I suspect my thermostat is a dirty, no-good, cheatin' liar (who may have shot my Pa)
January 12, 2011 8:42 AM   Subscribe

My house is cold, and I suspect something's wrong with the thermostat. But I know next to nothing about how home HVAC systems work. Other weird stuff inside...

We bought our current house in the fall of '07. The first winter that came along we suspected something was off with our HVAC system. The home has 2 AC units: one for each floor. Both thermostats are programmable, and I programmed them to hover around 70-72 F on the weekends and weeknights, and 68-70 during the weekday daytime hours when we're at work. The great room (carpeted) on the 1st floor has a double-height ceiling; a 2nd floor landing leading to the bedrooms overlooks it. The kitchen and sitting room next to it are all tile flooring.

I suspect multiple problems. I know there are a few drafts in the house; I've found several and plugged them up as best as I can for the time being. The 1st floor has about a 1-ft tall zone of frigid air that just hangs on the floor. I can sit in my chair and be fairly warm but my feet will be freezing. The circuit breaker on the heating unit has tripped several times. The downstairs thermostat shows temps that I'd guess are 3-5 (or more) degrees higher that what the air temp actually is. The weird thing is that if I go reset the heating unit breaker, the thermostat will come back on and display a much different temp than it did 10 seconds earlier. Example: this morning it was showing 71 F. That didn't seem right so I went and reset the breaker. Came back in and it was showing 69. I've also found it locked up before; I came home from work one day and it was freezing. The thermostat showed 72 but it feels like a meat locker. I tried fiddling with the controls but nothing would respond; it'd literally locked up. Reset the breaker, and it suddenly shows 58 degrees!

I've done some Googling on the thermostat problem and found some suggestions that I'll give a try (cleaning or leveling it, re-calibrating the anticipator, but none addressed why resetting the circuit breaker seems to fix it, at least in the short term. Which is why I came here.

One last weird thing. While trying to educate myself as to how the HVAC systems work, I noticed that the systems seem to be two more-or-less distinct systems: the heating and the cooling. The outside compressors are part of the cooling system, right? Well, both of mine seem to run almost constantly, but I haven't had the cooling on in months. Are they supposed to be running? They both make a loud grinding (presumably when they start up; the 1st floor unit is a lot lounder than the 2nd floor unit is). I think that may be due to some shrub branches next to them, but the fact that they're running at all seems odd.

Sorry for the long post, but this is the 4th year of this going on. The first 3 it wasn't bad because the winters are generally mild; we really only needed to run the heat extensively for a few weeks. But this winter has been particularly brutal already and we're just about to hit the coldest part of the year for us.
posted by ChrisLSU to Home & Garden (21 answers total) 1 user marked this as a favorite
Are you sure you don't have a heat pump? Your AC compressor(s) should absolutely not be running in the winter. We have two compressors as we have two zones, and each is controlled by a breaker. I turn the breakers off in the winter. Programmable thermostats have batteries (usually AA). Try replacing the batteries. If you don't have the instruction sheet for the thermostat (only nuts like me save that stuff) look online for a pdf of the instructions on the manufacturers web site.
posted by fixedgear at 8:52 AM on January 12, 2011

Response by poster: Just a few more nuggets to add that I forgot to mention.

a. The house is all-electric. No gas.

b. I haven't taken a separate reading of the air temp with another thermometer. That's at the top of my list once we get out of this snowstorm that's shut the city down (gotta buy them first).

c. During the summer the AC seems to be a little off as well, although not nearly as bad.

d. All the vents are in the ceilings on both floors. The furnace is in the top-floor attic, almost at the highest point of the house. At least I think it's the furnace; it's a big refrigerator-sized box wrapped in insulation.

e. The master suite is always toasty warm (thankfully). It's right next to the great room and connected by a short L-shaped hall. You can walk out of the bedroom door and actually feel the exact point where you leave the warmth and start getting cold. Very little temperature gradation; it's really stark.
posted by ChrisLSU at 8:53 AM on January 12, 2011

Response by poster: @fixedgear. I have no idea if we have a heat pump or not. Can you give me some tips on how to find out?
posted by ChrisLSU at 8:55 AM on January 12, 2011

I don't have central air so parts of this are outside my experience, but I'm 99% sure that the outdoor AC units should not be operating at all during the winter. The breaker absolutely should not be tripping.

