Honeywell IAQ config - DOD not functioning.

[smitty599]

I am trying to double check the wiring setup on my new system that I having trouble with. I want to be able to control humidity by reducing the blower speed and purchased the IAQ with the install to do so. But I'm not having that functionality and contractor says it is correct. Please proof or add comments.


Honeywell Vision Pro IAQ
Trane XL15i straight cool 4TTX5049E1
Trane XV80 furnace TUDC080B9V4
Trane coil 4TXCC060BC3

*Cut jumper 14 on XV80 between R and BK
*XV80 dips selected to disable Comfort R
*Jumper R and DHM1 on EIM
*Jumper O and Y and Ylo on XV80

EIM XV80
C C
R R
RC-na
RH-na
HUM1-na
HUM2-na
DHM1
DHM2 BK
VNT1-na
VNT2-na
W1 W1
W2 W2
W3-na
Y- Y
Y2-na
L-na
G G

Does anything look out of line or incorrect?
Thanks in advance!

[beenthere]

Doesn't look like it wired right. And did the installer set up the sat to do DOD. It has to be told to do it.

[odilla]

I'm told that he did do so. But it doesn't seem to be working. I've looked at the wiring and listened to him on the phone and have gathered the posted notes based off his. I haven't been into the stat myself but he explained as he went and I think he has calculated each setup parameter correctly...but I'm hardly a reliable judge based on my lack of knowledge of this stuff. But when the thermostat indicates it is dehumidifying, there is no response from the unit XV80 which is why I suspect the wiring config I referenced earlier.

[beenthere]

Mis configured, and mis wired.

The wiring you posted, is not correct.

[odilla]

As I suspected, unfortunately. I'll have to find a tactful way of questioning him again without telling his business.

Thanks!

[beenthere]

Did you register under 2 names.

[mark beiser]

Per what you posted, the system is wired correctly.

It is more "correct" to jumper between R and O instead of Y and O, but it doesn't hurt anything, and accomplishes the same function.
It also isn't necessary to include Ylo in the jumpering to O on a single stage system, but again, it doesn't hurt the function of the system.

Make sure they have Installer Setup item #379 set to option #1, "Dehumidify with air conditioning". If it is set on option #2, the blower operation will be the reverse of what it should be.

[beenthere]

Mark. Look at that wiring again. Its not right for the stat to control it as it should.

[mark beiser]

Mark. Look at that wiring again. Its not right for the stat to control it as it should.

They have R to DHM1 jumpered, and DHM2 goes to BK in the furnace, exactly as it should be.

The only thing I see that is not completely "correct" is the jumper between O, Y and Ylo on the furnace, but it isn't causing any problems. The jumper to O is only actually needed if Comfort-R is being used, and the installation instructions call for it to be between R and O.
Years ago they used to call for it between Y and O for single stage systems, or Ylo and O for the 2 compressor systems, but that apparently confused some people, so they simplified it to jumpering between R and O.

I also prefer to leave Comfort-R enabled.

[beenthere]

Comfort R enabled is a waste of energy when the outdoor ambient is about 60% of design. most homes don't need 7.5 minutes of slowed blower time then.

[mark beiser]

Comfort R enabled is a waste of energy when the outdoor ambient is about 60% of design. most homes don't need 7.5 minutes of slowed blower time then.

Around here we usually need a running start at dehumidification when the outdoor temperatures are in the 80's and low 90's, even with dehumidification control.
It is actually when we are at or near design conditions that Comfort-R loses its benefit, and extra dehumidification is rarely needed.

[beenthere]

If the stat is slowing the blower and doing DOD, then how would the indoor RH be high enough to need to use comfort r.

[mark beiser]

I've never put much thought into it before this thread, but yeah, not using Comfort-R when demand dehumidification is available would save a few cents a day without giving up much dehumidification.

Back on topic, I'm curious what installer setup options are set in the OP's thermostat.

[motoguy128]

If the stat is slowing the blower and doing DOD, then how would the indoor RH be high enough to need to use comfort r.


He might be leaving the fan set to ON, he could have an oversized coil and worse and oversized AC unit as well. All 3 combiend, and DOD, won't gain much if the run times are short. He might need to start out at a lower CFM/ton for normal airflow and drop it by 20% from there. A balance of comfort and efficiency.

[beenthere]

He might be leaving the fan set to ON, he could have an oversized coil and worse and oversized AC unit as well. All 3 combiend, and DOD, won't gain much if the run times are short. He might need to start out at a lower CFM/ton for normal airflow and drop it by 20% from there. A balance of comfort and efficiency.


Then the stat will keep the blower slowed for the entire run time. Making comfort r still not needed.

[mark beiser]

To continue the off topic over analyzation of Comfort-R and DOD, if the system was a heat pump, and you wanted to take advantage of the comfort benefit of "hot heat pump mode" in the heating season, you would still need to have Comfort-R enabled.

Of course, you could always use an outdoor thermostat to prevent the indoor blower from doing the Comfort-R profile when it is warm enough out for cooling.;)

[motoguy128]

Some thermostats use the ability to slow the blower 20% for "hot heat pump" mode... so you still might not need Comfort R.