Carrier performance variable speed dehumidification

[CoolIsGood]

FV4C V/S air handler and ecobee thermostat.

When the thermostat makes a call to dehumidify, the air volume does not change at all.

This is what the contractor tells me:

The thermostat is configured as such: R (on air handler) to ecobee relay #3 in, ecobee relay #3 out to Dh terminal on air handler. It's just a simple circuit from R to the relay, and then from the relay to the Dh terminal.

As per Carrier documentation, the air handler will dehumidify (reduce fan speed to 80%) when the Dh terminal is DE-ENERGIZED. That means when the Dh terminal has 24v, it will NOT dehumidify.

So during normal operation, the thermostat has the relay closed, and Dh receives 24v. When there is a call to dehumidify, the thermostat opens the relay and Dh has no voltage. After confirming that Dh did not have any voltage, no change in air flow was observed. Jumper J1 is also removed as per Carrier instructions.

Fan speed is adjusted up on the control board from Nominal (350CFM/ton) to Hi (400CFM/ton) for regular cooling. I don't know if this somehow disables Dh.

Any ideas?

[Nytefog]

Doesn't that air handler support the Carrier infinity control? What is the full model number and serial number?

[CoolIsGood]

Doesn't that air handler support the Carrier infinity control? What is the full model number and serial number?

I don't see how your question is relevant to my situation

The FE4 is infinity control. The FV4 is also variable speed but with thermidistat control.

[RoBoTeq]

How are you determining that the blower is not decreasing in volume when the current between R and Dhum is interrupted? You cannot test a variable speed blower with the access panel removed.

[CoolIsGood]

How are you determining that the blower is not decreasing in volume when the current between R and Dhum is interrupted? You cannot test a variable speed blower with the access panel removed.

The access panel was only removed to make sure that the thermostat relay was actually opening and closing and that Dh was in fact being de-energized on a call to dehumidify. After this the panel was replaced and the tech put a probe into the supply to measure air flow and velocity. No change was observed between regular and dehumidify modes.

[HP41CV]

Fan speed is adjusted up on the control board from Nominal (350CFM/ton) to Hi (400CFM/ton) for regular cooling. I don't know if this somehow disables Dh.

Any ideas?

I strongly suspect that you've hit upon the reason here.

Either that, or it doesn't work without an Infinity thermostat, perhaps?

[CoolIsGood]

I strongly suspect that you've hit upon the reason here.

Either that, or it doesn't work without an Infinity thermostat, perhaps?

Perhaps we will give that a shot, even though the Carrier literature says nothing about this happening.

It works with any thermidistat, according to Carrier docs.

[CoolIsGood]

Bump, any ideas?

[ecobee_tech]

The issue here is the ecobee stat is energizing the relay on a call for dehumidification which is opposite to what the Carrier unit requires. Depending on the version of your thermsotat is may require an upgrade (which we can do remotely) or just a simple setting change to reverse the logic.
Have your contractor give us (ecobee tech support a call) and we can help get you up and running.

[CoolIsGood]

The issue here is the ecobee stat is energizing the relay on a call for dehumidification which is opposite to what the Carrier unit requires. Depending on the version of your thermsotat is may require an upgrade (which we can do remotely) or just a simple setting change to reverse the logic.
Have your contractor give us (ecobee tech support a call) and we can help get you up and running.


I have the latest beta firmware update which allows me to specify open or closed relay on a call to dehumidify. The current setting is set to OPEN the relay on dehumidify which will de-energize the Dh terminal on the air handler. The contractor did in fact confirm with a voltmeter that the relay was OPEN on a call to dehumidify and CLOSED for regular cooling.

[DeltaT]

This system and these type of systems have a lot of internal thought process before they make a decision to change anything, including fan speed. Yours may be set up correctly or incorrectly but that can only be found out by going through the entire set-up procedure by someone who is familiar again.

If you are expecting the fan to go to a lower speed once the dehumidification mode is calling, that may not be true as the internal thought of the processor will make the final decision base on other inputs to the processor.

