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Thermostat placement


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#1 signal15

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Posted 11 October 2011 - 03:11 PM

My thermostat is down the hallway to the bedrooms. The air in that hallway is fairly stagnant. Is there a good way to determine the optimal location for the thermostat? I was thinking on the wall between my kitchen/dining area and the great room since there is more airflow there.

#2 Edge540

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Posted 11 October 2011 - 04:49 PM

Typically the thermostat is placed nearish the most central cold air return for the system it is controling.

#3 Work2Play

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Posted 12 October 2011 - 04:46 AM

You generally want it on an interior wall in an open part of the home where there's good airflow. Keep it out of direct sunlight; generally not directly in the path of air from a vent. Near the return works in some cases; depends on the layout of the home.

There are also a lot of thermostats out there that'll accept a remote temperature sensor - or possibly balance between two sensors.

#4 Rupp

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Posted 12 October 2011 - 07:34 AM

Yes, both of mine are within 3-4 feet of my air returns which is what the HVAC guy stated when I had my new systems installed this summer.

#5 Dan (electron)

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Posted 12 October 2011 - 08:04 AM

For several years now, I have been having the issue where my AC unit runs continuously, all day, whenever it is hot outside. It just can't catch up, and I already had them inspect/clean the unit. I have no returns in my living room, where the thermostat is located (probably the same wall signal15 wants to use for his thermostat location), closest air return is probably 15' away. Could this be the reason why my unit runs so long? The living room is attached to the dining room & kitchen, and is one large open space.

#6 video321

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Posted 12 October 2011 - 08:35 AM

For several years now, I have been having the issue where my AC unit runs continuously, all day, whenever it is hot outside. It just can't catch up, and I already had them inspect/clean the unit. I have no returns in my living room, where the thermostat is located (probably the same wall signal15 wants to use for his thermostat location), closest air return is probably 15' away. Could this be the reason why my unit runs so long? The living room is attached to the dining room & kitchen, and is one large open space.

Without knowing more and assuming the unit is properly sized, I'd say no. It has more to do with the heat load on an extremely hot day especially if there is an attic directly above this zone. Mine does the same thing.

#7 signal15

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Posted 12 October 2011 - 10:38 AM

Ok, well, I'm definitely going to move it. The largest/most central air return is currently near it, but the thermostat is down the hall from it. I'll move it to the other side of it where it's more out in the open in the great room.

As far as AC running all the time, I had that same problem at this house and my last one. Here are the things that alleviated it:
- Check the outside coil and make sure it's not clogged up with cottonwood or leaves.
- The dust on the outside coil will impact performance, spray it with one of those soap sprayers for the hose, let it soak for a couple of mins, and then rinse well.
- Check your inside ducts for air leaks in the ceiling/walls. Seal them with foil tape or duct mastic. This made a huge improvement in my last house for both AC and winter heating. I was losing a ton of air into the ceiling and walls.
- If you're using a restrictive filter, make sure the manufacturer approves of it. A MERV11 filter in a furnace made for no more than a MERV8 is going to significantly impact airflow. Some furnaces that have the skinny 1" filters can easily be upgraded to 4" thick filters with a tin snips. This will improve airflow.
- Close curtains/blinds to keep the sun from coming in.
- Hire a duct cleaning company to come out and get the crap out of your ducts. Even if the house is new, the returns are likely coated with sheetrock dust and other crap.
- Get an HVAC guy out that knows how to balance a system. Most have no idea and just wing it.

#8 Work2Play

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Posted 12 October 2011 - 11:59 PM

I agree with 95% of that... If the unit is running too long, it's because the thermostat says it's not getting to the right temperature - are the rooms around freezing cold and just that one area is too warm? If not, it's not shutting off because it's not keeping up.

Regarding this:

- Hire a duct cleaning company to come out and get the crap out of your ducts. Even if the house is new, the returns are likely coated with sheetrock dust and other crap.

That's about the most controversial one I've come across - the people who sell the service swear by it, but I've yet to hear a single HVAC person endorse it - the ones I've talked to have all agreed that you're more likely to damage your ducts and create air leaks and that it's best not to screw with them.

#9 fwd03

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Posted 13 October 2011 - 10:52 PM

If the duct is dirty, remove the filter, let fan blow full speed, that should clean out most the dust. If you keep using good quality filter, it is unlikely to get too dusty.

#10 Lou Apo

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Posted 14 October 2011 - 07:48 AM

Far and away, the most comfortable house will be one that is very well insulated and with a properly balanced hvac unit. In a home such as this the temp will be very consistent throughout the house and free of drafts. Thermostat placement on virtually any interior wall of the house will yield a good result in this situation.(not near a heat producing thing like stove or shower)

Avoid putting it somewhere that has wild swings in temp that don't reflect the "real" temp of the house. Like in the kitchen or where a door is opened that might blow on it. Outside walls of course are not good.

Near the air return duct is usually good becuase the air moves that way from all over the house and mixes so it tends to represent a good average of the house. Nicer hvac systems will put air returns in most rooms of the house so this doesn't really apply very well for that.

If your unit runs continuously on a hot day, and all of your rooms are not cool, your problem has nothing to do with the thermostat placement, your system is simply not capable of cooling. It could be undersized, or it could be that it needs service.

Before moving your thermostat, put thermometers around the house and see just how much difference there is. If you find that there is more than 3 degree temp difference, you should look at rebalancing the system. This test only is meaningful if the outside temp is significantly hot or cold. Doing it on a 72 degree day isn't going to tell you anything, but a 10 degree day will tell you a lot. If you have a poorly insulated house, you will probably never get it right. Poor insulation will cause certain rooms to gain or lose heat faster or slower and it will be different for different weather. So you pretty much are screwed unless you zone the system and put a thermostat in each room. For example, the west side of the house will take on a lot of heat on a sunny afternoon, but on a hot cloudy day it will be the same as the east side.

If your house is poorly insulated and you don't care to replace the windows and re-insulate the walls, and you don't care to zone the system, your best bet is to put the thermostat in the room you use most.

Edited by Lou Apo, 14 October 2011 - 07:54 AM.


#11 signal15

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Posted 14 October 2011 - 02:29 PM

If the duct is dirty, remove the filter, let fan blow full speed, that should clean out most the dust. If you keep using good quality filter, it is unlikely to get too dusty.


No! The ducts that get dirty are the returns. If you remove the filter, you'll clog up your AC coil and other crap with dirt. If you have dirt in your supply side, then there is a problem somewhere.

I had the ducts cleaned at my old house, and it made a world of difference, but they were coated all the way around with about an inch of dust bunnies.

#12 Dan (electron)

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Posted 14 October 2011 - 05:31 PM

My apologies to signal15 for highjacking this tread. I was mostly concerned that placing the thermostat on a common wall in an open space might be a problem. I do appreciate the responses tho, I'll have to give it some more thought.




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