FAQ: Create an all-around z-wave presence in a 4,000 sq ft home?

project_wholehouse

(Clair) #1

Is there a way to create an all-around “z-wave presence” in my 4000 sq ft home?
My home is not just a two story block home. It is a one story, spread out “ranch style”, so it really covers 4,000 sq ft on horizontal terrain.

What I want to do is create a z-wave mesh that is available anywhere in my home, similar to my WiFi system. (In the WiFi case, I simply distributed Unifi AP-Pro’s throughout the home so that all spaces are covered.) So . . . how can I do something similar with Z-wave? I don’t want to worry about NOT having a Z-Wave signal available. I just want it to be there when/if I need it.

Any suggestions and/or words of wisdom?


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(Brian Diehl) #2

Anything that connects to mains power will be able to act as a Z-Wave repeater. This would include in-wall outlets, in-wall switches, and even the plug-in outlet modules (pocket sockets).

If you are going to use a Z-Wave lock on any door, you’ll want a mains powered device nearby for beaming.

Battery powered devices (open/close sensors, motion sensors, etc) do not act as repeaters due to the fact it would drain the battery too quickly.

It’s as simple as adding an outlet or two per room, and maybe some replacement light and dimmer switches (these are very useful as you can use cheap bulbs without needing to buy into a brand or product line like Philips Hue, Cree, TCP, GE Link, etc).


#4

It may be possible, depending on the exact layout, dimensions, and materials.

If your home was perfectly square, it would be about 64 feet in each direction. That would be very doable.

But if instead it is a 15’ by 267’ rectangle, you may run into problems.

It should be possible to create multiple zones in the home, each with its own hub, and get coverage that way. But it may not be possible just with a single hub.

Although the newest generation, Z wave plus, does have a longer range than previous generations it’s still A much shorter distance then Wi-Fi. . The theoretical range for Zwave plus through clear air with no obstacles is about 150 feet for one “hop.” That’s between one device and the next, or the hub and one device.

Zwave’s 4 hop limit

There are two problems. Zwave is limited to four hops per message. (Zigbee does allow for more, and the zigbee home automation profile which SmartThings uses allows for 15 hops into the hub and 15 out, or a max of 30 for one message.) So your theoretical maximum with zwave plus is 600 feet in each direction from each centrally-placed hub. In theory, that would cover that rectangle.

The difference between theory and practice

The problem is that there’s typically a really big difference between theory and practice. Local architecture usually has many things that interfere with the signal and cause it to stop short of the theoretical maximum. Large metal objects, including cars in garages and refrigerators in the kitchens. Concrete, brick, tinted glass, certain kinds of insulation, water pipes inside The walls, even metallic wallpaper can reduce signal. Humidity either indoors or outdoors also causes problems.

As a practical matter, we typically assume a maximum of 60 feet per hop of Zwave plus signal inside a typical home. You may get more, but you may get considerably less. If the walls are made of brick, Adobe, or concrete, you may get only 15 to 20 feet of signal for some hops.

If your house is that rectangle shape we mentioned, you would need to get about 135 feet of signal (divided by 4 hops) in each direction. That might be pushing it depending on the local architecture. It would definitely be pushing it if you included any of the previous generation Z wave devices rather than using all zwave plus.

The booster question

(Right around now, people usually ask about boosting the signal, as you might do with Wi-Fi. But that’s not available for Zwave. Per the specification, these are very low energy protocols. They do have a Max ceiling, and most devices are already set to the max. Although there are single purpose specialty devices you can buy that are described as repeaters and signal boosters, they were created for the third generation of zwave, and are not really needed now. Nor will they increase signal strength in most cases for current generation devices. Now we just use dual purpose devices, a device like a light switch that can also act as a repeater.)

It certainly true that most mains-powered devices Will act as a repeater, but that just gets you to the next hop. It can’t increase the number of hops above the four hop maximum.

So…if you locate the hub centrally, use only Zwave plus devices, the architecture allows for hops of at least 40 feet, you’ve placed devices that can repeat (typically light switches and wall receptacles) strategically, and the walls are not made out of brick or concrete, there’s a good chance that one hub will work.

But there are many factors that might create problems just depending on the local architecture.

The alternative: multiple zones

What you can do in that case, however, is to set up multiple hubs, defining each one as a location.

Coordinating these is easier with some Systems then with others. It’s not particularly easy with SmartThings. But you may be able to do what you want, it’s just going to depend on the specific use cases.

