T Rex Family

T Rex Family

Thursday, March 26, 2009

Mr. Scott Does Damage Control

(or How Rube Goldberg Beat an Open Limit Switch)

T Rex Dad here, guest blogging.

This week the Rex household suffered a serious power outage. My 'engineering' skills were again to be put to the test. Electricity to our home was off for almost exactly five hours starting at 10pm until about 3:10am. The T Rex was asleep in bed when the power went out, and we quickly followed since it was clear this was not just a 'blip'. We got ready for bed by the light of our emergency flashlights, put another blanket on our Little Guy, and went to sleep. It was 68 degrees in the hall outside our bedroom at 10:30, and 69 in T Rex's room. The furnace, although gas fired, is electrically controlled, so we were hoping the power would come back on soon. It was supposed to get down to 38 degrees that night...

Five hours later, I was awakened by the sound of our furnace fan starting up. Warp power restored! Or was it? I checked on T Rex; he was still covered by blankets but it was 63 degrees in his room. Our room was a chilly 62. (We have wireless thermometers in Thomas' room with the "Base" in our bedroom, in case you are wondering how we know all these temperatures). Reassured by the drone of the furnace fan, I returned to bed. It would be warm soon.

Two uncomfortable hours later, colder than ever, I lay awake in bed, "frigidly fuming." Something was wrong. It was COLD, and, although the furnace fan was running and running, only cold air was coming out of the vent. A quick check of the thermostat reported, YES, the furnace was on and the temp was set to 68. But the actual temperature read 59. Yes, 59 degrees. Groggy, shivering, and unhappy, I knew something had to be done. I didn't bother checking the temperature in Thomas' room. If I felt cold, he would be freezing. Something was wrong with our furnace. So out to the garage to see what I could do.

Our furnace

My first step was to look through the window of the furnace. No blue flame. Just the drone of the fan running. Mmm. My next step was to cycle the power breaker on the furnace. The power outage 'broke' it, right? Maybe cycling the power again would fix it. Click, off. Fan stops. Wait.... Click, on. Fan starts up. No blue flame. No glow of an attempted light up. The 'core' of our furnace was dead. Sigh. Groggily (it is 5:07 am), I get the tall ladder, a flashlight, and a screwdriver, and proceed to examine the top service window leading into the brains of the furnace. Visible inside this window is an LED light which SHOULD be glowing a stead red meaning "I'm working". Nope. It is blinking... ONE, TWO, THREE, FOUR. Pause, and repeat. That's an error code the 'brain' of our furnace was putting out. Something is DEFINITELY wrong. However, it's good that the 'brain' knows it. Maybe something can be done.

Carefully, I opened the cover of our furnace. Now (and I am NOT recommending that ANYONE try this or ANY furnace repair themselves), there are two parts to a furnace like ours. The top part is where the 'brain' is, along with the fan that blows the heated air. The bottom part is where the burner is. When you open either door cover, a safety switch stops the furnace. (This is to protect people like me from the blue hot flames found inside all working furnaces) Most importantly to me at this point, the inside of the top door has a wiring diagram of the workings of the furnace and a list of error codes for that blinking LED light. It's a short list. Four blinks clearly indicate this error:

OPEN LIMIT SWITCH -- AUX LIMIT OPEN / MAIN LIMIT OPEN

What exactly in the heck does that mean? It could have said "The dilithium crystals in the warp core regulator are burned out" and that would have made more sense.

An attempt to look up this error via the Internet proved futile. Our Internet is down. The power bump has killed our DSL router!! GREAT (fixing our Internet problem is a whole other story). Luckily for us, I have a wireless cellular card on a laptop that does not need a DSL line. I am able to look up this error. Turns out this is fairly common problem. The power spike likely reset one or more sensors that monitor air flow in our furnace. It does not 'see' air flow, so will not allow the burners to ignite. Depending on the type of furnace, there are several sensors which give this information and MAY have reset switches. If they don't have switches, the sensor is likely burnt out and will need replacing before the furnace will ignite. You can try and 'short' the sensor manually, causing a bypass, but even I am not that crazy. At least not right now. So let's HOPE our sensors have switches. Back to the wiring diagram I go in order to find the sensors....


