Wiring for Omnistat 2

E

emrosenberg

Member
I'm putting together my list of wires to be pulled for my renovation.  I plan to use the Omnistat 2 for thermostats, and eventually hook them up to an Omnipro for automation and remote monitoring capabilities, however I won't be getting around to that for a while.  I'd like to have the HVAC guy hook up the Omnistat's for 'regular' use when he installs our new system.  I assume he'll pull the correct wires for that use, but what additional wires do I need to pull from the Omni panel location to the thermostat locations so that I can eventually connect them?  Would a 22/4 run be sufficient?
 
22/4 is fine, you only need 3 conductors for the OmniStat2 to a Omni family panel.  I ran a Cat6 as I had a lot handy and it's easy to run.  They also offer a remote temp sensor option, which the docs say should be a 2 wire with shield connection.
 
Optionally, you could add Zigbee to your Omni panel and go with the wireless Zigbee OmniStat2 version as well.  (Although I personally think the wired version is easier to setup and debug.)
 
Do the remote temperature sensors attach to the thermostat or do they go through the Omni panel?  I thought about the zigbee ones, but they are much more expensive, and when given the option I prefer wired connections.  I suppose it would allow me to utilize a different controller at some point, but by that time I'm sure they'll be much more interesting options for thermostats.
 
Do the remote temperature sensors attach to the thermostat or do they go through the Omni panel?
 
The Omnistat 2 wire remote temperature sensor connects directly to the thermostat.  You can set the thermostat to use the external temperature sensor or both internal and external (average).
 
There are also wired temperature and temperature/humidity sensors that connect to the Omni panel.
 
pete_c said:
Do the remote temperature sensors attach to the thermostat or do they go through the Omni panel?
 
The Omnistat 2 wire remote temperature sensor connects directly to the thermostat.  You can set the thermostat to use the external temperature sensor or both internal and external (average).
 
There are also wired temperature and temperature/humidity sensors that connect to the Omni panel.
Click to expand...
Would the wired ones which connect to the Omni panel relay the data to the thermostat for averaging?  If so, is there a reason (cost, etc.) to prefer one over the other?
 
Would the wired ones which connect to the Omni panel relay the data to the thermostat for averaging?
 
No.
 
I have an outdoor wired to the panel sensor which shows the temperature on the Omnistat.
 
If so, is there a reason (cost, etc.) to prefer one over the other?
 
The 2 wire sensor averages / is used directly by the thermostat. 
 
The external sensors can be utilized in automation scripts / external software control.
 
pete_c said:
Would the wired ones which connect to the Omni panel relay the data to the thermostat for averaging?
 
No.
 
I have an outdoor wired to the panel sensor which shows the temperature on the Omnistat.
 
If so, is there a reason (cost, etc.) to prefer one over the other?
 
The 2 wire sensor averages / is used directly by the thermostat. 
 
The external sensors can be utilized in automation scripts / external software control.
Click to expand...
Thank you.  I'll speak with the HVAC specialist and see what he recommends as far as remote sensors and placements and then run 22/2 from the OmniStats to those locations.
I'll leave the temperature driven automation to my imagination for now.
 
Yup; most of the labor / resources to a forced air system is related to balancing the supply and the returns (much tin cutting). 
 
I never touch the thermostat much; rather I look more at the temperature balancing.   Here I use both types of sensors. 
 
Utilize the HAI isolation relay / power supply board (left over from the RC-80 days).  Not sure if it is needed these days.
 
The Omnistat 2 sits on a dining room wall (we rarely utilize the dining room).
 
I have an electronic air cleaner with charcoal filters on one side and regular filters on the other side.  I replace these once a month and wash the spares.  The blower fan is on 24/7 (low speed) to continuously circulate the air.
 
I run a whole house humidifier during the winter and a dehumidifier during the summer and zone the returns a bit from summer to winter / winter to summer.
 
Old (and now retired) HVAC friend and company owner always would mention to try to cool the home with one ice cube and heat it with one candle.
 
emrosenberg said:
Thank you.  I'll speak with the HVAC specialist and see what he recommends as far as remote sensors and placements and then run 22/2 from the OmniStats to those locations.
I'll leave the temperature driven automation to my imagination for now.
Click to expand...
Just remember that the OmniStat2 can only control a 2-stage AC unit, and CAN'T control features like a variable speed fan or variable speed compressors. If you have a unit with those you are out-of-luck. Also, an OmniStat2 can be hooked to a standard zone controller but NOT the proprietary ones some HVAC units are using today. 
 
