel but it may be advantageous
for PLC signal strength to install it in a location near the Envoy and/or network enclosure.
Locating the Envoy
In most applications, the PLC can work reliably for distances up to 250 feet. However, when the PV system
and the Envoy are isolated from the site loads, the Envoy and microinverters can communicate at distances
greater than 500 feet. Site loads can affect the impedance of the wiring and can add electrical noise. These
factors can have a significant impact on PLC.
To ensure quality PLC between the Enphase microinverters and the Envoy, we recommend installing a
dedicated circuit to feed the Envoy. This simple step can greatly improve the PLC by separating the
communication signals from the site loads. An arc fault (AFCI) breaker can feed this receptacle.
The dedicated Envoy receptacle can be installed by the broadband router or at another convenient location.
The Envoy can be installed in the residence or in an outdoor-rated box. If the Envoy is not located near the
router, then an alternate network connection must be made between the Envoy and the router. To do this,
you can use a hardwired CAT5/CAT6 connection, an Ethernet bridge, or aftermarket wireless components. A
variety of networking solutions are discussed later in this document. (See Network Configuration of the Envoy
Gateway on page 14.)
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Multi-Tenant/Multi-Home Design
Special Considerations for New Home Developments
In new construction projects, homebuilders will frequently install a dedicated Envoy receptacle near the
network distribution system at a convenient location for mounting the Envoy. If a solar load center is installed,
the Envoy receptacle can be wired directly from that load center.
In a new construction project, there is the advantage of being able to run the networking and electrical wiring
in the walls while they are still open. This makes it very practical to run Type NM cables (non-metallic cable,
i.e., Romex) in the walls and attic for the microinverter output circuits and for a dedicated Envoy receptacle.
SolaDeck rooftop combiner boxes can provide for a quick transition from the Enphase cabling to the nonmetallic cabling.
Sample Electrical Schematic for Residential New Construction
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Multi-Tenant/Multi-Home Design
Considerations for High Density Retrofit Projects Multiple Homes on a
Common Transformer
When installing multiple Enphase systems and multiple Envoys in a single neighborhood and on a common
utility transformer, you must make sure that the systems are commissioned individually and that the Envoy’s
seven-day device scan is disabled after commissioning. This is because the communications signals can
travel between residences being fed by a common utility transformer. Disabling the device scan prevents
neighboring microinverter serial numbers from populating the Envoy’s database. (See the step-by-step
procedure in Mounting the Envoy Outdoors in a Custom Enclosure on page 13 for more details.)
For retrofit construction, it is most common to run the conduit on outside of the house. For these
applications, most integrators will install the Envoy at the broadband router. When the Envoy is first plugged
in to a receptacle, it reports the communication strength within a few minutes. If the communication strength
shows two bars or fewer, another location should be tried. If it is difficult to find a good location, a dedicated
Envoy in an outdoor rated enclosure will generally ensure good PLC between the Envoy and the
microinverters. (See the step-by-step procedure in Commissioning Multiple Envoys on page 12 for more
details.)
Sample Electrical Schematic for High Density Residential Retrofits
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Multi-Tenant/Multi-Home Design
Multi-Tenant Developments up to 100kW With Distributed Points of
Interconnection
This section discusses the best practices for installing a multi-tenant photovoltaic generation system that
feeds multiple residence service meters or subpanels. In addition, these meters or subpanels are distributed
across the project at each tenant residence. In this scenario, the modules can be installed as one large array
or multiple smaller arrays, but the microinverter output circuits feed the distributed meters or tenant
subpanels as multiple smaller systems.
In these applications, it is best practice to
terminate the microinverter output circuits
at the tenant subpanels. This reduces the
amount of wiring needed to interconnect
the systems to the existing electrical
system. A separate Envoy should be
installed at each residence subpanel.
If the microinverter output circuits are
tied to the existing tenant load
centers, a separate Envoy or LCF
must used at each tenant load
center.
