ION ORACLE - Electrical Equipment Layout

ELECTRICAL EQUIPMENT LAYOUT

DESIGN

1 | PLANNING FOR THE EQUIPMENT

BASELINE DT

Below is an example of a typical electrical line diagram depicting the full wiring schedule with each BOS component. Modules are on the very right with the point of interconnection appearing on the left as a load side breaker.

This can all be quite confusing at first, but the BASELINE DT will give you instruction about what utility BOS equipment is needed based on whatever utility you are working with.

BOS COMPONENTS

The first thing to understand when planning your wall equipment layout is general dimensions. Below are general dimensions for the most common BOS components. Note that the combiner panel is always required for PV installations. Utility BOS equipment will include production meters and AC disconnects and we will only install what is required by the specific utility we're working with. On some projects, the utility will require both a production meter and AC disconnect. Some might require only an AC disconnect. Some may not require any special BOS components at all.

COMBINER PANEL

A combiner panel is a BOS component used to consolidate PV circuits for the purpose of solar interconnection.

The purpose of this is to create one single output for the purpose of tying into the existing electrical system
This is also where the PV production monitoring hardware is also housed.

This is how the combiner equipment is represented on the electrical diagram.

The combiner equipment we currently use has the following dimensions:

height of 20"
width of 15"

PV METER

PV meters are used to track PV production for Net Metering purposes.

Some utilities install bi-directional meters for net metering purposes and no PV meter socket would be installed in this case.
Other utilities will require a second production meter to be installed specifically to track PV production.

This is how the PV production meter is represented on the electrical diagram.

The PV meter socket will be sourced by availability and sizes can vary. This graphic was composed using median dimensions for a 200A lever bypass type meter enclosure:

height of 16"
width of 12"

AC DISCONNECT

Two types of general AC disconnects you will see:

Fusible AC disconnect
Non-fusible AC disconnect

AC disconnects are installed under the following circumstances:

Utility required for rapid shutdown and equipment isolation purposes. (non-fused)
Tap type interconnections require a fusible disconnect.

In general, non fusible AC disconnects may be a couple inches shorter in height than a fusible AC disconnect, however, they will generally share the same general width.

Note that 30A disconnects are about 30% smaller than 60A disconnects:

If you are landing 30A or more of PV, you will be using a 60A AC disconnect when required by the utility.
Anything smaller with be a 30A disconnect.

This is how the non-fusible AC disconnect is represented on the electrical diagram.

The photo to the right shows what the internal wiring of a fusible disconnect looks like. Note that the internal components take up slightly more space than the internal components of a non-fusible disconnect due to the fuse sockets.

Fusible disconnects will be needed when performing any outdoor tap type interconnection.

This is how the fusible disconnect is represented on the electrical diagram.

Fusible and non-fusible disconnects will be sourced by availability and sizes can vary. This graphic was composed using median dimensions for a 60A fusible disconnect enclosure:

height of 16"
width of 8"

HOW MUCH SPACE WILL YOU NEED?

This is a factor that will depend on the required equipment and how you can orient it. You will have less constraints when there are less utility required BOS components. Likewise, when you have clear space with no obstructions by the meter, you won't need to worry quite as much. Below, we'll explore some basic guidelines to help you:

COMBINER + PV METER + AC DISCONNECT

When positioned side-by-side, you will need approximately 4' of clear wall space to work with to fit all of this equipment.

Stacking equipment can help reduce the footprint, however, you need to ensure that any disconnect does not exceed 6'6" above grade per NEC 404.8(A):

NEC 404.8 Accessibility and Grouping

(A) Location

All switches and circuit breakers used as switches shall be located so that they may be operated from a readily accessible place. They shall be installed such that the center of the grip of the operating handle of the switch or circuit breaker, when in its highest position, is not more than 2.0 m (6 ft 7 in.) above the floor or working platform.

Also note that the combiner panel is not part of the utility required equipment, so it doesn't necessarily need to be accessible by the utility. Combiner panels are permitted to be installed remote from the other wall equipment if needed.

COMBINER + AC DISCONNECT

In general, if you have two BOS wall components beside each other, you can expect that they will need 3' of clearance to fit into.

