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O and B wiring issue - no heat pump

hram
Community Member

hram_0-1691616592448.jpeg

This thermostat is the master in a 3 zone system - no heat pump, forced air and oil heating but we still have o and b wires. I have installed the slave, with a C wire adapter (Green to C wire, Y and R, no O or B) and the system works. Now I am stumped as the master has the following wires (in the photo):

Top - W   Rh  B   Rc  (jumper between Rh and Rc)

Botttom - C (G into C and labeled, with the C wire adapter)     O    Y

B wire is Blue and O wire is Brown. Obviously both cant go into O/B in the Nest. Have seen suggestions to make the O into C and the B into O/B in the Nest (to control heating/cooling, and which will leave the current C wire (previous swapped G) out).

Any help highly appreciated!

4 Recommended AnswerS

CoolingWizard
Platinum Product Expert
Platinum Product Expert

There is no affordable zone controller that will handle three HVAC equipment. You will need one zone controller for each of the air handlers that has dampers in the ducts. The smart residential smart controllers I prefer are the ecojay SmartZone 4X. 

AC Cooling Wizard

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CoolingWizard
Platinum Product Expert
Platinum Product Expert

@hram , Those EMC ST zone controllers are dumb devices and that require the #1 thermostat to control and set the system mode. The reason I prefer the EcoJay SmartZone is they will allow any zone thermostat to activated the system and thermostat 1 is still the priority thermostat. Additionally they are capable of Supporting the Nest Thermostat in heat pump duel fuel mode.  They are easily configured and programmed. 
As to those O and B wire, you will not need them. 

The Honeywell and the ECM 300 have a more complex configuration process. 

AC Cooling Wizard

NestPro, Google Pro, Mechanical Engineer and HVAC service company owner. If my answer solved your problem, click Recommend this Answer below, and If it helped you, please give a Kudo.

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CoolingWizard
Platinum Product Expert
Platinum Product Expert

@hram ,

With the ST-2E there can only be 1 master thermostat. The thermostat connected to TSTAT-1 is the master controlling thermostat.  TSTAT-1 sets the system mode of heating or cooling using the O and B wires. No other thermostat can change the system mode. 
Using Nest Thermostats connected to the EcoJay 4X, priority is given to thermostat #1, however, if thermostat 1 is not calling for heat or cooling, any other thermostat attached can make the call for heat or cooling.  Unlike the limit ST-2E, you do not need a unique O or B control wire.  The Y and W wires are used for Cooling and Heating 

Will you be replacing all your thermostats with Nest Thermostats?

 

AC Cooling Wizard

 

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CoolingWizard
Platinum Product Expert
Platinum Product Expert

@hram ,

in all reality, the dampers are motors, the damper is sort of a valve on the inside of the duck, and the motor is what opens and closes that valve to allow the air to either flow or not flow so they are indeed the same thing 

AC Cooling Wizard

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21 REPLIES 21

CoolingWizard
Platinum Product Expert
Platinum Product Expert

@hram ,

Some zone controllers are not very intelligent.  The master must signal a system mode change by activating either the O terminal or the B terminal.  Those non-intelligent zone controllers require a thermostat subbase that is set up to to activate heat, by internally connecting the R wire to the B terminal or cooling by connect R to O.  

Unfortunately you are not correct on the use of the OB.  All heat pumps have a reversing valve to switch from Heating to Cooling or from Cooling to Heating.  The Y terminal is what activates the compressor.  The G terminal is what activates the indoor blower fan. The W terminal activates your heating system.  

When you have a zone controller the HVAC equipment is connected to the Zone Controller HVAC Equipment Terminal Block, and the thermostats connect to a TSTAT terminal blacks as well. Typically the thermostat that is attached to the TSTAT 1, is the thermostat that controls the system mode ie., Heat or Cool.  All other thermostats attached to the zone controller simply signal the controller to open or close a damper motor.  

There is no Thermostat in the world that can tell what color the wire is.  The color is so the technician can ensure that say W is connected to W between the thermostat and the HVAC equipment.  

Now then, if your zone controller needs thermostat 1 to activate the O or B, a partial work around is easy to wire the Nest Thermostat to do that.  You will use only the R, C, G, Y, and W terminals in the Nest Thermostat. At the Zone controller, the Thermostat 1, has the white wire on W, with a jumper wire to the B terminal. And the Yellow wire on the Nest Y to the zone controller TSTAT-1 Y terminal with a jumper wire to O.

