A)Inducer, not induction. Don’t know why, but I always get a kick out of it in these threads when the OP finally makes the move over to the word inducer. The type of motor used may be an induction type motor ( I think it is), but it induces a draft. It’s subtle and virtually everyone (myself included) says induction the first handful of times.
B)The inducer runs the entire time the furnace is on. It’s what draws fresh air in, through the heat exchange and the exhausts it out to the outdoors. It it stops running during the cycle, one sensor or another will kick your furnace off.
Anyways, the inducer motor comes on as soon as the T-stat calls for heat. It’s the first thing the control board does. It shuts off either when the t-stat tells the control board it’s satisfied or soon after that. I’m not totally sure what you’re trying to accomplish, but that’s when the inducer turns on and off.
The inducer runs for the whole burn. If there is a call for heat, the inducer should be running in concert with the burners. In other words, the burners should NEVER be allowed to burn without the inducer running, for *any *length of time.
I would never recommend jumping the pressure switch. Running the burners without the inducer gets unsafe immediately.
Furnaces have gotten much smarter. The board isn’t satisfied seeing a closed pressure switch, because a faulty pressure switch that has failed closed could be dangerous. The furnace requires the switch to be open at the inception of a call for heat. The inducer starts and the switch closes. So…the board wants to "see’ the switch close. If the switch is already closed on a call for heat, the furnace won’t respond.
[QUOTE=raindog]
…(although most people accidentally replace stats that are fine. It is overwhelmingly not the stat that s the problem)
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How often do stats just go goofy? Our furnace was acting like the stack limit switch was tripping about a month ago. The stat would call for heat, the inducer starts up, followed by the gas valve opening, then the burner would run for a few minutes, then it would cut out, but the blower stayed on. Power-cycling the furnace would reset it and allow it to run for a while again.
I called the landlord to say it was cold here (the joys of renting…) and the guy he sent out did about thirty seconds of visual troubleshooting, said the stat was bad and replaced it. Amazingly, he was right, as we haven’t had any trouble since then.
Not knowing the intimate secrets of stats, it seems like the thing decided to short out internally, connecting R to G for a blower on call, and no amount of flipping the on/auto or heat/off switches would shut off the blower or restore heat.
The original and replacement stats are very basic. No batteries or setback capacity, but as son as I have the extra bucks, I’m putting in a Nest.
I’ve been eying up the Nest system. I have a t-stat that I thought I would love. I bought it because it can, randomly, cycle the fan on and off to keep the temp in the house even. I was hoping to bring my AC bill down a bit. I haven’t used that feature in a while as I found a better way to bring my bill down and I get worried about shortening the life of my main blower.
My system is programmable, but my days aren’t. Sometimes I get home at 3, sometimes I get home at 7, it’s always different and when I go to work I drop the temp pretty far. It takes about 45 minutes to bring it back up to comfortable. There’s other wifi systems out there as well, but this one just brought it back to my attention. It would be nice to say “Okay, I’m on my way home now” and pull up an app on my phone to kick the heat on. At least then it would have a 10 minute head start.
Just remember. $250 programmable multistage Honeywell. Generic wifi system. Nest. $20 round gold thing with a dial. They’re all just glorified on/off switches.
My big issue, the reason I put in an expensive t-stat with the circulator was that one room was really cold, all the time, no matter what I did. I finally tracked it down to drafty windows. My windows were put in in 1997. I bought my house in 2005. They should not have been drafty when they were less then 10 years old. From what I can tell, it has nothing to do with age or wear and tear, they’re just crappy, low end, contractor grade windows. Unfortunately, I don’t have thousands of dollars to replace them with good windows, so for now all I can do is listen to my furnace kick on and off every 10 minutes all winter.
Does yellow go to red for A/C? I seem to remember that.
It just went through a prolonged spasm trying to start - the LED’s never did anything other than flash in unison - I replaced the batteries in the t’stat. Turns out that the relay I heard was the t’stat. Trouble with them being so close.
I dunno, but even a blind squirrel finds a nut from time to time.
I don’t have enough information, and of course I wasn’t there, but based on what you’re describing the stat wouldn’t have been one of the first 7 or 8 things I looked at, if at all.
And I couldn’t have troubleshooted that visually in 30 seconds. Replacing stats is exceptionally common with homeowners and inexperienced/ unqualified guys. Exceptionally common.
I can’t tell you how many calls I’ve been on where I’ve been called after a trip to Home Depot and a new stat installed—and the unit is doing the same thing as before.