There are a number of community members who have multiple hubs being used as different locations, and they may be able to speak more to it.

The following link is to the official Z wave alliance FAQ on range.


#5

It may also help to understand a little more about the difference in design philosophy between Wi-Fi devices and Zwave devices.

WiFi depends on the signal strength from the access point being strong enough to reach each individual device on the network

Wi-Fi uses a “star” topology, with each device is connected directly to the router or an access point. There is a fixed route for messages to that device. The broadcast signal is pretty strong. Each individual device uses a lot of power, which is why typical battery life is about 10 hours. The messages that are sent are strong and relatively fast. Also, because of that fixed route, there is a built in serial nature to the messages. All of this is why Wi-Fi is so good for streaming music or video.

Zwave uses a lot less Power, and depends on a relay system to pass messages around until they reach their destination.

Z wave uses a “mesh” topology. Instead of a fixed route for messages, each message gets passed around from device to device until it gets to its final destination. There can be many different paths that the message can take. Each individual device is designed to be as low power as possible, in part to make the batteries last as long as they can, and in part to reduce the cost of each individual device. The messages are low power, fairly slow, short range, usually tiny, and do not have enforced sequencing, meaning if you send out two messages at once you can’t guarantee what order they will arrive in.

You definitely don’t want to do streaming video over a mesh network. But mesh can be a great match for home automation, particularly for battery-powered sensors, because you can get battery life of a year or more and each individual device can be very inexpensive.

You will often hear people talk about creating “a strong mesh.” This is a network that offers many different pathways for each possible message. Usually with Wi-Fi, the more devices you add, the slower the network runs. But with a mesh topology, the more devices there are, quite often the more quickly messages will get through, because there are more pathways to choose from. And again, the design intent is that each individual message is tiny.

A “hop” is just any message being passed along from one device to another device. It’s a big relay system. The devices are allowed to talk directly to each other without going back to the hub each time if they’re just passing messages along. (The devices are also smart enough to go as far as they can each time, so you don’t use up hops just because there are more devices in the room.)

However, battery-powered devices are not part of the relay transmitter system. They can only be recipients. That’s because relaying messages for other nodes would use too much battery life. So only the mains-powered devices are an active part of the relay. Typically light switches, wall receptacles, and micro relays.

Two ways to plan a Zwave network

So with Wi-Fi, you get full house coverage by making sure there is a strong signal from each access point to anywhere in their zone. Every device in that zone will talk directly to that access point each time.

With Z wave, The most comprehensive way to make sure you get a strong mesh is by installing mains-powered Zwave plus devices every 40 to 60 feet (depending on the local architecture), and ideally two of these per room so that there are more choices for relaying messages. Again, most typically this is done just by putting in light switches, plug in pocket sockets, in wall micros, and in wall receptacles.

Of course, that might be more devices than you want to pay for. The alternative is to actually decide where your battery-powered devices will be, and then plan a “backbone” of repeating devices that will reach those specific battery powered devices in the fewest number of hops. In this kind of approach, it’s pretty common for people to just run repeaters, for example, down a central hallway rather than putting them into every individual room. You might even skip areas where you know you don’t plan to have any battery-powered devices.

With either method, you can always add more repeaters later if you find that you need them, as long as you don’t exceed that maximum of four hops to get to the intended recipient device.

Summary

Zwave networks typically use about 25% of the energy draw of a Wi-Fi network that accomplishes the same thing. They also usually require much less human maintenance, both because of longer battery life for the individual devices and because the network does its own routing.

Because the primary goals are low energy use and low device cost, the relay method is used to extend the coverage area, rather than just boosting the signal from the central hub.

So you plan a mesh network by thinking about where the individual relay devices will go, and you strengthen the mesh by adding more of those relay participants, rather than a stronger broadcast signal from a central router. :sunglasses:


(Brianh) #6

I’ve got a one story 4100 sq ft house. I have the hub in the middl of the house. So far I haven’t had to buy any range extenders. The ZigBee and Z-Wave mesh networks seem to be doing their job.


(Clair) #7

Wish that were the case for me, BrianH. I’m getting 20-25’ max in some directions. In another direction, however, I can’t get the signal to go past 10’ where my exterior metal door/lock is located. I had hoped the signal would travel past that door to another door/lock about 15’ past the first door. Guess I’ll have to figure out a good mesh plan using the info from JDRoberts.


