Automated HVAC Zoning

[Wigalo]

Hey Guys,

We are months away from breaking ground on a custom construction home. One of the things that I'm determined to get right is the HVAC. In particular, I want each major area to be controlled on it's own zone. The house will be 2 stories with about 7300 sq ft of living area. Based on the layout of the home, I'm thinking that we'll need 9 independently controlled zones.

I've selected Omni Pro II as the Automation board ( have the Aegis 2000 in our current house, it's bullet proof, I'm familiar with the programming and the Omni is basically the same unit) Currently I have my Aegis set up to manage the com T stats. (ie set back at night, when alarm "armed", etc) What I'm looking for though is True automation of the zones.

I ran across this post on the site, but the member hasn't logged on since early december....

[i]HVAC
COMPLETE HVAC CONTROL. Luckily, we started this project in the building phase. Because of this we were able to install motorized dampers into the HVAC system. The home has a single furnace on each floor, each floor has 3 zones. A total of 9 zones and 9 thermos. This has been absolutely amazing to watch. The software has been loaded to monitor living conditions and trends. It's been amazing watching how precise it has kept the different temperature in each zone and "learning" the best way to utilize the system.
*Very Basic Example" -- During the winter it has learned that it is much more effective to generally use the lower level furnace and let the heat rise to the higher floors. The entire house has stayed within 9/10 of 1 degree in all zones 97% of the time. The local gas and electric company actually knocked on the door and asked "curious" questions as to the low utility usage of this home opposed to the others in the neighborhood. I can't tell you how ecstatics my inner geek was this point.[/i]

This type of automation of the HVAC is exactly what I'm looking for.

Does anyone know what software he may have loaded? If a variable speed blower is present...is the zoning program smart enough to make sure that if only 1 or 2 zones are calling for heat/cool, the excess air is either being "dumped" into another zone, or ramping the fan speed down? Is there an interface that I would use instead of the traditional zone controller, or do they make a zone controller that interfaces with HA?

Just to give you a bit more of what I'm going for, check this site out...

www.homecomfortzones.com

All the zone boards that I've found only allow control of the communicating t stats(change temp, fan status via automation) but no logical input from sensors/conditions of HA or monitoring of living conditions or trends. I would basically like to do all that JClarke's or Homecomfort's system (ie use active mixing of air between too hot and too cool zones before system calls for heat or air, monitor static pressure in plenum and ramp variable speed fan up or down depending on number of zones calling for conditioning) but automated.

What do you guys think, is this possible??

 

[CollinR]

Sounds great but having it learn is somewhat intense.

I have a customer whom installed a micro unit in the master suite and basically only controls that for much of the year. She is motivated strictly by cost reduction at the expense of comfort in the main areas though.

You might consider this idea as well though as running a small unit somewhere in the system may be a major bonus.

 

[Wigalo]

Sounds great but having it learn is somewhat intense.

I have a customer whom installed a micro unit in the master suite and basically only controls that for much of the year. She is motivated strictly by cost reduction at the expense of comfort in the main areas though.

You might consider this idea as well though as running a small unit somewhere in the system may be a major bonus.

Yeah, you re right CollinR, "Learning" or artificial intelligence may not be realistic, but I think something like what the Home Comfort zone system could do is.

Anyone else with any feedback?

 

[Wigalo]

Ok, so since no one else has anything to offer, I'm going to write my own "Automated HVAC" script. It'll be at least a year before it's up and running, but I will start working on it now, so that hopefully it's perfected by move in day.

I got a prelim bid from my HVAC guy. We are going to go with Geo thermal, and he'll be installing a 5 ton Climate Master Tranquility Series water to air variable speed unit to take care of the downstairs load and 4 ton unit to service the 2nd floor.


What I want to accomplish:

1. Reduce overconditioning. Eventhough my current home has 2 zones (upstairs/down), the master is still always warmer than the rest of the upstairs...to get it comfortable, the kids' room and everywhere else upstairs for that matter is too cold.

2. Reduce conditioning of unused rooms...If guest bedroom is unoccupied, I don't want to pay to condition it.

3. Use automation panel for set back i.e. when alarm away and winter flag on then set temp 65 degrees.

4. Smart Circulation. I would like to be able to balance temps by mixing and circulating air w/out calling for heat or cooling when possible.

Here's where you all come in...I'll jot down some ideas of how I will accomplish the above, and look forward to you sharing your expertise on how to improve on my ideas.

EQUIPMENT
I had a Manual J done, so I know the exact CFM requirements for each zone. I will have him run the supply duct as well as a return for every zone to optimize the "air mixing effect" to minimize the need for conditioned air. In addition to dampers being placed on the supply duct for each zone, they will also be placed on the return duct.

