Why are OmniStats so da** temperamental?

B

BryanE

Active Member
Sorry for the rant but every time I install these thermostats I have a problem. This same issue has occurred with the RC80 series, then RC80B, and now the RC-1000 OmniStat 2. Apparently every furnace on the planet doesn’t output the proper 24VAC. That being the case, why doesn’t HAI build the thermostat to compensate for this or why not include the extra power supply with the unit?

In our current install we have three newer (mid 90’s) Bryant furnaces, all traditional single stage setups. We wired up the first RC-1000 and powered up the furnace… the thermostat powers up for about 2 seconds and then just shuts off. I can plug in any off the shelf thermostat and it works without issue. Why does the customer now have to pay another $30+ for a “power supply�

:D Errrrr… sorry guys, rough night.
 
Because there are lots of hardware/software types working in the world who haven't a clue how to make robust equipment.
 
Bryan - See this thread although the issue sounds reversed.

Try turning off the backlight on the RC-1000 and see if it works. Also check the wiring. As much wiring as I have done and as simple as it may be, I think I may have had an intermittent connection. May not be it at all, but at least its a few simple things to try.

My guess is that a very high percentage of the stat/furnace combos work out of the box, therefore HAI tries to keep the price lower by not including the 'optional if needed' power supply. If you regularly run into installs where you need them, perhaps you should just quote your customer the $30 higher price up front and give them a discount if it turns out its not needed?
 
Steve said:
Try turning off the backlight on the RC-1000 and see if it works. Also check the wiring. As much wiring as I have done and as simple as it may be, I think I may have had an intermittent connection. May not be it at all, but at least its a few simple things to try.
Click to expand...

Can you turn the backlight off without powering up the thermostat?

Still sounds like a half baked solution.
 
HAI thermostats require a common which most non-communicating thermostats do not. Make sure you have a common wire and if it is there, make sure it is hooked up on the HVAC side. Since most non-communicating thermostats don't need it, it does not get hooked up a lot of times. Not having a common connected to the the thermostat will cause the behavior that you are seeing. It is most likely resetting when it calls for heat/cool correct?
 
BryanE,
I am sorry to hear you are having difficulties installing the Omnistat. It does sounds like you will need to either install a common, a power supply module, or turn off the backlight. The backlight can be turned off if the thermostat can power up long enough for you to do so. If it does not I suggest you connect it directly to a 24VAC transformer temporarily to change this setting.

The Omnistat does not require a common in all situations. The older mercury thermostats has no electronics so it did not require a common. This was a very common thermostat, so a lot of houses were wired for this. When the first digital thermostats came out, they required very little power (dim backlight, mostly non-communicating). This power was either sourced from batteries, or power stealing from the HVAC relays. Power stealing is the term used when the thermostat trickles in little bits of current from the HVAC relay, enough to power the thermostat, but not enough current to turn on the relay, thus turning on a stage.

A lot of work was done on the Omnistat to keep the power consumption down so that it can be retrofit in most power stealing homes. Unfortunately the nice backlight, uses about 75% of the total power. The Omnistat will be able to power steal this power from most homes, but the amount of power that can be used is dependent on the HVAC relay, so this can vary.

A power supply module is not automatically included in the Omnistat because most homes do not have a use for it. All heat pumps already have a common. A lot of older homes can retrofit using power stealing. It is becoming a more common practice to run a common (even if not connected) in newer construction. There are still a number of homes that will have this problem you are experiencing Bryan, but the numbers are dwindling and it did not justify adding the expense to bundle this module in all Omnistat's.

Please let me know if you have any more questions or concerns,
Ryan
 
Ryan, (or others)
I purchased a used HAI RC-122 communicating thermostat many months ago.
Today, for the first time out of the box I plugged it in.
The heater immediately starts, but the LCD is backlit with no segments viewable.
If I click any of the buttons, no visual indication can be seen. So I am looking at a blank backlit display.
Does this thermostat sound broken? No segments display on powerup.
Hoping I didn't get burned by a used sale....
Hoping it is a wiring problem (doubtful) or some setting that the original user had the thermostat in that disables the display (don't see those choices in the installation manual).

Thanx for the feedback (prepared for the worst)
 
Hi,
Any feedback?

Thanx
David

DavidL said:
Ryan, (or others)
I purchased a used HAI RC-122 communicating thermostat many months ago.
Today, for the first time out of the box I plugged it in.
The heater immediately starts, but the LCD is backlit with no segments viewable.
If I click any of the buttons, no visual indication can be seen. So I am looking at a blank backlit display.
Does this thermostat sound broken? No segments display on powerup.
Hoping I didn't get burned by a used sale....
Hoping it is a wiring problem (doubtful) or some setting that the original user had the thermostat in that disables the display (don't see those choices in the installation manual).

Thanx for the feedback (prepared for the worst)
Click to expand...
 
DavidL said:
Ryan, (or others)
I purchased a used HAI RC-122 communicating thermostat many months ago.
Today, for the first time out of the box I plugged it in.
The heater immediately starts, but the LCD is backlit with no segments viewable...
Click to expand...

You could always just power it up with a wall wart to see if it powers on properly.
 
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