Also, one interesting thing the Omnistat2 can do is you can connect an external temp sensor to it and you can set it as an outdoor temp sensor.  For example say that the Omni panel is deep inside your house, but you have a thermostat relatively close to outside, you can hook the outside temp sensor up to the thermostat instead of using a sensor hooked up to a zone. I'm not sure if anyone ever does this, but you can.
 
pete_c said:
I never touch the thermostat much; rather I look more at the temperature balancing. 
Click to expand...
While this depends on where you live and your utility rates, you can do AMAZING things with an OmniStat2 and lots of Omni programming.  My highest electric bill this year has been $129 and I live in AZ where its already been 112 this year.
Everyday the systems reads the outdoor temperature at sunrise, and based on that temperature it switches into one of 4 modes. The hotter that day will be, the colder it makes the house in the morning when our rates are super cheap, $.04/KWH. then once the rates rise at noon, the AC turns off, with all the granite and tile doing the rest to keep it all cool.  It rarely get above 82 by 7pm when the rates drop, and 82 is pretty cool for us Arizona people. Should it get hotter than that, the AC is allowed to run 20 minutes per hour, but so far this year it hasn't had to.  
 
Our high rates really aren't that high, just $.08/KWH, but what we do have is a peak charge of $13.50 per KW based on the highest peak usage in ANY hour of the month during the high period. (No peak charge in the low period.)  
 
So I figure my OmniStat2 saves me about $1000/year in utilities. Its an understatement to say it has paid for itself. :eek:  
 
ano said:
For example say that the Omni panel is deep inside your house, but you have a thermostat relatively close to outside, you can hook the outside temp sensor up to the thermostat instead of using a sensor hooked up to a zone. I'm not sure if anyone ever does this, but you can.
Click to expand...
Where is the outside temperature defined in the OPII panel?
 
ano said:
While this depends on where you live and your utility rates, you can do AMAZING things with an OmniStat2 and lots of Omni programming.  My highest electric bill this year has been $129 and I live in AZ where its already been 112 this year.
Everyday the systems reads the outdoor temperature at sunrise, and based on that temperature it switches into one of 4 modes. The hotter that day will be, the colder it makes the house in the morning when our rates are super cheap, $.04/KWH. then once the rates rise at noon, the AC turns off, with all the granite and tile doing the rest to keep it all cool.  It rarely get above 82 by 7pm when the rates drop, and 82 is pretty cool for us Arizona people. Should it get hotter than that, the AC is allowed to run 20 minutes per hour, but so far this year it hasn't had to.  
 
Our high rates really aren't that high, just $.08/KWH, but what we do have is a peak charge of $13.50 per KW based on the highest peak usage in ANY hour of the month during the high period. (No peak charge in the low period.)  
 
So I figure my OmniStat2 saves me about $1000/year in utilities. Its an understatement to say it has paid for itself. :eek:  
Click to expand...
This is a great idea I'm going to convey to my mother in AZ.  She doesn't have an HAI panel, but she could at least set some programmed setpoints to chill lower prior to rate hike timeslots.
 
The Omnistat2 manual mentions 3 external sensors, 2 using a temperature extender.  Has anyone ever seen one of these?
 
JonW said:
Where is the outside temperature defined in the OPII panel?
Click to expand...
I'm not sure I understand your question. If you use something like an extended temp sensor, then you set the zone type to "extended outdoor temp sensor."  If you use a temp sensor connected to an Omnistat2, there is a setting in the Omnistat installer menu to make it an "outdoor temp sensor."  In either case the outside temperature can appear on all OmniStats if you have that turned it. It should also appear under temp sensors in PC Access. I bet if you have multiple outdoor temp sensors, they are averaged, but don't know for sure.
 
cobra said:
The Omnistat2 manual mentions 3 external sensors, 2 using a temperature extender.  Has anyone ever seen one of these?
Click to expand...
Yes its called a Leviton 95A03-1TWH.  Its basically a remote control for the OmniStat2, but note it requires a separate power supply so that makes it pretty pricey.
 
JonW said:
This is a great idea I'm going to convey to my mother in AZ.  She doesn't have an HAI panel, but she could at least set some programmed setpoints to chill lower prior to rate hike timeslots.
Click to expand...
Lately the electric utility here has been battling solar in any way they can. The high electric rates are now from 12 noon - 7pm, but since solar panels put out their peak output at noon, and output goes down toward sunset, the utility now wants to change their high rate from 3pm - 8 pm and change solar users to this rate to make sure they are charged the most money when their solar output is low. This would be good for me because it shortens the high time by two hours.
 
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