Now here is the problem, since the zone controller is not very intelligent, the system will only turn on when Nest on TSTAT-1 is calling for Heat or Cooling.  If TSTAT-1 is satisfied, the system will turn off even if TSTAT-2 is still calling for cooling.  Your current thermostat when the mode switch is in Heating, internally connects R to B even when the thermostat is not calling for heat. When any TSTAT in the system calls for heat by connecting R to W, the Zone Controller will activate the heat.  If a thermostat calls for cooling while the system mode switch is in heating, nothing will happen.  Remember, the TSTAT 1 is the controlling thermostat.  

What need to do is consider an upgrade to Zone Controller that is a smart/intelligent controller.  

AC Cooling Wizard

NestPro, Google Pro, Mechanical Engineer and HVAC service company owner. If my answer solved your problem, click Recommend this Answer below, and If it helped you, please give a Kudo.

Thanks for the detailed response, highly appreciated! The workaround doesnt really work - will make the zones ineffective. Ie the master tstat 1 will have to work to make others work, so rather than 5 different zones currently, the whole home will work effectively as one. 

 

I have EWC ST 2E right now (cant upload photo, will try to do it on the original post), we have three ACs and three handlers, 2 Tstats that are masters and three slaves. Which controller would you recommend - ease of swapping out is important, so is to have the current wires work rather than putting additional wiring. 

 

 

CoolingWizard
Platinum Product Expert
Platinum Product Expert

There is no affordable zone controller that will handle three HVAC equipment. You will need one zone controller for each of the air handlers that has dampers in the ducts. The smart residential smart controllers I prefer are the ecojay SmartZone 4X. 

AC Cooling Wizard

NestPro, Google Pro, Mechanical Engineer and HVAC service company owner. If my answer solved your problem, click Recommend this Answer below, and If it helped you, please give a Kudo.

hram
Community Member

image4503.jpg

hram
Community Member

Got it - smartzone 4x is better than honeywell or ecm 300 (recommended by a maintenance tech)? Based on the wiring in the above photo, how hard is it to rewire? Do I have to get additional wiring in (o wire?) ? Getting rid of wires - like the o and b wires, is to just leave them out right? 

 

Thanks for the help!

CoolingWizard
Platinum Product Expert
Platinum Product Expert

@hram , Those EMC ST zone controllers are dumb devices and that require the #1 thermostat to control and set the system mode. The reason I prefer the EcoJay SmartZone is they will allow any zone thermostat to activated the system and thermostat 1 is still the priority thermostat. Additionally they are capable of Supporting the Nest Thermostat in heat pump duel fuel mode.  They are easily configured and programmed. 
As to those O and B wire, you will not need them. 

The Honeywell and the ECM 300 have a more complex configuration process. 

AC Cooling Wizard

NestPro, Google Pro, Mechanical Engineer and HVAC service company owner. If my answer solved your problem, click Recommend this Answer below, and If it helped you, please give a Kudo.

Eco Jay is indeed Amazons Choice. But when I look at the panels, I am confused:

- This is fine: Current EWC panel has Zone 1 and 2 Tstats on the right, and those wires will go to the Eco Jay Tstats on the left. Same with teh System wires - EWC has them on the left bottom and Eco has them on the right top as Equipment.

- Eco has dampers, I have no idea what those wires are on the EWC

- EWC has the Zone 1 and 2 motors on the left - there seems to be nothing with that label on the Eco. Also - how does the Eco control the three ACs and Airhandlers (through the Equipment wires?)?

- EWC has 24v power on the left middle and Eco has them on the left bottom, which is fine.

Super helpful if you can let me know, thanks much. I would like to be sure I am upto this before I take out the EWC!

CoolingWizard
Platinum Product Expert
Platinum Product Expert

No residential zone controller can control more 1 HVAC system. Each HVAC system has its own duct system. If you have three separate systems, and if each system has separate zoned areas, you would need a separate zone controller for each system. What you have is a 3-Zone duct system and single HVAC system. The EcoJay 4X supports up to four zones.  As for wiring your Zone Damper Motors. the terminal is numbered M1, M2, M4, and M6.

