In the beginning, my house was unbearable. Tri-level in Arizona with 25 year old A/C, I guess you'd see what I'm talking about. Of course, I wanted it to be better, but didn't have the clue how, time to do it, or the money to do it, plus some common sense to investigate the problem before trying to solve it, so I ended up here.

I've read some things that I've never heard about, or paid attention to.

Like air return. Not a single house I've lived in either in Iowa, Illinois, or Arizona had it. My house didn't have it either, so after some consideration I've just cut the holes in the doors, and put the $6 "air return grill" items from Home Depot over them - worked like a charm.

In a last year, I've been asking all my friends and neighbors whether they have air return or not. Nobody did. That strikes me as funny, given that the proper air return seems to be a hot topic here, and we're talking about Arizona, where the cooling is critical.

Oh well.

Then, I found out about multizone systems. Brief estimate showed me that using off-the-shelf equipment is going to cost me something starting with $5000+ for entry-level equipment, which was out of question at the time. Then I started to explore the alternatives.

First useful source I've found was http://www.hometoys.com/htinews/aug99/articles/muziani/muziani.htm, but it didn't tell me how to actually control the servos with the computer. Well, that took some time, now take a look at http://servomaster.sourceforge.net/, you will find all the answers that I was able to dig since last summer.

Then there was a problem of the sensors, one of the obvious choices was X10, but I've rejected it after fiddling with the devices for a while - it is slow, not secure, not reliable. And the prices were just over the roof.

I ended up with using 1-Wire devices from http://www.dalsemi.com/ - a sensor is going to cost you about $3, and $10 for RS-232 controller. Same devices could be used to control the A/C - see the other thread named "controlling A/C with computer".

In the end, I have a multizone system that cost me (to date) $450 in parts, plus some labor, plus a lot of R&D, including, but not limited to, HVAC, embedded systems, process control.

Right now I don't have the actual A/C connected to it - there's a backorder on one of the parts that I need, but you can already take a look at the results here - it's working in a passive mode:

http://freehold.crocodile.org:8080/image_archive/

Take a look at the green line in the night on the 32 hours or 8 days graph - this room is controlled now. For comparison, take look at the cyan line. (update: the cyan line is also controlled since Feb 3)

btw, BamaCracker, remember the "Funny A/C behavior" thread? It did it again, as soon as the temperature dropped below the freezing point - on Jan 31. Hope I get rid of this unit soon.

The reason for this post is - I want to run it by the professionals, give some hope to HOs, and maybe we can do something better together

Anyway, my $0.02.

[Edited by vt on 02-04-2002 at 10:04 PM]
__________________
--vt

Can you put a diagram on here showing how all this is connected?
How many zone's and can you control it by room or is it
only using computor?
are the servos connected to damper's?
$450 todate + Labor, How Much (Time /$$$) R+D (how much Time
and /$$$ worth)
need to see this laid out, how it is all connected so i get better understanding. and how your connecting to equipment.

Tell customer's about adding return's but do not like cost,
then tell them what you did as less cost solution, they
do not want holes in door's loose priveisy.
ex. spelling only 1 cup coffee so far.

[Edited by Dependableairservice on 02-03-2002 at 05:21 AM]

Did you use some kind of controller built yourself like the one pictured in this diagram? Looks really cool. Alot of work, but pretty neat. Did you build your own controller?

maybe not enough or on the upper floors. They all have some return air or the furnace would just overheat and shut off in 2 minutes. I think you lived in some poorly designed houses and cutting holes in the doors is not a great thing to do. Most doors have a space under them which helps move air around. Every room should have a return. Next house you buy, chk it out better. Zoning is nice, and would really help in a tri-level house.
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Hey cockroach, don't bug me!

Dependableairservice:

I don't have a diagram, but it looks pretty simple:

Yes, it is connected to the computer.

COM1: sensor controller, then CAT5 cable with the sensors daisy-chained
COM2: servo controller, then 16 gauge ground/power cable, spare wires in the sensor cable used to route the PWM signal to servos, then servo booster right next to each servo.

Number of zones is limited only by the ability of the servo controller - with reasonable cost within $100 for just a servo controller, the number will most probably be 255. The sensor protocol doesn't have that limitation.

The servos may be connected to dampers, in my case they're connected to the registers. Not an ideal solution, however, damn practical. It works.