My guess? The stat was a coincidence and the unit failure fixed itself, and it just looks like the stat was the issue, or; he got lucky, or; he’s really, really good. Really good. (and he might be. I’m not dissing him)
Maybe pass out heavy sweaters and drop the temp? I wear my bathrobe around the house - this thing has little or no insulation and trying to raise the temp 30 degrees is asking it to run continuously.
Try dialing the temp down 1 degree - you will find the system’s “comfort zone” - a point past which the cost of each additional degree shoots up.
[QUOTE=raindog]
My guess? The stat was a coincidence and the unit failure fixed itself, and it just looks like the stat was the issue, or; he got lucky, or; he’s really, really good. Really good. (and he might be. I’m not dissing him)
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I think he’s a blind squirrel. This is the same guy who when presented with a non-running air conditioner last summer immediately launched into adding more refrigerant without bothering to check subcooling or superheat after replacing a failed compressor motor cap. :rolleyes: To his credit, the cap was visibly bad, but unless he’s some sort of Jedi Master air conditioner whisperer, I’m suspicious of his abilities.
OK - It’s a t’stat problem.
If I take a jumper across the thermostat terminals it works fine - so there is no loose wire causing intermittent start/stop.
I have another t’stat which I swapped in - it clicks, but does nothing as to turning on the furnace - not even the inducer.
Re-installed the first - back to the start/stop - but it is taking longer to finally catch.
The blower switch on the t’stat works properly - it is just the call for heat that is screwing up.
Is it even possible that the furnace has some level of resistance which is met by a jumper but not by the circuit on a thermostat? One t’stat acting up is one thing - for the second to not only act up, but to do even less seems a bit odd.
I still have the toggle switch I rigged for A/C all those years ago - but switching a toggle to get heat off and on all day and night is not a welcome idea.
Depending on the age of the stats, it might be the stat[s], but I’m loathe to condemn one stat, let alone two. They’re usually not bad.
If it’s a new stat, it may not be configured incorrectly. If it’s configured for a heat pump, the delay is the stat waiting for second stage, the point in which the W terminal is energized.
if it works right 100% of the time with a jumper at the stat location, (100% of the time), but not with the stat, I’m probably condemning the stat. But it sounds a little weird.
I know this is basic and probably not the problem, but have you checked and/or replaced your filter recently? I ‘fixed’ 2 people’s furnaces this winter by replacing their filter. They think I am som esort of HVAC demigod when I actually no next to nothing about it
A clogged filter or condenser coil would slow down air flow, cause heat to build up, trip the limit switch and shut the entire unit down…but this would happen after the entire unit has come online and been running for a bit.
The problem the OP is describing is that his furnace is quitting after only the inducer is running. At this point the filter doesn’t have any air moving through it yet.
Oh - in addition to this happening WAY upstream from “clogged filter”, we can rule that out - this house is so cheaply built, it does even HAVE a filter.
Think of all the money I’m saving by not having to replace a filter element!
When your AC stops working the answer is going to be “because you don’t have a filter so the coils are clogged and the low air flow caused them to ice up”.
It is the thermostat enough of the time that I have 4 different models on my truck. Stats *do *go bad, and they get replaced.
The back story is that the stat gets accused 50 or 100 times for every time it’s actually guilty. Homeowners of all stripes, and inexperienced HVAC guys want to replace the stat. It’s entirely logical; it’s the one thing you can see and manipulate. If you turn to heat or A/C and it doesn’t respond, your brain logically thinks: It’s not doing what I told it to do.
So…Many times every year I see brand spanking new stats on the wall that represent somebody’s logical guess as to what’s wrong. And, of course, if I’m there it’s because the guess was wrong.
Even among customers who don’t replace the stat first (and that would be most of them) it’s rarely the stat. In the summer I’ll replace 3 bad stats. I’ll replace 50 bad capacitors alone. Same with heating. I’ll replace 1 or 2 stats, and 40 ignitors, and clean countless flame sensors.
So maybe it was the stat and it’s licked. Yiippeee.
Well, when your AC does stop working in the dead of summer on a hot humid day, the first thing I want you to do is set the switch that says COOL-OFF-HEAT to OFF and the fan switch to ON and let that run for about an hour.
If water comes dripping out of the evaporator tube (above the furnace) and the AC works again, the first thing we’ll need to look at (since you don’t have a filter) is cleaning the coils.
There’s probably an access panel in the plenum and something like this makes it a much easier job. Don’t bend the coils/fins and don’t cut your knuckles on the coils or arms on the sheet metal.
