Omnistat

serky

Member
Hi all,
 
I have a couple of Omnistats that always revert back to the green backlight.  They might stay a few days or hours at my chosen color but eventually go back to default.  What could be happening to do this?
 
Thanks,
 
Jason
 
Never seen this happen here, but I've only used one.  Do you have more than the two?   Are they connected to any other system or standalone?
 
serky said:
Hi all,
 
I have a couple of Omnistats that always revert back to the green backlight.  They might stay a few days or hours at my chosen color but eventually go back to default.  What could be happening to do this?
 
Thanks,
 
Jason
Mine does the same thing.
 
@Ano,
 
A few months back you mentioned updating a capacitor inside of the OmniStat2.  IE:
 
Well, cracked it open and replaced the 100 mf cap. with a 470 mf cap. Solved the problem.  I wasn't 100% certain but took a wild guess this was the power supply cap. so a bigger one provides some extra boost when the voltage drops when AC kicks in.
 
Did this work for you?
 
pete_c said:
@Ano,
 
A few months back you mentioned updating a capacitor inside of the OmniStat2.  IE:
 
Well, cracked it open and replaced the 100 mf cap. with a 470 mf cap. Solved the problem.  I wasn't 100% certain but took a wild guess this was the power supply cap. so a bigger one provides some extra boost when the voltage drops when AC kicks in.
 
Did this work for you?
It worked for a bit, but now it does the same thing again, so, no not a great fix.
 
there has to be surges from the power transformer. I added an MOV, but no luck.
 
Actually, I did have problems with my initial Omnistat serial connection to the automation system.  Picked it up used on eBay, so got a good deal on price, then had trouble when I wired it in.  Got in touch with HAI/Leviton support, it went in for repair, and they said it was so old they would need to replace it (non-repairable.)  I paid a repair charge and they shipped me a new one, no problems since.  They had a flat $55 repair fee, which seemed fairly reasonable.
 
I think I had some initial power problems as well (due to thermostat loop without common & power to the wall), I ran serial lines anyway, so also connected common and problems went away.
 
Yeah here my issue is not related to the OP issue of the Omnistat2 issue of the color resetting itself while running.
 
So if you remove the power and pull the thermostat out and put it back in it will go back to the color you have programmed or will it go to the default green color?
 
Here purchased the Omnistat2 when it was first available. 
 
I left it on my trinkets shelf for about a year or two as the RC-80 was doing fine then one day decided to install it.
 
This was around the time that I started to have the network/serial/time off issue. (NIC issues)
 
It was replaced 3 times in a month or so here and the color changing to default stayed.  (a few years back now).
 
Here though have never had an issue with the color resetting itself on it's own.
 
These days though never look at the Omnistat2 and typically just look at temps via theOmnitouch screens. 
 
We'll it cost $7500 but I think the problem is fixed.  Changed out my 20-year old Trane unit for a new one, but of course kept the Omnistat2.  Well worth the cost to not see that ugly green color ever again.
 
UPDATE: OK I lied twice. I believed that totally replacing my HVAC system with a new unit fixed this problem. IT DIDN'T. Soon after I wrote that it turned green again. Hrrrrrr..

BUT, I do believe that I have fixed it, and it has been working correctly for a week. No green. The fix was easy and cheap, so you won't be out much if it doesn't work for you.

This fix takes two components, a .0047 uf 100V min. disk capacitor, and a small rf choke, maybe 0.1 mH. Just make sure the DC resistance is 1 ohm or less.

Terminals 1 and 2 of the Omnistat should be shunted together. connect the capacitor to terminals #1/2 on one side and terminal #3 on the other side.
Then remove the wire that was connected to terminal #3, and add in the choke, one side to the wire (common wire), and the other to terminal #3.

That is it. Both parts should be very small and fit in without too much problem.

ALWAYS turn OFF the air handler breaker before working on the thermostat. I have heard of problems my NOT doing this.

What this does is create an rf filter for the powerline. For me it works. Really. :wacko:

Additional info: The capacitor is .0047 uf which is 470 pf. A voltage rating of 100V or higher is fine. You might see 300V or 600V which is fine. You may see an AC rating instead and 30VAC or higher is fine.
 
 
Seems like a lot of extra work to fix an otherwise outdated looking thermostat that doesn't offer much in the way of modern features.... and I can't imagine telling customers that we had to apply a bandage to their thermostat so that it would work properly.
 
Good job though on resolving the issue though - I love DIY, just wish flagship products didn't need some much TLC. :)
 
StarTrekDoors said:
Seems like a lot of extra work to fix an otherwise outdated looking thermostat that doesn't offer much in the way of modern features.... and I can't imagine telling customers that we had to apply a bandage to their thermostat so that it would work properly.
 
Good job though on resolving the issue though - I love DIY, just wish flagship products didn't need some much TLC. :)
As thermostats go, I wouldn't exactly say "it doesn't offer much in the way of modern features"
 
Lets see, you can change the display color, and it can be activated by motion. Supports 2 stage air, 3 stage heat, Zigbee, serial, and an Omni connection. It can control both a humidifier and dehumidifier. Can cycle the fan, can support external temp sensors, and even supports an external control unit w built-in temp sensor, actually I think it can support multiple of these. 
 
So what "modern features" does it not support, and what other thermostat supports all these plus these other "modern" features?  I think for a non-proprietary thermostat, it holds up pretty well.
 
Never paid attention but how do you control a dehumidifier with the Omnistat 2.
 
IE: here use the whole house humidifier in the winter when temperatures are very cold (midwest) and a large humidifier in the basement only when temperatures are high.  The humidifier control is on the humidifier device.
 
Personally the only modern feature I can think of is a cloud connection which I wouldn't use if I had anyways.  I can still get to the thermostat via my cell phone or OmniTouch screen or 3rd party software touchscreen.
 
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