Expenses - I don't have an exact breakdown, but majority of it is, surprisingly, CAT5 cable and bells and whistles like CAT5 jacks ($4+ a piece) and wall boxes.

Labor - wiring is a killer. Since this is an ongoing project and I didn't want to dive into expenses until all details are finalized, I just took a staple gun and stapled the cables to the wall. I guess if this flies, it would make sense to engage a professional wiring contractor, but be ready - the prices may be $75+ per drop.

Labor again - 15 minutes with a hacksaw and drill, and the register is motorized. 1 servo, 1 L-shaped aluminium piece, 1 brass wire to make a pushrod, 4 holes - done.

Time - see, it is a kind of a hobby to me, and I have a daytime work to take care of, so let me put it this way - on a backburner, I've been doing it since last August. There's a software controller that takes care of it - all you can imagine in the multizone thermostat, plus some extras like ability to run it from a web browser half a world away, shut the room off on a schedule, handle "leave" mode in a better way than it is usually done - for those who can make sense out of it, it's about 10K lines of Java code, not counting the underlying libraries. I don't expect it to be any more than 15K lines.

As for wiring - it can be made wireless, estimate for the sensors is good - gonna cost less than cable and cost of wiring it, but you still have to have power at the registers to move it. This has to be investigated.

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--vt

tgram:

Controller is mostly software, see the previous post.

With the current cost of a good rugged embedded computer that you can just nail to the wall in the garage getting close to $500 and dropping, and everybody having the computer in their house, often without even realizing it, it doesn't make sense to invest in hardware solutions anymore.

I'll try to put together a diagram, it'll help me to understand better what exactly have I done, too
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--vt

vt, you have a good hold on the control end of zoning, but I am not convinced you have the input on the problems of refrigeration and heating when air flow is altered.

Have you taken into consideration what to do with extra conditioning when all but one zone are being called for? What about excess air? High temperature differentials due to low air flow? freeze stats? By-pass dampers? Head pressure controls?

These are all items that must be taken into to consideration.

Take a lesson from the MD. Highway Administration. They decided that because flagmen were in such a dangerous position due to drivers who did not see them and therefore do not move over or slow down they would replace flagmen with arm waving dummies. This controlled the safety of the men, but for only a few months when the dummies were of no more use. The reason, the dummies could not jump out of the way and were systematically destroyed.

Don't let an impressive control system destroy your equipment.
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Robin Boyd

Do you have kids? Cause those holes in the doors may disrupt your sex life, even if you lock the doors. Just a thought.
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Hey cockroach, don't bug me!

Robin Boyd:

It is quite possible that I've overlooked some things, though I've tried to cover all I could see.

what to do with extra conditioning when all but one zone are being called for:

If there's less than all zones calling, initially, the registers/dampers for the "happy" rooms are being closed - you can safely ignore some pressure increase. As less and less rooms want the A/C, there are multiple factors involved: some rooms that closed a while ago may need it again, so the registers there may partially or fully open again, plus, exactly as with pressure bypass damper, it is possible to have some rooms (usually big ones) as "dump zones". Plus, if there's a variable speed fan and multistage unit, the solution is obvious.

As a matter of fact, I was designing the system with a multistage A/C in mind, however, since the primary design goal was to provide a drop-in replacement for a thermostat, the abstraction used is N-stage M-speed unit, with N and M values of 1 allowed.

High temperature differentials due to low air flow: I'm not quite sure what you mean.

By-pass dampers: covered above?

Head pressure controls & freeze stats:

I understand that the head pressure control is not a standard part of residential multizone systems on the market, at least, they are not advertized. If I get it right, the head pressure has to have a nonlinear negative feedback with the fan speed and the ambient temperature, so if it turns out to be a factor, I can add a handler for that - see, the software solution (as opposed to firmware and hardware) provides an infinite flexibility Also, I might be able to find appropriate heuristics for a given house, unit and ambient temp.

I was also thinking about adding a sensor at the start of the cooled air flow and modifying the behavior of the system depending on the temperature difference - like, shutting the compressor off and keeping the fan running if it is necessary.