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Multi-Tenant/Multi-Home Design
Sample Electrical Schematic for Multi-Tenant Installations with Multiple Systems Back-Feeding
Multiple Service Meters at Distributed Locations
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Multi-Tenant/Multi-Home Design
Multi-Tenant Developments up to 100kW With the Microinverter Output
Circuits all Terminating at a Common Location
This section discusses the best practices for installing a multi-tenant photovoltaic generation system that
feeds multiple residence service meters at a single location. In this scenario, separate sub-arrays feed the
multiple tenant meters.
In these systems, a single Envoy may be able to monitor the entire multi-tenant building or a cluster of
meters that are co-located. One case where this can work is when the microinverter output circuits are all
terminated at a common meter location, as shown in the following image. If the meters are installed on a
common utility transformer, the communication signals will likely pass between the meters, and a single
Envoy can be used to monitor multiple systems. This will work best when the Envoy is co-located at the
meters’ location and all the systems’ microinverters are located with 200 ft. of wire length from the Envoy. A
single Envoy can monitor up to 500 microinverters.
If multiple Envoys are used on a common utility transformer, it is important to turn on each Envoy and its
related system individually and to disable the device scan before commissioning another Envoy and system.
(See the step-by-step procedure in Commissioning Multiple Envoys on page 12 for more details.)
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Multi-Tenant/Multi-Home Design
Sample Electrical Schematic for Multi-Tenant Developments Up to 100kW with Multiple Systems
Terminating at a Common Point of Interconnection
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September 24, 2012
Multi-Tenant/Multi-Home Design
Multi-Tenant Developments over 100kW
This section discusses the best practices for installing a multi-tenant photovoltaic generation system with
more than 500 microinverters on a common utility transformer. Some special considerations must be taken
into account to ensure reliable communications.
A single Envoy can monitor up to 500 microinverters. With more than 500, monitoring is adversely affected.
In systems with more than 500 microinverters, separate communication domains must be set up. The
separate Envoy communication domains must be equipped with Line Communication Filters (LCFs) or with
transformers. Since using transformers is not practical in most multi-tenant applications, LCFs are the best
solution.
Designing with Line Communication Filters
The LCF isolates the communication domains from each other. The LCF includes an Envoy inside and is
rated for outdoor installations. The Envoy is powered directly by the LCF’s utility input, removing the need to
install a dedicated receptacle for the Envoy. Installing an LCF requires that the PV system microinverters are
wired into the PV input side of the LCF (on the right side).
The LCF is rated for a maximum of 100A of continuous current and can be fed by a 125A circuit breaker or
over-current protective device (OCPD). The 125A rating is a limiting factor when designing systems with
LCFs. The LCFs 125A rating impacts where it is
located and how many microinverters can be
installed on it. See the following table for details
on the number of microinverters that can be
installed on an LCF.
Multi-tenant systems greater than 100kW may
require a separate LCF for each electric service
meter.
Enphase offers free design review services to
assist you in designing commercial and multitenant projects. Reach out to your Enphase
account representative or contact Enphase at
http://enphase.com/contactus.
Maximum Number of Microinverters per 125A LCF
Microinverter
Model
Microinverter
Watts
System Voltage
Microinverters per
LCF
AC System Size
in kW
M215-60 at 240
215
240
111
24
M215-60 at 208
215
208
166
36
M190-72-240
190
240
126
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M190-72-208
190
208
189
36
M210-84-240
210
240
114
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M210-84-208
210
208
171
36
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September 24, 2012
Multi-Tenant/Multi-Home Design
Sample Electrical Schematic for Multi-Tenant Installations Greater than 100kW with Line
Communication Filters on each Electric Service Meter
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September 24, 2012
Multi-Tenant/Multi-Home Design
Commissioning Multiple Envoys
Properly commissioning the Envoys is critical to the success of the project. The Envoy should be installed
and connected to the Internet about an hour before the installation is completed and before the
microinverters are producing power. If multiple Enphase systems are being installed in the same
neighborhood and on the same utility transformer, take care to ensure that only one system is commissioned
at a time.
Follow these steps to commission the Envoy in a multi-Envoy environment:
1. Plug in the Envoy to a standard, 120Vac receptacle
2. Plug in the Local Area Network connection to the Envoy and verify that the green “link light” on the
back of the Envoy is illuminated.
