Whole house Dehumidifier Install Question

[donkeykong]

Hey Guys . I got a question about installing a whole house Dehumidifier Aprilaire . I followed directions but the 8" round duct I have connected to it gets real hot .I have it pulling from the main Duct intop the Dehum arrow pointing towards Return of Furnace .. I have the correct length of round duct from main duct and from the Dehum to the Return .. Am I doing something wrong or is the 8" Duct suppose to get hot ? How do I know this is working properly ..anyone have experience putting these in ? this is my first one ..Please Help anyone Thanks .

[ddettlaff]

The dehumidifier will add aboult 1/2 ton of heat to the system, so the outlet air will be about 20F warmer.

In most installations the dehumidifier pulls from the return and pushes into the supply. This prevents the dry dehumidified air from re-evaporating any moisture off of the coil.

In addition the dehumidifier's onboard control may read an odd dew point if the air conditioner and dehumidifier are on at the same time. the unit may or may not run because of that dew point reading.

Doug

[2heat]

In other words, if the Furnace fan is running and there is a call for dehumidification, the dehumidifier's internal fan will overcome the tendency for the air to want to flow from the supply side, backwards through the dehumidifier to the return. Is that a correct statement????????

[adrianf]

In other words, if the Furnace fan is running and there is a call for dehumidification, the dehumidifier's internal fan will overcome the tendency for the air to want to flow from the supply side, backwards through the dehumidifier to the return. Is that a correct statement????????

Yes up to rated static pressure. The unit comes with ok installation instructions which I believe call for a n/c damper on the discharge air side when ducted to A/C system.

[skippedover]

So why are you even running a whole house DEhumidifier in the furnace heating mode? Most people need to ADD humidity to the air when heating and removed humidity (moisture) during the cooling season. What gives?

[adrianf]

So why are you even running a whole house DEhumidifier in the furnace heating mode? Most people need to ADD humidity to the air when heating and removed humidity (moisture) during the cooling season. What gives?

That's a darn good question. Living in a swamp that went right by me.

[skippedover]

That's a darn good question. Living in a swamp that went right by me.

Okay but don't you keep the swamp outdoors? Here's my confusion. :confused: When air is heated (furnace running) it's ability to hold mositure increases. So normally, when you heat the place, it dries out. Now from doing blower door tests and being educated in the realm, I know that if a home is very tight, a family of 4 is frequently able (not in a starter mansion but a normal sized home for a family of 4) to provide enough humidity to satisfy the home needs through showering, cooking, breathing, etc. Most homes leak more than that so the clients need humidity added because they're bringing in cold air and heating it. So is the problem that you're bringing in cold, swampy, moisture laden air and it's almost fog when it comes in so even heating the air won't decrease the moisture content to 50%?? :eek: Have you actually measured the RELATIVE humidity level in the home? Just curious. :confused:

[adrianf]

Skippedover

I think you have me confused with the op. We don't have much use for furnaces in Southwest Florida.

[dan sw fl]

Pretty weird when a seven-month old OP thread gets resurrected.

[adrianf]

I'm posting to get my 30 posts so I can be a professional.:D So I'll post just about anything with minimal discrimination.

[2heat]

Sorry, my question had nothing to do with running in the heat mode. Let me restate the question:

If you set up the Aprilaire whole house dehum to turn on the "A/C / Furnace" fan when there is a call for dehumidification. Will the dehumidifier's internal fan overcome the tendency for the air to want to flow backwards from the supply side, through the dehumidifier, and then back to the return.

The installation book shows that as one of their correct installations.

It just seems odd. Like it would be some kind of blower force fight.

[adrianf]

The dehumidifier will work as designed as long as installed properly. The static pressure has to fall within the unit's capability. see post #4

[skippedover]

The dehumidifier will work as designed as long as installed properly. The static pressure has to fall within the unit's capability. see post #4

Sorry 'bout the earlier confusion adrianf. I agree with this posting. Install it as shown and it will work. You may need a damper if it's only operating during one season as there will be by-pass air during operation of the system with the WHD not operating.