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Do you have a DEhumidifier?

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TinktheSprite 5
sdanielmcev 2
Emperor of Kingwood 2
Judas 1
Prolix Raconteur 2
urabunchcats 2
tinnman 2

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TinktheSprite --- 128 days ago -

We save a lot of energy usage here and can be comfy at 77-78 degrees in the home. But sometimes we get up to 65% humidity inside! That is the only reason why we turn down the a/c. Was wondering if a dehumidifier would help? Would it run less electricity than the HVAC? 

Prolix Raconteur --- 128 days ago -

We run 2 of them (2600 SF house), esp in the summer. Makes a huge difference in the "coolness" of the air being moved around and the efficiency of the AC units. This time of year we literally have to empty the buckets twice a day. The plants don't mind! 

Judas --- 128 days ago -

Dehumidifiers create heat. 

TinktheSprite --- 128 days ago -

Yes, there is heat output. But probably not enough to require more a/c I think? Prolix? Do you notice the output of heat? 

Prolix Raconteur --- 128 days ago -

They do kick out heat, esp older models. I think it's offset by the increased cooling efficiency of the dryer air. At least that's my take. The house definitely feels cooler at 76 or 77 with them running versus not running. 

TinktheSprite --- 127 days ago -

I bit the bullet and bought 2-20 pint dehumidifiers at Costco, one for upstairs one for downstairs even though they said it covers 3800 sq feet (our house is NOT 6000 sq ft!!). $159. Not a bad price in comparison to others I have looked at. And cheaper than buying 2 free standing air conditioners. Unpacked it, plugged it in, and it started to work. The house is down to 42% in just 2 hours! And about 3-4 cups of water in the collection bucket. I know my HVAC is working less. Best decision we've made in a long time! There is warm air coming from the top. It's not heat, just warm-ish air. I am sure the ceiling fan is circulating it. Thanks for your input Prolix 

tinnman --- 127 days ago -

An air conditioner is, in fact, a dehumidifier. Your air conditioner removes heat and humidity from the air leaving you with cool, dry air.

If you still have issues with humidity, then you need to look at the central air conditioner in your house and see where the inefficiency is.

A dehumidifier is a small air conditioner. If it plugs into your wall, then it's really nothing more than a window unit a/c and those are very expensive to operate. I think you'll find that the dehumidifier is going to cause your electricity bills to go up.

While your central system is operating less while using the dehumidifier, I think you'll find that you are actually spending more in order to achieve what the central system was designed to do in the first place.

A simple adjustment to your blower speed will solve humidity issues more times than not. 

Emperor of Kingwood --- 127 days ago -

An air conditioner is, in fact, a dehumidifier. Your air conditioner removes heat and humidity from the air leaving you with cool, dry air.

If you still have issues with humidity, then you need to look at the central air conditioner in your house and see where the inefficiency is.

A dehumidifier is a small air conditioner. If it plugs into your wall, then it's really nothing more than a window unit a/c and those are very expensive to operate. I think you'll find that the dehumidifier is going to cause your electricity bills to go up.

While your central system is operating less while using the dehumidifier, I think you'll find that you are actually spending more in order to achieve what the central system was designed to do in the first place.

A simple adjustment to your blower speed will solve humidity issues more times than not.



Yes, yes and yes. 

urabunchcats --- 127 days ago -

Is a slower or higher blower speed better at removing humidity? 

Emperor of Kingwood --- 127 days ago -

The amount of heat and moisture remove by AC is directly related to the surface area and temperature of the evaporator coils as well as the air flow across them. Its a balance, you can't arbitrarily increase airflow across the evaporator without increasing its surface area so that its temperature stays constant. 

urabunchcats --- 127 days ago -

The surface area of the evaporator coil(s) in all of our existing AC systems are set and not a variable that can be easily controlled. (without replacing them) For this discussion let's say they are well engineered and of an adequate size for our homes.

Outside Temp - Obviously can't be controlled - by us anyway.

I have a relatively modern system that allows me to adjust the blower speed a great deal.

How do I go about determining the "better/best" speed to set the blower speed?

Are there pros/cons regarding the different speeds? 

sdanielmcev --- 127 days ago -

There are differing theories on blower speed effectiveness. The one I adhere to is fast speed creates more wind, but less cooling per volume of air. (The air passes too fast over the coils to be effectively cooled or heated.
Probably the most common problem I run into is poorly distributed return air. High ceilings are the worst idea in this climate, with houses being on slabs. The heat gets trapped up there, and expands downward. Since there is this idioic idea that return air vents are usually near the ground, this heat does not get cooled. Even if your vents are in the ceiling, as vents are directional. The vents should be on the wall near the ceiling. 

sdanielmcev --- 127 days ago -

Yes, there is heat output. But probably not enough to require more a/c I think? Prolix? Do you notice the output of heat

A good dehumidifier should be vented to the outside. 

