[Home LAN] (2) Designing Home LAN Wiring
In this installment, we will consider the design of home LAN wiring.
If you are building a new detached house, please use this as a reference and provide instructions to your architect.
If you live in an existing detached house that you own and think, 'Oh no,' then
please consult an electrical contractor, or feel free to drill holes in walls, peel back walls, or crawl into attics or under floors yourself.
If you live in a condominium you own, I think it is fine to destroy the interior as long as it does not affect the structural frame. I would recommend avoiding chipping or opening holes in the structural frame.
■ Cable Length
For standard LANs, we use a transmission method called Ethernet (such as 1000BASE-T). These have limitations on cable wiring (they cannot be too long or too short!). You may have heard IT department staff talking about placing a relay HUB because a cable exceeded 100m in an office or similar environment.
In the case of logical network engineers, they are sometimes referring to the distance between device ports (e.g., between a PC and a HUB). This is correct from an Ethernet perspective. *It seems this was calculated based on the transmission speed of electricity. You can find it if you look up packet collision detection. Since there are almost no opportunities to see repeater HUBs anymore, we no longer need to be conscious of this. When I experimented with this in the past, there was no actual impact up to around 110m in PC-to-PC communication that ignored collisions.
★ Rules for CAT5e Standards
・Equipment cable (patch cord): For use between equipment (PC, HUB, etc.) and the outlet
→ "1m to 5m"
・Horizontal fixed wiring: The section between outlets, laid in walls, under floors, etc.
→ 90m or less
・Total extension distance: For example, the total distance between a PC and a router, or between device ports
→ 100m or less
*It seems a rule has also been established that up to 100m is OK for direct connection between device ports with plug-to-plug LAN cables.
However, if the connector tab breaks when plugging or unplugging, repair and replacement are troublesome, so I would not recommend it from an operational standpoint.
■ Designing wiring based on floor plans and network configuration
We will consider the floor plan and network configuration (equipment placement) to satisfy the conditions in the previous section.
When calculating distances from a floor plan, please do not calculate using straight-line distances. Be sure to confirm with the architect whether the wiring space is in the attic or under the floor.
Let's consider the cable length as the longest path in the wiring section.
Calculations like √2 for a square room may result in exceeding the limit distance after actual construction.
Let's read the following dimensions from the floor plan.
① Outlet (wall): Approx. 170mm from the floor, approx. 25mm depth
② Horizontal wiring: Vertical direction: ceiling height, horizontal direction
Horizontal direction: From the outlet position along the wall, find a place where the cable can exit the room
that is not a load-bearing wall or fire wall, and calculate the distance to that point from the floor plan.
③ Distance for cable wiring from the IDF
(①×2) + (②×rooms passed through) ≧ 90m
The light blue lines are fixed horizontal cables, and the lengths are about 20m to 30m each.
Perhaps because it is a wooden structure (2x4 construction method), it became longer relative to the building scale.
If you do not consult thoroughly with the architect at the stage of developing the construction plan, you will fail.
The MDF board is also affected by the location where NTT East/West optical cables are brought in. Confirm the location of the utility pole (or the startup point in undergrounded areas) with the architect and have them put it on the drawing. Of course, it is also important to have them prepare hanging hardware, conduits, and pull wires, including spares.
Don't forget to request 100V power outlets in each place where you will pull optical lines and LAN cables! It would be a shame to have designed the LAN only to find there is no power for the router...
■ Calculating necessary materials
Add the cutting margin and the slack for cable pulling to the LAN cable calculated in the section above to calculate the total length of cable to purchase. Since cables are sold in 200m or 300m rolls, calculate so that the cable can be cut without waste from those units, and purchase by rounding up to the unit.
For connectors (jacks), purchase the number of lines to be laid × 2 (for both ends).
Also, it is better not to skimp on tools (especially nippers and cutters). A blade and a horse... are only as good as how they are used.
For patch cords, purchase the necessary number of ready-made products. Trying to buy tools and crimp them yourself will be a cause of trouble.
*How to calculate patch cords
If you prepare the number of ports for the SW (HUB) to be installed, you should not run out.
These materials can be purchased from appropriate online stores (MonotaRO, Yodobashi, etc.).
The floor plans you receive from the house manufacturer are not just for considering the layout. They contain various plans, so read them thoroughly.
It is better to refuse 3D drawings or perspectives and use that man-hour to make plan revisions; you will be able to create a network in the building that you can be satisfied with.
That's all for this time. The next theme is planned to be either construction or theory.