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[KDR]

Thought I would share my newest X10 project with everyone. I have a house built in 1921 and I would venture to say that it has had every type of heating system known to man. There is an old coal chute boarded up and a fuel oil pipe capped off. At some point I suspect there where natural gas heaters in most of the rooms since there where gas pipes coming up through the floors in most of the rooms and a wood burning fireplace. When a forced air furnace was put in 2 heat ducts where run upstairs. Each duct comes up into a wall between 2 rooms and those 2 rooms share the one duct. So needless to say the upstairs does not get good heat or AC. On the other hand I have a living room that could be used as a meat locker when the AC is running and the opposite when the heat is on. X10 to the rescure.

I just purchased 6 24vac dampers and 6 120vac booster fans rated at 250 CFM. I am in the middle of installing them now and what a big difference its made so far. I am able to close off or open up rooms and redirect the airflow to cool and heat individual rooms. Right now everything is controlled using X10 outlets and some appliance modules. I setup a series of macros that work on back to back timers to open and close rooms for a 24 hour period. Since our living habits don't change much day to day timers work just great.

Phase 2 of this project will be to install a outside duct with a damper and tie it into the cold air return to the furnace to bring in fresh air or cooler air. When I get to this part of the project I will be looking at air duct temperature sensors to control outside air intake.

I would like to hear from anyone who has done any X10 incorporating into their HVAC system or any ideas you might have. Doing HVAC is an expensive project and I am trying to plan several steps ahead so as not to respend money making changes half way through.

^{----------------KDR}

[Puck]

Nice project KDR!

I can't wait to hear more as you get going; especially when you get to the point of automatic control instead of timers.

Alway enjoy reading about new automation projects.

[Boiler]

KDR,

That's a big project.  I started on zoning 7years ago for a new construction home.  After combing through engineering HVAC manuals, software calculators, and rules of thumb for sizing my system - I wound up with 5 different answers.  I chickened out and hired a "zoning specialist" to size the furnace, A/C, and ductwork for my house (new construction).  I figured I wanted another HVAC "oldtimer", that had already lived though all the wrong answers, to design the system.  At least I did install the dampers and zone control components (saved a little dignity).

Your retrofit is a lot tougher.  Your system is fully constrained. 

I know you're technically oriented, so I apologize in advance if you've already researched the following.

From your description, I gather you are using register dampers.  I'm not sure whether the boost fans are register style or inline.

Your major challenge will be to maintain enough air flow across you heat exchanger/A-coil to keep your system from over temping/freezing up the A-coil.  If your system over temps your furnace should shut down (you will be taking "life" out of your heat exchanger).  Most furnaces do not have sensors on the A-coil.  If it freezes, your efficiency will go to nil (it's a block of ice but with far less surface area than your coil). You also run the risk of transferring fluid back to the compressor which will destroy it.  Picture cranking over an engine with the cylinders full of water - things will break.

There are two methods for preventing a loss of flow across the A-coil/heat exchanger

• Zone sizing - making sure each zone can support enough flow to keep the system operating efficiently
• Bypassing - installing a bypass duct to shunt flow back into the return side of the furnace

Since you have only one run to the second floor, you will almost certainly need some sort of bypass to keep the airflow constant across your system.  This can be simple a simple adjustable counter weighted  damper fed back to the return or a dump zone.  You'll need to adjust the counter weight to provide sufficient flow for your minimum system configuration (X dampers closed).

If you have any friends in the business, now is the time to start asking questions. 

As I said at the beginning, I'm a EE that has "played" with this (and chickened out).  I know just enough to be dangerous.

[KDR]

Thanks for the input Boiler gives me some things to look for, monitor and watch out for. When I moved in about 8 years ago I did have a new furnace and central air system put in. At that time the tech doubled the size of the cold air return, he installed a duct with a damper that goes back into the cold air return and my humidifier is in that line as well.

I remember he spent about 2 hours checking air flow and adjusting blower speeds and limits. The furnace has a ton of electronics and I do know that the blower speed is continuously adjustable within preset limits. (Thought about changing it at one time but glad i didn't) The furnace has barometric sensors on both sides of the blower and the blower will change speeds on its own to a degree. I always thought it was to lessen the load on the blower if vents were closed off but now I see it is probably to maintain a set air flow across the heat exchanger and A-frame. If I remember right the blower runs faster in the heating mode then the cooling mode. The booster fans and dampers are all in-line duct style. They are located within 5 to 10 feet of the furnace. That is the only area I have access to.

My thought with the booster fans was as follows. Since I will be closing off ducts to reroute air I didn't want to start creating excessive back pressure since you can only push so much air through a 6" duct. So the booster fan acts more like a fan to suck out the air in the furnace and get it into the duct. Oddly enough the exposed ducts are all 6" lines but where it enters the walls and floors its all 7".

I hope the only challenge I will be faced with going forward will be in automating the ducts and fans using X10. I have seen zoning controllers and duct sensors but at this time I am going to stick with X10 for the controls. I will keep an eye out for icing on the A-frame but I think the furnace may be smart enough to control that as long as I don't play with its controls. Any electrical connections to the furnace will only be tie ins to the thermostat circuit if any.

^{----------------KDR}

[Boiler]

Nice furnace!.  Sound like it has quite a bit of built in smarts.

When you are operating your zone dampers, you may want to take note of your blower speed and the cycle rate (on/off) of your furnace.  If the furnace does have over/under temp protection, It will "short cycle" to protect itself.  This would be a good indication that you don't have enough air flow.

[dave w]

KDR

I did a similar but much smaller scale project when living in Michigan. Had two bedrooms on duct "dog legs" which were always cold in winter and warm in summer. I put "boost" fans in each room's HVAC duct and had home control system turn on the fans based on the occupant turning on the rooms lights. Neither bedroom was used as a true bedroom, and room lights were always needed when the rooms were occupied. So turning on the boost fans when the lights came on was an easy solution. Motion sensors would have accomplish the room occupied task also. The boost fans worked well enough to make the rooms more comfortable. I didn't want to use dampers for fear of messing up the HVAC balance for the rest of the house. Worked good and was pretty simple to accomplish.