HVAC Zoning

[Ximat]

Good Day All,

I apologize if this has been covered previously, I can't seem to find any topics about it.

I have. Two story house and seem to deal with the traditional heating and cooling issues that a two story house poses. All bedrooms are upstairs... When heating the house the downstairs gets comfy but the upstairs is too cold... If I adjust to get the upstairs comfy then the downstairs is a scorcher.... And vice-versa with cooling.

I have been looking at dampers, and have tried to mentally plan out some type of zoning system that uses dampers, timers, occupancy sensing, etc but can't seem to figure it all out.

So I ask this question to the ore advanced folks here on CT. Has anyone done something like this with their HVAC system?

Getting a separate system for the upstairs or upgrading my current system to a traditional zoned system is not cost feasible at the moment.

Thank you for your insight.

X

 

[RAM]

One gotcha to watch out for any time you start playing around with your forced air furnace is to make sure you don't restrict air flow too much. If you merely restrict the amount of air going to the downstairs with a damper you may lower the total system airflow amount to the point that you can damage the heat exchanger in your furnace. You may want to consult with an HVAC guy to make sure this doesn't happen.

 

[Ximat]

RAM,

Good point, and something I've thought about as well.

Thank you!

X

 

[picta]

I had a two story house with forced air and heat and zoned it "after the fact" with dampers. I got all parts from RCS: 6 zone dampers, RCS zone controller and a pressure relieve valve. The pressure valve is VERY important to have in order to maintain a healthy system. I also got an outdoor air valve for fresh air and hired an HVAC professional to install them. The system worked great for many years and I had it integrated with my HA system via controller's RS232 port. It could even alternate different rooms between heat and air. I don't know if the 6-zone RCS controller is still available, but I have seen a 4-zone version on the market. I think RCS site has(had) a diagram of the damper based system.

 

[signal15]

You might try having someone with a flow hood come and balance the system before you go the route of zoning. Typically, you identify how many trunk lines you have and the length of each one. By code in most states, each vent will have its own damper if you reach down in it. You start by taking the flow reading of the vent at the end of the longest run. You take that measurement, and turn the damper closed a little on the next one so it matches. Then you do the same for the next. When you get to the end of the first one, you adjust the trunk damper on the next longest one so the end vent has the same flow as the last vent on the first trunk. Then you continue down the line.

The idea behind it is that all of your vents in the house will be putting out the same volume of air, thus distributing the air more evenly in the house. I had similar problems as you, and I had this done. The guy that did it did a horrible job, the vents closest to the furnace pump out 4 times as much air as the rest of them. But, it was better than before and it's reduced the temp differential significantly in my house. To find someone that supposedly knows how to do this, go to the website of the National Comfort Institute and search for a certified HVAC guy. Most HVAC guys I've encountered are useless and have no idea what the hell they are doing. I'm going to redo mine, but I'm going to do it myself because the only HVAC guy I've found near me that knows what he's doing only does commercial buildings now. I just need to figure out how to get my hands on a flow hood for a day or two, they are $1200+.

If you wanna do a zoning system yourself, it's not for the faint of heart. There are a lot of things you need to worry about. Check out this site for info, and for equipment to do it:
http://diy-zoning.sourceforge.net/

Don't just go whacking stuff in, you're likely to burn out your blower due to high static pressure, or worse yet you could damage the heat exchanger by not having enough airflow over it and having it overheat.

 

[JimS]

Sounds like you need more airflow to the upper area in both heating and cooling. If the airflow issue was different for heating and cooling then zoning might be required but it sounds like you could improve things just by opening up the upper ducts and possibly partially closing the lower ducts. As mentioned you need to watch closing the ducts too much. I would guess the furnace/AC is in the basement or lower floor? Often the vents near the furnace move more air than ones far away because the long ducts to the farther locations give additional restriction.

 

[frijoli]

Sounds like you need more airflow to the upper area in both heating and cooling. If the airflow issue was different for heating and cooling then zoning might be required but it sounds like you could improve things just by opening up the upper ducts and possibly partially closing the lower ducts. As mentioned you need to watch closing the ducts too much. I would guess the furnace/AC is in the basement or lower floor? Often the vents near the furnace move more air than ones far away because the long ducts to the farther locations give additional restriction.

This is the case in my house. My lower floor is 80% below grade. In the winter I need more heat down there and in the summer I need more air upstairs. Flow balancing will work if one room or zone is consistently wrong. Meaning it never has enough heating OR cooling.

I am in the process of doing zoning to mine(in the planning phase) and I will use RCS components as well.

Clay

 

[picta]

Here is a diagram from the RCS site for 6 zone system