My situation is as follows. I currently have a honeywell ct87k which only has three wires w,y,r. I have one air unit with 2 zone dampers. I want to switch to programmable ones to save energy so I bought the rth6300 however when I hook up the letters it doesn't turn on and then finally it did but wouldn't shut off. I think the issue is that I am trying to use a heat and cool thermostat but thought it would work. I wired the R to Rc on the new one, the Y to Y and the W to w. I think the issue is that on the old one Y and W are really for open and close damper, whereas on the new one W is heat?? Any help would be greatly appreciated,

I think the new stat might have to be, or be set to auto-changeover.

Thanks a lot I will try it.. Makes sense that one I have doesn't have auto change. Appreciate it.

One additional question, will that autochange over work even if I only have AC hooked up to it. I guess the idea is it will hit the temperature and then trigger the white heat wire signal which will shut the damper on the ac unit? Does that sound right?

I don't know exactly what you have, but here's how I would approach the problem from scratch.

Assumptions:

1. Only AC
2. Thermostat controls fan in AC mode
3. Dampers can be:
a) Power to open, power to close
b) Power to open, spring to close
c) Power to close, spring to open
4. 2 thermostats

I'm going to think outloud for a bit.

What if I wanted either stat to turn on the air handler (Fan)?
I'd parallel the fan contacts.
What if I wanted cool to start the AC
I'd parallel the cool contacts

Then I'd go OOps, I have dampers to move.

So I'll use 2 relays with double pole, double throw contacts and use one contact on each for the fan and the other for cool and I'd parallel them like I did before.

Now I have two separate contacts to control the dampers. If it were spring to open and power to close, I'd arrange the set of NC contacts to open their respective damper. I might require an extra relay fro tis if I had power to open/power to close.

So, hopefully you can see that there are numerous options. Heat and cool make things tricky and so does power to open and power to close and multiple zones make things tricky as well.

In a zoning panel, the outputs of the stat would be converted to optically coupled inputs to a micro-controller. Then only a few relays would be used to control the furnace/AC

In fancier systems, the dampers can be modulated from full open to full closed and there would be safegards in place so that all the dampers can't be all closed at the same time.

When you think about it in the heat/cool mode, heating means damper open and cooling means damper open.

One thing to note is this termostat only controls the AC, there is no fan mode on the old thermosat that worked, it was either on or off. You can turn the unit on from any one zone and then the second zone once you click it on will open the damper. I seems like it should be so easy but its so frustrating. The house is onl 9 yrs old. The CT87 which has R,W,Y works perfectly. There has to be a programmable version that would also? I bought the auto switch one and will try tonight but still not sure how the signal from W (heat) will shut unit off. I am an accountant that is somewhat handy so this is all new to me. Appreciate all your help and if there is every financial advise you need feel free to ask

The manual for the CT87 is here: Product

That's such a standard stat, there should be no problem getting the others to work.

The RTH6300 manuals are here:

Default - Honeywell Environmental And Combustion Controls

R will have to be connected to Rc
Set it up for heating and cooling and gas or oil heat.

I know. It seems so easy which is so frustrating.. I am going to try and again tonight and try the auto switch one also. Will let you know how it goes. Again thanks.

Here's a crazy question, can I combine my two separate onto 1 thermostat? I don't think so because I will end up with two heats?

Two separate what?

Do you have one t-stat for cool and another for heat with two differnet air handlers?

What do you have anyway? Do you even know?

I have basebaord hot water heat with a boiler and three zones and three separate thermostats for each zone. I have one air handler in the attic with two zone value for and two thermostats for this. Whoever built this house was retarded...

I have basebaord hot water heat with a boiler and three zones and three separate thermostats for each zone. I have one air handler in the attic with two zone value for and two thermostats for this. Whoever built this house was retarded...

Yipes! That would drive me nuts.

Here is a manual for the zone controller for a zoned system: http://www.aprilaire.com/themes/aa/en/manuals/6504.pdf

I'm not sure how to make it all work for you though.

Three identical areas for heat and cool would al least make it attemptable.

Here is another one: HVAC 6-Zone Controller - Temperature Control

Thinking about your Ct87k, it would be very easy to wire in the following fashion:

1= stat #1; 2 = stat #2

R1, R2 = Cooling xformer (Hot)
G1 to damper #1 (power to open, spring to close)
G2 to damper #2 (power to open, spring to close)
Y1, Y2 = Cooling call

C (other side of xformer) to other side of dampers.