By the way, do I have to ask for availability of the head pressure controls when getting a new A/C or it can be retrofitted anywhere? (I mean, without a tenfold price increase?)
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--vt

It takes Dice to think of that...:-)

I'm also a home automation amateur, using the Ocelot controller. With the basic controller costing about $150 and amybe an $80 I/O module, a very intelligent and reliable (doesn't need a running PC) zoning controller can be made. Plus the fact that you can alter the decision algorithm at will, with different anticipation levels and deadbands for each zone, etc. if you like. It certainly is something I would myself consider if I needed zoning. The only thing that does need some thought is the airflow patterns depending on the zones calling for heat or cool. I think the project is certainly worth persuing.


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If you don't know what you're doing, do it neatly

Diceman:

Good point However, the sound isolation in the most of the houses is so bad already, it doesn't really matter. As for visibility, the grills should take care of that.
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--vt

Guy:

I was thinking about Ocelot initially, but the cost scared me away. Point is, why should I spend that much if I already have a computer that's been running 24x7 for the last four years?

However, I can see your point too, and there are alternatives I'm thinking about - like I said, one of them is an embedded computer, and there's couple of others.

From the practical standpoint, computer makes the best sense to me at this stage - the development is not complete yet, and if I take enough care of the code to be platform-independent (so far it is, it's 100% Java), I can run it anywhere later.
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--vt

It's just that I don't like trusting something as critical as HVAC to a running PC. Isn't the Homevision controller also stand-alone ? Are you still depending on a PC for the damper control (you are referring to COM1 and COM2...)?
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If you don't know what you're doing, do it neatly

Guy:

Actually, I should have mentioned that I'm not running Windows on my PC - it's Linux.

I have no doubts about Linux reliability (vs. Windows) - I've had a development box run over 400 days non-stop of heavy usage, had to be shut down because of the power outage.

I do depend on the computer to do everything: get the sensor input, make decisions, invoke the actuators.

Let me put it this way: I'm open to considerations about the hardware platform (hell, I might just use PlayStation - it's got more than enough power), but I'not ready for it now - the model (like M in MVC) is not complete yet.

What I know for sure is that running the computer today is an overkill for this application, unless it is just one of the tasks (like in my case: this is just a background process). However, the constant price drops may quite possibly justify spending a couple of hundred bucks on such a task.

Besides, I didn't even mention the other connections - motion sensors, home security, you name it. All in all, taking further integration into account, it is a good solution from the scalability point of view.
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--vt

Around here, every house I've looked at, from the Elcheapo I rent, to the $600,000 dollar one my boss is trying to sell, all have 8"x8" holes in the doors, with "no-vision" grilles painted to match the door. I've never lived anywhere where the heat and a/c is done like they do it here, and it's really bugging me.

The opening under the door can be made larger with no money spent, no "special" tools and results equal to a hole in the door, but I prefer individual returns.

VT; the airflow problem is much bigger than most people realize, and we end up putting dump zones in the hallway near the return. Then we add temp sensors to the return duct, so that when mixed air gets too cold (or hot) mechanical heating and cooling are disabled.

Almost any unit can have pressure controls added.

Last time we discussed the weird affect of your unit when the temperature drops, you had a service guy coming out. What did he find? Do you, or do you not, have supplemental heat? Was he able to repair the broken ductwork on the roof? Did he have any idea about the apparent cutout of your system during freezing weather?
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There are no stupid questions. . .just a lot of inquisitive idiots.

BamaCracker:

The opening under the door quite often gets closed by the carpet guys just installing the next layer, or a carpet too thick, without realizing what those holes are for - this is how it is in some rooms in my current house.

As for the service guy, I didn't get to that. The temperature rose, the problem never manifested itself again, out of sight, out of mind. I've patched all the things I could find myself, and decided to just get it done properly when I replace the A/C.
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--vt

reading what you worte and trying to understand, will wait
for diagram, I have enought problems getting computor to
work, due you realy thing the HO will be able to wire,and program all this to make it work without duing damage to there equipment? Not to be smart on this, there are a lot of HO who have trouble replacing a themostat.

Dependableairservice:

There are alternatives.

People like myself (there's a whole bunch of them, take look at http://slashdot.org/) wouldn't be afraid to do this, in fact, they dare to do things I can't even think about without shuddering

People who wouldn't be bothered to deal with messy wiring and soldering and stuff, but are OK with a thought of having a computer to run their A/C fall into a second category.

People who don't know what the computer is can be dealt with in yet another way: some sort of embedded system, not necessarily even a computer, as Guy rightfully pointed out.