Your thermostats should have some sort of setting to switch from heating mode to cooling mode. You should switch the thermostats to heating mode every Fall when the weather cools off, and back to cooling mode every spring when it starts to warm up. Have you done that?

On preview -- disregard the above if you've got a heat pump. I know almost nothing about heat pumps. Also, ceiling-mounted registers are probably part of the problem.
posted by jon1270 at 8:56 AM on January 12, 2011

You can walk out of the bedroom door and actually feel the exact point where you leave the warmth and start getting cold. Very little temperature gradation; it's really stark.

Do you, by chance, have drafts around your windows or underneath door jams, around these areas outside your bedroom? We have the same kind of stark temperature change between certain rooms in our home, and it comes from old windows and doors in the colder rooms.

Single-pane windows are bad insulators. You might look into plastic sheeting around windows and door "snakes", essentially a long, thin bag of sand that is placed against a door jam to keep the drafts out.
posted by Blazecock Pileon at 8:59 AM on January 12, 2011

Can you take pictures of everything you have and post them for us (thermostats, compressor units, attic unit, anything in the utility area in the basement)?

This is very hard to discuss without knowing exactly what you're dealing with - especially if you are unsure of the proper names for the equipment.
posted by davey_darling at 9:01 AM on January 12, 2011

I've a friend with a heat pump. I agree that's probably the only reason your outdoor compressors would be running during the cold season. He has an emergency 'boost' switch in the event it gets too cold for his heat pump, his furnace will kick on. My state offers inexpensive home energy usage assessments, if yours has something similar the folks who come out will find and plug leaks and can explain what you have today.

Otherwise have a salesperson from an HVAC company come out and evaluate what you have and make recommendations. Even if you don't buy anything the conversation should be enlightening.
posted by These Premises Are Alarmed at 9:25 AM on January 12, 2011

Response by poster: A few more points just to address some comments:

I counted up the number of vents on the first floor a while back and found 13. Five of those are in the master suite. Since the bedroom door is the only exit from the suite, it's not really surprising to me that it stays really warm. The air pressure in the bedroom is higher than in the rest of the house; the door will slam shut unless left open more than halfway. I closed all but 2 of the bedroom vents in an effort to get more warm air thru the rest of the house.

The house is brand-new; we moved in once it was finished. All the windows are double-pane glass, but the glass and the jams are still bone-cold. I've checked the flues on both fireplaces (wood-burning) and confirmed they're closed.

This occurred to me just now. The downstairs thermostat is on the great room wall dividing the great room from the master bedroom. There's no insulation in the wall (pretty sure of that). Since the bedroom is always warm, could there be a situation where the thermostat is reading some of the residual warmth on the bedroom side of the wall?

I'll see if I can get some pictures up later today.
posted by ChrisLSU at 9:36 AM on January 12, 2011

"The house is brand-new; we moved in once it was finished"
Call your builder and ask for a refresher on how the heating system operates. Something is seriously wrong if a brand new house has major heating system issues 3 years after being built.
posted by cosmicbandito at 9:41 AM on January 12, 2011

Since the bedroom is always warm, could there be a situation where the thermostat is reading some of the residual warmth on the bedroom side of the wall?

Absolutely, but it sounds like your problems are more complicated than that.
posted by jon1270 at 9:43 AM on January 12, 2011

Do you have forced air heat and a slab floor? If so that's probably why the great room is always cold: warm air rises and your great room is a chimney. Hows the insulation-in-the-attic situation?
posted by fshgrl at 10:00 AM on January 12, 2011

Your outside units should be running in the winter and summer. They are "sucking in" air from outside and pushing it through cold coils (for your A/C in the summer) or through a heating element (for your heat in the winter). This provides "faster" air (hot or cold) to push through your ductwork.
posted by kuanes at 10:16 AM on January 12, 2011

~ The outside compressors are part of the cooling system, right? Well, both of mine seem to run almost constantly, but I haven't had the cooling on in months.
~ The furnace is in the top-floor attic, almost at the highest point of the house. At least I think it's the furnace; it's a big refrigerator-sized box wrapped in insulation.

This leads me to believe you have only a heat pump system, and no actual furnace in the home. That big, wrapped box in your attic is the air-handler for the heat pump/AC. If you had a real furnace, it would be on the ground floor or basement, not in the attic.
posted by Thorzdad at 10:18 AM on January 12, 2011

If you had a real furnace, it would be on the ground floor or basement, not in the attic.

