[swkeith]

In my house we always find that NW and SW bedrooms are always much colder (about 4-5.5 degrees) than the Master BR (SE corner). The NE bedroom is somewhere in-between. The thermostat is in the Master and the furnace (just for the upper level) is across the hall and a few feet down from the master.

What is strange to me is that the two rooms on the West side are colder if it is 20 degrees out or 90. It would clearly make sense being airflow if it changed in the summer and winter but it doesn't. We typically will set our AC and Heat to 71 and expect the other two rooms to be between 67 and at times as cold as 65.5.

We're going to try dealing with this by opening and closing the air ducts to direct more heat to that side in the winter and less AC in the summer but I'm just wondering how this type of phenomenon is possible. Also if there are better ways to try and solve the issue. I've heard a 2-3 degrees difference could be normal but this seems excessive.

Thanks.

 

[Doc Holliday]

Thermostat and main return air should be in a neutral part of the home such as in a central hallway, not in a bedroom.

 

[user1007]

Thermostat and main return air should be in a neutral part of the home such as in a central hallway, not in a bedroom.

Yup. And you might think about moving it. Right now the thermostat is reacting to the climate in the most cozy bedroom?

If the duct work has levers and flaps, try feathering them too.

 

[hvac benny]

It would appear to me that the master bedroom has a much higher heat gain than the two bedrooms. During the heating season, it requires less heat. It reaches the set temp much faster than the two bedrooms and therefore they remain colder. During cooling season, it requires more cooling and therefore the two bedrooms are overcooled. I would wager that the master has large south facing windows, and that the t-stat is exposed to direct sunlight. I only place the t-stat in the master bedroom if it is its own zone or the homeowner requests it to be placed there, otherwise I put it in the hallway, out of direct sunlight and away from the supply vents and returns.

 

[swkeith]

Interesting. There are large south facing windows in the MBr however the drapes are almost always left closed. That being said, now that I think about it, the thermostat is sitting right next to an A/V touchpanel as well as the light switch. There is also a plasma TV on the same wall a little bit away. I wonder if all of the above is contributing to it being exposed to a lot more heat.

How big of a deal is it move the location of the thermostat? The only place I can think of moving it would be further down the hallway but that would put it closer to the room with the furnace which wouldn't be ideal. I wonder if we just had it on the opposite side of the wall (outside the bedroom) if that would be better than where it is right now.

 

[Happybg81]

I am dealing with basically the same thing in my one year old house. Kids bedrooms on one side stay cold, rest of house including master on other side stay what thermostat is set at. Thermostat is in great room in center of house. Contractor has no idea what is causing this. Any ideas?

 

[fabrk8r]

Poorly designed duct system or improper air balancing.

 

[Doc Holliday]

Square footage of rooms. Since it takes a longer time to cool more square footage and I'm guessing your great room is triple the size of your kid's rooms, the poor kids are getting frozen out quickly while the system is continually running to satisfy the mass square footage of the great room via the stat.

Your great room is big, isn't it? Much bigger than these other rooms? Just like the OP, his master bedroom is much bigger than the rest of the rooms so while these other rooms have been satisfied a long time ago they are still receiving cold air as the stat on the other side of the house is not satisfied thus continually dropping the temperature in these other rooms way below set point of thermostat. Simple really.

Move the stat down into the hallway and if you feel the need to do so to assist, add a return air in the great room to pull some of the heat out, up high if it's open foyer as heat rises. You can never have too much return air so that is not an issue, if you want to add return(s).

 

[Doc Holliday]

Poorly designed duct system or improper air balancing.

Could be that too.

 

[Happybg81]

What you say make sense, but why would those rooms stay colder in the winter too? Also, we have large 24x24 returns in the hallways on both sides of the great room and one smaller register size return in each bedroom and three of the smaller ones in the great room area(it is large, 35x35). Furnace sits at center of house in unfinished basement with exact size trunks going each direction with exact same number of runs off of them.

 

[Doc Holliday]

What you say make sense, but why would those rooms stay colder in the winter too? Also, we have large 24x24 returns in the hallways on both sides of the great room and one smaller register size return in each bedroom and three of the smaller ones in the great room area(it is large, 35x35). Furnace sits at center of house in unfinished basement with exact size trunks going each direction with exact same number of runs off of them.

Many variables. A system has what is known as CFM which is cubic foot per minute of air delivered. On average if not a heat pump system than that nominal air flow per single ton would be 400 CFM of air delivery available. So let's say you have a five ton so that would be 400 x 5 = 2000 CFM. From there each room's sqaure footage is taken into consideration as to how much of that 2000 cfms will be delivered to it. Whenever one room's cfm is calculated that number is deducted from the remainder of the total allowable cfm to be distributed to the rest of the home. Each certain amount of cfm required for each room that is being delivered matches to a certain size of duct. One size duct can only deliver so much air. Too little of a duct and that rooms air will be lessened, restricted on it's way. Too much and the adverse and sometimes contractors have to guess a slight bit and sometimes those guesses need adjusting after the fact which relates to the last poster's air balancing or improper design suggestion.

Then there is actual heat load calculations which fit into the entirety of a home's amount of heat/cooling needed which directly reflects upon the total tonnage, cfm, per room and total.

Leaky duct runs is a possiblility. Placement of returns and supplys and the throw of the air into a room. Insulation used to protect the air in the ducts while it's on it's way.

So, so many things to consider.

 

[Happybg81]

Yeah, that's basically where we've been for awhile. Contractor has HVAC certificate and showed me all of the calculations he used, but those rooms are still colder year round. Not unbearable but noticeable. Thanks for taking the time to answer though.