Ahah!! I bet you that is a big part of the problem.
Nope, I swear on my eyeballs it’s true. But keep in mind that the furnance has been running now since 2:30 when I got home from errands. After many hours it does hit and keep temperature better.
Agree. Without question there are insulation problems here.
I think the Span resolution will make a big difference.
Wait. Only kind of joking???
Yipes. That sounds… painful. And oddly… personal. :eek:
Well, my Span only goes up to 3. So I’ll see how much help that is. Also, just noticed I done spelt furnace wrong in my title.
I’d be pretty annoyed at a thermostat that controlled to more than +/- .5 degF. A total span of 3 would drive me nuts.
Did Joey P’s suggestion about thermostat span help? If it did it’s good information but I suspect it’s attacking the symptom not the problem.
The problem may be that the t-stat is not sensing the correct temperature. Is the furnace air blowing directly on the t-stat from the supply registers?
You mentioned at the beginning that the air “roars” out of the registers, perhaps the blower should be running at a lower speed.
On most T-stats the minimum +/- is 1 degF. Less then that and you would have a near constant cycling and would drive you more nuts then you realize. It also isn’t good for the equipment as well as being less efficient.
I fully suspect that to be the case. I was just trying to offer a solution for major complaint which seems to be the cycling. The reason for the cycling still should be addressed though.
Good idea, I hadn’t thought of that. Carol is that a possibility? I’m thinking it’s probably not since we had the furnace running for a solid 23 minutes, but it’s worth walking over and checking into. Anything blowing on it? Is it in the sun (during the day)? Near any other heat sources like a stove, fridge, TV, computer, lamp, track light pointing at it etc?
Carol the Impaler what you described in post 10# is most commonly caused by a unit “cycling on the limits.” I think Joey P is probably right.
Although many things (some of them uncommon) can cause this, I’d check the following:
Unless you’ve done this, I would repeat Joey P’s experiment, making sure to see if the burners-----not just the fan----stay on during the whole time the stat is calling for heat. It is possible that the furnace is overheating and the furnace stays warm enough to keep the blower on, but without your awareness it is periodically cycling the burners off due to an overheated condition.
The way to check this: Most manufacturers will design a “temperature rise” of 35°-70F. What that means is that the furnace will warm the incoming air (return air) 35-70 degrees. So…if your return air is 70, the air leaving the furnace will be 105-140. (assuming you’re using natural gas) What is the temperature of the air coming out of the furnace? If it’s hotter, that’s usually an indicator of a dirty coil or anything that would inhibit air flow. If your air temp leaving the furnace is much more that 125ish, I’d suspect a furnace that’s running hot and cycling on the limits. (which is unsafe, btw)
other experiences…
Unless your furnace is 35+ it has no belt.
It usually isn’t the stat. That doesn’t keep homeowners of all stripes from changing them out. Its a logical assumption, but usually wrong.
Bearings going bad will usually whine, rumble, or make some other noise. Metal on metal is usually a squirrel cage that’s rubbing against the fan housing. The set screw has come loose and the squirrel cage has shifted. Most modern blower motors have sealed bearings and need no oil.
Digital stats have different forms of “adaptive intelligence.” What that means is that if you program it to be comfortable at 6:00 am, it will learn what time it needs to start to be comfortable at 6:00am. IOW, it isn’t starting at 6:00 am, it recognizes it needs to be at set point at 6:00 am, so it will start earlier.
Other potential issues
A main high limit going bad. Maybe the furnace is not too hot, but the limit is weakening.
Where is your return air duct? Read the temperature at the return air register. Then read the return air at the furnace. They should be within 1°. If it is colder at the furnace than it is at the register you likely have some return air duct that is compromised/broken and you’re picking up cold attic/crawlspace air. IOW, you’re trying to heat the neighborhood.
A flame sensor. Pay close attention to the burners at start up. Do the burners ever shut off after 1-3 seconds? If so, you have a dirty flame sensor, an easy and inexpensive DIY fix.
can you tell us the brand and model of the furnace and stat?
Just throwing stuff on the wall to see what sticks…
A “roaring” air noise may be an indicator of a dirty coil. Just as putting your thumb over the garden hose will cause greater velocity, a dirty coil may cause greater noise/velocity.