Any testing done by anyone who is not working directly with and in the processor will need to give the system a lot of time before an expected change may be implemented by the processor. It's the process of the electronic design to take in all the information first, wait to see if anything changes, then make a decision to change, stay the same, turn off or turn on a component or the entire system.

Translated, if you are looking for immediate changes it may not be possible due to the very nature of its design. Give the system plenty of time to do it's "thinking" before you state it's not opperating correctly.

[CoolIsGood]

This system and these type of systems have a lot of internal thought process before they make a decision to change anything, including fan speed. Yours may be set up correctly or incorrectly but that can only be found out by going through the entire set-up procedure by someone who is familiar again.

If you are expecting the fan to go to a lower speed once the dehumidification mode is calling, that may not be true as the internal thought of the processor will make the final decision base on other inputs to the processor.

Any testing done by anyone who is not working directly with and in the processor will need to give the system a lot of time before an expected change may be implemented by the processor. It's the process of the electronic design to take in all the information first, wait to see if anything changes, then make a decision to change, stay the same, turn off or turn on a component or the entire system.

Translated, if you are looking for immediate changes it may not be possible due to the very nature of its design. Give the system plenty of time to do it's "thinking" before you state it's not opperating correctly.

With all due respect, I think you are giving the "system" too much credit. The only "thinking" that this entry level V/S air handler does is adjusting fan speed to meet the set CFM. This is the only variable that the air handler is able to calculate on its own, every other command is controlled by another entity. The air handler knows nothing about the current humidity, temp, delta T, NOTHING.

My contractor suspects that the smartboard might be defective. We'll see.

Edit: Also the Carrier documentation does not specify that there is any delay for the fan speed to drop. Would you like me to post a PDF of dehumidify logic sequence?

[SBKold]

Im not a Carrier dealer but have worked on a plenty-

doubt that there is a delay on that dehum call.

Ive definately had this problem before and it usually is because the board was not configured right -

or the control board was not wired correctly to sense cool mode. It thinks it is heating.

[CoolIsGood]

Im not a Carrier dealer but have worked on a plenty-

doubt that there is a delay on that dehum call.

Ive definately had this problem before and it usually is because the board was not configured right -

or the control board was not wired correctly to sense cool mode. It thinks it is heating.

Ok now we are getting somewhere.

I'll have the wiring double checked.

Thanks for your help.

[SBKold]

Ok now we are getting somewhere.

I'll have the wiring double checked.

Thanks for your help.

You are very welcome.

Also ask the contractor if there were any special changes on the board to enable the DH terminal.

[SBKold]

*

[CoolIsGood]

You are very welcome.

Also ask the contractor if there were any special changes on the board to enable the DH terminal.

Jumper J1 was pulled.

[SBKold]

Ok double check that jumper.

There are 2.

We are back now to the board seeing heat mode.

[teddy bear]

Slow the fan to get a 25^F temp drop across the coil. This maxs the amount of dehumidification you can get. You will not get too dry. In fact during light cooling load days with high outdoor dew points, you will be damp inside. When this is unacceptable, get a good whole house dehu to maintain <50%RH during wet cool weather.
Regards TB

[CoolIsGood]

Ok double check that jumper.

There are 2.

We are back now to the board seeing heat mode.

That sounds like a great idea. I will definitely relay the message.

I don't understand how it's even possible for the AH to be running in heat mode when I'm actually getting cold air from the vents. Wouldn't I be getting hot air?

Isn't closing the circuit from R to O the only difference between cool and heat?

[SBKold]

Is O hooked up to a/handler board?

[CoolIsGood]

Is O hooked up to a/handler board?

Yes and according to the thermostat, it is being energized on a call for cool.

[SonicExplorer]

My first reaction was that if you've verified the relay is reacting then the right jumper was probably not pulled. However, apparently you've checked that already.

For whatever it's worth, I just got a 3 ton Carrier system with your same air handler and actually had to instruct the tech how to connect it to work properly for dehume mode since they don't wire very many with my stat. I use a Honeywell VisionPro800 IAQ and everything works fine. By the way, once the relay throws the blower does react immediately, no delay.

Sonic