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post #1 of 57 Old 07-12-2004, 03:34 PM - Thread Starter
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My basement seems to hover between 65% and 70% humidity in the basement, and 60% to 65% upstairs.

The AC cooling coil should dehumidify the air - and I've been playing with fan speed settings and things trying to acheive 35 to 40% relative humidity.... because above 40% and you invite mold and creepy critters - below 35% and it's sore throat time.

If I run the furnace fan 24/7 (so the fan is always on at 38% CFM) then the humidity goes up 5%. I think that water sits in the tray in the bottom of the furnace evaporator coil between AC cycles, and the fan evaporates it back into the house. So I'm not running the fan all the time anymore.

My air conditioner removes about 30 liters (63 US pints liquid) per day of water, as measured by a bucket. Temperature is currently set at 23C (74F)
I also run a cheap noisy portable dehumidifier in the basement for 8 hours a night that removes another 5 liters per day (10 US pints).
I have an air-to-air-heat-exchanger which is supposed to remove some humidity, but I'm not sure it does anything. Right now the humidity outside is 66%, and the humidity inside the basement is 64%.

My local HVAC contractor recommended a more efficient coil in the furnace, but I don't think that's going to help enough. They also suggested a smaller air conditioner, which would work fine this month, but it always gets much hotter outside, and inside, in August/September than it is right now, so I think the AC is sized correctly.

Temperatures by month can be found here:
http://www.city.hamilton.on.ca/BUSIN...on/default.asp

Yesterday the outside temperature was 32C and the inside temperature was 22C without any strain.

They set the furnace to 1st stage 730cfm and 2nd stage 1130 cfm. At this speed it puts out a stream of water out the drain hose that's about 1/8" in diameter. I changed it a couple weeks back down to 1st stage 595cfm and 2nd stage 850 cfm. At this speed it puts out a stream of water out the drain hose that's about 1/16" in diameter. But at the lower fan speed it runs longer and seems to remove more liters/pints per day.

The AC is a Lennox HS29-24. I think the 24 is 24000 BTU, hence 2 ton. SEER 12.95. It came with a new evaporator coil and new lines (liquid and vapor) between the outside and inside. One is 1/4" and the other is 1/2". There's a filter on the line. But more interesting is a freon valve that regulates the amount of freon based on the difference in temperature between the liquid and vapor lines -- apparently this helps SEER efficiency.

The difference in temperature between the return air and the forced air is more than 20F. That is, when the return air is 65F the forced air is 40F. I stuck two meat thermomiters into the ducts permanently so it's easy to check (not accurate down in this range I'd bet, but close enough for subtraction). As an experiment I turned the AC down to 19C -- any lower and I'd be worried that the forced air would drop too close to 32F -- no problem for the AC and I had to put on a sweater which was amusing but I turned the thermostat back up to a more normal temperature.

As a potential solution to my humidity problem, I've been thinking of ordering a Santa Fe portable dehumidifier (100 pints per day, $1081US + shipping etc) (not the RX) from these guys
http://www.thermastor.com/DesktopDefault.aspx?tabid=271
Or alternatively having my hvac contractor install a Ultra-Aire 150H dehumidifier (150 pints per day, estimated $3200 US including installation) from the same people. Word on the internet is that these are good units.

Since dehumidifiers heat the room a bit, the AC would also run a little more when it's humid. It's my hope that in the warmer dryer August/Sept that the dehumidifier would not run at all and that the AC would do the job.

What do you think? Is it enough pints? Is this the way to go, or is there a better way?

House is approximately (10m x 5.6m x 7.5m, or 420m^3; 33' x 18' x 25', or 14850 ft^3)

Here's another gaget that's compatable with my furnace as an optional extra
Quote:
CCB1 EfficiencyPlus Humidity Control (Optional)
Electronic control (35H00) installs next to room thermostat, allows selection of desired indoor humidity level during cooling mode.
During heating season control is inoperable.
CCB1 controls indoor humidity by changing indoor blower speed and compressor speed (two speed outdoor units)
Humidity level is adjusted with vertical set point slide on scale of 40% thru 60%, 50% recommended setting.
Five indicator LED’s in a bar graph configuration (MIN – MAX) indicate difference in actual relative humidity and set point, indicates demand imposed on system equipment, more lights on, the longer equipment will operate to obtain desired humidity level. No lights on, humidity is at or below set point.

