Aprilaire 8800 eating batteries?

[giesen]

I just tested right off the pins of the thermostat (to confirm it's not a connection problem between the thermostat and the backplate). I wrapped some wires around the actual pins that mate in the backplate and ran them out to a multimeter. Same result. 28.7 VAC.

 

[giesen]

Double drat.
 
Well at this point I would have to resort to swapping in a new unit.
 
You've got power but the thermostat is not working.
 
And the thermostat senses when it is disconnected from the power.
 
So the power is getting to the power sensing circuitry but is not powering the thermostat.
 
It would seem that something in the power circuitry of the thermostat has failed.
 
The documents don't indicate there is a fuse of any sort.
 
 
One last thing you might try is to disconnect everything BUT the R and C terminals and see if the thermostat powers up.

 
Strange that both lonebrave and I would have the exact same problem, maybe it's some sort of defect they're having... I'll see if I can give Aprilaire a call tomorrow and get down to the bottom of this..

 

[fcwilt]

That sort of problem is not unheard of.
 
At least you've probably done all the testing they are going to ask you to do.

 

[giesen]

I got an email from Aprilaire today (I haven't tried it yet, but I'll try when I get home):
 
The symptoms that you are describing are usually a result of the batteries being installed prior to actually mounting it on the subbase.  This can be corrected by: removing the thermostat from the subbase, removing the batteries from the thermostat, wait for screen to go completely blank, put thermostat on the subbase, wait for the thermostat display to reappear, install batteries, and set time and date.  All other settings, address, nodes, HVAC settings, will not be lost in this process. The reason this happens is that when the batteries are installed first the thermostat sees the power source coming from the batteries and will ignore the 24-30vac on the “R” and “C” terminals.

 

[fcwilt]

I got an email from Aprilaire today (I haven't tried it yet, but I'll try when I get home):
 
 The reason this happens is that when the batteries are installed first the thermostat sees the power source coming from the batteries and will ignore the 24-30vac on the “R” and “C” terminals.

 
Well at least they had something to say.
 
I hope it works.
 
If the thermostat does in fact do what they say that is, IMO, a design flaw.
 
I didn't see anything in the documentation stating when the batteries should be installed.
 
Did you?

 

[giesen]

Well at least they had something to say.
 
I hope it works.
 
If the thermostat does in fact do what they say that is, IMO, a design flaw.
 
I didn't see anything in the documentation stating when the batteries should be installed.
 
Did you?

 
There's nothing in the installation manual that even mentions installing the batteries, other than saying batteries must be installed for for the time and date to be backed up.
 
The only thing I can find in the *owner's manual* is:
 

Operation
Batteries are not required for proper operation. The
thermostat is a 24VAC powered device with a battery
back-up for the clock.
The thermostat has a memory backup that saves the
thermostat’s settings in case of a power interruption.
The system settings will be retained but the clock will
reset after 90 seconds with no battery or AC power.
Replace the batteries every year or when the low
battery indicator comes on.
The reset button located under the battery cover can be
used to reset the thermostat to factory defaults.
 
 
Certainly nothing that describes that behaviour. It seems a little strange as before mounting it my first instinct was to install the batteries (since it's easier with the thermostat in your hands than mounted on a wall). So I'd agree it's a bit of a design flaw, or at a minimum a documentation flaw. I suspect they did it this way because the batteries can either be used (apparently) to run the device completely or as a battery backup, and depending on the order you install them it selects the mode. Clearly that should be documented though.

 

[BraveSirRobbin]

Curious:  Is the common wire (C) in place?

 

[giesen]

Well I just tried it, and still same problem. I removed the thermostat, removed the batteries, and put the thermostat back on the backplate without batteries. It never lights up. I emailed Aprilaire again, I'll see what they say when they respond tomorrow.

 

[lonebrave]

Sorry, got busy with some stuff and wasn't able to troubleshoot any more.

Well I just tried it, and still same problem. I removed the thermostat, removed the batteries, and put the thermostat back on the backplate without batteries. It never lights up. I emailed Aprilaire again, I'll see what they say when they respond tomorrow.

 
My t-stat functions the same as yours, based on everything you've described. I'm definitely interested in hearing what Aprilaire has to say next. I have another unit to be installed on my other HVAC system, but have been holding off until I got this problem solved. I really don't want to be replacing batteries in both units every few weeks.

 

[fcwilt]

Well I just tried it, and still same problem. I removed the thermostat, removed the batteries, and put the thermostat back on the backplate without batteries. It never lights up. I emailed Aprilaire again, I'll see what they say when they respond tomorrow.

 
Actually that behavior makes more sense then having the unit ignore power if the batteries were inserted first.
 
So are we back to the unit being defective?
 
Or is it very senstive to over voltage and the 28 volts is shutting it down?

 

[giesen]

Actually that behavior makes more sense then having the unit ignore power if the batteries were inserted first.
 
So are we back to the unit being defective?
 
Or is it very senstive to over voltage and the 28 volts is shutting it down?

 
According to the spec sheet and manual it says it will take 18V-30V. I know we're a bit on the high side of that but I did mention the voltage to Aprilaire in my email and they didn't say anything about it. So my thoughts are swinging back to it's defective (either that or I am )

 

[lonebrave]

According to the spec sheet and manual it says it will take 18V-30V. I know we're a bit on the high side of that but I did mention the voltage to Aprilaire in my email and they didn't say anything about it. So my thoughts are swinging back to it's defective (either that or I am )

I'll try installing the second t-stat in place of the one I'm having problems with. Hopefully that one functions correctly. If not, and it turns out there is a mfg defect, maybe it will help narrow down the bad batch.

 

[fcwilt]

According to the spec sheet and manual it says it will take 18V-30V. I know we're a bit on the high side of that but I did mention the voltage to Aprilaire in my email and they didn't say anything about it. So my thoughts are swinging back to it's defective (either that or I am )

 
Well let's assume the spec sheet is correct and your 28.x volts is not a problem.
 
As I am running out of idea we are back to the unit being defective.
 
Two questions:
 
1. Has it ever worked?
 
2. Did you try disconnecting all connections except for R and C?

 

[giesen]

Well let's assume the spec sheet is correct and your 28.x volts is not a problem.
 
As I am running out of idea we are back to the unit being defective.
 
Two questions:
 
1. Has it ever worked?
 
2. Did you try disconnecting all connections except for R and C?

 
It has never worked (I've had it installed for about a month, and it died on me in the middle of the night after about 2 weeks because the batteries were dead, I'm now on my second set of batteries).
 
I have not yet tried #2, but I will try it when I get home. Aprilaire has asked me to send a picture of my backplate to show them all the connections which I will do at the same time.
 
*EDIT* - Just to be clear, the thermostat works perfectly except for the battery issue. I have it being controlled by my Elk (and in turn my ISY994i)

 

[fcwilt]

It has never worked (I've had it installed for about a month, and it died on me in the middle of the night after about 2 weeks because the batteries were dead, I'm now on my second set of batteries).
 
I have not yet tried #2, but I will try it when I get home. Aprilaire has asked me to send a picture of my backplate to show them all the connections which I will do at the same time.
 
*EDIT* - Just to be clear, the thermostat works perfectly except for the battery issue. I have it being controlled by my Elk (and in turn my ISY994i)

 
Having to change batteries every 2 to 4 weeks is not my idea of a good time. :wacko:
 
The R and C only test is a long shot but it's the best I've got at this point.