M1 is the power Common

M2 puts out a constant 24VAC

M4 is energized to OPEN the damper, this is NO

M6 is energized to CLOSE the damper. This is NC

 Now some damper motors use a spring to close so those motors do not need M6.

I hope this helps,

AC Cooling Wizard

NestPro, Google Pro, Mechanical Engineer and HVAC service company owner. If my answer solved your problem, click Recommend this Answer below, and If it helped you, please give a Kudo.

Thanks so much for the prompt reply! For clarity, we have:

- 3 separate AC units, and

- 3 air handlers (two in the attic and one in the basement.

- No heat pump - the boiler system has oil burner for heating air (and water)

- EWC ST 2E is the only controller, 2 masters (with 0 and B separate wires - the issue), 2 slaves (no O or B wires) , one more slave (has only an O wire, no B)

CoolingWizard
Platinum Product Expert
Platinum Product Expert

@hram ,

With the ST-2E there can only be 1 master thermostat. The thermostat connected to TSTAT-1 is the master controlling thermostat.  TSTAT-1 sets the system mode of heating or cooling using the O and B wires. No other thermostat can change the system mode. 
Using Nest Thermostats connected to the EcoJay 4X, priority is given to thermostat #1, however, if thermostat 1 is not calling for heat or cooling, any other thermostat attached can make the call for heat or cooling.  Unlike the limit ST-2E, you do not need a unique O or B control wire.  The Y and W wires are used for Cooling and Heating 

Will you be replacing all your thermostats with Nest Thermostats?

 

AC Cooling Wizard

 

NestPro, Google Pro, Mechanical Engineer and HVAC service company owner. If my answer solved your problem, click Recommend this Answer below, and If it helped you, please give a Kudo.

hram
Community Member

Looking to change all 5 thermostats (chaged 3 already, the issue is with the 2 that have the O and B wires - they are the masters).

I stand corrected - I hve 2 control panels, one in the basement and one in the attic, and it seems each one has the one master tstat. Each should also have one slave, but I am not sure about the 5th tstat, which is a slave and is connected to the basement. I think it may have jumpers - it can call for cooling and heating on its own (it is in a side bedroom). I think I will need 2 control panels, but have to figure out the second slave for one of them - how is it wired... The wiring looks very similar on both panels except on one panel there is a jumper from R to R1. 

CoolingWizard
Platinum Product Expert
Platinum Product Expert

The Jumper between R down to R1 does not make sense.  I will need to do some research. Keep in kind the limitation of these EWC ST zone controllers.  There must be the master thermostat that connects to R1. The master thermostat sets the system mode.  That is when the master thermostat sets the mode switch to HEAT, it sends 24VAC from the R1 to the B.  When the master thermostats sets the mode switch to COOL, it sends 24AC to the O.  If the master thermostat puts the mode switch to OFF, the EWC- ST will be off.  

What you should do if you want to use Nest Thermostats, you need to manually set the system mode on the ST-2E.  Think of this as a HEAT or COOL switch.  You would need to change the system mode each season.  The switch would take R1, and in one position it connects to B and the other it connects to O.  To achieve this you will need a SPDT switch for each ST-2E controller. 

A better option is to invest in a more intelligent zone controller like the ECOJAY 2X or 4X. 

AC Cooling Wizard

NestPro, Google Pro, Mechanical Engineer and HVAC service company owner. If my answer solved your problem, click Recommend this Answer below, and If it helped you, please give a Kudo.

hram
Community Member

hram_2-1692141641964.jpegYes - planning to buy two Ecojay Smartzone 2x panels, and adding photos of the attic (above) and basement (below, with the jumper). I am confused about the wires in the Motor contacts in the EWC panel - they probably go in the Damper contacts in the Ecojay panel. Also, I have a total of 5 thermostats/5 zones, where 2 are masters (with o and b both wires), 2 are slaves (no o or b) and one is a question mark (has a B wire, no O wire). So should I get a two 2x panels to replace or should i get one 1x and one 4x panel - and where would the wires go on a 4x panel? I have reached out to Ecojay too if they could help before I buy rather than buy and replace... Appreciate all the help!