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post #2 of 57 Old 07-12-2004, 05:43 PM
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I work with electronics and we try and keep the lab assembly rooms between 40% & 60% RH. Anything below 40$ and you are inviting Mr Electron and his friends to not play nicely with your equipment. Above 60% and you get mildew. The biggest cause of mold/mildew is moist stagnant air. Even if you go near 60%and the air is moving and being filtered..it should remain relatively safe. In general we try and keep around 45-50% in lab since it is very comfortable.

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post #3 of 57 Old 07-12-2004, 07:18 PM - Thread Starter
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Hi Trepidati0n:

I agree and concur that between 45% & 50% RH is what I want. :)
My question is how to accomplish that.

Since I'm going to be building a relatively soundproof home theater, possibly with three layers of gypsum on one leaf, I'll have stagnant air in the wall space. So I need to defeat the humidity before I can start building.

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post #4 of 57 Old 07-12-2004, 10:41 PM
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Be careful at 60%. This is the magic number where rust forms. A lot of sheet metal inside your HT gear is steel and while anodized, the edges where sheared are not and will rust. The rust can spread under through the anodozied layer.

40% is optimum. Less than 25% invites static problems. The way humidity is controlled in commercial applications is electric re-heat. The air is chilled down below a comfortable level and re-heated. As you can guess this process is not very energy saving politically correct.

A poor mans alternative to such a system is a space heater in the HT. This will kill some of the humidity as well as force the AC to cool longer thus removing more water from the air. But you will pay for it. At least the space heater is quite unlike a dehumidfier.
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post #5 of 57 Old 07-13-2004, 03:47 AM
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LOL... as far as a space heater goes, I've got at least three of them in my HT: the projector (~250w in operation), a tube preamp and a tube power amp. And all those other pieces of equipment pile on too - Tivo alone dumps another ~85w into the room.

Seriously, isn't the answer a somewhat more efficient dehumidifier?
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post #6 of 57 Old 07-13-2004, 07:43 AM
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I've got a standard standalone dehumidifier that sits in the storage area of the basement and dumps straight into the sump. I keep all of the doors open - including the theater space - and it works great. Humidity stays in the low 40s.

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post #7 of 57 Old 07-13-2004, 08:46 PM - Thread Starter
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What kind of dehumidifier did you get?
Another brand I've heard some good news about is the 65pint a day Maytag M7DH65B2A.

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post #8 of 57 Old 07-13-2004, 11:06 PM
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Quote:
Originally posted by BasementBob
What kind of dehumidifier did you get?
Another brand I've heard some good news about is the 65pint a day Maytag M7DH65B2A.
The small portables are a pain unless you direct connect the drain. Assuming you can do that have you considered just buying multiple of those. Above you mentioned $1000 and $3000 solutions and it looks like the Maytag is about $300. You may be able to get away with 3 and then use only 1 in the not so humid months (rotating them each year). Just a thought at 1am...zzzz

Consider ones like this one ( http://www.store.yahoo.com/air-n-wat...idehodeby.html ) that has features like:

- Soft-Touch Electronic Control Panel <-- nice
- Displays the room humidity <-- nice
- Four Humidity Settings for 60%, 50%, 35% and Continuous dehumidification
- High and Low Fan Settings
- Auto Defrost (De-icer) <-- nice
- Automatically turns off when it is too cold for the compressor to run well
- Washable air filter that is easily removed for cleaning

Scott Fauque (F200) - - - Fauque's PMT (Personal Movie Theater) (as of 26-Nov-2001)
Good timber does not grow with ease; the stronger the wind, the stronger the trees. -- J. Willard Marriott
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post #9 of 57 Old 07-14-2004, 04:19 AM
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I have a Fedders 65 pint which sounds like the same as the Maytag, similar model number. I've seen some at Home Depot that look the same. I think they are Maytag, but are probably made by the same manufacturer.

Works fine. You can empty the bucket or hook up a line to empty directly into the sump. I have been doing the same as Randy, keeping the doors open when not in use.

Paul
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post #10 of 57 Old 07-14-2004, 05:22 AM
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Don't know the brand - I've had it for years - probably something that came from Sears or Home Depot.

Randy

 
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post #11 of 57 Old 07-14-2004, 08:32 AM - Thread Starter
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I have a little dehumidifier right now. the 28 pint per day Simplicity Dehumidifier (from Canadian Tire). It's obviously not doing the job. It certainly doesn't remove 28 pints a day. It's more like 2 liters (4pints) per 8 hours at 23C/73F.

