The only terminals that you should be connecting to the dehumidifier from the eim are the Us.

The yellow and blue from the dehumidifier go to the U1 terminals on the eim.

G is for air handler or furnace fan and doesn't get connected to the dehumidifier.

The C does not get connected either - it gets connected to furnace/air handler control board. The dehumidifier has its own transformer as shown in the schematic.

You can't mix circuits up running on two transformers, they must stay isolated.

The U terminals are isolated from the air handler or furnace control circuit. When there's a call to dehumidify from the stat, closes U1 terminals and turns on dehumidifier.

Eventually the thermostat will control Heat, AC, Ventilation and dehumidifier. For now I just want to connect the dehumidifier.
Any advice would be greatly appreciated.

The thermostat needs to get power from the air handler or furnace's control transformer to work.

Do it all at once.

You'll need to go through the programming menu to get it to do what you want it to and there's configuration for heating/cooling, not just accessories.

What make and model thermostat are you using? Is it a honeywell?

 

The only terminals that you should be connecting to the dehumidifier from the eim are the Us.

The yellow and blue from the dehumidifier go to the U1 terminals on the eim.

G is for air handler or furnace fan and doesn't get connected to the dehumidifier.

The C does not get connected either - it gets connected to furnace/air handler control board. The dehumidifier has its own transformer as shown in the schematic.

You can't mix circuits up running on two transformers, they must stay isolated.

The U terminals are isolated from the air handler or furnace control circuit. When there's a call to dehumidify from the stat, closes U1 terminals and turns on dehumidifier.





The thermostat needs to get power from the air handler or furnace's control transformer to work.

Do it all at once.

You'll need to go through the programming menu to get it to do what you want it to and there's configuration for heating/cooling, not just accessories.

What make and model thermostat are you using? Is it a honeywell?

Thanks for the quick and thorough response. What you said makes sense and is very clear and I attached an image of how I interpreted it. The thermostat is the Honeywell Prestige IAQ.



However, temporarily I need to power the thermostat to run the dehumidifier on it's own. I won't be connecting to the Ac or heat to the thermostat for some time and I just want to run the dehumidifier in the basement on it's own now.

 

Connect the C of the EIM and the C dehumidifier together. Then also connect the yellow of the dehumidifier to the R of the EIM just above the C where you have the red line drawn.

Just connect the yellow and blue of the dehumidifier to the U1 terminals.

 

Why bother though when it will have to be changed to run the rest of the system?

Might as well just connect R and C to air handler or furnace right away to power the stat.

 

For just controlling the dehumidifier, do as beenthere suggested. The thermostat and module will get its power from the dehumidifier's transformer.

Once you hook it up to control everything, disconnect R and C from dehumidifier.

 

Thanks again user_12345a and beenthere, much appreciated! Going to connect it tonight.

 

Thermostat is connected and dehumidifier is working fine in basement. Brings humidity down to 45% in basement in no time. First and second floors not so much so time to start tapping in to the HVAC ductwork.


I want to start by tapping into the first floor supply duct and then add fresh air intake. The first floor return and first two branches of supply are at one end of the house and the first branches are right at the beginning of the supply duct off the air handler. Not a lot of room to add dehumidifier supply.



Do I have to add the dehumidifier supply before any branched ducts or can it be tapped into the supply after the first two branched ducts?

 

I think the outlet should go into the return, not supply.

What does the installation manual say?

You may find that just running the furnace fan will distribute the dehumidified air okay without ducting assuming the basement has return air.

 

If you tap it into the return. Then you should set up the thermostat NOT to run it when the A/C is running. As the dehumidifier will increase the ADP and the A/C will remove less moisture while the dehumidifier runs.


If you run the blower all the time, then it has to tap into the plenum. If you don't run the blower all the time, then you can tap it into the supply trunk like you want.

 

I plan to use the alternate install method from the manual tapping into the supply rather than the return. This way the dehumidifier can blow without using the air handler and the dry air won't run over the wet coils.



What will happen if I tap into the AC supply after the first few branches? Will it still distribute properly or or does it have to tie in before the first branches?

 

It still works fine without the A/C or fan running. With the A/C running, the first branches receive only the normal A/C or fan only air.

 

Thanks. I was worried if I tied into the middle of the trunk it wouldn't distribute to all the branches since it is smaller on the end and larger near the air handler.

 

The air will travel in both directions. So all supplies will get some air.

 

Thanks again beenthere! Hope to connect to the supply this week.