I will have communicating T Stats in the "Master Zones" with Temp Sensors in the "Slave Zones".
Temp probes in all return registers and in the Plenum
Electronic Barometric Relief bypass damper (to compensate if only 1 or 2 zones are calling for condtioned air)
occupancy sensors

EXECUTION:

MIX: If zone "kids room" Zone "K"calls for heat AND any other zone (A for example) is above setpoint THEN Open "Zone K" supply and return damper; Open return Damper zone (A) AND if Plenum temp is less than zone (A) then open supply damper and if fan is off then fan on.

My hope is that this will effectively use mixing of current air to bring rooms to desired comfort level. If the rest of the home doesn't need conditioned air, the fan is much less of an energy consumer than the furnace or a/c.

Since this post is so long, I'll stop there for now. If there's interest, I'll share other ideas...Hope this post enables my family and others on this board to have a perfectly conditioned house.

 

[lizaoreo]

I'd be interested in the script you've written to automate your HVAC if you don't mind

 

[Herdfan]

I have an Arzel Zoning unit in my house. http://www.arzelzoning.com/

The nice thing is it works with regular thermostats, so you could use the HAI's with no problem.

The problem with what you seem to be wanting to do is that there is little or no logic in this system. Any H1 or H2 calls are initiated by the stats, not a logic based system. But the board is "dumb" in that if one zone is called H2, then all zones get H2. The only place it saves money is I can just cool the bedrooms at night or just heat the living area in the eveing.

The only logic my system has, which is connected to a Crestron system, is that if all 4 upstairs zones are calling for heat, and no basement lights are on, the basement heat will kick on. I have also found that the basement gas heat tends to moderate the upstairs.

I have it set up so that I have 2 dumps zones for excess air. In the summer, I dump the excess at the top of the vaulted great room. This room is the hardest to coll and can always use extra cool air. In the winter, I dump excess air into the garage. (yes I know this is a code violation, but I don't care as I want a warm garage ) I have a manual damper that I open and close when we switch from heat to cool.

If I ever build another house, I will use more smaller units to zone and not a zoning system. It will cost more upfront, but then you are not wasting air that goes to the dump zones.

 

[sic0048]

In the winter, I dump excess air into the garage. (yes I know this is a code violation, but I don't care as I want a warm garage ) I have a manual damper that I open and close when we switch from heat to cool.

I've never thought about it, but I assume it is a code violation due to the fact that you've opened your HVAC system up to a potential carbon monoxide source (cars running in the garage). Thereby increasing the chances of poisoning the occupants in the house. You might consider an adding an automatic damper inline with that garage vent and programming the system to open the damper when the HVAC system is dumping heat into the garage and leave it closed all other times. I'm sure that wouldn't make the system meet code, but it certainly would help protect the occupants in the house to some extent. Just a thought.

 

[drozwood90]

I looked at those Arzel Systems...seemed pretty neat. Aside from the initial cost (The one I wanted was way too much for what I wanted to pay).

So, I am "rolling" my own. Basically, I'll have a custom circuit on the dampers.

As there is a PC involved...

The circuit will get a heart-beat from the server. If the heartbeat goes away, i.e. the server is down for whatever reason, the dampers will go from the current state to "dumb" open mode. This ensures the system can maintain itself without the PC.

I plan to have feedback from each room to try to get a "top-floor" "bottom-floor" 2 Zone system. Potentially have the system "learn" to slightly dampen the various rooms around the house to better equalize the system.

Dunno...lots to play with...lots to consider.

--Dan

 

[pete_c]

What is the prevailing methodology for supplies and returns in a home?

I noticed in my current home that my second floor has all of the returns high and all of the supplies low. On the first floor its a mixture of both with returns high and low and supplies low.

In my old home which had two zones the second floor had all of the supplies in the ceilings and only one return in the hallway. The first floor had a mix of high and low returns and low supplies. In FL (1 story) the supplies are all in the ceiling and their is only one return (large) in one ceiling.

 

[drozwood90]

My house is shaped like an "L"

Top floor has a large return on the "center" area (where the two straight lines converge to make the 90deg angle).
All supplies are on the floor.

Bottom floor has a large return in the kitchen area (off-center on one of the legs).
All supplies are still on the floor.

---------

I can't remember which is which, but there is about 3-4" diameter difference in the two returns. When I look at them it makes sense...but I can't remember if the upper floor is larger, or the bottom floor...

If I had to guess, I think the bottom floor return is larger (as the furnace is actually RIGHT below that return)...but I'm thinking the top floor on is larger...with the assumption they were trying to make the "pull" the same on both returns...

If anyone cares, I'll take a look tonight.

--Dan

 

[sic0048]

I'm not an HVAC designer, but I think smaller returns in more locations is going to be much more efficient that larger returns in few places. Having more returns would also make it easier to zone a system IMHO.

If I was building a system from scratch, at the very least I would demand to have a return located in every bedroom rather than one large return in the hall. That way people can have their door closed and still get HVAC flow. As it stands now, most older homes don't have returns in every bedroom and therefore get rooms that have very little HVAC flow through them. In fact most houses have great flows through the hallways and little flow in each room. This makes for pretty inefficient systems and uneven temperatures in some parts of the house.

