bsmt, unless you chance having water thru ceiling --
& like climbing so you can clean dehum --

boy, I wish our outside RH% was so low!!!

mine is 90ppd & in crawl -- portable --
manual states don't run when ambient < 70F

 

Hello Patrick,

I am a S.Texas homeowner and a big fan of having a dehumidifier, have learned to prefer the house drier than many people. Your climate is *so* different from mine, which has temperature range 77-97 lately with near 100% RH at the overnight low. My Manual J design conditions are 94F with 77F wet bulb, yours are 80F with 68 wet bulb -- much cooler and drier. Under those weather conditions, does it even make sense to expect the AC to do much
dehumidification? This being mid-summer, isn't your AC running fairly long cycles? Or does it rarely run long cycles because of mild weather or oversizing?

In my house in summer, there are long AC runtimes and the AC alone does a good job of humidity removal (the dehu is still plugged in but runs very little). Both AC units are set up to improve humidity removal with lowered airspeeds controlled by the (Totaline 1400) thermostats, one unit is 2-stage where 1st stage runs extremely long runtimes. So I would adequately study the question (via HVAC pro) why your present AC is not doing a good job of dehumidification already.

My own dehu is a Thermastor rated 86 pints/day. It is a standalone located in a laundry room, with the Thermastor's high efficiency not enough heat is given off to make even a small laundry room uncomfortable. Although not tied into ductwork, it effectively reduces humidity in spring and fall throughout the 3400 sqft house. Based on that, another option that works for you may be such a standalone model in the basement. Although your house is larger than the "2500 sqft" that Thermastor generally recommends for its smaller units, that too is a sqft rule of thumb and I tend to think you do not need a larger unit.

You could test out the concept in your environment for a fraction of the price, by buying a cheap 65 pint/day model and running it for a test period. It would emit more heat due to being less energy efficient, but you could use that experience to project what your house would be like with a better dehu. My hypothesis is it would either solve your problem or almost solve it to your satisfaction, and that direct experience would be worth the price of purchase and later re-sale or disposal.

Even Teddy Bear who is a professional advocate of dehus, will point out their greatest benefit is during wet mild weather when the AC is not called for temperature purposes. He is faithful enough to his customer base not to oversell, wish everybody were like that. Would not hurt to telephone Thermastor and discuss your application with them.

Best wishes -- Pstu

 

Thanks for the replies!

Between the basement and the 1st floor there is just one door opening, although in thinking about it more ... If I just put an ~90 pint stand alone in the basement and turn just the fan on the furnace air handler, (supplies 1st floor and basement with the return on the 1st floor), to circulate the air between both floors ... shouldn't this be about as effective as ducted 90 pint unit unit?
Patrick

 

Don't run the furnace fan set to on. That will re-evaporate water on the evaporator coil and raise the house humidity. Try the ducted dehumidifier as a stand alone, if that doesn't do it, tie it into the ducts.

 

Ducting may not have the same importance as it does with heating and air conditioning. With AC, if you don't have airflow it will take only minutes for the conditions to become uncomfortable. With humidity things move much more slowly. That is my reason for being optimistic the standalone dehu will please you with its results. Several of the Thermastor models are designed to be installed either way, you risk little by trying the standalone installation first.

One exception I think: if you can identify a significant humidity source, it seems right to stop the problem at its source and before it spreads. Perhaps the basement might be that humidity source. In my case it seems to be the bathrooms and I have placed a small portable (Soleus brand) dehu in the bathroom for that reason. While I have not tried it, I suspect that a ducted central model would not perform as well for that purpose.

Again, I would want to exhaust the possibility the AC itself may be not performing well. Your relatively high readings in the middle of summer makes me suspect that. But even if so, there will surely be many mild days when the AC won't run and presumably you still will want lower humidity.

My pet theory is it would be nice to design built-in dehus fit into the wall of a bathroom, thus intending to transform it from the dampest place in the house, to the driest place. And per my expectations that would lower the whole house humidity effectively as well. Only wish I had a zillion dollars to try out that theory, I would build identical houses with that one difference and realistically test how it works<g>.

Best of luck -- Pstu

 

Thanks for the assist fellow members. The Honeywell 90 will do the job in your climate. Locate the unit in the basement with an independent return from the 1st floor. Discharge the dry air into the supply of lower level air conditioning. A free stand +90 pint dehu (like Santa Fe) will probably maintain humidity. You may need some fan operation to mix the dry air. Keep us posted. Dehu TB

 

Thanks everyone this has been very helpful!

When installing the Honeywell DH90
Read a good bit about recomendations for the VisionPRO IAQ controler. Although very cool, I already have programable thermastats, (but without control for the DH90).
-Will I need to keep changing the settings on the W8150 controller, (that comes with the DH90), or is it set just once for all year long?
-Is the need for more control having to do with the outside ventilation and is it recommended to add the ventilation option?
Patrick

 

The 9000 is the control center that replaces your Tstat. Properly set up, it will control the correct fresh air ventilation (requires damper kit for DH90) & RH for your home. Do it right the 1st time.

 

I put a 50 pint dehumidifier in the basement and that did the trick! No need for the 90pint ducted one. (Have AC on the 2nd floor and loft and just the air handler on the furance for the 1st floor and basement). The AC was struggling to keep the upper floors at just above 50%, and the 1st and basement was averaging 55-60%. Now with just the added 50 pint in the basement, the whole house is staying at 45 to 48%.
Thanks again everyone for the help!
Patrick

 

Happy for your success. Checked your outdoor dew and you are mid-range right now. The test is with high dew point and wind. Also an issue of durability and energy efficiency. There will be times you will wish for a better, more durable dehu. Next time get a good one. Best regards, Dehu TB