TinktheSprite --- 127 days ago -

We are poor and have one unit for a two story house. The upstairs is much more humid and than down stairs and have always considered a unit up there to control potential mold. Even after emptying 1/4 of the tank last night at midnight. This morning, after 8 hours or so, the units shut off because the water tanks were full. (The banana trees are loving the water!) I know both units are working to clear the air of the initial moisture. Already I can feel the difference @ 40% as the HCAV works together with the units. I hope once most of the moisture is gone, the units can be set on their timers, dropped to a lower speed setting, and run periodically or when I am boiling water,etc.. $159 unit does not vent to the outside but as I said, the heat from it is negligible. Today will be the real test of measuring temperature and humidity. I do know one thing, this is working, getting the lowest humidity in our home ever, and we feel better already! This is an Energy Star product. I hope it doesn't affect our electricity bill as much.

Our HVAC guy adjusted our ceiling vents so that they point towards the outside of the house. He says it would cool the whole room/house better that way. I can't remember his reasoning, (he used to work commercial HVAC) but at the time it made sense to me. I want a new HVAC. Ours is not old-old but 10 years old makes a difference in efficiency and performance. One day we will bite the bullet on that one! But next up, new insulation...

ETA Since DD has moved back home temporarily, I think this will also help her allergies. 

TinktheSprite --- 126 days ago -

Just a note here. Aside from rocking this new dehumidifier, we have a NEST thermostat. Now that the humidity has been lowered, a money saving feature I have not seen before on NEST has appeared. When the humidity drops, NEST activates a feature called "Airwave". Airwave learns my a/c, turns the expensive compressor off (10?) minutes before the target temperature to let the less-expensive-to-run-fan continue cooling. Sweet deal!! So far, we've emptied 2 full buckets out of each machine just today and kept the house at 40%RH. This is a new valuable water source. Can't drink it, but plants are loving it! 

tinnman --- 126 days ago -

The surface area of the evaporator coil(s) in all of our existing AC systems are set and not a variable that can be easily controlled. (without replacing them) For this discussion let's say they are well engineered and of an adequate size for our homes.

Outside Temp - Obviously can't be controlled - by us anyway.

I have a relatively modern system that allows me to adjust the blower speed a great deal.

How do I go about determining the "better/best" speed to set the blower speed?

Are there pros/cons regarding the different speeds?




So...let's talk fan speed. First off, I want to start the conversation by saying that I have had my Class A license in the State for over 20 years. Lots of residential and commercial experience. So, my opinions on this matter are rooted in a big azz dose of been there and done that...for close to 30 years.

In most residential furnaces manufactured in the last 10 years, there is an ECM motor. Electronically Commutated Motor. These motors are set up to deliver a specific cfm requirement, and in some cases, have the ability to adjust to ambient conditions. ECM motors are easy to adjust and must be adjusted to suit the lifestyles of the occupants of the house.

There are also true variable speed motors. These motors run off of DC voltage and can be adjusted from 30% of capacity all the way up to 100% of needed capacity, in .1 increments.

So, there are literally 700 different fan settings that are available in a communicating motor. These settings are controlled by the furnace and the condenser. These two pieces literally communicate with each other in order to deliver the optimum amount of cooling and air. The amount of capacity needed is determined by various inputs. Ambient indoor temp, outdoor temp, outdoor humidity and indoor humidity. The tstat used for these systems will be programmed for a specific temp and humidity level and the system works to meet those needs.

For those that have a simple PSC (Permanent Split Capacitor) motor, your system is not very adjustable. The actual rpm of the motor can be adjusted, but only manually and only by adjusting the motor's wiring. Kind of complicated for a standard do it yourselfer.

A licensed, reputable contractor should be able to do a load analysis, called a Manual J, in order to pinpoint exactly how much capacity and cfm your home needs. This analysis is done room by room. Also, tstat placement is critical for comfort cooling. Putting the tstat close to a return air may not always be the best place....especially if the system needs to run a little longer for humidity control.

So, to answer the original question, I would have a Manual J done on the house to determine overall heat load, capacity needs, and cfm needs from room to room. Once that info is in hand, adjustments can be made simply, and in most cases, fairly inexpensively. 

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