[ChezSean]

We had a new furnace (Daikin DM97MC) and AC unit (Daikin DX18TC) installed in the summer. It's connected to an Ecobee Smart thermostat. The installer who did the wiring was grumpy and didn't like the Ecobee but they got it done. AC was fine all summer and heat has worked this winter... but...
the humidifier doesn't work.
There was no power getting to it so I checked the wiring and they wired it up to the DEHUM connection instead of the HUM connection on the control board. That prompted me to check the other wiring, and I don't think these dual-stage units are wired right at all. I have attached the wiring "as is" and what I think it should be. Just looking for some advice before I call them back to fix this mess...

as-is

should be ?

 

[ChezSean]

not sure about the orange connection from the AC unit...it's not connected to anything at the moment.

 

[user_12345a]

I don't know how your heat worked without the W wires connected. u sure your diagram is right?

The eco-bee is not the right stat to use on that furnace; you need a modulating stat so heat output actually tracks demand. You can use an eco-bee but i believe it will slowly modulate up as the cycle goes on. can look it up later to see how it works.


In a/c mode did it stage properly or just run at one speed?

 

[ChezSean]

I will check the wiring again but the heat is on right now. I think the ac only ran at one speed, it's been a few months. We already had the Ecobee when the furnace was installed but it was being used on an old single stage furnace so they changed the wiring.

 

[ChezSean]

my bad... I missed one white wire and confused it for another. So there W1 is connected and the AC also has a white wire going to C ... but it's still all "1-stage" when it could be 2.

current wiring looks like this:

 

[ChezSean]

on the furnace install guide, it says to run a jumper from L1 to one of the HUM connections. All the L1 slots are taken, there is one left but it has part of a plastic cover on it, can I still use that one or is it blocked so it can't be used ? (not sure if it's just covered to keep something from contacting it when not in use)

 

[yuri]

If it is a modulating furnace you can use a single stage thermostat and it will use a algorithm to check the length of cycles and adjust the modulating from them. It is better with a 2 stage tstat and even better with a Communicating tstat but it can work with all 3.

If the hum terminals put out 24 volts when the heat is on they are safe to use with a 24 volt humidifier. However there are some that produce 120 volts so you need to check or read the manual.

If it is a 2 stage AC you need a Y2 wire.

 

[ChezSean]

Yes thanks... the L1 thing was for a line level humidifier . It says to feed the other terminal from R for a 24v. Learned a bunch today.

 

[beenthere]

Y2 of the furnace needs to be connected to the thermostat. And then the thermostat needs to be set up to control a 2 stage A/C.

 

[user_12345a]

The algorithm on goodman/amana's/daikin's mod furnace is terrible. Only york's mod is fully featured, can modulate up and down on a single stage stat.

With both the single stage or two stage t-stat it just keeps on ramping up, a few minutes at a time until it hits 100%.

With two stage t-stat it can fire starting a 80% with a w2 call, but doesn't drop down when w2 call ends, it stays at the same firing rate and satisfied the stat quickly.

Only with a super-expensive communicating mod stat will this furnace actually track heat loss, modulate, not just ramp and satisfy. It's brute force and ignorance at work; lazy programming too.

The same goes for all brands other than york and maybe lennox. (not up to date)

High end equipment is a total waste of money unless put in right with the correct non-crippling controls.

 

[ChezSean]

thanks for the info. We bought an old house with a super old, oversized furnace and undersized AC unit. We already had the Ecobee and the thermostat here was broken so we put it in. When it came time to replace the HVAC stuff the company said the Ecobee would work (didn't know they would wire it this way). I can likely get a CTK04 for near cost if that will really make a huge difference compared to correctly setting up the 2 stage settings on the Ecobee...

 

[yuri]

I would get their communicating thermostat. You paid a LOT of money and why not get all the features and performance.


Rheem has a truly modulating furnace with a gas valve that uses varying voltage.

Lennox is truly modulating as the gas valve is vacuum operated not a 3 stage like others.

If you use a Communicating tstat usually you cannot use the RWYG terminals for a humidifier as it bypasses them. Some people energise the humidifier from W and C but once you go Comm Tstat you will have no W signal. You can add a 120 volt relay and run the N/O normally open contacts thru the humidifier and a 24 volt transformer.

Usually most brands have a 24 volt HUM terminal and some also have the 120 volt terminals.

 

[beenthere]

If a communicating thermostat has humidification ability, then the Hum terminal is energized on a call for heat when the stat calls for more humidity(maybe not Lennox). Or has separate terminals for it that the communicating control/stat has control over.

 

[yuri]

I found a pic of the wiring diagram and it has no 24 volt HUM terminals just 120 volt.

On the Lennox SLP they recommend a seperate 24 volt isolating relay for a humidifier if using the Comm. tstat. The MOD boards are so VERY expensive they don't want to add any load to W or other terminals it seems.

Probably same with Daikin.

 

[ChezSean]

The manual says I can energize the HUM terminal from L1 for line voltage and R for 24volt but doesn't distinguish between using the comm method or "legacy" wiring

 

[yuri]

If you use legacy then your are using a regular tstat which will give you the 24 volts on W from the tstat. Terminal strip is not hot at W, it is a input.

Comm stat uses a digital signal of varying DC voltages.

However you can use a Comm stat and legacy AC as the board will feed 24 volts to Y and Y2 as it knows to do that with a Comm stat. With legacy Y and Y2 are inputs. If the AC can use a Comm stat feature/wiring then that is better as it gets feedback and has more functions like de-humidification program on some brands. Have to check the AC manual to see if it has that feature. ( apparently it is from their website ).

You have some VERY nice high tech equipment. Too bad the installer does not understand it. Not that uncommon it seems.

Not sure why they would tell you to use R as it is hot all the time and the humidifier can run w/o the fan in that case. I use W so it turns on with the heat. Daikin is very new to the furnace biz so maybe they have not twigged on to that fact.

At the end of the day I would use a ComfortNet Comm tstat for both the furnace and AC to get all the features and programs. I would put a 120 volt coil isolating relay on the Line HUM terminals and run the humidifier thru the N/O and use a 20 va 24 volt transformer to power it. Usually they come with one but sometimes they get thrown away and run off the furnace power.

 

[user_12345a]

Dealers are supposed to understand, no? Seems like they aren't offering proper training to the dealers.

 

[ChezSean]

If I had gotten the corresponding thermostat they would have had no problem as its only 4 wires for everything... but the humidifier was the last thing they hooked up and I guess they wanted to get out of there. Says dehum right on the connection haha.

 

[pbyrond]

I have a similar question to this so thought I'd try to resurrect this. We have an Armstrong furnace with Comfortsync communicating thermostat. The installer connected both wires from the flow-through humidifier water solenoid to the "Hum" terminals on the furnace. The humidifier never runs even though the thermostat says it should be.

I found this wiring diagram in the manual and it looks to me like one wire from the humidifier should be connected to "C", and there should be a jumper from "W" to one of the "Hum" terminals. I'm fairly handy with DIY and wiring etc but I don't want to screw up either! Does my fix sound correct?

I assume the two Hum connections are just both sides of a switch that is controlled by the humidistat, and so need power to one side (either 24v or 120v depending on the type of humidifier being used). I confirmed that the humidifier is enabled as an equipment option in the comfortsync setup screen.

image to follow...

 

[pbyrond]

Guess I'm too new here - can't post a link to the image
I saved it to my album instead