 

[pete_c]

I noticed in three of the bedrooms the supplies are in the floor near the windows and the returns are high. In the MB there are three supplies on the floor and high and low returns on every wall. This room though has a vaulted ceiling and the other three do not. Nothing in the hallways but there is a large open area from the first floor up to the second floor (little balcony area).

 

[pete_c]

Wigalo -

An FYI.

When we decided to build I asked the contractor for zoned HVAC, paying for the upgrades and addtions as an additional cost to base.

I mentioned dampers and such on the returns and supplies. The contractor / building company and I got into a bit of an altercation because after the contract was signed - their HVAC person's definition of zoning was different than mine. While paying for the additions the HVAC subcontract was only providing a minimal upgrade to base. The term zoned was in the contract but the interpretation was somewhat off.

 

[drozwood90]

I'm not an HVAC designer, but I think smaller returns in more locations is going to be much more efficient that larger returns in few places. Having more returns would also make it easier to zone a system IMHO.

If I was building a system from scratch, at the very least I would demand to have a return located in every bedroom rather than one large return in the hall. That way people can have their door closed and still get HVAC flow. As it stands now, most older homes don't have returns in every bedroom and therefore get rooms that have very little HVAC flow through them. In fact most houses have great flows through the hallways and little flow in each room. This makes for pretty inefficient systems and uneven temperatures in some parts of the house.

I think it depends on the house. In my house, it made sense to have a few returns. I would have liked on in the bathrooms...but...oh well...

If it was a ranch, I can see a vent and return / room. The way my place is laid out, all rooms are central to where the return is. Literally a big L (with both legs the same distance). All the "cool" (heating season) or "hot" (cooling season) gets pushed OUT of the rooms and into the hall, which is then sucked into the return. I guess the one thing that I'd like to understand better is, they (according to the guys I spoke to when installing) made my system so it was 50% efficient in summer and 50% in winter...from the standpoint of returns... They told me, without Zones, In Winter I'd want more air pulled from upstairs so I wouldn't have to heat as much air...but in summer I want more air pulled from downstairs.

I personally think having 2 zones would be better...as in winter, I want more air pulled / pushed to downstairs during the day, and more air pushed pulled upstairs during the night. This being EITHER case of winter or summer. For this I'd want to average the upstairs temperatures / room...for downstairs I would do the same. Then using the controllers I'm in queue to make, I'd be able to "tune" each room in Winter and summer to some heating / cooling point within a tolerance of the set-point (of course with some hysteresis).

I originally wanted to do more Zones, but I thought that would be overkill and probably hurt my system. I was told me the HVAC guys that so long as I left about 75% of the air flow, my system wouldn't need a dump zone / or one of those "feedback" damper things (opens when the pressure gets too high as too many flappers are closed). So, I was just going to take the locations that the valves are in now as "nominal", then adjust 50-75% "more" off for each vent that needs to be turned "off". Still allowing some airflow, but forcing more into the areas that warrent it. I was then thinking, what about the return air? Shouldn't I dampen that as well? I mean, if I am still pulling equal amounts of air from both returns...I'd be sucking in the "cooler" (warming season) air that I don't really want to cool...dunno, so much to consider...

BUT to keep it simple...I'm just going to start with temperature in every room...average those values with hysteresis, to come up with a "zoned" temperature. If the system doesn't continue to see direct control by the PC, the system drops everything back to where it is now as "nominal" being controlled by the Thermostat in the downstairs (i.e. the control that the PC would have over turning the Furnace on / off will only be a request to a uController that will have it's own heartbeat...so it can override the PC's request to turn the furnace on / off and allow the system to function as if there was no PC there). This means that I would need to open up the setpoints on the normal thermostat as a "failsafe" more then a "turn the furnace on at this temp off at this".

There's a lot to cover...if you just get a multizone controller...it should do most of that decision making itself...but it'll only have a few data points for temp. I wanted to be able to help a "room" out by looking at average, min / max temps., humidity levels, maybe a few other things. It'll get complex fast...but I think it should work out for me.

I dunno... 6 of one dozen, 1/2 dozen of the other in most cases?

--Dan

 

[Herdfan]

I've never thought about it, but I assume it is a code violation due to the fact that you've opened your HVAC system up to a potential carbon monoxide source (cars running in the garage). Thereby increasing the chances of poisoning the occupants in the house. You might consider an adding an automatic damper inline with that garage vent and programming the system to open the damper when the HVAC system is dumping heat into the garage and leave it closed all other times.

Don't keep the cars in there anyway.

There is an inline damper. When the pressure in the main duct exceeds a certain threshold, the damper opens allowing excess air to flow to the dump zones.

In the original setup, the excess air flowed back into the return, but if either of the two smallest zones were operating alone, dumping all that excess cold air back into the return was causing the unit to freeze up as there was not enough airflow over the coils.