Furnace Kicking Off

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Furnace Kicking Off

Postby noodle24 » Tue Jan 24, 2012 2:19 pm

I've been a homeowner for about 2 years now, and until recently never changed the air filter. Finally, I changed filters to the Filtrete Dust Reduction 300 filter. However, within a couple days, I noticed that my heater started having periods where the pilot would kick off, and the furnace would only blow cold air. After frequently experiencing this, I put the old 2 year filter back in, which by the way is a Filtrete Maximum Allergen, and never had a problem.

Based on this, I decided to go with a higher quality filter, and opted for the Filtrete Ultra Allergen. Again, I started experiencing the same thing where the furnace would stop producing heat and instead only blowing cold air. Again, I put my old Maximum Allergen filter back in and have yet to have a problem.

My question is is this plausible, or is it merely a coincidence that the filter is causing this? I've read in my instruction manual to replace my filter with a "high-velocity" filter. Is my Maximum Allergen filter "high-velocity" while the other two weren't? Is there something else with the filter that could be causing my furnace to shut off?
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- Furnace Kicking Off

Postby Freon » Tue Jan 24, 2012 3:27 pm

The first thing to determine is exactly how the furnace is turning off. If the difference between the filters is air flow resistance then it is possible the more restrictive filter is causing enough lack of air flow thru the heat exchanger to make the furnace high limit safety trip. But that is speculation until you watch what happens during one of these shutdown cycles.

Normally, if the high limit trips, the main burner will shutdown and the blower will continue. On some furnaces the burner should reignite once the heat exchange temperature has cooled, assuming the thermostat set temperature has not been reached. Now if your furnace blower just runs and the main burner does not reignite then you may have a different issue.

Are there any blinking lights on the control board? Does the blower, when it's blowing cold air, eventually stop on its own?
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- Furnace Kicking Off

Postby noodle24 » Tue Jan 24, 2012 5:39 pm

The burner will shut off, but the blower will continue. I believe sometimes it eventually shuts off, but one night it was blowing cold air for over 45 minutes. Our temperature was set on 70 and when I looked the real temperature was at 65.

Something else that's interesting that I didn't mention yet, whenever I notice that the vents were blowing cold air, if I go to the thermostat and turn it off, then put it back on heat again, it goes back to producing heat as normal. It works every time Also, FYI there are no blinking lights. When I look at the current settings on the thermostat everything appears normal.
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- Furnace Kicking Off

Postby how » Wed Jan 25, 2012 1:08 am

The age/ brand and model of furnace would help.

Turning down the thermostat for a while and turning it back on is the same reset action as turning the power off to a furnace and then turning it back on. A furnace that has experienced a hard lock out is reset that way. I think you should be doing a temp rise on your furnace. It will tell you if the furnace is really running hotter than it's designed for (limiting out) and whether a particular filter is OK or not.
On your hot air plenum, just beyond the sight line of the heat exchanger, there should be a 1/8th to 1/4 " hole that the original installers made to do this test. It might have tape over it. If you can't find it, make your own hole and stick in a thermometer when the furnace has been running hot for at least 10 Minutes. Take that measurement and subtract the present room air temp from it. What you have left is called the temp rise of the furnace. If you look at the rating plate on the furnace it will list the recommended temp rise for your furnace.
If you go over that temp rise you risk limiting out the furnace. You can test this with your different filters in place to see what works and what doesn't. You can moderate an over heating situation by using a cheaper filter/ opening up all your heating outlets/ making sure nothing is blocking the return air grill/ increasing the fan speed/ (reducing the gas flow but leave this one to a PRO) /cleaning a dirty fan cage/ replacing a faulty run capaciter/cleaning a dirty ac coil/ etc.
Let us know what you find out?
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