Hi, I have a Carrier furnace with variable fan which I usually run constantly and I never hear it as it runs at low speed. However, in the last week or so it has started to run only at full speed and is very loud. What could be causing this? TIA!
Is it possible the furnace filter is dirty? This type of restriction will sometimes cause the motor speed to ramp up.
I change it every 3 months, it was just changed about a month ago.
You have an air flow issue, check your return openings make sure no one put a furniture or something in front of it.
Return vents are all clear. .. even if a bit dusty lol
Oddly, I just turned on my A/C and the multi-speed fan stages are still working fine there. I am beginning to think this has something to do with my thermostat.
So once my house reached set A/C temp and the A/C turned off, the fan speed kicked into full speed again. So strange.
Does your fan still blow even if you turn the fan off on your thermostat?
Do you have an HRV or a ventilation switch near the thermostat? Both will cause the furnace fan to run if they are interlocked with the furnace.
Quote from: Sergroum on May 26, 2023, 07:55:49 PMDoes your fan still blow even if you turn the fan off on your thermostat?
Nope, if I turn the fan off on the thermostat, it shuts down.
Quote from: Admin on May 26, 2023, 08:11:49 PMDo you have an HRV or a ventilation switch near the thermostat? Both will cause the furnace fan to run if they are interlocked with the furnace.
I don't have either. The issue isn't that the fan is running, I have it set to run always. The issue is that its running full speed where it used to run at a slower speed and was not heard. Something has triggered it to run full speed when it is set to always on and the A/C and heat are off.
Do you have an Infinity thermostat by chance?
Quote from: Admin on May 27, 2023, 07:32:33 AMDo you have an Infinity thermostat by chance?
The thermostat is an ecobee
Well I assume nobody has messed with the dip switch settings in the furnace.
My first step would probably be to disconnect the G wire in the furnace and install a jumper wire between the R terminal and G terminal and see if the continuous fan speed is still higher than normal.
It's possible there is an issue with the microprocessor or something has caused a restriction in the ductwork that is causing the fan speed to increase.
And this is the Ecobee set to control the fan or set to allow the furnace to control the fan?
Quote from: Admin on May 29, 2023, 03:55:36 AMWell I assume nobody has messed with the dip switch settings in the furnace.
My first step would probably be to disconnect the G wire in the furnace and install a jumper wire between the R terminal and G terminal and see if the continuous fan speed is still higher than normal.
It's possible there is an issue with the microprocessor or something has caused a restriction in the ductwork that is causing the fan speed to increase.
And this is the Ecobee set to control the fan or set to allow the furnace to control the fan?
The ecobee is not wired to control fan speed, I let the furnace take care of that. I wouldn't think there is any issues in the duct work as the fan speed works as normal when running the A/C. No one has been inside the furnace, but I will have a look in there at some point today to make sure no wires have come loose or anything simple. I am also considering rewiring and setting up the ecobee to control fan speed to see if that does anything.
Ok so I just had a look at everything. All in the furnace is snug now and no loose wires (the comm wire terminal was a bit loose, but I think the connection was still ok. I tightened it down).
I cannot re-wire my ecobee for fan speed control at the thermostat as I had planned as I don't have the multiple G wires & I think it can only be done if you do, I only have one, so I guess that plan is out.
Did you just replace your thermostat with an Ecobee? I don't understand how you had low speed continuous fan without G connected. You only need one G wire and when you turn the Ecobee fan on, it should enable the low speed in the furnace. There is a setting in the Ecobee menu and I would leave the furnace set to control the fan. But the Ecobee will still control the continuous low speed fan if you turn it on.
You can get a PEK adapter if you don't have enough wires.
Quote from: Admin on May 29, 2023, 06:48:17 PMDid you just replace your thermostat with an Ecobee? I don't understand how you had low speed continuous fan without G connected. You only need one G wire and when you turn the Ecobee fan on, it should enable the low speed in the furnace. There is a setting in the Ecobee menu and I would leave the furnace set to control the fan. But the Ecobee will still control the continuous low speed fan if you turn it on.
You can get a PEK adapter if you don't have enough wires.
