Can I do this with the ADC T-2000’s humidy sensor (and configurable terminal) ???
24 Volt Dehumidistat Wiring (Goodman/Amana)
The optional usage of a dehumidistat allows the furnace’s circulator blower to operate at a slightly lower speed (85% of desired speed) during a combined thermostat call for cooling and dehumidistat call for dehumidification. This can be done through an independent dehumidistat or through a thermostat’s DEHUM terminal (if available). This lower blower speed enhances dehumidification of the conditioned air as it passes through the AC coil.
For proper function, a dehumidistat applied to this furnace must operate on 24 VAC and utilize a switch which opens on humidity rise.
To install/connect a dehumidistat(edited):
2. Secure the dehumidistat neutral wire (typically the white lead) to the terminal marked “DEHUM” on the furnace integrated control module.
3. Secure the dehumidistat hot wire (typically the black lead) to the terminal marked “R” on the furnace integrated control module.
See the attached instructions from Alarm.com regarding installation of the ADC-T2000 with humidifier or dehumidifier.
I couldn’t speak to the features of a third party product, but what you are describing sounds like a two wire control. Rh on the Tstat would already be connected to your R (24VAC hot wire) and you would connect the DEHUM to Z.
The T2000 must be firmware 1.5 or higher, and the panel will have firmware requirements. For Concord, Module v185b
When configured for humidity control in ADC, does T-2000 Z terminal OPEN on a humidity setpoint call(rise)?
I’ll need to check continuity to see if there is 24VAC on the DEHUM wire to Rh, but if there is 24V present — likely? (or unclear in OEM excerpt above) the ADC app note caution == looks like I need a relay to protect T-2000?
I may be overthinking this?: the ADC Caution on 24VAC in the note you shared would be for dehumidify systems where T2000 needs to interrupt or complete a 24V dehumidifier relay control circuit; vs. simply opening a sensing signal on the air handler-furnace control board ----in this case “DEHUM” terminal
I may be overthinking this?: the ADC Caution on 24VAC in the note you shared would be for dehumidify systems where T2000 needs to interrupt or complete a 24V dehumidifier relay control circuit; vs. simply opening a sensing signal on the air handler-furnace control board —-in this case “DEHUM” terminal
Technically from the sound of what you posted from the device manual, the T2000 would be interrupting a circuit, by breaking the Neutral connection though, not the hot connection, if Z is intended to open upon humidity rise.
I’m checking with ADC if this is standard operation when Z is configured as Dehumidifier. I think it is, as the primary difference between a Humidistat and Dehumidistat is that latter is normally closed, and the circuit opens when the humidity drops to cut function. EDIT: If your device requires the circuit to open as Humidity rises, it may have a non-standard function. I would need to see the product manual/model number to know more. That seems counter-intuitive if it is a power circuit
Unfortunately the documentation for the T2000 doesn’t specify the terminal function yet, but I will update here when I hear back.
So, thinking about this and looking at documentation, I can tell you how the ADC T2000 will function:
When the Z terminal is configured as a humidifier the switch will open on humidity rise, stopping the flow of 24VAC power to the Z terminal and connected humidifier.
As humidity drops below the configured setpoint the switch will close, re-activating the humidifier.
When the Z terminal is configured as a dehumidifier the switch will close on humidity rise, activating the dehumidifier.
As humidity drops below the configured setpoint the switch will open, stopping the flow of power.
This is still confusing.
Described functionality below would/should be a “benchmark” for the ADC T-2000 and the cloud-based logic.
(Honeywell IAQ Stat’s for one example do exactly this and their dehum/aux—“Z” terminal equivalent) is configured as N/O OR N/C in the setup)
Air handler(furnace) with a variable speed blower has two calls an advanced thermostat(with humidity sensor) can request:
COOLING
DEHUM (dehumidify)
Cooling request simply runs the furnace blower at “normal speed” (outside condenser on)
Dehumidify request runs the furnace blower at a “slower speed” (outside condenser on) to get more condensation and removing more humidity (latent), but not cooling the house as fast(sensible).
[The T-Stat/ADC logic settings also should allow a simultaneous COOLING call when T-2000 DEHUM is called. IF ADC logic does not allow a COOLING call when DEHUM is called, there is still a humidity reduction benefit—circulator fan still runs slower when temperature does eventually call for COOLING.]
The temperature may go lower than set point in order to achieve correct humidity level (if ADC logic allows) thus the house may be colder then desired.
Given you comment on T-2000 Z terminal function, I would set it as “humidistat” in ADC so when it got, to say 55%RH, circuit is open, this slowing the circulator fan operation during cooling & high humidity, even though connected to the “DEHUM terminal” on the furnace per above.
The description above is from ADC provided instruction and description of the Tstat Z-terminal.
It is hard to manipulate humidity for testing, but I can confirm that the rest state for Humidifier and Dehumidifier is Open when outside of the trigger parameters.
Voltage is delivered through Z when the humidity rises above a set level for dehumidifier.
Voltage is delivered through Z when the humidity drops below a set level for humidifier.
This is intended for powered external humidifiers/dehumidifiers. The T2000 uses a “Smart Humidity Control” which allows dehumidification logic in the back-end as long as central cooling stage is available.
To verify how your unit works, whether it is looking for voltage change or dry contact, we would need the model number of the furnace/hvac with this dehumidification option with the variable speed blower. What is the model number of your unit or can you link the manual where you are finding the info?
If you need just a Normally closed dry contact circuit for the variable blower, you would want to use a 24VAC triggered relay.
Ok yeah, ADC intent for Z is a bit different. Maybe I can get it to work here…
OEM: “OPENS ON HUMIDITY RISE” = ADC: “closes when humidity drops” ???
So, I could setup Z as ADC/T2000 “humidifier” control rather than use a relay to get N/C logic; and humidity logic would actually be controlling dehumidify enhancing circulator fan speed reduction.
No need to use relay to change NO-NC logic…
This would always slow the fan when humidity is above “humidifiers” setpoint AND stat calls for cooling (one stage AC in my setup)
Ok yeah, ADC intent for Z is a bit different. Maybe I can get it to work here…
OEM: “OPENS ON HUMIDITY RISE” = ADC: “closes when humidity drops” ???
Setup Z Term T2000 as “humidifier” control (i.e. not use a relay to get N/C logic); and humidity logic would actually be controlling the dehumidify-enhancing circulator fan speed reduction.
This would always slow the fan when humidity is above “humidifier” setpoint AND T2000 calls for cooling (one-stage AC) PROVIDED ADC logic allows call for cool AND call(Z term) for “(de)humidify” at same time.
OEM board looking for contact activation/sensing similar to other thermostat terminals, see attached. The OEM dehumidistat wiring (attached) is what this control board would be “expecting”.
OEM board looking for contact activation/sensing similar to other thermostat terminals, see attached. The OEM dehumidistat wiring (attached) is what this control board would be “expecting”.
Based on the manual I would say yeah it looks like it is just looking for 24VAC on the Dehum terminal from a SPST switch in a humidistat.
R would already be connected to the Tstat Rh, and Z would pass 24VAC back to Dehum. However I would not use it this way.
You should use a relay still because there is other logic tied to Humidifier vs Dehumidifier status in ADC such as dehumidify only occurring in Cool or Auto Mode.
The relay can reverse the logic and when triggered, open a N/C circuit fed from R and back to Dehum.
