I know you have extensive experience dealing with IAQ and EIM and has been kind enough to give extremely helpful advice on the correct setting for Dehumidify on Demand.

I need your advice to correct set up this with W8835, the better HW zone control board. Obviously, I don't trust my contracor to do it properly. So far, they haven't done it right with TH5421 yet.

From what I get, it should be like this. Please either confirm or correct the following.

- 3 ton Trane Heat pump XL15i with air handler 4TEE3F40B1

- dip switch for best humidity control (use DOD):
normal mode: on-off-off-off-off-off-on-off for 400cfm per ton?
5 & 6 off alone will shut off Comfort-R, right?

- on IAQ: in program install setting
0370 set to 1
0379 set to 1

- Wiring on W8835:
Remove Jumper from DHM 1 / DHM 2 if have any
Remove the R to BK jumper
Jumper R to DHM 1 on W8835
Wire Air Handler BK to DHM 2 on W8835

Anything other steps?

If anyone knows this, please chime in.

Thanks in advance.

As described above the 4TEE3F40 dip switches are correct for 400cfm per ton for 3 tons. 5 and 6 are for comfort R which I suggest turning off if using the IAQ thermostat.

Hopefully I can explain the wiring of dehumidification better using the IAQ,

Since you programed 379 to 1 this makes the DHM1 and DHM2 Normally Closed contacts.

Inside the 4TEE3 you have a BK terminal this should not be jumper-ed to R inside to the air handler rather ran out to the DHM2 terminal on the thermostat to complete the wiring loop.
So Wiring would be inside the W8835 control panel R jumped to DHM1 then from the DHM2 terminal a wire ran back to air handler's BK terminal.
When calling for de-humidification, the DHM1 and DHM2 contact opens and power is lost on the BK terminal causing fan to slow down.

You will use the 1, 2, 3 communicating terminals on the IAQ thermostat and these terminals run back for each zone on the W8835.

There is a test mode in the IAQ I would recommend testing the thermostats out on each one and remembering to exit out of test mode before going to another IAQ thermostat for testing.

I am suppose to do a 2-zones. The framing at 3rd floor attic hasn't been completed yet so for now we are just using IAQ and TH5421 for 2nd floor. Later we will use W8835 with two IAQ for 2 zones. Everything is fine other than the contractor didn't enable DOD, I got the impression he doesn't really understand DOD feature. Everytime I told him I want HW VP IAQ because I want DOD he was like oh pretty much all trane board/or HW 8000 has dehumification features. Grrr!

They will come back in a few weeks to complete the zoning and given that it's difficult to trust them set it right I thought I tap your excellent expertise and prepare for myself.

Anyway, just make sure I understand it right. I draw the following line on the pic and 2 other questions. Correct me if I were wrong.

From t-stat

Btw I forgot to mention I have a 8 KW Aux backup heat strip, at the moment is wired on W1, is this about right?

He told me the Aux Heat strip will come on at 3 degree lower the set temprature. For example, if I set the temprature to 68 F and the current room temprature is 66 F, the heat pump heat-on will come up but if the room temprature is only 64 F, the aux heap strip will kick in first until it reaches 65 F then the Heat pump. Unless I put an outdoor temp sensor I won't be able to "lockout" say only let the heat strip comes on at 35 F. Does this make sense?

Again, thank you so much. I hope you have a great vocation. Your web site looks great and lots of people praise your work. I wish you live in NC.

Air Handler Dip Switches
with 8kw is correct as is
needs 1100 cfm minimum with Aux heat.
7=on
8=off

Trane does have (Comfort R) dehumidification, but it doesn't control humidity and I actually think it can create it with having the fan run an extra 3 minutes when the compressor shuts off.
I like the IAQ, the HW TH8321U has humidity features and is better than comfort R but I always insist on spending a few extra dollars and getting the best thermostat your system can use because it controls what you have better.

Next,
high as in importance is your zone dampers and bypass damper and where they are going to implement the bypass damper.

I would recommend using a pressure controlled bypass damper.
The bypass damper with a counter weight I do not like at all.
I recommend the EWC bypass pressure controlled damper. Their EBD bypass damper uses the LM-24 Bilemo motor. Bilemo motors are heavy duty and are used in commercial applications.

the bypass damper needs to be sized right, by subtracting the cfm's of the smallest zone to the total of 1200cfm you have.

I have to choose which battle to engage as I seem have a more problematic issuse about the ducts that they did.

Here is the pic shows a supply is sandwiched in between w returns, is this very air flow restrictive?

From t-stat

The next pic shows a spaghetti duct work. One bedroom and the master bath down below have had very weak air flow. Is there any better solution than what they have done? Looks awful to me.

From t-stat

What about the following drawing of mine? Will it be better or will it be problematic in some other ways? (i.e. the weights will have a negative impact for all the flex if I hang the supply duct off the rafters like this.

From t-stat

Any suggestion?

-dan

the duct crossover is fair, sometimes it unavoidable and it does not look like it is pinched in a way that would be of real concern.

The suretape that was used is not my favorite I use Nashua or Poleyken foil tape guy.
They did use mastic which is good so the tape or seems will not come appart.

there is no need to lift the duct up.
my concern is they used 10" flex which gives around 400cfm with (6) 6" duct that would require 660cfm. 12" can handle 800cfm and with your zoning I would have went this way.
I would have replaced that whole line and then routed it in a way that it wouldn't be pinched in that one section.

for hanging it, not sure if it would benefit much.
I wish for you they would have just made it look more uniform, (better/cleaner).

The only reason I thought about hanging it, is that the interwoven 10" duct, goes down on the floor and make a slight turn back to connect to the hard duck where the (6) 6" flex are connected. I thought hanging it will prevent a nose-dive angle and make it horizotal straight with where it hooks to the take off from the plenum. Plus, it makes a better connection at where the new alum flex is at - as now, they have to make a huge curve.

I have 3 tons, total 15 registers for downstair 2nd floor (zone 1) and 5 more for the to be finished on 3rd floor attic (zone 2). That's 20 boots all together on 1200 CFM of 3 ton unit. I know each register won't have full flow of velocity but figure each will deliver about 60 CFM. So I thought it will be fine to have this 10" supply flex to hook up with these (6) 6" flex.

From trunk to all registers all I have are 6" flex. Does that mean I have to have a 2000 CFM system because I have total 20 registers and each with a 6" flex? BTW, 3 ton is based on load calc and I hope this will be fine. I'm a little nervous based on what you said.

Was your old system a 3 ton system?
If your load calc called for a 3 ton system then it will be ok. I'm just a stickler when it comes to duct design, but if your old system ran ok before you shouldn't see any difference with it now since your new addition will be a zone of it's own.