Armstrong + humidifier + IAQ = weird behavior
My contractor couldn't answer me : - (
I have a Armstrong air advantage model G2D93CT100D20C-2A (93% efficiency) with a whole house humidifier and its installed with a VisionPRO IAQ YTH9421C1002 version 2 (as you can see, I did read on the Internet a little bit before posting!!).
The Armstrong G2D93... is it a 2 stage heater with a multi-speed PCS blower motor. It's a NG gas furnace.
Now here's what I noticed:
Ventilation is on because humidity is too low or because IAQ wants to move the air around the house!!! At one point, the temperature in the house is too low and here's the problem. The blower stops, the burner goes on and the blower starts again. Is it *really* supposed to be like that? I don't like it, I'd rather have the blower to stay on instead of wasting electricity and premature break down of the blower. Am I dreaming or is this possible?
I also notice that the blower seems to always run at the same speed... like if there's no variable speed???
Any comments are welcome.
More furnaces are stopping the blower to fire the furnace. Carrier & Rheem have for some time. Haven't had enough exposure to that furnace to know if they do or not. This just gives the heat exchanger a minute or so to get warm. I don't recall that being a variable speed furnace. Probably 4 or 5 speed motor. Low fire is lowest, contant fan & high fire typically medium low or medium. If you have a 5 ton A/C, it would use high. Or even if you don't most installers aren't smart enough to properly set the speed.
Your'e right it is only running at one speed. You have a multi-speed psc motor not a variable speed motor. You can select different speeds based on temp drop across the heat exchanger but only one for heat and one for cool. Your gas valve is also a two stage. It starts out low and times itself for high fire unless you have a two stage thermostat. I do believe armstrong has a web page to find out about your furnace. When you cycle the air in the house generally the conditioned air blower is maintained on the lower heat speed.
You're right, it's a fixed 4 speeds motor and my A/C is a 4 tons.
Originally Posted by BaldLoonie
I wish the motor wouldn't stop, so I hope there's a configuration jumper in the furnace.
As for the motor speed, I was under the impression that the IAQ and/or furnace would be smart enough to adjust by itself but it doesn't at all??? Is the problem with the thermostat not being able to manage a multi-speed motor???
I paid extra for all of this but it ain't working as expected. If anyone can guide me with the color cabling / termination so I can at least tell my contractor what he did wrong, that would be really really great.
Last edited by belanger; 03-03-2008 at 03:16 PM.
Reason: just some typo...
The board doesn't let you defeat the stopping of the blower.
The IAQ can't control the blower. It will do what the function being asked of it. Until cooling is called for, you should see 2 speeds, low fire which is likely constant fan speed (I was wrong earlier) and a stepped up speed when you go to high fire.
Only thing the IAQ can do is slow the blower in times of high humidity if you have a variable speed blower. Then there's a tap on the board for this. The board actually does this function anyway.
I'm not too sure I understand correctly so I'm not sure what to tell my contractor...
Originally Posted by krd
Correct me if I'm wrong...
The blower speed can be set to one of the 4 speeds for each of the 2 modes: heating & cooling -- right? So there's no intelligence at all???
So even if I lower the temperature when I'm away, when I come back home (at this time of the year) the 2 stage heater will go on but the blower speed won't go faster even if it would make sense??? If this is true, I'm falling off my chair!
I would imagine in a 2 stage configuration that if the 2nd heating stage kicks in, the blower would run faster.
My IAQ is a 2 stage "heat" thermostart... I can confirm at least this does work properly as expected.
This makes sense now. So perhaps my contractor didn't lower the speed for "low fire" and this might explain why the blower runs at the same speed on low and high fire.
Originally Posted by BaldLoonie
Hope I got this right and if so, I'll call him tomorrow!
Odds are he left them where they come. Let me see what that is. That is medium low for low heat & constant fan and medium for high heat. Chances are you won't notice the difference between those 2. There's about 120 CFM diff between the 2.
most 2 stage furnaces do not have much of a difference in blower speed between low and high fire.......
will never get what you expected out of a multi-speed blower....
I may be wrong but I do not think, but you do not get the varible speed blower unless it is the 95% the 93% is low and high fire but singal speed blower. The inducer is 2 speeds with the gas valve but not the blower motor.
Now as far as the blower shuting down on the call 4 heat the Armstrong has always done that and it is in the board.
I think you confused a multi-speed blower with a ECM motor which armstrong also does install on their high end furnaces. It varies the speed with the demand. I have that set up exactly and you really can't tell the difference as it modulates.Since a replacement motor of this type is extremely expensive to replace If I had to do it over again I would have a multi speed installed in mine.
I'm afraid you got more thermostat, then you have furnace.
Originally Posted by belanger
There is no "intelligence", it cannot think. Manufacturers put this tag on thermostats and furnaces, but it is misleading.IMHO
They can log previous temperatures and times and adjust accordingly, but they are still just a computer at best.
You should have with your blower:
High Fire speed
Low Fire speed
Before you criticize someone, walk a mile in their shoes...that way you are a mile from them and have their shoes