High air noises, coupled with high discharge air temperatures (greater that 120ish) makes me go looking for air flow issues.
It’s Joey P’s fault for my verbosity. He asked where I was. 
All furnaces have a delay at the end of a call for heat to allow the furnace to deliver the last remaining heat content into the house. This delay is accomplished by shutting down the burners when the stat is “satisfied” and having the blower run another 90-120 seconds.
Theres 2 reasons for this: 1) It keeps the furnace cool. 2) You paid for the heat, so it makes sense to bring it into the home for your comfort.
However…that’s only for 90 seconds or so. If its on long enough for you to perceive “cool air” that suggests to me a furnace that id cycling on the limit.
IOW, the stat is not satisfied, and there is still a call for heat. But a safety device has shut down the burners, and the fan continues to run. The fan cools the furnace down and Voila! the burners are allowed to come back on.
I learned about this in an odd way. I walked into work to hear. “Hey Joey, the furnace has been running for three solid hours.” Well, since it was still a normal temp in the building I concluded it hadn’t actually been firing for that long, so it must have been the fan. Some voltage testing and wire following led me to this odd thing with a dial and some buttons on it (what I later learned was the limit switch). Hmm, I thought…I’ll bet if I [swift blow with a screwdriver handle] yup that did it…“ok” I announced proudly to anyone within earshot, “I need a new one of these brown things.” (FTR, I knew what it was, I just like being overly vague).
Some sandpaper, may be all that’s needed, but, a quick look at the circuit board should for a for a flashing LED should diagnose that and a host of other possible issues.
Like forgetting that your multimeter is in continuity mode and trying to test voltage and blowing a fuse on the circuit board :smack:
RE: the span suggestion. Has helped some, the cycles are longer. But the problem continues about the constant cycling.
As to the roar, I’ll have to wait until my landlord is back to have him check the furnace out. Again.
Nope, not near any heat sources. Unless you count my burning anger. Heh.
Roger. The grating metal on metal sound is gone since my landlord greased the furnace up. (I swear to God, I can’t stop spelling that word wrong.) I wouldn’t mind my furnace being all considerate of my needs at 5:30AM if it didn’t have the godawful roar. In the meantime, I’ll reset the program so start at 6:30.
Stupid question… are the return air duct and the return air register the same thing? What is the difference between reading the temp at the return air register vs. the return air at the furnace?
The stat is a Hunter 44110. The furnace is a Tempstar N8MPN oro N8MPL (that’s what the manual says, I can’t find a model number on the unit).
A fan and a blower are the same thing? Forgive please, my ignorance, but I don’t want to assume I undersand your questions.
Here’s how it goes based on my observations just now at the furnace. The system powers up. Burners start one to two minutes later? Blower starts about a minute later? Burners stay on for a good ten minutes, then shut off. Blowers shut off two or so minutes after that. Then the whole system shuts off. IOW, the blower is not running constantly.
I don’t have any kind of thermometer that could measure the air temp.
The burners run consistently until they shut off at the end of the cycle. The LED flashes normal, according to the guide on the furnace (IOW, in a hearbeat pattern, dimmer then brighter, dimmer than brighter).
No, The registers blow air, the returns suck air. An easy way to tell is to hold a piece of paper up to the grate. When the furnace is running the returns will hold the paper up against the grate while the register will (as you might guess) blow it away. What Raindog is asking you to do is check the temp at one of the returns and at the furnace. I’ll admit, I don’t fully understand where he’s going with this, but the easiest way is going to be with an infrared thermometer (in layman’s terms a laser thermometer). Let the furnace run for a while, in face, I think you could just let the fan run for a few minutes. Check the temp of one of the grates. Now go to the basement and check the temperature of the sheet metal surrounding the filter area. Actually, even better (if you do have a laser thermometer), slide the filter out and check it. The sheet metal might be cold from the basement.
I think what he’s suggesting is that if there’s a big drop from the return grate to the basement that it’s possible that your sucking in cold air somewhere and just making more work for your furnace and it’s taking longer to heat the house. But I argue that unless it is a helluva a break this probably wouldn’t be the case since A)once it does get to temp, the house isn’t maintaining temp and B)newer furnaces pull outside air in by design.
OTOH (and maybe this what you were getting at) it could be making the noise.