Complete frustration with my system
(Clair) #8

JDRoberts, I have a situation where my front exterior door/lock is blocking the z-wave signal to my garage entrance door/lock. There’s not a plug outlet between the doors to extend (mesh) the signal toward the garage door, but there are outlets in the garage itself. I was wondering if anyone makes a 2-part system that would do something like this: “z-wave device #1” plugs into an AC outlet in my entryway hallway and receives the signal from my hub. It, then transmits the z-wave signal via the AC wire to another outlet in my garage where I have “z-wave device #2” plugged in. Device #2 gets the signal transmited over the AC wire from “device #1” and then transmits it wirelessly to the lock on my garage door.
I know they have those things for wifi transmission, but I couldn’t find any z-wave products in my searching. Do you know of an available 2-part z-wave device like that?


#9

None that I know, Zwave is an RF protocol, not wired.

You might take a look at some of the outbuilding connection topics for some of the possible options when you have a metal door. Even if the topic discusses Zigbee, the same approaches will apply to

The main idea is that with the exception of some storage sheds, most residential buildings are not airtight. That leaves a lot of places for signal to get through. And the signal is 360°.

so the signal doesn’t have to go through the door itself if it can go through the wall next to the door or a rubber seal around the door or a window near the door.

But the door lock, as a battery-operated device, is not going to repeat the messages for any other devices. So it may be as simple as putting a mains-powered device on that wall, typically a light switch or even a plug in pocket socket. Then seeing if enough signal can get through the wall to the other side, and pick it up with another pocket socket or light switch or even a repeating light bulb there. (Just make sure everything is the same protocol. Zwave can only repeat for zwave, Zigbee can only repeat for Zigbee.)

However, if the walls are concrete or brick or Adobe, then it gets much more difficult.

Personally, I usually begin these kind of troubleshooting efforts with two pocket sockets, because they are easy to move around. Just see if you can get one on one side of the wall to talk to one on the other side of the wall. Once you know you can get signal through the wall, you have a lot more options.

If you do have concrete walls or otherwise can’t get the two pocket sockets to communicate, then you have to start looking at either minor remodels or putting a relay inside the wall.

edited to add there is now a how to article in the community – created wiki on how to automate an outbuilding which has more information on dealing with architectural blocks:

http://thingsthataresmart.wiki/index.php?title=How_to_Automate_an_Outbuilding


(Amauri Viguera) #10

I have a 2 story house that’s just shy of 3800 square feet and I had to move the hub to a somewhat-central location, and I have repeaters at intervals to be able to get to my garage doors (on one end of the house) as well as the TCP bulbs spread out all over the first/second floors and the Schlage locks.

The repeaters / extenders work, and it’s definitely possible to get coverage over that large of a house, but it does take some planning and extra hardware.


(Paul) #11

Hey @JDRoberts I’m wondering if you can clarify something about Zwave hops for me. Imagine I have the following setup where a bunch of devices are arranged in a long line.

Hub—Device 1—Device 2—Device 3—Device 4—Device 5

Obviously Device 5 is too many hops from the hub. However, if the distance from Device 3 to Device 5 is less than the practical range limit, will the Zwave mesh know to route signals like this:

Hub—Device 1—Device 2—Device 3—Device 4
And
Hub—Device 1—Device 2—Device 3----------------Device 5

Or does having Device 4 physically between Device 3 and Device 5 create problems?


#12

The addressing protocols are more complex, they won’t have a problem with the example you gave. It gets handled in different ways which is why I don’t want to be more specific but it won’t hurt if you think of it as the device choosing the neighbor which is Farthest away each time, so right at the edge of the hop. They are by bypassing any other repeaters that are closer.

Like I said, in reality it’s more complex than that, and there are issues like secure messaging and beaming repeaters and stuff which favor one neighbor over another.

But the main point is that there’s no problem, you don’t use up your zwave hops because you have multiple repeaters close to each other. :sunglasses:


(Paul) #13

Awesome. That’s what I thought. Thanks so much!


(Võ Thanh Minh) #14

Why not?
An account SmartThings can attach multiple Hub SmartThings.

A virtual hub was created with devices physical hubs there.

Their programming work to be done on the virtual hub.

It’s great for developers who are not used to IFTTT.

Suggest SmartThings upgraded to meet the large apartments.