What's wrong with my furnace?

[mkirsch1]

Apologies if this was double-posted.

My furnace seems to be running way too often, upwards of 30 minutes every 30 minutes. It doesn't seem to matter how cold it gets outside, it's always the same.

One thing that bothers me is, with the system "professionally" balanced, the temperature at the registers was in the low 70's using an infrared thermometer. I've since closed off the vents to all unoccupied/unused rooms in the house, and even with just the living room and main hallway heated, the vent temperature is still only in the upper 80's. My understanding is that it should be around 100 degrees.

I think all the heat is going up the chimney. The exhaust pipe on the furnace is RIPPING hot, can't even put my hand near it. It's putting out a clean blue flame. Changing the filter didn't help. Pros say the furnace is in perfect working order.

The furnace itself is a 1999 Amana, but I can't tell which model because the labels are all in French (I'm in upstate NY, not Quebec) and apparently use technical terms that the online translators can't deal with. It's either a 48,000 or 65,000 BTU unit, depending on which part of the label you read.

Mostly, I'm sick of being cold and listening to the furnace fan howl all the time. I've got plenty of insulation (R38 batts over R19 in the ceiliing joists). Walls are R11 with an extra inch of styrofoam and housewrap under the siding. Windows are all double-pane vinyl units. It's a pretty tight house, as I can't feel any drafts or hear any whistles in high winds.

[ransley]

Do you have AC, a friend of mine had his ac coil so clogged no air would go through it. Get another pro out, somebody is missing something, Your furnace is trying to heat the rooms you turned off, also maybe your thermostat is set for no swing in temperature.

[PaPaPeng]

That's your problem. The walls should be R30. The insulation effectiveness (ie reducing heat loss) graph plot rises steeply from zero to R30 then flattens off. That is beyond R30 you won't realise much more insulation gain. But R 11 is certainly pretty low on insulation effectiveness.

[mkirsch1]

So if I put more insulation in my walls, the furnace will stop blowing cool air? That doesn't make sense.

[JoeSpareBedroom]

If you're anywhere near Rochester, I can recommend a heating company that's terrific.

[PaPaPeng]

I am not so sure about the explanation for you furnace not blowing hotter air. It sounds like there is a large mass of colder air in the house and it takes all of the 30 minutes to warm it up to the set temperature. Most of that air is recirculated air drawn from the rooms back into the furnace. Someone knowledgeable will have to see the furnace running to troubleshoot. It can be you. Put a thermometer in the hot air plenum, more thermometers some distance away in the main trunk and see what the readings are. That should provide a clue.

I don't have the answer for the furnace. On insulation try asking your city hall agency that deals with home construction permits and ask how it can be done in your location. Its just that when I built my house (1980, sweat equity program for people on limited income) that was what the construction class instructor told me. It sounds like yours is an older house (>80 yrs?) when such things were not well understood or insulation was absent altogether. Some of these older houses had insulation added as an afterthought and the studs weren't deep enough to put in thicker insulation. Insulation batts have to be loose to trap air pockets. Squeezing R30 batts and compressing them into a thinner wall space is ineffective.

Effective insulation means that less heat will be lost through the walls by conduction. Sealing the gaps around the doors, windows, electrical boxes, etc. will reduce heat loss by convection (ie escaping warm air and letting in cold air).

[TD]

ransley wrote in news:7b81a643-3594-487b-9945- [e-mail]:

It's broken.

[ransley]

Its not insulation, do you have AC, get the unit serviced by a different Pro.

[samurai]

How many square feet is your house? The furnace sounds like it is a mid-low efficient, at about 75%. 65,000 Btu input, 48,000 Btu Output.

1) Check your furnace filter, be sure it is not clogged. 2) Try a digital Thermostat. I just replaced mine with a Honeywell touch screen, my furnace runs different now, the cycle times are closer, and the on/off times are different. Also, the fan does not run as long as it use to. 3) Check that the air return vents are not clogged either. 4) Thermocouples could be dirty, a cleaning with steel wool may help.

It also sounds like partly the thermostat is not telling the furnce it has achieved temperature, and not shutting off. Or if it is an older furnce, then there may be a problem with the upper/lower limits switches of the furnace.

Let us know what you've tried and what the solution was.

samurai.

[ransley]

has any tech actualy Looked at the AC coil and cleaned the unit, a super hot stack indicates otherwise.

[Edwin Pawlowski]

Has it always been like that? It does not sound right that the chimney would be that hot. Perhaps you need a new pro to look at it.

[Robert Hancock]

The run time part doesn't really seem like much of a problem..

You'd have to check the temperature rise at the furnace plenum and compare it to the specs. That does sound low though.

Unless it's a 90% or higher efficiency model, the exhaust will usually run way too hot to touch, so I can't really tell if what you're describing is abnormal or not.

Temperature rise check would be the first thing I would do/have done..

[mkirsch1]

By coincedence, I am near Rochester.

[mkirsch1]

I'm thinking it's not insulation... My insulation isn't R30, but it's at least R19 overall, which is standard for this area. Sheesh, I'd need 2x8 studs to keep an R30 batt fluffy! I just finished putting R19 between the floor joists along the foundation walls too.

I've got AC, but if the coil was clogged, wouldn't I notice low air flow and high register temperatures?

[JoeSpareBedroom]

Prepare to fall in love with a heating company.

Hawn Heating

482-2499

Doug Hawn is the owner, and you'll often end up talking to him on the phone. He's extremely knowledgable. Learned from his dad, Al Hawn, who's still somewhat active in the business. I've used them since 1983, when they were recommended to us by the people we bought our first house from. The technicians they send to my home are ALWAYS courteous, picky about details, willing to explain things, and they wipe their feet. I never got the feeling they were trying to sell me something I didn't need. Matter of fact, Al Hawn helped me milk a couple more years of life out of the old furnace in my previous home, by teaching me what I could do in terms of maintenance.

They're on Winton Road near Blossom. Nice showroom. They did an installation for a friend who lived 30 miles away, so I know they're service range goes at least that far.

While we're on the subject of word of mouth, here's a name to have around, if you never need appliances or service. Another amazing company:

[ransley]

company:

If the ac coil is clogged heat goes up the chimney, not to the registers, to even see mine I had to cut open the sheet metal surrounding it

[mkirsch1]

I've heard of them, and seen their van(s) around town. Thanks!

As an update, I went around with some clear packing tape last night and covered over the cold air intakes in the unheated rooms. Something said in this thread got me to thinking that it might work more efficiently if it wasn't trying to heat the COLD air. Maybe it's all in my head, but I think it made a difference both with the register temperature, and how often the furnace runs. Gotta take the IR thermometer home tonight, and start taking notes again.

[do_see]

That's stupid. You've just restricted the airflow to the furnace heating vents.

[JoeSpareBedroom]

Similar: A friend of mine had her ancient furnace replaced last year. When the installers were done and testing the new unit, something was very obviously wrong with the air flow. On further investigation, they found that two of the cold air returns had been stuffed with fiberglass insulation. Based on other amazing home maintenance screwups we saw around the house, it was most likely the previous owners, who were experienced break-it-yourselfers.

[dpb]

That's absurd.

There's virtually no house w/ _walls_ of R30.

2x4 wall cavity w/ fiberglass is R11 (2x6 will yield R19). The inch of styrofoam is another R5 for a total of about R16. The rest of the wall exterior sheathing and interior drywall while not insulation per se, will add another fraction. That's a plenty-well insulated wall.

--