3. The Envoy should display “+Web” after four or five minutes.
4. Once the Envoy has connected to the Web, it will automatically update its software. Do not unplug
the Envoy during this time. The Envoy display will display “Upgrading… Do Not Unplug.” The
software update will last for 30 minutes or longer, depending on the connection speed and software
version. The Envoy will display “-Web” for about two minutes after the new software has been
updated, but should quickly return to “+Web”.
5. Upon startup, the Envoy will begin a seven-day device scan for new devices. If it detects any
devices in the first hour before the solar array is powered on, they have been "poached" from a
neighboring system. Use a laptop to access the Envoy Device Conditions and Controls menu and
delete them, or contact Enphase Customer Support at [email protected].
6. Once the installation is complete and all electrical panels and junction boxes have been properly
closed and covered, turn on the photovoltaic system that is associated with this Envoy. The Envoy
should now begin to populate its database with the microinverters on site. This generally takes about
20 minutes, but can take longer. This will not work at night as the microinverters operate only during
daylight hours. (They are powered on by DC solar power.)
7. Once the Envoy has populated its database with all of the microinverters at the site, hold down the
“menu button” on the right side of the Envoy until the display reads “Disable New Device
Scan.” A new device scan should never be allowed to run for the default seven days, because it will
be able to “poach” neighboring microinverters when they first power-up each morning.
Once the device scan has been disabled, you can now move to commissioning another Envoy in the
community.
8. As an additional precaution, you can send a request to Enphase Customer Support at
[email protected] to “Inhibit Device Scanning” at the site so that no further device scans
can be run by the site owner.
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Multi-Tenant/Multi-Home Design
Mounting the Envoy Outdoors in a Custom Enclosure
When mounting an Envoy in an outdoor location, use an LCF or a custom enclosure.
When installing the Envoy in an
outdoor location, use an outdoor
rated electrical enclosure.
This custom enclosure must be
large enough to house the Envoy
and a dedicated receptacle to
power the Envoy. The enclosure
can be metal or PVC.
You can also locate an Ethernet
bridge, wireless bridge, or other
networking components in this
enclosure.
The Envoy’s outdoor enclosure must meet the following requirements:
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NEMA 4 outdoor rated enclosure, metal or PVC. One possible solution would be a Cantex
Enclosure, Part# 5133714.
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Minimum recommended dimensions of 12” x 12” x 4”
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Contains a GFCI receptacle, installed in a 1-gang metal box and with a cover. The GFCI should be
fed by a 15A OCPD and minimum #14 conductors (as per NEC).
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Ideally, the enclosure should be in a location that is shaded from midday sun. However, the Envoy is
rated for environments up to 65°C / 149°F.
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September 24, 2012
Multi-Tenant/Multi-Home Design
Network Configuration of the Envoy Gateway
With all Enphase installations, communication between the array and the Envoy is key to system monitoring
and maintenance. The Envoy communicates with the microinverters in the solar array via the premises power
line wiring. The Envoy also communicates with Enlighten site via its LAN (Local Area Network) cable,
connected to the premises broadband Internet connection.
The Envoy, in this sense, acts just like another computer in the house or business, connecting through a
standard Ethernet LAN cable and using standard TCP/IP protocols.
While it is a trivial task to make this connection in a single residence, a multi-residence installation requires
additional considerations.
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Typical Network Setups
Typical Ethernet Network Topology: Type 1 with Enphase Envoy
In a typical residential networking setup, the LAN (Local Area Network) portion is what is on the “inside” of
the local network. In the diagram below, that would encompass Computer-A, Computer-B, the Envoy and
the router.
The WAN (Wide Area Network) portion is what is on the “outside” of the local network. In the diagram above,
that would encompass the “WAN” port of the router and the DSL/cable modem. The WAN is the upstream
connection to the Internet.
The router may also include wireless (WiFi) services, and there may be one or more laptop computers in the
residence that access that router via WiFi.
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Typical Ethernet Network Topology: Type 2
The typical LAN/WAN setup is a little more involved, but the components are the same. The diagram below
reflects a typical small network design.
The computers are connected to the Network Switch via standard Ethernet cables. The computers with
wireless (WiFi) capability access the LAN via a separate wireless access point, which itself is connected to
the network switch.