It is not terribly unusual for a furnace to be mounted in an attic, especially in warmer climates.

Again, without pics we are all just making wild-ass guesses here.
posted by davey_darling at 11:13 AM on January 12, 2011

Response by poster: Here are some pics:

First, the thermostat downstairs. The upstairs unit is identical.

The compressors. I thought the smaller one was for the upstairs, but we had an AC guy out after the first winter and he said the smaller one was actually for the downstairs.


The attic unit. It's probably not a furnace, but an air handler instead. There are two identical units in the attic. Not wrapped in insulation (sorry, my mistake). The one pictured is connected to the return in the great room.

Pic 1
Pic 2

Sorry the the quality; they're taken with my iPod Touch (no flash). And if they're upside down, sorry. I don't know why imageshack does that.

To answer some comments: Yes, the house in on a slab. That's why I suspected my floor was so cold. And I figured the reason the great room was always cold was because all the heat was rising upstairs. However, my parents house has a large foyer that opens all the way up to the second floor ceiling with a landing above it also, and their house is toasty. But they also have a crawlspace and floor vents.

I think it's multiple issues, but I also think something's wrong with the thermostat. It did that little "display wrong temp, reset breaker, now it's reading 3 degrees lower" thing again when I went home for lunch.
posted by ChrisLSU at 11:53 AM on January 12, 2011

Response by poster: To answer some other things:

Insulation in the attic appears good. I didn't notice any gaps in it. It's a mix of roll-out and blown-out insulation. Roll-out in on the angles and blown-out is on the flat parts. The attic was not as cold as I was expecting, considering it's below freezing outside. In fact, it felt like the attic wasn't much colder than the great room (maybe 10-15 colder).

We actually noticed the issue after the first winter. We had some guys some out (under our 1-year home warranty with the developer) to take a look at everything. We told him that the great room was very cold while the bedroom stays very warm, and he went to the attic and supposedly fiddled with the unit to move more air from the bedroom vents to other downstairs vents. I cannot confirm whether he actually did anything or not. He was also the one who told me the smaller compressor was for the downstairs unit.
posted by ChrisLSU at 12:10 PM on January 12, 2011

The "EMER"(gency) setting on your thermostat would indicate that you have some sort of heat pump system in place.

You should know that heat pump systems work in a way that those who grew up with more conventional (forced air, radiators) systems are not used to. The heat pump will slowly bring your house up to temperature and then maintain that temperature - it is not the same as, for example, a forced air furnace that lets the house cool and then kicks in to blow hot air throughout the house.

I think that what you are seeing when it is displaying the "wrong temperature" is actually the set point, that is, the temperature that the heat pump is attempting to maintain. The actual temperature is displayed in the same spot as the time (the display alternates from time to temp). (this appears to be the manual for your thermostat, or one very much like it)

The first thing I would try would be to turn off the setbacks you have programmed - heat pumps are most effective when they are running almost continuously to maintain a set temperature.
posted by davey_darling at 12:52 PM on January 12, 2011

We also have a heat pump system. One of the biggest differences is that when you have a heat pump, the air coming out of the vents never feels really warm. It's more like room temperature. (which means it's almost cold right now)

We purchased our home 1.5 years ago. We replaced the two older thermostats with programmable. We keep it 60 when we're at work or sleeping and 68 when we're home (I am super stingy energy-wise). That said, it has been so cold the heat pumps sound like they are always running just to get it to 67. These past 2 winters seem to have been unusually cold.

The brand of thermostat you have really makes a difference. I wish we had purchased Hunter thermostats; we went with Honeywell to save a few bucks. But after searching through forums, etc, I really think Hunter is the way to go. Replacing the thermostats may be an initial step you want to consider. That's a pretty easy DIY job.

Although your insulation is probably fine given the age of your house, you may want to have an energy audit. Our local electric utility offers a program where an energy auditor will come out to your home and check out your windows/door, insulation, heating/cooling systems--all for free. You may want to check to see if your utility offers similar programs? Good luck!
posted by Kronur at 1:29 PM on January 12, 2011

So you have two complete units outside?? Moreover, they're controlled by two separate thermostats, I guess that at least makes some sense. Anyway, wow. If any commenter can explain the logic behind this, please do because I'm pretty ignorant of the reasoning here.

