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  1. #1
    Join Date
    Apr 2006
    Posts
    98

    What kind of thermometer and where to put it?

    We have a problem with uneven temperatures. I want to check my whole house but I don't know what kind of thermometer is accurate enough to be taken seriously by my HVAC company. I also don't know how to choose the place to put it in each room.

    Is there a cheap thermometer that's accurate so I can get one for each room? Maybe at Home Depot, Lowes, Target, Ace Hardware or some other chain store so I can get it quickly? Or is there one that costs a little more but registers very quickly so I can take it from room to room?

    I have a couple little inexpensive digital thermometers that I've compared to the thermostat but I can't tell if they're accurate. They're also slow to change when I move them to a different room.

    Thanks for your help.

  2. #2
    Join Date
    Aug 2009
    Posts
    164
    A $15 thermometer from any hardware store is accurate enough. Take readings in all rooms but you will need to let the thermometer rest in each room for at least 5 or 10 minutes to settle down.

  3. #3
    Join Date
    Feb 2007
    Posts
    999
    Quote Originally Posted by Big Unit View Post
    A $15 thermometer from any hardware store is accurate enough. Take readings in all rooms but you will need to let the thermometer rest in each room for at least 5 or 10 minutes to settle down.
    Agree! Your local supermarket may have a decent one (with hold display) for the same price.

    While they will probably be off a degree or three, the error will be insignificant, as you will be measuring the difference (a few degrees) in temperature between rooms.

    If you want, you can calibrate the thermometer at 2 points; a glass of ice and water (32*), and boiling water (212).

    Amp

  4. #4
    Join Date
    Apr 2006
    Posts
    98

    Do you mean digital?

    Do you mean just get one and move it from room to room?

    Or get one for each room, then calibrate them all so they read the same? I don't get how to do that. Won't water ruin a thermometer that has a hold display?

    Since it's just a few degrees, doesn't it have to be accurate?

    I must be missing something. It's one of those days.

    Thanks for your help.

  5. #5
    Join Date
    Aug 2009
    Posts
    164
    As Amp stated it doesn't need to be right on with the temp.. You are not looking for an average temp. at the end but a difference in temp.. Use the same thermometer and set it in one room for 10 min. write down the temp. then move it to another room for ten min., write down the temp. and keep repeating the process until you're done. Then you will be able to look at what you wrote down and see that the kitchen is 3 deg. cooler than the living room or whatever your measurements happen to be. Just be aware when doing this of heat coming through windows from sunlight or from the oven in the kitchen and so on.

  6. #6
    Join Date
    May 2008
    Location
    Missouri
    Posts
    3,618

    Talking

    Why are you needing to "get back" with your HVAC company about uneven temperatures?? You may be "suffering" from simple physics, heat rises, cold air falls, and the sun comes up in the east and goes down in the west, and oh yeah, colder air blows out of the North. Have you tried simply running the HVAC unit's fan on continuous?? This usually evens out most temperature differences. I remember one gal we had that kept complaining about un-even temperatures, however once we checked it out, we found the east windows solar gain, and the west windows solar gain accounted for all the un-even temperatures. She even admitted that the home seemed to "even out" during the night! She had only 3 degress of difference, however she also refused to run the fan to compensate. Impossible to "fix".
    Now if you are getting 15 to 20 degrees, then that is a horse of a different color. Just a couple is common.

  7. #7
    Join Date
    May 2008
    Location
    Missouri
    Posts
    3,618
    Oh yeah, forgot the gal who called us out on an emergency call on Thanksgiving when her CO detector went off. She had been cooking the Thanksgiving meal for 6 hours with a gas cookstove! Imagine the CO build up since she had no vent hood to the outside!

  8. #8
    Join Date
    Apr 2006
    Posts
    98
    We got a whole new system. We told them we had a problem with uneven temperatures. They said they could fix it if we replaced most of our ductwork so we did. We also upgraded to a variable speed unit because they said it would make the system extremely quiet, save electricity and help even out the temperatures.

    Now they say our house is old, our windows are old, we have too much glass, there wasn't a good place to put the return, etc, etc. We talked about all this before they did the work and they said it would not be a problem.

    The rooms near the thermostat stay around 76 but our family room is very uncomfortable even with the ceiling fan on. Yesterday, it got up to around 93 outside and it was 87 in the family room according to my digital thermometer. In the summer it's much hotter out and doesn't cool off at night so it's a lot worse.

    The air is very strong from the registers near the thermostat but not so much in the family room. We tried adjusting the other registers but even with them closed most of the way it only helped a little. Plus the air is so strong there that it got really loud.

    I think we kept the fan on in the summer but I can't remember. We have allergies so we like to keep it circulating through the filter. It's not great though since the kitchen register is right over the stove. It blows right on you and makes it hard to use the gas stove.

  9. #9
    Join Date
    Jan 2004
    Location
    PA
    Posts
    68,795
    Sounds like they put back in the same size duct work as they took out.

    Do you know if that is the case.
    Contractor locator map

    How-to-apply-for-Professional

    How many times must one fix something before it is fixed?

  10. #10
    Join Date
    May 2008
    Location
    Missouri
    Posts
    3,618
    Sounds like you have an air balance/flow problem as your variation in Temp. seems too high. Need to have them back and run an air flow check on entire house and give you a list of registers and airflow from each. Usually this will show what the problem is that is causing your variation in temps.

  11. #11
    Join Date
    Oct 2004
    Location
    Harrisburg, Pa
    Posts
    63

    Balance the system first

    It sounds like your system is out of balance. I am assuming you closed floor registers in rooms where the air flow was strong in an attempt to push air to rooms where air flow was weak. This action will most often result in noise issues and does little to relieve your problem. Ask your installer if they put in balancing dampers on the take offs from the main supply trunk. This is where balancing should be done. Have you installers come back and balance the system with instruments. They should be able to give the cfm at each register.
    Good Luck

  12. #12
    Join Date
    Apr 2006
    Posts
    98

    Should all the registers be wide open for the air flow check?

    Never heard of an air flow check but it sounds like that's what we need. Is that what I should call it when I ask them? Each time I complained they checked the unit which is on the roof and said it's fine.

    The system is part hard duct and part flex. I don't think they ever balanced it. I don't know if we have balancing dampers, never heard of them.

    I think they told us to adjust the registers. They replaced our old registers with ones called OBD registers. They also called them registers with butterfly dampers. They're either in the ceiling or on a wall near the ceiling.

    They said the old flex duct to the family room was too small and was part of the problem. They said they'd enlarge it but it's in the attic so I'm not sure. I'll try to find out.

    Thanks for the suggestions. They're really helpful.

  13. #13
    Join Date
    Feb 2007
    Posts
    999
    Quote Originally Posted by tucson View Post

    Or get one for each room, then calibrate them all so they read the same? I don't get how to do that. Won't water ruin a thermometer that has a hold display?

    Since it's just a few degrees, doesn't it have to be accurate?

    I must be missing something. It's one of those days.
    You don't have to calibrate the thermometer. I only mentioned it in case you wanted to see how much of an error it has. Assuming a range of room temperatures of about 10 degrees, any inherent error will be of no consequence.

    As water will damage any electronic instrument, only the metal stem is immersed in the hot/cold water.

    Amp

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