Both HAI thermostats dead at the same time?

[hgupta1]

I guess as it always happens, my system went wonky while I was out of town.  In this case, my two RC-80 thermostats that were connected to my Elk M1 died.   I've disconnected the communication wires, but still I get a blank screen... not even the standard screen when you power up with all lights activated.  Any ideas?  
 
I heard there were bad storms in the area, and maybe I got hit with a power surge?  The Elk M1 itself seems okay, but I am at a loss here on how to troubleshoot.
 
 
 
 

 

[tmbrown97]

Are these connected to the same zoned HVAC system, or two separate?  One way for a tstat to go blank is if the fuse inside the air handler blows - it's on the control board inside the air unit and it's an automotive style fuse usually.  Don't ask how I know that one so well  :blink:
 
Otherwise you at least check all the breakers?  There'll be 240V ones for the outdoor unit; then a separate 120V one to the air handler - that's generally where the power comes from to power up the thermostats.

 

[pete_c]

One way for a tstat to go blank is if the fuse inside the air handler blows - it's on the control board inside the air unit and it's an automotive style fuse usually.

 
+1
 
Another "thing" to look at maybe is a status LED blinking on the motherboard of the HVAC air handler if its on.
 
The little "one of by land two if by sea" blinking diagnostic LED pattern gets a bit extensive. 
 
There is a little chart written on the cover of the lower pieces of the handler.
 
In the early 2000's I would get into some heavy discussions relating to what the automating thermostat was doing and my "HVAC" Guru would suggest to fall back on the old "el cheapo" circular analog thermostat to validate the HVAC functions.

 

[hgupta1]

Thanks for the responses.   It is two separate air handlers that are only linked by same electrical panel and Elk M1XSP via the comm wires.  Even with the comm wires disconnected, I can't get it to come on.  The fuses tested good, and I picked up a couple of cheapo thermostats.  They both work fine with the cheapo thermostats.  So something must have killed both omnistats.
 
If I can't get these to work, is there a newer better option?  I like the Nests thermostats, but it doesn't look like they integrate with my Elk.  

 

[tmbrown97]

The tried and true thermostats for automation are AprilAire, OmniStat and RCS.  Nest isn't there and I wouldn't expect it to be - ever, really.  Elk just isn't that progressive.
 
RC80 was an older style (I had one in my last house) - the OmniStat2 might be more robust and it sure looks better - IMO it's the best looking of the automation-friendly tstats.

 

[hgupta1]

Thanks.  I'm leaning towards the Omnistat2  because I assume I won't have to make any wiring changes.    Is that right?
 
Also, I don't have a common wire on my upstairs unit and the RC80 never functioned right in the summer.    It would try to turn the fan and the compressor on at the same time and end up resetting itself.  My solution was to just leave the fan running all summer so that it only had to kick the compressor on.  Does the Omnistat2 require the common wire?

 

[tmbrown97]

Generally speaking most of the smarter thermostats do need the common wire as that's how they get the power they need to operate locally.
 
One solution is this "Add a wire" that uses a diode to split two of the terminals over one wire.
 
Otherwise you can wire it differently so that the fan follows the unit with on/off instead of always being on - there's some great info here:  http://www.hvacproblemsolver.com/new-thermostat.asp
 
Lastly - you did say it was the upstairs thermostat - generally speaking upstairs walls are really easy to access to drop in a new wire if necessary.

 

[pete_c]

Here I had purchased the Omnistat2 and it sat on my to do list for a couple of years.  The RC80 did continue to work just fine. 
 
I finally did remove the RC80 and install the Omnistat2. 
 
Thinking I installed the RC80 early in the 2000's and the Omnistat 2 late in the 2000's.
 
I like the look of the Omnistat 2 more than the RC80.   Well too if you are comfortable with the look of the RC80; they are inexpensive today. 
 
Here the change in thermostat dinged the WAF.
 
Something new to learn with new buttons and such, aggravating my automation efforts in the home.

 

[hgupta1]

Thanks guys.  
 
Unfortunately, I just have never been able to locate the spot on the upstairs HVAC to attach the C-wire, and the old RC80 wouldn't work with the kit I bought to add power separately (not sure if I screwed up or got a bad kit).
 
 
I decided to go with the Omnistat2, but am debating between the one with zigbee or without.  Can the one with Zigbee be hardwired to the elkm1xsp?

 

[tmbrown97]

Don't think so - to keep it safe I think you need to stick with RS232.

 

[pete_c]

I have the serial Omnitstat2.
 
I have been told that the ZIgbee ones have the serial pieces in them still. (such that you can connect the Zigbee ones serially if you choose).
 
I don't know personally though.
 
My old home had zoned HVAC with the unit in one closet on the second floor. 
 
The wires for the thermostat were tacked or wire wrapped to the conduit on the side with the power on or off switch.  They were a PITA to get to as they went to the rear of the closet.  Over the years in that home I created / cut an access panel in another closet which was adjacent to the HVAC closet.   It was a little walk in closet such that I made the access panel large enough to be able to do some work on the unit itself.  (well added water lines and more wires for a humidifier connection on said unit).

 

[tmbrown97]

If you post the model of your air handler I'm sure there's enough creative googlers around here that could help you find the place to connect the common wire.  Some older units have odd terminology but I've always been able to find the answers online with some searching.  

 

[ano]

I have the serial Omnitstat2.
 
I have been told that the ZIgbee ones have the serial pieces in them still. (such that you can connect the Zigbee ones serially if you choose).
 
I don't know personally though.

Yes, the Zigbee ones can even maintain both connections at the same time. I do that so the wired one acts as  repeater for the Zigbee ones.