We've had this system for about 5 years and it's been pretty nice.
It has 2 Zones with variable Speed AC. We primarily only use Zone 1 (with Evolution Thermostat).
Normally in Winter or Summer we can barely hear it once it reaches temp it runs real slow and maintains temp.
It's hard to know if it was shutting off before because it was so quiet. Pretty sure it was cycling because thermostat didn't always say "gas heating..."
Lately we can hear the vents a lot and hear when it shuts down. That's not normal.
I checked codes, few odd ones from long ago and some power failures etc. I cleared them to be sure nothing recent is coming up.
LED on control board is steady amber.
I tried putting the system in "Low" heat mode manually with DIP switches and R & W shorted. That had the same sound as being faster than normal.
It's definitely running "slow" because I also tried high and that is really cruising. But not as quiet as before.
I've gone through the setup / install a couple times and no change.
When running it shows
gas heat: 40%
indoor CFM: 330
Blower RPM: 736
Static pressure: 0.59
Inducer RPM: 1675
Which seems reasonable. If we hadn't known what it sounded like before we'd think it'a all normal.
When I run the airflow test I get (different results than in the install)
full CFM: 1070
Static pressure: 1.25
blower RPM: 1224 (with red warning "too high...")
Changed filter just in case.
Reading manual it says something about old controllers will get warning of too high and is normal. But not 100% sure on that.
During install it runs a similar airflow test and that never gets a warning.
full CFM: 906
static pressure: 1.5
blower RPM: 1101
Repeated the above several times and got the same thing.
Zone 2 runs very quiet. Although I didn't run it long nor recall how it used to sound, since we run it so little.
One other history tid bit. We sometimes leave in winter for the ski slopes and our "Away" is at 50F.
When we come back and fire up heat it cranks up nicely.
But sometimes never seems to get back to "modulating" (running blower real slow and lower furnace heat) to maintain temp (e.g. never gets back to inaudible).
It gets stuck on this higher speed (not necessarily the highest). I just reboot it and it goes back to normal. It never liked high heat rise mode.
It didn't happen often and reboot always fixed it. But it's behaving a little like that (a lot like it actually) and reboot is not clearing it.
But we don't recognize if this is the same (audible) speed it would get stuck at. It will still cycle in both cases. It just won't slow down.
Only time it seemed too correctly behave like this is when it was like -10F out. Where it lowest speed was not enough to maintain temp. That was kind of expected.
But it's been like 20-30F
So the way it's behaving it acts like it's stuck in non modulating mode or just not dropping to a super low heat/blower speed mode.
Why does Home and Away show different CFM numbers? Can I manually set them?
What could be wrong? Static pressure gauge off by a bit?
Where is the static pressure gauge for the blower? I see ones for the burner, but not one for the blower.
Since it's so subtly 'broken" I think hiring someone could be a money pit. Also it's hard to find knowledgable service techs. Installers were not the best.
Could the thermostat be faulty?
It has 2 Zones with variable Speed AC. We primarily only use Zone 1 (with Evolution Thermostat).
Normally in Winter or Summer we can barely hear it once it reaches temp it runs real slow and maintains temp.
It's hard to know if it was shutting off before because it was so quiet. Pretty sure it was cycling because thermostat didn't always say "gas heating..."
Lately we can hear the vents a lot and hear when it shuts down. That's not normal.
I checked codes, few odd ones from long ago and some power failures etc. I cleared them to be sure nothing recent is coming up.
LED on control board is steady amber.
I tried putting the system in "Low" heat mode manually with DIP switches and R & W shorted. That had the same sound as being faster than normal.
It's definitely running "slow" because I also tried high and that is really cruising. But not as quiet as before.
I've gone through the setup / install a couple times and no change.
When running it shows
gas heat: 40%
indoor CFM: 330
Blower RPM: 736
Static pressure: 0.59
Inducer RPM: 1675
Which seems reasonable. If we hadn't known what it sounded like before we'd think it'a all normal.
When I run the airflow test I get (different results than in the install)
full CFM: 1070
Static pressure: 1.25
blower RPM: 1224 (with red warning "too high...")
Changed filter just in case.
Reading manual it says something about old controllers will get warning of too high and is normal. But not 100% sure on that.
During install it runs a similar airflow test and that never gets a warning.
full CFM: 906
static pressure: 1.5
blower RPM: 1101
Repeated the above several times and got the same thing.
Zone 2 runs very quiet. Although I didn't run it long nor recall how it used to sound, since we run it so little.
One other history tid bit. We sometimes leave in winter for the ski slopes and our "Away" is at 50F.
When we come back and fire up heat it cranks up nicely.
But sometimes never seems to get back to "modulating" (running blower real slow and lower furnace heat) to maintain temp (e.g. never gets back to inaudible).
It gets stuck on this higher speed (not necessarily the highest). I just reboot it and it goes back to normal. It never liked high heat rise mode.
It didn't happen often and reboot always fixed it. But it's behaving a little like that (a lot like it actually) and reboot is not clearing it.
But we don't recognize if this is the same (audible) speed it would get stuck at. It will still cycle in both cases. It just won't slow down.
Only time it seemed too correctly behave like this is when it was like -10F out. Where it lowest speed was not enough to maintain temp. That was kind of expected.
But it's been like 20-30F
So the way it's behaving it acts like it's stuck in non modulating mode or just not dropping to a super low heat/blower speed mode.
Why does Home and Away show different CFM numbers? Can I manually set them?
What could be wrong? Static pressure gauge off by a bit?
Where is the static pressure gauge for the blower? I see ones for the burner, but not one for the blower.
Since it's so subtly 'broken" I think hiring someone could be a money pit. Also it's hard to find knowledgable service techs. Installers were not the best.
Could the thermostat be faulty?
source https://hvac-talk.com/vbb/showthread.php?2226631-Bryant-978M-with-Evolution-Thermostat-not-dropping-into-quot-modulating-quot-heat&goto=newpost
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