The $1000 Thermastore Santa Fe's advantages are more pints per day, it actually has published ratings of pints per day down to 55F (as opposed to saying that it still works there), and the biggie is that it "is also ultra-efficient, removing two to three times more water for the same cost as operating a standard residential dehumidifier". "If there is a 65-pint load per day in the house, it will cost approximately $20 per month to operate the Santa Fe to remove this amount of water. In comparison, it would cost about $59 per month to remove the same amount of water using one 25-pint and one 40-pint residential dehumidifier". "First and foremost, two fifty-pint residential dehumidifiers do not equal the water removal capacity of one Santa Fe in a basement application. The Association of Home Appliance Manufacturers (AHAM) rating system used for dehumidifiers reflects the performance at 80F and 60% RH. It is a mistake to assume that equal performance at these conditions means equal performance in the cooler conditions present in basements. In fact, all of the residential dehumidifiers that we have found, even those that contain a defrost feature, do not recommend operation below 65ºF and in some cases 70ºF. The performance of typical residential dehumidifiers at these temperatures is minimal, if they function at all. The Santa Fe dehumidifier is designed to operate in temperatures down to 55ºF and will still remove over 60 pints a day at 60ºF and 60% RH. "
So, it works cooler, and costs less to run (payback interval). Who knows how loud it is. Getting it fixed if it fails will be a problem here.

The Maytag was recommended by someone I was talking to as being something that they replaced an unsatisfactory one with. Also at
http://www.epinions.com/pr-Maytag_M7...A_Dehumidifier it says it's 64 decibels @ 4', and there are lots of negative comments about Kenmore, Whirlpool.

The one ScottF200 recommended above is quieter at 52db (who knows how far away), but I can't find any comments about it from people who've used it as to its effectiveness.

I don't remember which dehumidifier it was, but I found a comment somewhere that it was a 'good humidifier' because the top was flat and he could put a coffee cup on it. Ahem. :(

My plan is to stop by Home Depot and see what they've got and try it. It's returnable. If that doesn't work, then I'll try the Santa Fe. There's no local distributer, so there may be customs issues in addition to the cost.

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post #12 of 57 Old 07-14-2004, 09:13 AM
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Y'all are talking about how to get rid of the moisture once in the air.

How 'bout figuring out where it's coming from and putting a stop to it? (Or is your ambient that high?)

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post #13 of 57 Old 07-14-2004, 09:24 AM
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Quote:
Originally posted by DMF
Y'all are talking about how to get rid of the moisture once in the air.
How 'bout figuring out where it's coming from and putting a stop to it? (Or is your ambient that high?)
My guess...from Bob's original post: "Right now the humidity outside is 66%, and the humidity inside the basement is 64%. "

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post #14 of 57 Old 07-14-2004, 09:37 AM - Thread Starter
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I've got some aluminum foil duct-taped to the wall and the slab at the moment. I want to leave it for a few more hours to see if it's coming through the concrete. (i.e. if it's moist/wet on the foil after I remove it)

It's very humid outside (more than 80%). Inside it's 67%

Obviously I don't know where the humidity is coming from.

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post #15 of 57 Old 07-14-2004, 12:06 PM
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"Right now the humidity outside is 66%, and the humidity inside the basement is 64%. "

That doesn't tell you much without knowing the relative temperatures.

Modern houses have little air entering from outside (unless you cycle the door a lot). A couple passes through the A/C and much of the moisture will have been removed.

Assuming that it is hot outside (the A/C is running), then 75' @ 67% inside is already a lot drier. It could be fed by outside air.

Here's a test: first thing in the morning, check the inside humidity. One assumes that there will be a minimum of air exchange overnight, so the inside humidity will be much closer to equilibrium. (Of course, the A/C won't be on so much either, but net trend should be toward equilibrium.) If it isn't much drier in the morning, I'd say you have an internal moisture source.

(Assuming also that the basement air is being processed by the A/C...)