Of course, we're talking about multilevel pricing scheme already.

As for programming the actual product, I have my kids test-drive the result Actually, I put together a nice control panel that simulates the thermostat on the wall and may be used as a human interface prototype - they didn't have any problems with it. 10 buttons is all it takes. A while ago, I've read an article about what a nightmare the thermostat I have (Honeywell Chronotherm III) is, I hope I've learned a good lesson there.
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--vt

I hope this works, I'm just saying that a lot of people
will have trouble doing this, shoot there are probly
10 year old kid's that know more about computor's that I
ever will, But that is like this buiness, eveytime you
learn a system the mfg.'s come up with something new.
It's all a learning process and I'm an always learning.
I know there are smart house's that can controll eveything
so I will have to start learning more about this.
Keep us informed .

Dependableairservice:

Couldn't agree with you more.

I now work with the kids who were born later than the equipment I started to learn on was discontinued. I had to discard more stuff due to obsolescence than some of them ever knew ;/

I hope this works, too, 'cause I'm gonna drive it all the way to the finish line.

Thanks for all the help, I've learned something today
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--vt

vt, I also learned a while back that it's the OS and not the PC that makes a machine reliable. My work is not in hvac but in computing; I maintain about 80 customers all running SCO Unix and all these machines, from the fanciest Compaq and Dell servers to the cheapest clones, just keep running for months, even years! I myself have a server (running Windows NT 4.0 with SP6) and it hasn't failed me yet. I have it running a voice mail/automation IVR system of my own creation (written in VB5) as well as a logging application for all hvac activity (compressor cycles, defrosts, etc.) I also use it as a Remote Access Server to access my own machines and the Internet. I keep adding to it all the time...But for the actual home automation macros and logic, I still prefer the Ocelot; it's so reliable its boring. I don't have the hvac on it though, there is no need for that, but I still have an X-10 module to shutdown the air conditioning if I want (so I can stop it and turn it back on coming back, say, from vacation ahead of time.
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If you don't know what you're doing, do it neatly

Guy:

Just give me a couple of months

As for WinNT and WinXP, people claim they're reliable, I don't believe it myself, but will take your word on that, since I've stopped using Windows in 1995.

However, in this context we're talking about regular Win95/98 that 99.999% of the customers have, I don't know how well that will turn out. Right now my wife is working on her course on Win95, and I actually hear her learning the non-printable English quite well

Plus, I'm very concerned with the kind of licensing that is coming with WinXP, and the current licensing for WinNT puts it out of consideration immediately.

Seriously, I'm leaning towards TINI, but didn't have time to investigate it yet.
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--vt

I also play in HA as well (HAI OmniPro & Ocelot). I admire what your trying to do, and hope you will post your final results when complete.

When I create something related to HA in our house that is "custom", I fear what might happen if I left this earth unexpectedly, and my wife was left to deal with my hobby for a critical home system. For this reason, I've kept to the mainstream for the critical system. Trying to sell a home with such a system would also bring up similar concerns. I try to keep a notebook with documentation of the more unique stuff.

I am currently setting up a 24x7 PC to act as a home server. One of the things I've also started doing is logging simple furnace runtime data on the OmniPro. My plan is to move this over to Homeseer on the PC server via an interface with the Ocelot (doing it on the OmniPro is pretty ugly). Guy: I'd very much like to discuss with you your approach to logging HVAC events on your PC.

seismo:

In case I get hit by a truck, I plan to just have all this stuff to be connected to the A/C in one point: where the thermostat is plugged in. Same goes for selling the house, though I don't plan on doing so for quite a while.

Ideally, I want this to be a commercially available solution with proper support, so it shouldn't be a concern.

Guy: I'd also like to hear how do you deal with the logging.

Unrelated question, is there a module that reports the energy consumption? One of the design goals was the energy consumption minimization, however, I have no direct way of getting this information, except logging when does the A/C switch on and off, which misses the start peak.
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--vt

vt -

Could you characterize the start peak and just add it to every cycle? Wouldn't the start peak look the same for every start?

I expect my energy consumption analysis will get much more complex if I switch to a modulating furnace as bulk runtime really won't tell you anything about actual energy consumption. Actually, beyond being a diagnostic tool to find problems, (e.g. quantify poor initial design in my case) I'm questioning the long term benefit of logging this data although I suppose you might see hints of system issues before a failure happens.