Aprilaire 700A not working except in test mode

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Old 12-13-07, 02:43 PM
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Aprilaire 700A not working except in test mode

Our contractor installed the unit on the return duct in Auto mode. We placed the outdoor temp sensor outside of the house. For some unknown reason, the humidstate always shows indoor humidity as 34%. The unit works in test mode. I can see the green light on, fan blowing, and water draining. But in real operating mode, I have never seen it on. Turning the nob from 1 to 7 does nothing to it. The unit won't respond. Our outdoor temp is 40F ~ 60F. So it can not be caused by low temp outside. Is it because the outdoor sensor is bad, or the humidstat fails to control the unit, or some wiring problem? Your advise is highly appreciated.
 
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Old 12-13-07, 08:56 PM
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Originally Posted by siena_s_dad View Post
Our contractor installed the unit on the return duct
Not a really good spot for this style of humidifier.. You are going to be using TONS of water to keep up.. Is it on hot or cold water?


We placed the outdoor temp sensor outside of the house. Our outdoor temp is 40F ~ 60F. So it can not be caused by low temp outside.
There is nothing wrong with it.. With the sensor, I think I recall someone who has an Apirlaire as well has stated that it won't run when temp is above 40˚. No need for humidity for this warm of temp outside.

It will run when the temp is colder.
 
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Old 12-13-07, 09:35 PM
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We connected it to hot water. Yeah, we are in SF bay area so it is not too cold here in winter. But when the furnace is constantly on, we get down to 20%+ humidity. Wife and kid have either asthma or allergy. When we can bring the humidity to 45%~50%, they get a lot healthier.

The owner's manual did say that the unit is capable of delivering 45% humidity when temp is 40F+. So it is hard to believe they would design something to shut off above 40F. The contractor couldn't figure it out, either, this being his first Aprilaire installation.
 
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Old 12-13-07, 09:53 PM
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Then remove the outdoor sensor, and the Manual Mode bypass.

Why did they put the humidifier on the return?
 
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Old 12-13-07, 11:10 PM
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It was installed on the return because there is no room on the supply. The HVAC guy put some AC pipes right in front of the supply. We didn't want to make him re-do the AC.
 
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Old 12-14-07, 06:53 AM
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Ok, Just plan on it working longer to try to achive the goal since you have no heat in the return duct to help eveperate the water from the pad. The hot water is going to help some, but it's going to use more water than you may of gotten with a bypass unit on the return.
 
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Old 12-14-07, 09:09 AM
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Originally Posted by siena_s_dad View Post
Our contractor installed the unit on the return duct in Auto mode. We placed the outdoor temp sensor outside of the house. For some unknown reason, the humidstate always shows indoor humidity as 34%. The unit works in test mode. I can see the green light on, fan blowing, and water draining. But in real operating mode, I have never seen it on. Turning the nob from 1 to 7 does nothing to it. The unit won't respond. Our outdoor temp is 40F ~ 60F. So it can not be caused by low temp outside. Is it because the outdoor sensor is bad, or the humidstat fails to control the unit, or some wiring problem? Your advise is highly appreciated.
I wanted to respond to this thread as I am too having the same trouble. Initially it was setup as auto but I noticed the humidity not changing so I turned the humidifier off and changed the mode to manual. Aprilaire includes a little temp/humidifier that I have placed in one room in my house and I taped it to the return duct to try and get as accurate of a reading as I would on the humidistat located on the return side in the basement.

My humidty on the gauge is showing between 29-35% but yet the humidistat consistently reads 44%.

I have had the number change twice on me, both times by shutting off power to the furnace. Once it read 43, it stayed like that for 24 hours ( I checked it at least 6 times during that day) Another day it read 48%. I then reset it again and it went back to 44. The humidstat seems like it is stuck or the reading is static. Two weeks later and countless trips to the basement the stupid thing still reads 44%.

I understand that their can be a margin of error between the two gauges but 29% compared to 45% That doesn't make sense.
 
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Old 12-17-07, 02:31 PM
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Just want to post an update of my further investigation.

Since the unit works in test/reset mode only, it leads me to think that maybe the unit was unable to sense the furnace blowing and heat call. The contractor confirmed that he didn't wire from the furnace common to the humidifier control. I thought we solved the mystery. But after he added that wiring relay, still no luck.

Then we switched to manual mode by unpluging the outdoor sensor from ODT slot and put in the manual resistor. Well, still the same old thing.

The manual did say that the unit won't operate below -30F and above 60F. So our temp range is normal. The fact our contractor forgot to made a critical wire tells me that there might be other things he didn't do right.