Again, this could be reduced by simply stacking equipment or installing the combiner remote from the utility equipment if necessary.

When stacked, you could be working with as little as 18" of space for clearance if needed.

GENERAL WORKING CLEARANCES

In this section, we will review some of the basics of electrical equipment clearance as well as introduce some concepts to help you plan your layout around obstructions.

110.32 Work Space About Equipment

Sufficient space shall be provided and maintained about electrical equipment to permit ready and safe operation and maintenance of such equipment. Where energized parts are exposed, the minimum clear work space shall be not less than 2.0 m (6 ½ ft) high (measured vertically from the floor or platform) and the width of the equipment or 914 mm (3 ft) wide (measured parallel to the equipment), whichever is greater. The depth shall be as required in 110.34(A). In all cases, the work space shall permit at least a 90-degree opening of doors or hinged panels.

The most important factor is the working depth. There shouldn't be anything obstructing within 3' in front of the electrical equipment. The height (6'6") and width (30") requirements are a window with the electrical equipment permitted to be located anywhere within this window.

GAS METERS

Working clearance around gas meters/diaphragms are usually dictated by the utility. We will follow the general rules that most utilities follow as seen on the right:

a clear 3' radius around the diaphragm will be required.
A clear 3' zone vertically above the meter is required up to 10'

All areas outside of these clear zones are permitted for us to mount our equipment.

If the existing service does not comply to this, flag for PER.

A/C UNITS

give extra attention around A/C and other mechanical units. These units should not be obstructing the needed working clearance:

Do not plan to mount equipment directly behind a mechanical unit.
Look for viable areas on either side of these mechanical units.
If the existing service is fully obstructed by a mechanical unit, flag for PER

EGRESS WINDOWS

For a window to be considered a point of egress, it will need to meet the following criteria:

The window is operable, meaning it can be manually opened or closed.
The open side of the window must be at least 2' wide.

We are mainly concerned about egress windows on the first level or whichever level is on grade with the electrical equipment.

DO NOT PLAN TO MOUNT BELOW ANY POINT OF EGRESS.

STAIRS

Our new equipment should never be mounted directly over stairs. This is most often seen on decks and flood platforms.

You may install over an even grade like a deck or flood platform, however, you should never install electrical equipment over or under a stairway associated with such platforms.

If the existing service is fully obstructed by a mechanical unit, flag for PER

SHRUBS, BUSHES & OTHER VEGITATION

Another very common clearance issue is overgrowth in front of existing electrical equipment.

But in a case like this, should we move "A" & "B", just "A", or just "B"

It's easy to get tripped up on a situation like this, but the fact of the mater is, the existing equipment will be perfectly within working clearance if we simply remove "A"
We can even likely fit some or all of the new PV equipment directly to the right of the meter and still have 30" of space for the meter and new equipment to occupy making it perfectly within working clearance.

The Designer would need to create a homeowner obligation to remove the vegetation in front of the existing equipment.

More in depth information on working clearance can be found in Electrical Services - Code Violations

2 | EXAMPLES

EXAMPLE 1

In this example, we're dealing with a pretty tight space next to the meter/main and sub panel. There's very little possibility of fitting all the equipment to the right of the sub panel, but we can likely stack the utility equipment there and mount the combiner elsewhere:

Note that we need to stay clear of any window well on the basement level or at grade level with the equipment.
The best course of action here is to mount the combiner on the other side of the window well/fence.

EXAMPLE 2

In the photo to the right you will notice that there is well over 4' of clearance beside the meter/MSP to the left.

The one thing to be aware of is that there appears to be a gas meter just out of frame in this photo, but you can see one of the connected gas lines peaking into the frame.
Instruction should be given to the install crew to allow proper clearance around the gas meter.

EXAMPLE 3

In this photo, we have about 3-4 feet of clearance to the left of the meter. The equipment will definitely fit if stacked.

Note that we require a PV meter and AC disconnect on this one. If only an AC disconnect was required, we could mount the combiner and AC disconnect side-by-side no problem.