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post #16 of 57 Old 07-14-2004, 12:14 PM
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Concrete is a very porous material. It will sweat in the summer and freeze you in the winter. Everything around my house is clay so I imagine my exterior basement wall is damp most of the year. My house was built in 62 so I also imagine building products and technics were not as good as they are now. We had an addition put on last year and I got a chance to see some of the existing foundation. There was no gravel or tar on the existing foundation. There was weeping tile although I imagine with all that clay it probably doesn't do a very good job to redirect the water.
I've put plastic vapour barriers on my walls and basement floor to help keep the moisture down. In-fact my basement these days seems quite livable.
I'm also thinking about looking into a sealant for my basement floor in my utility room.
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post #17 of 57 Old 07-14-2004, 01:39 PM - Thread Starter
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Quote:
That doesn't tell you much without knowing the relative temperatures
Of course. Outside it's 25C at 82%, inside it's 22C at 67% in the basement. The AC is not running very much right now, perhaps 5% of the time.

Tomorrow the HVAC company will be leveling my furnace evaporator coil because I believe the tray is retaining water due to a tilt away from the drain spout (bad for humidity, bad for bacteria). They will also be installing a humidistat control called Lennox Signature Stat. This will replace my existing Honeywell thermostat.
http://www.sunbeltair.com/PDF/Lennox...natureStat.pdf
Approximate cost of the SignatureStat is $450 CDN.

I went to the local Home Depot, and they were sold out of the Maytag 65 pint dehumidifiers, and they don't carry anything larger. So they checked the computer and phoned a Home Depot in the next city over and they had one in stock. So I drove there. The orange blazer dude in the asyle said "I don't know who you were talking too, but we sold the last one of those yesterday. We're getting some more on Monday. Would you like me to check stores in other cities for you?"
I'll wait till Monday.

Oh. I did the foil test where I duct tape a 1'x1' sheet of aluminum foil to each of the concrete slab and the concrete foundation wall and leave it for 24 hours. I left it for more than that, perhaps 28 hours. I removed it a few minutes ago and it was dry. Not just no beads of water, I mean dry to the touch. Dryer than my desk. Dryer than the stack of paper in my printer. Dry. Not arid like the desert, just relatively speaking it seemed dryer to the touch. Silly me, I should have compared the two sides of the aluminum foil for dryness, but I didn't do that.

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post #18 of 57 Old 07-14-2004, 02:05 PM
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is your system closed and not sucking outside air?

also, have you tried to put the thermostat cooler to 72-F (to allow the ac unit to run more) and measured humidity? that would determine if your AC unit is capable of lowering humidity, as 74-F is pretty warm imho for central AC on hot humid days.

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post #19 of 57 Old 07-14-2004, 02:14 PM
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Quote:
Originally posted by BasementBob
Approximate cost of the SignatureStat is $450 CDN.
$450 (even canadian) for a thermostat? It better make pancakes and coffee on cold mornings for that price.
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post #20 of 57 Old 07-14-2004, 02:18 PM - Thread Starter
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Quote:
is your system closed and not sucking outside air
The AC gets its air from the returns inside the house.
I have an air-to-air-heat-exchanger (heat recovery ventalation) unit which exchanges air with the outside.
I have 1 hour timer fans on all my bathrooms/showers, which dispose of the humidity after a shower, and presumably suck outside air into the house through various cracks throughout the entire structure.

Quote:
also, have you tried to put the thermostat cooler to 72-F (to allow the ac unit to run more) and measured humidity? that would determine if your AC unit is capable of lowering humidity, as 74-F is pretty warm imho for central AC on hot humid days.
I turned it down to 19C/65F one day just to see if it would cool the house that low. It did. When I put on a sweater in the summer time I thought that was a rediculous waste of energy and turned it back up. I didn't check the humidity when I did that.

Inside my fridge is 5C/40F, at about 35% humidity.

Using the AC for humidity control obviously only works when it's running. And using AC for humidty control works better with a low fan speed. You want the AC running all the time, with just enough cool to keep the temperature that you want, and that combination will give you maximum humidity removal. Hence the new SignitureStat. It should let the AC run a bit more at a low fan speed. It's probably only another 5% of humidity removal efficiency, so it's really a $450 experiment. But we'll see.

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post #21 of 57 Old 07-14-2004, 02:22 PM - Thread Starter
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The $450 includes installation. I was expecting $200, but right now I don't care. The humidity is stoping me from building an HT, and it's distracting me from my office work.
I've already spent a ton moving the furnace and all the ductwork, replacing the furnace, replacing the AC, so what's another $450. :(

I have a robotic vacumme cleaner, and a coffee maker with a timer, but nothing to solve the pancake problem yet.