The network switch is connected upstream to the router. The router then plugs into the wall plate where the
business has a DSL or T1 connection to the Internet.
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Multi-Tenant/Multi-Home Design
Using Ethernet Bridges with the Enphase Envoy
Envoy-to-LAN
In the event that wired LAN connectivity is not available in the room where the Envoy is placed (to maximize
Envoy-to-microinverter communications) then a pair of Ethernet Bridges can be used. These are commonly
referred to as “home plugs”. The pair of home plugs allows the Envoy to connect back to the broadband
router without the need for additional Ethernet cabling.
Making the Connection
1. Place the Envoy in a location that is near the load center. Plug the Envoy’s power cord directly into
an electrical wall socket. (Do not use a UPS battery backup or a power strip.)
2. Plug one of the home plug devices into the same wall socket as the Envoy’s power cord.
3. Connect one end of the Ethernet LAN cable into the network connection on the Envoy. Connect the
other end of that LAN cable into the home plug.
4. Plug the other home plug into a wall-socket near the broadband router.
5. Connect one end of a second Ethernet LAN cable into that second home plug. Connect the other
end of that LAN cable into the broadband router.
Reference the diagram:
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Multi-Tenant/Multi-Home Design
Typical Enphase Energy Multi-Tenant Deployment: Multiple LCFs
For large multi-tenant and commercial projects, use multiple LCFs to isolate the Envoys from each other. In
this scenario, each of the Envoys communicates (via the power lines) with its own collection of
microinverters. Each collection of microinverters is called a “communications domain”. The following diagram
shows two LCFs, each with their own microinverters and attached photovoltaic (PV) modules.
This model can scale as large as you need. For another collection of fewer than 500 microinverters, add
another LCF with built-in Envoy to build discrete groups (LCF+Envoy+Microinverters) each in their own
communications domain. Using the filtering mechanism of the LCF, the power line communications from one
communications domain is isolated and separated from any others.
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Multi-Tenant/Multi-Home Design
Multi-Tenant Deployment with an Ethernet Network using a Wireless LAN
The installer may want to use a wireless access point to provide Internet connectivity to one or more of the
Envoys and/or LCFs.
In this scenario, only the wireless access point needs the hard-wired connection to an Internet switch/router.
In turn, it provides WiFi services to each of the Envoys.
The Envoy does not have wireless capability built in, so each requires its own wireless Ethernet “bridge” to
pass data from the Envoy to the wireless access point as shown in the following diagram.
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Multi-Tenant/Multi-Home Design
Wireless Technologies
Consumer-grade WiFi devices have varying ranges of operation. Not all WiFi vendors specify the
unobstructed distance for which their product will provide wireless coverage.
Wireless specification 802.11g is the current standard, with 802.11n recently ratified. Check vendor
specifications for claims of distance/coverage, and remember to factor in obstructions, such as buildings,
walls, etc.
Wireless Vendors:
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Linksys: http://home.cisco.com/en-us/wireless/linksys/
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Netgear: http://www.netgear.com
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Ubiquity Networks: http://www.ubnt.com/
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Meraki: http://meraki.com/
Wireless Routers
WiFi routers provide a wireless gateway to the Internet. Wireless vendors Linksys and Netgear produce WiFi
routers that are installed in large numbers and that are solid and reliable. Units come with installation DVDs
and software for easy setup, have excellent documentation, and come with phone or online technical
support.
Wireless Ethernet Bridges
A wireless Ethernet bridge converts a wired Ethernet device for use on a wireless network. (Think of it as an
external wireless network card). The Linksys WET610N and Netgear WNCE2001 are often recommended.
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Wireless Hi-Gain Antenna Systems for Long Distance Communications
Wireless Hi-Gain Antenna systems are for use when the distance from the Envoy or LCF to a wireless router
is over 500 feet. Ubiquity Networks directional Nanostation 2 is recommended. The system is made for
outdoor use, and a variety of mounting brackets are available. Configuration is accomplished through a web
interface, and a number of tools are available to verify signal strength between devices.