EXAMPLE 4

In this example, we have an egress window to the right:

It looks to be an operable window.
it appears that the side of the house is on a hill, so it is likely that this window would only be about 4-5' above the ground

It is best not to mount under this window is possible. It would be much better to mount to the left. Note that we can mount around communication boxes as seen here under where the new equipment is rendered. This would not be considered an obstruction of work space clearance.

EXAMPLE 5

This one is a little tricky. The existing meter is behind the AC unit, but there appears to be a 30" path between the fence and the AC where it could be accessed by the utility. This would be somewhat of a gray area. Here at ION, in a situation like this, we are at liberty to allow for the existing service to be grandfathered in as is but we need to ensure that our new equipment will not be directly behind the AC unit.

The best case would be to try to locate all the new equipment between the fence and the AC unit if possible.
It would be best to leave instructions in the installer notes to install the combiner panel remote from the utility equipment if needed to allow for working clearance.

EXAMPLE 6

In this example, we have an AC unit to the left, and a gas meter to the right. It is always preferred to mount all the new equipment grouped together, either side-by-side or stacked, however, in this instance, the risk of encroaching on working clearance by doing so would not be worth it. The best option is to mount the utility equipment on one side of the meter/msp and the combiner on the other.

This needs to be communicated to the install crew as clearly as possible using the installer notes.

EXAMPLE 7

In this example, we have decent space on either side of the meter/main for the equipment, but the clear winner is right of the MSP to avoid the gas meter.

EXAMPLE 8

In this example, We have space on the left between the meter and an apparent window well where equipment can be stacked. There is not ample room between the gas meter and the existing meter for us to mount new BOS components:

Note that this utility is requiring a non-fusible disconnect in addition to the fusible disconnect that would be needed for the tap type connection.
- Watch out for odd utility requirements like this because, as you can see, it can cause some additional considerations for equipment placement.
- This will mainly be seen in some of the Colorado AHJ integrated utilities like Colorado Springs or Manitou Springs.

EXAMPLE 9

This is an example of a time you should definitely add notes to the installer stating that the AC disconnect should be grouped with the meter while the combiner can be placed behind the fence.

Most utilities will not consider equipment accessible if they are located behind the fence.

EXAMPLE 10

This is another example of a time where you might instruct installers to install the combiner remotely from the utility required equipment.

There is not enough data in this photo to conclude if the combiner could be mounted directly next to the utility equipment or not.
Simply leaving this type of instruction will be more cost effective than asking for a resurvey just to confirm a location for the combiner box.

EXAMPLE 11

This is a very common townhome/multifamily home example:

Space is extremely limited at the meter.
There is a small space on the other side of the garage that could probably house an AC disconnect and maybe a PV meter if needed.
The designer should plan to mount the combiner panel in the garage back-to-back with the meter.

EXAMPLE 12

In this example, we have a gas meter in close proximity to the electrical equipment and gasolines running fully along the wall and crossing over the existing service riser.

So what are our considerations here?

We need to ensure proper clearance around the gas regulator.
The gas lines themselves will not be considered a working clearance issue.

The equipment location is tight. The designer would need to give clear instruction that proper clearance is needed around the gas meter; the combiner could also be mounted on the other side of the meter/main if needed.

2 | INSTALL PHOTOS

INSTALL 1

In this example, no AC disconnect or PV meter was required by the utility. The combiner was installed beside the meter and the MSP is back to back on the same exterior wall.

INSTALL 2

In the example to the right, the PV was interconnected in the sub panel beside the meter main. Only an AC disconnect was required by the utility. It was designed with the combiner and AC disconnect side by side.

INSTALL 3

In this example, only an AC disconnect was required by the utility. The combiner was stacked above the AC disconnect to allow a proper 3' radius clearance around the gas meter.

INSTALL 4

In the photo to the right, the space beside the meter was tight. Equipment was stacked to allow proper installation beside the meter.

INSTALL 4

In the photo to the right, an indoor breaker type OCPD panel was installed beside the MSP to comply with service disconnect grouping requirements designated in NEC 230.72(A).

We also need to plan for working clearance for any new indoor OCPD panel in cases like this.

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Design & Engineering > Design 7 - Electrical BOS Equipment Layout

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