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post #22 of 57 Old 07-14-2004, 05:48 PM
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i hear you :)... but i would try going from 74 to 72F (as opposed to 65F) for 24 hours and remeasuring humidity, to determine how effective your air handler is at pulling out the humidity.

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post #23 of 57 Old 07-15-2004, 07:26 AM
 
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I have a similar problem and I was advised to put a return air grill in the basement. I have AC supply vents in the basement and no return. :(

I haven't tried yet, but it makes sense that it might move more basement air across that coil to dehumidfy it.

I have hesitations though that a return in the basement may take some "suction" away from the upper floors where I really need it for cooling.

Maybe I'm wrong and this system balances itself out.

Anyone using returns in their basements?
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post #24 of 57 Old 07-16-2004, 06:15 AM
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I have 3 returns in the finished portions of my basement - one in the HT, another in my office, and the third in the kids' playroom. The finished space in my basement measures around 600 sf. I haven't found that the increased amount of return air has had any negative effect on either of the existing 2 zones in the rest of the house. In fact, prior to having the HVAC work in my basement done, the HVAC guy tested the static pressure in my ductwork and found that it was lacking in return air volume. He told me that this is pretty common in new construction homes (less than 6 or 8 years old).

My basement is on the same zone as the first floor of the house. When the temps outside aren't high enough to get the first floor to call for cooling, the humidity in the basement definitely rises. In the last couple of weeks, it has climbed to about 60% in my HT. When that happens, I drag out the dehumidifier and let it run overnight (cheaper kWh's between 9:00 pm and 9:00 am for me here in NJ). By morning, the humidity is generally down to around 35% and stays that way for a couple/three days or so. When the humidity rises again, the cycle repeats...

Good luck,

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post #25 of 57 Old 07-17-2004, 01:22 PM
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Bob:

Unplug the HRV and re test for humidity. more than likely the HRV runs continuosly even if the furnace fan is not running, and it probably only circulates air inside six feet of the return duct in the basement. Are you sure that this an HRV and not a ERV? Check the HRV drain is it removing any water? HRVs and ERVs only remove moisture in the winter. They tend to bring it in, in our summer climate. By the way whats the humidity like in the rest of the house. Is the floor sealed?

Bill
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post #26 of 57 Old 07-17-2004, 03:02 PM - Thread Starter
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uxbridge

I don't know if it's an HRV (Heat recovery ventilator) or an ERV (energy recovery ventilator). It's got four pipes, that go through a 1' cube heat exchanger that looks like a bunch of coregated cardboard except it's made of plastic. You're right that it's attached to either end of a large return air duct in the basement, a little more than 6' apart.

I tried unplugging the HRV a few weeks back, and it didn't seem to make much of a difference. I haven't seen any water out of the drain hose from the bottom of the HRV this summer. Right now it's running.

Next floor up is 5% lower RH.

An amateur built the Ark. Titanic was built by professionals. Of course Noah took a little advice.
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post #27 of 57 Old 07-17-2004, 05:33 PM
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Have you folks looked into this solution? Air movement is eveything. It works well in my cabin up north..sort of pricy to get installed but is only a 150 watt draw when working....this solution may be too KISS

http://humidexatlantic.com/humidex_models_
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post #28 of 57 Old 07-18-2004, 07:25 AM
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Its not at all clear to me what the difference is between this and an ERV/HRV??? They both seem to be air exchangers and nothing more...
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post #29 of 57 Old 07-18-2004, 11:14 AM
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Actually the exchange units should be removing moisture from outside air in the summer. Outside air (high temp with moisture) is brought into the house passing thru a heat exchanger. Inside air passes through the exchanger (on it's way out of the house) cooling the outside air. Cooling the outside, humid air would cause water condensation to be drained off. How much, and if, would depend on relative humidity and temperature drop.

http://www.aprilaire.com/category.as...1DBB024BF068FA

http://www.guardianplusairsystems.com/docs/commonsv.pdf

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post #30 of 57 Old 07-19-2004, 09:20 AM
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What you describe is very common and is typically accomplished with re-heating the cooled air. You will need a control system that is capable of measuring humidity and activating de-humidification cycle - like honeywell PC-8900, but with all sensors and parts it's pricey. Additionally, you will need a real de-humidifier or air handler with heating coil in it.
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