G&Y would be energized when there is a call for cool and the air handler would turn on the fan. R1, R2 means R of stat 1 is connected to R of stat #2.

This, I believe, looks like it would work. w, y and r maybe colors and not terminals.

Thus when you just put the stat to fan ON, only the damper would open assuming the setpoint was set very hot (i.e. cool is off)

This makes a lot of sense and would easily implement dual zoning without the ability to run the fan separately.

Thinking out loud again:

Supposedly say you purchased the 6 zone controller and everything else worked out. 5 locations and some combination of sensors and stats. This is what I'm initially to believe.

Remember the zoning controller has priorites, heat is satisfied first which means heat and cool won't be on at the same time.

Cooling should be relatively easy to set up where Rc is separate from Rh so we assume a 2 transformer system. Wiring that side should be straightforward.

On the heat side, things get a little complicated.

Here is a typical hot water zoning controller. http://houseneeds.com/Shop/manuals/taco_zvc404.pdf

You basically implement the logic that says if the system is calling for heat, you want to turn a damper signal into a contact closure. i.e. common and open would energize a relay that would mimic a single thermostat. Calling for heat is looking for a signal on W and C which would be going to a real furnace and create a contact closure. This contact closure would supply power to the coils of the relays that would mimic the 2 conductor stat, thus the heating "virtual dampers" (zone valves) would only be driven open if there is a call for heat for a zone.

In theory, it seems as if it could work.

More info on RCS control systems is here: RCS Home Page

And with a little more logic, you can eliminate two thermostats at a single location.

Based on a heat or cool call divert the "damper" signals to a contact closure to the hydronic system or directly to a damper.

So, you can reduce those 5 thermostats to 3.

Thanks. I had the same thought last night as what I think you are saying. It clicked that these dampers are used for heating and cooling and the motor is wired the "opposite for coolin" so Y opens the damper, and W closes it. So I have programmed the new thermostat to heat only with the wiring being oppsoite I figured it would work and now it works, however when looking at the thermostat you have to remember when it says heat on, that really means A/C off. Seems retarded but all functionality works. Seems backwards but works fine. Do you see any issues with doing it this way. When I want the AC off, I just hold it at 90 degerees and when I want programming I set the pragraming like normal. I mean all a thermostat is is a switch right, it hits the temp and sends a signal to the AC unit then once temp is reached sends another signal. Do you think there are any issues with me doing it this way, like shorting something?? You really have been a great help with bouncing ideas off. Thanks again

A thermostat is a set of switches in the simplest sense.

But the older stat's were not. When the switch was on, it heated the spring a bit (This was called the anticipator) and it would force the stat to turn off a little sooner so the thermal mass of the house didn't swing the temperature too much.

Again, I don't know how your dampers operate. That would help. 2 wires? 3 wires?
What happens when you cut power. Just don't use the stat.

I'm thinking that one of those wires examples: (Y to R) turns on the AC and (W to R) open/closes the damper. That I would like to to test without a stat in place. Best to use two switches and wait a few minutes before changing their state.

There are three measured values:
1. Air handler state
2. Compressor state
3. Damper state

and four possible positions

Y W
0 0 Damper=? Air handler =? And compressor = ?
0 1
1 0
1 1

A (1) in a position means it's connected to R.

I want to see damper and compressor vary together and fan vary separately.

Once you fill in the table, we should be able to fix it.

Then maybe we can get the sense right.

The damper is a zone a trol. The wiring instructions on the damper say to wire R to 5 (function per damper manul says common of swith and makes to either 4 or 6 to operate damper), W to 4 (makes with 5 to drive motor open, since wires are reversed on mine its closing) and Y to 6 (makes with 5 to Close damper, but since reversed its opening) for cooling it says to reverse Y and W. This is what made me think to use the heat only function on the new thermostat since the wiring is opposite on the damper I can use the heat only and it will work. When I tested once the heat clicked off on the thermostat because it reach the desired temp the AC and Compressor went on and that zone was blowing air out of the room vents. The other zone was in the Heat on position and there was no air coming out, which makes sense because I was testing the one zone. So that means the unit is opening the proper damper and closing them upon the signal coming from the thermostat. Sorry to keep bothering you on this. I really think this work around works, just don't know if there are electrical issues. If there were would I know quickly. I test about 5 times including time shut offs, etc?

Someone from honeywell actually called me because I emailed their support. The guys said the way I did it is not common and that he thinks to make it make sense using a relay switch would work? Do you know anything about that? I on the other don't think so because the cool function on the thermostat won't know to open and close damper will it?