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Wireless Mesh Network
A wireless mesh network is a communications network made up of multiple wireless bridges and antennas
organized in a mesh topology. This topology would be used at sites with multiple buildings, where cabling
would be extremely difficult. Ubiquity Networks makes a weatherproof Nanostation 2 with PicoStation M
units. Meraki Networks also makes a weatherproof unit called the OD2, which is an Omni-directional WiFi
access point. The OD2 can to connect an LCF and transmit a signal to extend reach to other OD2 devices.
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Network Basics and Troubleshooting
DHCP and Self Assigned IP Address (169.254.x.x)
When the Envoy first boots up, it is configured to perform a DHCP (Dynamic Host Configuration Protocol)
broadcast, requesting an IP address from a DHCP source. This source can be a server/computer, but
almost all consumer-grade broadband routers also provide DHCP services as well, and this is the usual
source of IP addresses for network hosts (computers, laptops, and the Envoy).
If the LCD window of the Envoy displays an IP address beginning with “169.254.”, this means that the Envoy
was unable to receive an IP address from a DHCP source, and so it assigned this address to itself. Check
the Ethernet cabling and check that the router is providing DHCP services.
DHCP versus Static IP Addressing
If the site owner prefers not to use DHCP, the Envoy can be set up to use a static IP address.
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Use the Envoy’s web-interface to navigate to the ADMINISTRATION page. The Username is
“admin”, and password is “admin”. Click the “Network Connectivity” menu item. This allows you to
see if the Envoy is using DHCP or Static-IP, and allows you to change this setting if needed.
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Click “Check Network Connectivity” to view the Envoy connections.
For more information on how to use the Envoy Interface, refer to the Envoy Communications Gateway
Installation and Operation Manual at http://www.enphase.com.
WARNING: Do not change the Envoy DHCP setting to use a static IP address unless you also
reserve the same IP address on your broadband router. See the section on DHCP Reservations
in your router's setup manual. Failure to reserve the static IP address on the router will result in
duplicate IP addresses and intermittent Internet connection problems with your Envoy.
MAC Filtering
Check to see if “MAC Filtering” is in use at the site. This has nothing to do with Apple Macintosh computers,
but rather, refers to the MAC (Media Access Control) address that each individual network card possesses.
The MAC Address is a 48-bit address that uniquely identifies that piece of hardware. MAC Filtering, then, is a
security mechanism by which routers allow administrators to specify which devices can use the router for
access to the Internet. This prevents unauthorized devices from using your router to get to the Internet.
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An example of a MAC address would be: 00:17:F2:D6:B1:45
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MAC addresses contain six (6) pairs of characters, including any number 0-9 and letters A-F.
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The MAC address of the Envoy will begin with: 00:D0:69:41:
You will need to identify the specific MAC address of the Envoy so that you can add it to list of authorized
devices on the router. To do this, browse to the home page of the Envoy’s web-service using an ordinary
web-browser. The home page contains that specific Envoy’s MAC address. The MAC address is also
printed on a sticker on the back of the Envoy.
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Multi-Tenant/Multi-Home Design
Firewall Settings
The Envoy initiates outbound connections to Internet servers. Such connections may be restricted by
firewall rules set up on the site’s broadband router. Broadband routers typically allow all outbound
connections but restrict any/all inbound connections.
If outbound firewall rules are applied at the site, you must configure a static IP address for the Envoy and add
new rules that allow outbound access as follows:
Direction
Source
Protocol
Port
Destination
OUT
<Envoy IP address>
TCP
443
reports.enphaseenergy.com
OUT
<Envoy IP address>
TCP
443
securereports.enphaseenergy.com
OUT
<Envoy IP address>
TCP
443
home.enphaseenergy.com
OUT
<Envoy IP address>
UDP
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us.pool.ntp.org
The Envoy connects to these servers using their DNS names. If you add firewall rules for Envoy reporting,
Enphase recommends using the DNS names rather than the underlying IP addresses. This is because the IP
addresses are subject to change without notice.
WARNING: Do not change the Envoy DHCP setting to use a static IP address unless you also
reserve the same IP address on your broadband router. See the section on DHCP Reservations
in your router's setup manual. Failure to reserve the static IP address on the router will result in
duplicate IP addresses and intermittent Internet connection problems with your Envoy.
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