Help troubleshooting why furnace won't kick on

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Old 02-04-16, 07:07 PM
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Help troubleshooting why furnace won't kick on

We got home tonight and thought the house felt cool. Although the heat was set to 75, it was only 71 in the house. I cranked up the setting to 80 and went outside to see if could hear anything - nothing. I turned the AC unit on and it came on fine and was blowing cool air.

This system is about 15 years old and is a "gas pack" system. Over the past 5 years, just about every component has been replaced in this HVAC system (thankfully, we had a home warranty each time. Unfortunately, we decided not to buy one this year since nearly every component has been replaced).

I tried resetting the breakers for grins with no change. Is there anything I can check before calling the heating people?

This is a Carrier system.

To give you an idea of what has been replaced over the last 5 years:

circuit board
coil
gas valve
run capacitor and another capacitor (not named)
inducer assembly
motor and wheel (think this was the squirrel cage)


Thanks,

Andy
 
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Old 02-04-16, 07:35 PM
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By gas pack I assume you mean a packaged unit.... everything is outside.

A model number would be a big help to me.
 
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Old 02-04-16, 07:40 PM
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That's correct. It's one self-contained unit outside. On the cover of the manual it says "Combination Gas Heating/Electric Cooling Unit".

Model# 48GS-04209301
 
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Old 02-04-16, 07:57 PM
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The following should be a link to your manual including servicing. Your furnace has a control board with a fault LED on it. It will be flashing a code that you need to count and then look up in the chart. The code will tell us where the problem is.

I can't tell you exactly where the board is located. Some units have a sight glass where you can look in and see the flashing LED. If not you'll need to remove the access cover on the burner side to see it.

EquipmentManualsIntegration/Manuals/CRC4494.pdf
 
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Old 02-05-16, 04:56 AM
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Why didn't I think to look there? lol

Went out there this morning and it's flashing 6 times. Per the manual the cause is "IGC does not sense that induced-draft motor is operating."

IGC - Integrated Gas Unit Controller.

I called an HVAC company and they luckily have someone available later today, so hopefully this will be a quick (and relatively cheap) fix. I'll update once they have it going.

thanks for the info.

Andy
 
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Old 02-05-16, 01:28 PM
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<< "IGC does not sense that induced-draft motor is operating."
>>

That means that the pressure switch isn't closing.

A GOOD repairman will begin by connecting up a manometer to the pressure switch rubber tubing in order to see if the furnace is plugged up --- which it usually is.

When he has identified and corrected the problem, he will be rewarded by the manometer showing a normal pressure again, which will verify that he found the actual problem(s) and has corrected all of them.

Unfortunately, many repairman don't use or even have a manometer. Even if they do, many don't know how to use it properly.

They correct such problems through guessing, prayer and good luck.

Unfortunately, if those methods don't work, the homeowner has more problems.



Seattle Pioneer
 
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Old 02-05-16, 04:24 PM
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Well, it turned out to be a capacitor that had been replaced about four years ago. It tied into what I think was the motor that drives the squirrel cage (you can see it just above the burner assembly on pg. 16 of the document that PJMax provided). That motor was so hot you couldn't keep your hand on it more than a second. The minute he replaced it, the heater came back on.

Thanks for the help on this one.

Andy
 
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Old 02-05-16, 09:39 PM
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S.P. ....... no manometer needed on this baby.

This unit uses a draft inducer blower with a hall effect sensor. It actually senses the motor shaft turning. This unit is also one of the few where the draft inducer motor has a capacitor on it.
 
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