Aprilaire 8800 eating batteries?

[Del91574]

I know what was happening and why it was happening and the calcs to prove what happened, but due to the nature of the VA and other government entities....they provide parts and we provide the labor. No parts unless they are proven bad.
 
The scope just verified what was going on so the parts could be ordered. Bureaucracy at it's finest.

 

[giesen]

I installed an Aprilaire 8800 about two months ago, with the plan to connect it to my Elk once I get it installed. So far, the tstat has been great, except for the fact that it seems to be draining the batteries very quickly. My understanding was that it ran off the 24VAC that was provided to it via the transformer and Aprilaire distribution panel. In the two months that I've had the tstat installed, I've had to replace the batteries twice.
 
I've noticed that the house is overly warm in the morning. I checked the tstat and the display is blank and won't wake up. I've taken the tstat off the wall and put it back on...nothing. I've taken the batteries out and put them back in...nothing. I replaced the batteries with freshly charged ones (Eneloops) and everything works fine. The old batteries are put on the charger and it indicates that they don't have any remaining charge. I haven't put a meter on a set, yet, but will try that next time to see exactly how dead the batteries are.
 
Anyone run into this problem before? Is this normal? I thought the batteries were there to save settings in case the 24VAC power was lost.

 
 
lonebrave,
 
Did you get anywhere with this? I have the exact same problem, except I'm going through batteries every two weeks. I have an Aprilaire 8800, connected to an 8819 distribution panel, which is then connected the Aprilaire (Elk) power supply. I put a multimeter on the R and C pins (at the thermostat) and getting 28.6 VAC, so it's definitely getting power...

 

[fcwilt]

The batteries should last a year - they are for backup - the unit is intended to run off power from the HVAC gear (or equivalent source).
 
Do you have R and RC connected?

 

[giesen]

The batteries should last a year - they are for backup - the unit is intended to run off power from the HVAC gear (or equivalent source).
 
Do you have R and RC connected?

 
Frederick I know that's how it's supposed to work, but it's like it's not getting any power. As I said in my previous post, I put a multimeter on the R & C pins on the backplate and seeing 28.6 VAC
 
*EDIT*
 
The thermostat is not intended to use parasitic power from the HVAC system, but instead use a separate 24 VAC source (either direct or through the 8819 distribution panel) which I have.

 

[fcwilt]

Let's start over.
 
Do you have R and RC connected?
 
If not is there a wire to each one?
 
Does each one (R and RC) have power?

 

[giesen]

Let's start over.
 
Do you have R and RC connected?
 
If not is there a wire to each one?
 
Does each one (R and RC) have power?

 
 
My apologies, I originally read it as R and C.
 
Per this guide http://www.aprilairecontractor.com/products/category/thermostats/61526.pdf, I am hooked up like Figure 3 on Page 7 (I have a gas furnace with an air conditioner).
 
B+, A+, B-, A-, R, and C go to my 8819 distribution panel. RH is jumpered to RC. RC, Y, W, and G to my HVAC system. Reading 27.6 VAC between RC and G
 
*EDIT*
 
Just for the sake of clarify, R and RC are not supposed to be connected together according to the installation manual.

 

[fcwilt]

Your document is newer then mine and the wiring has changed slightly.
 
Since yours is newer let's assume it is correct and that mine is out of date.
 
So you have RH and RC jumper and they are connected to your HVAC gear. That's good.
 
Power for the thermostat is via R and C - separate from the power used to control the HVAC gear.
 
What is the reading between R and C?

 

[giesen]

Your document is newer then mine and the wiring has changed slightly.
 
Since yours is newer let's assume it is correct and that mine is out of date.
 
So you have RH and RC jumper and they are connected to your HVAC gear. That's good.
 
Power for the thermostat is via R and C - separate from the power used to control the HVAC gear.
 
What is the reading between R and C?

 
28.6 VAC

 

[fcwilt]

Well drat. Everything seems to be checking out OK.
 
The 28.6 is a little high (nominal would be 24).
 
The markings next to the terminal strip on the thermostat match the document so that should mean the document is the one you want.
 
Does the thermostat work OK without the batteries?

 

[giesen]

Well drat. Everything seems to be checking out OK.
 
The 28.6 is a little high (nominal would be 24).
 
The markings next to the terminal strip on the thermostat match the document so that should mean the document is the one you want.
 
Does the thermostat work OK without the batteries?

 
If I pull the batteries with the thermostat on the wall, it goes dead. If I pull it off the wall with the batteries on it, it shows the message "Power Outage"

 

[fcwilt]

The message "Power Outage" suggests that the thermostat is sensing the loss of the power coming in on R&C - which is what it should do.
 
But it should work fine without the batteries.
 
Hmm...
 
What is the reading between R and C when the batteries are removed?

 

[giesen]

The message "Power Outage" suggests that the thermostat is sensing the loss of the power coming in on R&C - which is what it should do.
 
But it should work fine without the batteries.
 
Hmm...
 
What is the reading between R and C when the batteries are removed?

 
That might be a little difficult to measure with the thermostat still on the wall... I'll see what I can do (my previous measurements are all on the terminal strip on the backplate with the thermostat removed)

 

[fcwilt]

Ahh...
 
That might be a clue.
 
If you were measuring the voltage with the thermostat removed you were NOT measuring the voltage under load.
 
It's possible to read a correct voltage with no load but when a load is applied (in this case the thermostat) the voltage drops below the minimum required for operation.
 
This of course implies a problem with the power source.
 
So take a couple of short pieces of wire and connect them to the R and C terminals (one each) and find a way to route them to some place where you can then measure the voltage with the thermostat in place.
 
I hope the reading is wrong - then you will have found the problem.

 

[giesen]

Ahh...
 
That might be a clue.
 
If you were measuring the voltage with the thermostat removed you were NOT measuring the voltage under load.
 
It's possible to read a correct voltage with no load but when a load is applied (in this case the thermostat) the voltage drops below the minimum required for operation.
 
This of course implies a problem with the power source.
 
So take a couple of short pieces of wire and connect them to the R and C terminals (one each) and find a way to route them to some place where you can then measure the voltage with the thermostat in place.
 
I hope the reading is wrong - then you will have found the problem.

 
28.7 VAC... with or without batteries...

 

[fcwilt]

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.