The PEK doesn't help with this, I got the info today that it isn't possible to control fan speed with my ecobee on my furnace as it is variable speed and not multi-speed. And I do have a G wire, I said I don't have multiple as in G1, 2, 3. I have a single G wire and it is connected. I have had the ecobee for 5 years, and only in the last 2 weeks the fan started running at high speed, on its own. I made no changes. It used to run on low, and now it runs on high, and I am trying to find out why.
Does the furnace heat still work? Sometimes when safeties trip open the fan will run in continuous high speed. See if there are any blinking error codes.
If all the Ecobee settings are correct it sounds like the problem is inside the furnace.
Heat appears to function, but as its 30+ outside I don't know if there is "actual" heat coming from it.
I had the same thing happen and I believe I have root-caused and found a workaround for this problem. Here is the email I've sent to ecobee tech support to help them fix the issue.
---- Ecobee Tech Support Email ---
I have debugged an issue with the ecobee 3 thermostat working in conjunction with Carrier furnaces and the continuous fan mode.
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Problem symptom - The fan is running at higher or lower than expected speed in continuous fan mode (not currently heating or cooling).
There are forum posts all over the internet with this problem and no answers.
In my case, I needed to do some work which required me removing and reinstalling the thermostat several times, upon which I found the continuous fan to be running much faster than before the work.
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Here is what is causing the problem. You have a subtle incompatibility with your firmware when connected to many Carrier furnaces.
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In my case, I have the 59tp6 model carrier furnace which has a 25-speed variable speed blower.
https://www.carrier.com/residential/en/us/products/furnaces/59tp6/
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Per the manual, the continuous fan speed is set by DIP switches on the controller board.
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However, the owner's manual (https://www.shareddocs.com/hvac/docs/1009/Public/0B/OM9GFRC-02.pdf) mentions this one vital fact and feature:
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"Continuous Fan Operation -Some thermostats have a "FAN" switch with two selections: AUTO and ON. When the thermostat is set on AUTO, the furnace blower cycles on and off, controlled by the thermostat. In ON position, the furnace blower runs continuously. Continuous fan keeps the temperature level in your home more evenly balanced. It also continuously filters the indoor air.
"On all but the base series furnace, the blower speed can be increased or decreased if desired due to change of seasons, large gatherings in your home, etc. Simply change your FAN from ON to OFF for 1 to 3 seconds (or AUTO depending on your thermostat), and then return to ON. The blower will switch to the next higher speed. There are at least three speeds to choose from. If the blower is running on its highest speed, a request to change will direct the blower to return to its lowest speed."
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The ecobee firmware is inadvertently exercising this feature and changing the fan speed unbeknownst to the user in certain circumstances.
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I don't know all the conditions upon which the firmware does this but I identified one solid case that I was able to exploit to cycle the fan speed back to it's lowest setting.
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When I change the mode of the furnace from "Heat" to "Heat/Cool" - this action obviously triggers toggling the voltage on the "G" wire within this 1-3 second window. The fan speed kicks up a notch. If I do this enough times (cycle between "Heat" and "Heat/Cool" using the ecobee app) - the fan speed will continuously step up and eventually jump back down to the lowest setting.
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Recommendation:
Ideal - I recommend you take advantage of this feature and add an option to the ecobee interface to allow the user to step cycle through fan speeds on a compatible furnace.
Non-ideal - At minimum, you need to fix the firmware so that is not accidentally exploiting this 1-3 second window in any cases. This is what is happening today and consumers are confused why their fan is running at a higher speed with no way for them to control it.
--- End of Email ---
I hope this information helps. I got an account on this site just so I could post this. :)
I'm late to the party but if Carrier furnaces are not used with the Infinity control quickly cycling Fan on / Fan off from the thermostat will change the continuous fan speed I believe there are 10 speeds before it recycles back to low
I gave this a try, now its definitely running at a lower speed, not the lowest, but not the highest either. So, this did make a difference!
But now it seems to be stuck on this one speed lol. Better than the highest though! at least its quieter now. I guess there is no way to see these ten speeds as you do this?