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Heating & Air Conditioning

Honeywell DR90 Dehumidifier installation

10 years ago

I am having somewhat of a dispute with my HVAC installer. He is very knowledgeable but rattles off information a-mile-a-minute and tells me to go to the internet to read about it. He recently suggested I install dehumidifiers - one in the basement to replace the portable ones I have there and one in the attic, ducted to the AH (Trane) to satisfy my request that we be able to dehumidify when it was too cool for AC but not yet cool enough for heat - those sometimes long, wet, cool springs and autumn months we have in the New England area. He suggested the DR90 but I read that that was sized for a whole house - too large for our basement, so I requested the DR65 for that and the DR90 for the attic AH. Prior to delivery of the equipment, I had some questions about using the DR90 (ventilated to the outside) in place of the ERV we were supposed to get. Long story short, I was told by the office he would answer my questions when he came out to the house on the day of the installation. The workers arrived first and began installation before the boss showed up. In the discussion we had, he bluntly said the DR90 didn't belong in my attic because (1) it was big and loud and (2) we didn't need dehumidification up there - only in the basement. However, since they had begun installation (had unpacked it and put it on the attic floor) I was stuck with it. The only option is to install it in the basement where we do need dehumiification. My question - which has not yet been addressed to my satisfaction by him - is can this model be installed as a free standing unit, without ducting it to the AH. I learned from a different Honeywell distributor that it has to be ducted to function correctly - something about pressure. Is this correct? Are we making a mistake if we try to get it working in the basement? If so, any suggestions for unloading this thing since I have to pay for it (including installation that he's charging) over $3K. I would like to recover some of the cost if possible. It's never been turned on - like new except no box. Thanks.

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Comments (3)

mike_home
10 years ago
Here is a link to the DR90 spec sheet. It shows it can operate without ducts. This would be fine for installation for a basement. How big is your basement and what is the humidity level?

This is a whole house unit so it is a little overkill for a basement, but it should work well. The house will get some benefit by leaving it unducted, but if you really are looking to control the humidity in the whole house then it would be better to integrate it into your duct work. The spec sheet shows several configurations you could use.

Is your attic finished and sealed? If it is not, then I agree installing a dehumidifier in a ventilated and unheated attic makes no sense. I find it curious your knowledgeable HVAC installer did not explain this to you when you first discussed the idea. Did he really suggest you should buy two whole house dehumidifiers?

If he is telling you to look it up on the internet then he is not very knowledgeable in my opinion. It only takes a few minutes to explain how a whole house dehumidifier should be installed.

Here is a link that might be useful: Honeywell DR90 spec sheet
ionized_gw
10 years ago
No, it does not have to be ducted to an hair handler.

Geez, the guy ought to be willing to talk to you if he is taking your money. He should be able to install equipment in your attic so it does not transmit noise to your living space.

The installation manual is readily available on the web. I see nothing that indicates that is must be ducted. It stands to reason that some ducting might increase its efficiency. First, you will have greater air flow from the remote areas of the basement. Second, it is designed to operate with some level of static pressure introduced with the ducts. Air flow decreases with additional duct length. The engineers designed the system to operate within a range of pressures, but there is an optimum. They don't say what that is in the manual. Can that be found out from Honeywell? I don't know, but I bet that is the figure that they used for their efficiency testing.

My question to you about ducting is, can some ducting be introduced in the basement? Is the basement unfinished? Why not introduce some ducts to increase air circulation and slow the air flow closer to the optimal range?

I am concerned that the D90 might be too big for your basement and will not run efficiently. What do you have down there now and how well does it keep the basement dry. We have to keep in mind that more efficient equipment will blow off less waste heat so the area will be cooler if everything works well.

More questions: Attic DH is dehumidifying the attic only, or it is hooked to an air handler that is conditioning the house and not the attic? The third, and less likely situation is that the attic is sealed and conditioned.
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10 years ago
In your other post about the Honeywell interface, you stated you now have a 2-stage AC. Is the the AC not doing a good job of controlling the humidity? Humidity control is one of the key benefits of a 2-stage condenser.

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