BTW, what is the model 50 current sensing relay for? Do I need that for Automatic mode?

Any ideas? Thanks.
 
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Old 12-17-07, 04:02 PM
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Wink

BTW, what is the model 50 current sensing relay for? Do I need that for Automatic mode?
You dont say how its wired in . You can use it on the blower wire to turn the humidifier on when the blower is running. We do not use that OTS put it on manual mode all the time. That green light you see should be the change water panel indicator. For the 600 and 700 the mode switch should be set on C.
 
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Old 12-20-07, 05:53 AM
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I am still having issues with my humidistat, I pulled it out of the cold air return and breathed on it a few times and then cut the power to it, turned it back on and got 96% humidity which is what I would expect. I put it back in the cold air return and checked on it the next morning ... still says 96% humidty. If I reset it again it will drop back down what gives???
 
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Old 12-20-07, 07:21 AM
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I wonder if ApilreAire knows about this? Seems like there have been a few poster stating that they never see any changes on this style of humidistat..
 
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Old 01-01-08, 04:53 PM
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Just want to post a follow-up to conclude the thread and thank everybody for helping. We finally got the unit to work. The problem was due to incorrect wiring by the contractor.

After a while, it was obvious that the humidstat was unable to sense the furnace operation. I looked into the wiring and realized that insteand of wiring into the W or G slot on the furnace main panel, our contractor mistakenly place dit into the Dehumidifier slot. I switched it back to W and G. Still no luck probably because the Aircon already occupied W and G. Finally, I followed the alternative wiring approach recommeded in manual to put it into the 24V Humidifier slot on the accessory panel. Lo and behold, it started to work.

The humidity level climbs very slowly. Lots of water drained. It took a week for it to finally reach 46%. I think this is as good as it gets.

Again, thanks everybody.
 
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Old 01-01-08, 05:13 PM
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Thanks for the update, and glad to see you got it working.

Enjoy the New Year!
 
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Old 10-21-08, 06:59 AM
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Similar problems - unit only operates in test mode

I'm having similar problems and I would really appreciate any help. I know for a fact that the humidifier never ran last winter. It was installed by a HVAC guy the winter before. I don't know if it ran then, so it's possible it has never worked. I'm now determined to get it working for this winter though.

I changed a couple wires around yesterday in my troubleshooting process. The Aprilaire 56 humidistat's R and C terminals are now connected to a 24V transformer, so it's always powered. The humidistat's H terminals are now directly connected to the solenoid (without using a current sensing relay on the blower. The blower motor on the 700A is connected to line voltage. So in theory there should be nothing stopping this device from operating.

It's wired using the remote thermistor to set it up in automatic mode. It will not kick on anywhere up to 7, but once I get to test mode it turns on for the normal 1 minute. I disconnected the thermistor leads and measured the resistance - 21kohm. So that is fine as far as I can tell. It corresponds to the outside temperature, and according to the manual is in the range where the humidifier will operate.

Since that didn't work, I swapped in the manual mode resistor which measured at 45kohm, and still the same behavior. The mode switch on the humidistat is set to power, as it should be.

There is nothing else I can think of that could be causing this unit to operate this way. Is the model 56 humidistat bad? Can it fail in this way?
 
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Old 10-21-08, 07:31 AM
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Originally Posted by PeterGriffen View Post
I changed a couple wires around yesterday in my troubleshooting process. The Aprilaire 56 humidistat's R and C terminals are now connected to a 24V transformer, so it's always powered. The humidistat's H terminals are now directly connected to the solenoid (without using a current sensing relay on the blower. The blower motor on the 700A is connected to line voltage. So in theory there should be nothing stopping this device from operating.
Do you have W/G and Cf wired up?
 
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Old 10-21-08, 07:56 AM
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The model of humidistat that i have, the Aprilaire model 56, does not have those terminals.
 
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Old 10-21-08, 08:13 AM
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Ok, Do you know what the humidity level is in the home now? If the humidity is higher, then it won't run.

If the humidity is say 40% or lower than it should run.

Where is the humidistat mounted?
 
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Old 10-21-08, 08:45 AM
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The humidistat is mounted to the return air duct.

Last winter the humidity was down to 20% and it was acting like this. Right now it's at about 45%.
 
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Old 10-21-08, 01:41 PM
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I am not sure what's the max setting they have on Aprilaire, but have you removed it from the duct to see it has been cut out in back of it?
 
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Old 10-28-08, 01:07 PM
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I have a working humidistat on my other furnace. Once it gets colder and the house humidity drops, I'm going to take that working one and put it in place of the non-working one and see what happens.
 
 

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