Wiring diagram

A spaghetti mess of a diagram later, it turns out there are four sensors, two in the bottom of the furnace, and two on top. An examination of the top two sensors reveals they are nearly impossible to reach.

Top of furnace (sensors are "easily accessible" behind gray pipes)

I open the bottom cover and examine those. They are right by the burners.

Bottom of furnace - sensors are bottom center

Close up of two sensors

Bad luck. They are just sensors with no reset switches. They are either OK, or dead. No fix. Drearily, I climb to the top of the ladder and, after various attempts, manage to scrunch my arm past pipes and tubes seeking the top sensors. It turns out it is impossible to touch the sensor with your hand while actually looking at them. In fact, I can barely SEE where they are (following the wires). Everything has to be done by touch. Wow. Who designed this thing? Feeling around, balanced on top of the ladder I find a tiny bump on the top of each sensors. A switch!?! I feel a tiny 'click' as I push each one in. Hope fills me as I back away and tentatively touch the 'safety' switch with tells the furnace the door is closed. (DO NOT TRY THIS YOURSELF FOLKS, I am telling you. This is for experienced Rube Goldberg - Mr.. Scott wanna-be's like me). As I push the switch, the furnace fan immediately starts up. I watch the burners through the still open bottom door as.... nothing happens. NOTHING. I am near despair. It is 5:52 am, and it is REALLY cold. Sighing and cursing, I release the 'safety' switch and the furnace fan immediately stops.

For some reason, I decide to try again. I really don't know why I did it. Never give up, I always say. So I carefully lever myself into the top compartment of the furnace, again balanced on the top of the ladder. I feel each little 'click' as the reset switches again depress. Again I back away and push the door 'safety' switch down . Immediately the fan starts running. And... a white glow starts up in the bottom compartment as the burner igniter starts up! I am filled with true joy as the #1 burner "CHUFFS" gas and a bright blue flame ignites. One by one in order, the four burners light up! WOO HOO! Seriously wondering how I succeeded, I release the door switch and carefully replace both covers. As I screw the top door tight against that safety switch, the furnace again ignites and the blue glow greet me happily through the observation window. I am so relieved. Warp power restored! In from the garage and straight for bed I go after first raising the thermostat to 70 degrees. It is 6:04am as I close my eyes. I have never been so happy to be a hack repairman. T RexMom and T Rex slept right through my repairs and the house, although cool throughout the morning at least there was warm air blowing!

Warp power has been restored - in other words, the bright blue flame as ignited!

**Lessons learned from the power outage:

-Push every reset button twice (oddly enough, this also fixed the Internet DSL router problem later in the day)

-Keep flashlights on hand and CHECK THE BATTERIES. Ours were dead flat. Luckily we keep spares

-Keep a hot water bottle (or three) around. We filled ours with water that was still hot right after the power went out and it kept beds warm all night. Recommended one per person

-Do NOT have ONLY cordless phones around. They don't work when the power is out Keep an old fashioned plug-into-the-wall phone hooked up. Wall phones work on separate power connections from normal house power so will function during a normal outage. We used our plug in phone to call and check in with the Power Company during the outage. (Our cell phones also worked)

-Have a family emergency plan in case the power goes out for an extended period. Our house is heated by gas, but needs electricity to ignite and function. We wished we had more hot water bottles! (and photovoltaic generation with battery back up. That is for the next house!)

4 comments:

Caitlin said...

I am so impressed that you figured that out! What an adventure! I am glad that TRex didn't wake up...

Anonymous said...

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How to Safely Operate a Portable Generator and Transfer Switch
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Generator Safety Frequently Asked Questions
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septembermom said...

Wow, good for you! You handled that great! Thanks for the helpful information too. I need to know those things. I rely on my husband too much in those kind of emergencies.

Sunny Austin said...

I had no idea furnace sensors had resets. Why?