Heater Not Keeping Up

All,
Last night, the temp here in Iowa dipped down to around -10 with a -35 degree windchill. This morning I noticed the temp was about 4 degrees off of where I had the thermostat set (It was set for 68, but the heater was running continuously to keep it at 64). Right now, the temp has risen to about -5 and the heater is running continuously to keep the house at about 66-67 degrees.
When you look at the windchill, I think this is probably one of the coldest days since I moved in 2 years ago.. Does this sound normal, or could there be an air flow problem? The amount of hot air coming out the vents seems to be normal compared to warmer days.
Thanks, Dan
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On Sun, 21 Dec 2008 08:33:31 -0800 (PST), snipped-for-privacy@googlemail.com wrote:

Close the windows
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Anything is possible, including the heating unit being undersized for the building
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RBM wrote:

Or house has poor insulation, or it could be as simple as dirty air fiter if it is force air furnace. Here, it's been -30C with windchill of -40C or so last two weeks. Our furnace has been running more than usual but keeping indoor temp. at constant 21C.
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I've only ever seen it get close to that once in 27 years here in CT but the house was still comfy. Tomorrow my new boiler is being installed and tomorrow night will be a good test. Prediction is 5F (-15C) overnight.
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Couple of possibilities. Heaters are designed for a certain temperature rise across the coil or heat exchanger. If the leaving air is above the entering air by the correct degrees, the heater is running properly.
Next is wind chill. The wind chill factor does not apply to inanimate object, only or skin where evaporative cooling makes us feel colder than the actual temperature. Wind will though, chill a house faster if there are leaks, poor windows, defective door weather striping etc. Check all of that stuff. Even a simple fix like a towel rolled up against a leaking door threshold helps.
Next factor is the design of the heating system. At some time the builder should have run the calculations of how much heat is required to keep your house at the design temperature under severe conditions. If -10 is the worst it ever gets there, it is about the limit of the system. If you often get say, -25, your system was not sized properly and should have been larger.
Fixes include adding more insulation and possibly some supplementary heat. Even baking cookies is a good idea on a day like this as the oven will add some heat to the house.
You did not say what type of fuel you have. Oil burners can be de-rated by putting in a smaller nozzle. If you have oil, be sure you have the appropriate nozzle for your burner.
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If the windows are old or drafty you could cover them with plastic. Also one of those electric oil filled heaters that look like a radiator might help...
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faster out of anything the creates heat.... but only down to the true air temperature, not below it.
Mark
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the low for sac city was -4. but beside that, i'd say you might have some serious air leaks. I'm sitting in a totally uninsulated house with no interior walls and I'm maintaining 65 with a properly sized (for insulated) system.
steve

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wrote:

re: "I'm sitting in a totally uninsulated house with no interior walls ..."
Why?
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137 yo farmhouse ripped down to studs and in progress. got tired of freezing in the fifth wheel. been in it for 2 years and we finally got the bath and kitchen functional in the house.
steve
re: "I'm sitting in a totally uninsulated house with no interior walls ..."
Why?
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A heating system should not be designed to maintain the set point 100% of the time. Instead it should maintain the set point, say, 99.5% of the time. Otherwise, that extra capacity that you installed to get from 99.5% to 100% would only be used 0.5% of the time, which is not cost-effective.
So if your heater is only outpaced once every two years, there's no problem with the sizing. Others have mentioned ways to reduce your house's heat loss, which would decrease the frequency that your current heater is outpaced by the cold weather.
Cheers, Wayne
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Exactly what I was thinking. If it rarely gets down to -10 with high wind, then having the furnace sized to handle a max 74 deg temp differential sounds reasonable. At my house that would equate to keeping it 70 inside, with it -4 outside. Here, I haven't seen that low of a temp in decades.
If it does get that cold frequently and you want it to be warmer, you probably need a larger furnace. But with that comes increased cost, both upfront and potentially operating cost as well. Before I worried about that, I'd carefully check insulation, ducting, widnows/doors, etc
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On Dec 21, 10:33am, snipped-for-privacy@googlemail.com wrote:

Now tell us when was the last time it was serviced, by anyone.
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It was serviced about a year ago.. They installed a new blower and checked everything out while they were in there.
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had a new blower furnace motor installed and it wouldnt heat house. he hooked heat side of it to the low speed wire,needed to be on the med speed motor wire.
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On Sun, 21 Dec 2008 08:33:31 -0800 (PST), snipped-for-privacy@googlemail.com wrote:

What kind of system. One time this might be normal is if the system is a heatpump with electric heat strips as backup. Our old unit would let the heatpump take care of things until the indoor temp dropped about four degrees below the setpoint on the thermostat, then it would kick in the heat strips. If you are running a heatpump in this sort of cold, switch it to emergency heat (the heatpump is wearing itself out for nothing) and turn up the temperature until it reaches something comfortable, ignoring what the thermostat setpoint shows.
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On Dec 21, 10:33am, snipped-for-privacy@googlemail.com wrote:

With it that cold everyone was sucking Ng, you may of had poor supply flow. To know get a load calculation, energy audit with blower door test. Do everything recomended and cut your bill 50% if you have an older home. Remember insulation code is minimum needed, the attic is the cheapest and most effective start point.
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