This is an odd suggestion but have you thought of shutting off one of the systems (via the circuit breaker) and seeing how things perform with only one system in operation. If nothing else, you gain data you otherwise wouldn't have.

Then again I'm from the deep south and have ZERO understanding of why any one unit home would have a need for two separate HVAC units, especially if they're both heat pumps. Efficiency usually dictates sizing the solo existing unit so that it runs at the optimum level for the given climate. Perhaps they were designing the system so that only one unit would be necessary during certain parts of the year (or if you use one part of the house exclusively, not likely). By doing so you could, hypothetically, shutdown the other unit and get a boost to the overall system efficiency by not operating one unit that is 'too large for the job' during certain parts of the year. I see several real world problems with this train of thought but I'm not an architect/builder (though I do have an engineering background).

I wouldn't do this for an extended period of time for risk of overloading something.

Final Note (reiterating what others have said):
As with any situation like this, fixing your leaks/drafts/windows if they are in need of it is the first and foremost priority. That high ceiling room should also have a fan installed (and spinning in the correct direction for the season) or you're really wasting money for zero gain.
posted by RolandOfEld at 1:33 PM on January 12, 2011

Response by poster: Well, I found out that my local utility offers a type of energy evaluation for free, so I'm going to call them and set something up. While browsing thru their web page, I also came across a tip to NOT use zone heating/cooling in an HVAC that uses a heat pump or air compressor. Which is what we were doing: closing unused doors and vents in order to move the air to other rooms. I opened up all the doors and vents I'd closed, and I'll be danged but the house is fairly comfortable right now. I still think we have some other issues, but we'll see how this goes for a while.
posted by ChrisLSU at 6:02 PM on January 12, 2011

Best answer: This is the answer I got from my husband, who has been in HVAC for 29 years:

1st problem. the cold floors (1' of much colder air) is called stratification. This is a problem with "Spec Homes". Your system was installed by the lowest bid contractor....yay for cheap (not really).
A return air vent at the floor level would eliminate this. However, it's not really a do-it-yourself task. Any reputable HVAC contractor will give a FREE quote to remedy this.

2nd. You have Bryant air handling units. They are made by CARRIER (think Chevrolet vs GMC trucks. same shit, different sticker). I have been installing this brand for over 15 years. IMO, some of the best residential equipment out there. I assume from your avitar that you live in the gulf coast (Geaux Tigers!...not the shitty war eagle tigers....Les Miles' Tigers). I'd bet my left testicle that you have a heat pump (or two) with emergency back-up heat strips. Your condensing units (outside thingys) have a "reversing valve" that allows your air conditioner to work in reverse...creating heat. This heat is mediocre at best, and fails at around 45 degrees outside ambient temperature. Hence...the emergency electric heat strips.
Breakers trip due to heat. Period. Several things can cause this, such as a dirty filter (change it once a month, they're cheap. do it or get nut cancer) improper wire gauge connected to the unit, or faulty breaker sizing. Please look at the nameplate on the units. Look for amperage. The amperage of the unit must be ~80% of the breaker size. Actually, it should list a minimum amperage rating. Look at the breaker you keep resetting and make sure it matches. If not....you have bigger problems and should consult either a HVAC company or a local electrician.

Finally, invest in two of these http://www.google.com/products/catalog?q=honeywell+vision+pro&oe=utf-8&rls=org.mozilla:en-US:official&client=firefox-a&um=1&ie=UTF-8&cid=1968412164249487271&ei=moMuTd-XL4-u8AbyysH7CQ&sa=X&oi=product_catalog_result&ct=result&resnum=5&ved=0CEAQ8wIwBA#

These are the best thermostats on the market.

Finally....Never close a vent. Airflow is critical. Given the typical market for residential construction, the systems are designed as cheap as possible. closing vents, doors, etc...will cause your airflow (CFM) to drop. This translates to a higher Delta T (temperature differential). In layman's terms, it creates a higher discharge temperature. More heat? should be a good thing, right? No. Modern air handling units (and furnaces) have high limit switches. They get hot, they open, no more heat. You manually trip breaker, and reset the board.
Open all your vents, change your filters (I buy the $5 1" pleated filters from Lowes, and I fix this shit for a living).
posted by tryniti at 9:03 PM on January 12, 2011 [2 favorites]

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