Attic panel

hram_3-1692141686172.jpeg

Basement panel - you can see the red jumper

 

 

 

CoolingWizard
Platinum Product Expert
Platinum Product Expert

@hram ,

That jumper wire is on the Equipment side. they are sending 24VAC out to the HVAC equipment or getting power from HVAC equipment. Normally there is a separate and dedicated transformer just for the EWC ST-2E.  The dedicated transformer is normally wired to the Transformer Block.  In your case, they are getting the power from your forced air handler.  On the transformer block the #1 is Power Common and the #2 is Power 24VAC.  The installer seems to have wired the Red wire to Common terminal.  To verify this we need to see where that red wire goes off to. 

Your zone damper motors are power open and  power close. On the damper motor connections, M1 wire is Power Common, the M2 is 24VAC power, the M4 is OPEN, and M6 is CLOSE. The M1 common is wired internally from the Transformer Common block terminal #1.  When a thermostat call for service, the ST-2E sends power to the M4 damper motor to open the damper.  When the thermostat controlling that damper is satisfied, the ST-2E sends power down the M6 wire to close the damper.  

The EcoJay has the equipment and thermostats connections on opposite sides than the EWC ST does.  Since neither of your current zone controllers supports more than two thermostat and two zones connected, the 5th thermostat must have its own equipment or it is attached to something else. 

I hope this helps. 

AC Cooling Wizard

NestPro, Google Pro, Mechanical Engineer and HVAC service company owner. If my answer solved your problem, click Recommend this Answer below, and If it helped you, please give a Kudo.

hram
Community Member

Hello CoolingWizard:  have ordered EcoJay and want to make sure I dont wire it incorrectly. On the EcoJay there are Damper 1 to 4 wires on the right side while on my current EWC there are only Zone 1 and 2 Motor wires on the top left. I assume damper is the same as motor and I will put the Motor wires into the Damper slots? Appreciate the help!

CoolingWizard
Platinum Product Expert
Platinum Product Expert

@hram ,

the EcoJay has its connections on opposite sides of the EWC. There will be thermostats connections, power connections, HVAC equipment connections and damper motor connections. You will book up the thermostat with all wires and the R will not be separated like the EWC.  The EcoJay has a 2-wire power connection for a dedicated transformer like the EWC. Feel free to reach out to me  if need realtime guidance. 

AC Cooling Wizard

NestPro, Google Pro, Mechanical Engineer and HVAC service company owner. If my answer solved your problem, click Recommend this Answer below, and If it helped you, please give a Kudo.

hram
Community Member

Thanks so much for the offer for realtime help - I may take you up on it (for a case of beers...summer is still around!). I think my question is more basic - I get the connectors on the opposite side for Ecojay vs EWC, question is does Ecojay call their connectors Dampers and EWC call them motors? IE can I take the wires from the EWC motors connectors and they will go into Dampers for Ecojay? 

CoolingWizard
Platinum Product Expert
Platinum Product Expert

@hram ,

in all reality, the dampers are motors, the damper is sort of a valve on the inside of the duck, and the motor is what opens and closes that valve to allow the air to either flow or not flow so they are indeed the same thing 

AC Cooling Wizard

NestPro, Google Pro, Mechanical Engineer and HVAC service company owner. If my answer solved your problem, click Recommend this Answer below, and If it helped you, please give a Kudo.

Hello CoolingWizard - got the 2x, have figured out the dampers (we have 2 dampers actually) on the ecojay vs EWC, and everything but am stuck on the 24v supply.

In the EWC, the supply is from the air handler, but there is a jumper from the 24v supply in to the Equipment terminals (you can see both the EWC photos above). I think the red jumper completes the circuit but want to be sure before I connect a jumper from 24v to Rh in the ecojay and short something. Your thoughts appreciated as always!

hram
Community Member

hram_0-1694204766107.jpeg

 

CoolingWizard
Platinum Product Expert
Platinum Product Expert

@hram ,

Typically you provide a dedicated transformer for the zone controller.  This wired to the terminal labeled transformer or Xfmr.  This powers the zone controller itself and the connection at the equipment terminals is what powers the transformers.  When you do not have a dedicated transformer you can use the power from the equipment to power the zone control board by putting a jumper from R and C. If you indeed have a transformer to dedicate to the zone board, connect it at PWR connector at the lower left corner.  If you do not have a dedicated transformer make sure you bring a common from the equipment and jumper equipment R and C to the PWR.

AC Cooling Wizard

NestPro, Google Pro, Mechanical Engineer and HVAC service company owner. If my answer solved your problem, click Recommend this Answer below, and If it helped you, please give a Kudo.