Humidity control in Sump Room

[ellisz]

I have a 300+ system up and running. I have a 100 gal sump, 33 gal refugium and a 100 gal frag tank behind my 180 gal display. I have a 85 gpd dehumidifier that can get my humidity down to 43% but due to the settings on the unit, it has to run continuously to do it. If I use a lower setting, it maintains 53%. Temps at 53% are 73 and temps at the 43% are 79.

I do have a return vent cut into my HVAC unit to help suck some of the humid air out. I also have a 4" vent fan that I use to blow air out of the house.

Would it help to cut another return? The sump room is about 10'x30' and is unfinished. I never really noticed a big difference after I cut the return in. I do keep my house fairly warm during the day so I wonder if my AC is not running enough? I can cut another return but due to the layout, it would be about 3-4ft from the other one unless I extended it with some flexible duct work.

Any ideas? I just want to keep the dehumidifier from running 24/7 and to keep the humidity to 45% or less.

 

[T Man]

Howdy ellisz, I would recommend that you add an additional supply run instead of return. Reason being ( I do not know what your particular AC system is set up like) but the effects of allowing humid air into a return air is... that if the ductwork is lined with insulation on the inside, there is a good chance that it will harbor the humidity and eventually lead to mold problems. If it is wrapped with insulation on the outside of the duct, there is the long term possibility of rotting the metal on the inside. And humidity, especially from saltwater is highly corrosive to the heat exchanger.
Another problem being that the humidity will also carry the fishy odor throughout the house, this is the reason there is no return pulled from kitchens, bathrooms and bedrooms- city and national codes mandate as such.
I recommend that you add the supply run and add a louver with a backdraft damper on it either in a window or through a wall to the outside of the dwelling. Another option is to control the climate in that single room independently with a window air conditioner in combination with the relief air louver I described above. I hope this helps some. TinMan

 

[ellisz]

My supply and return lines are all in the same area as the sump right now. I am planning on separating the sump room from the other room but I have had it like this for 2+ years. The lines are all sheet metal. There is not any insulation on the inside or outside of these lines.

I could tap the supply and a louvered vent. I figured this would help with heat/cooling but was not sure that it would do anything with the humidity. I actually got the idea of cutting a return in from a post in this forum. Was this not a good idea?

There are no windows in this area as it is in the unfinished area of my basement. I did cut a 4" hole in the brick a few years ago to run an exhaust vent. I have a 6" duct fan hooked up to it now.

Thanks

 

[T Man]

Generally unfinished basements by themselves are naturally humid and difficult to control - the addition of your tanks compounds the problem. It is not a common practice to pull return from basements either, if this is the only return in the dwelling I suggest that you block it off and pull it from the center of the dwelling upstairs. If you think about it, the return air in the basement is being sucked in and blown out in the same area and nothing more.
I will just go ahead and say that, yes it is wrong to pull humid air for return. If you want to verify this- it is in the Universal Mechanical code book available at libraries.
Stick with the supply run and consider the addition of a couple more of those vents that you have to the outside for relief. TinMan

 

[ellisz]

Let me add some more info. The basement is finished except of the sump room area. There is heating and cooling in all areas except for the sump room. I have 3 returns in the finished part of the basement. Here in the Midwest, finishing basements is pretty common. I have a walkout area of the basement but the sump room is not near this.

Currently, the AC pulls the humid air and sends it through out the house. The unit that it feeds supplies the finished basement and the rooms upstairs. On my last house, I actually had a humidifier on the HVAC unit. Winters get pretty dry. I figured this would be similar?

The dehumidifier can handle the room size as it will get the room to 43% but the meter is not able to be fine tuned so I cant dial in the humidity I want. I might just sell this one and get one with a digital dial. From an electricity standpoint, I would like to have the dehumidifier run a little less.

 

[Central Oregon]

Might want to give an HRV a shot in your situation. It would be cheaper to run than the Dehumidifier, because they are simply a small fan and a heat exchanger. At work I've did a few houses with indoor humidity problems ( pool or hottub ) and we used a large HRV to deal with the moisture. The fresh air also is a nice bonus. If you can mess with your heating system and add a return you can install an HRV yourself., they are simple and include instructions. Currently my work uses Trane ERV's, Life Breath, and Venmar units. All seem well made except the residental Venmar units they are plastic cased and look like toys compared to the other two.

 

[ellisz]

I will take look at these. I don't know anything about them.

 

[slandis3]

Where is a good place to get a HRV system?

 

[Central Oregon]

Not sure sometimes they are available on EBAY for good prices. The Trane Units are nice but you probably have to get one from a Trane Dealer. But I would call a HVAC contractor in your area to get info and prices. Then you can search Ebay and the internet without getting ripped off on price. A quick Google search will give you tons of info on these units, basically they exchange inside air for fresh outside air and transfer some of the heat between the incoming and out going streams. The life breaths have a drain to dump condensation and are probably the best choice for our use. Most of the advertisements I've seen show the inside of the Life Breath units.

 

[prugs]

I use this dehumidifier.
http://www.iaqsource.com/index.php?module=product&prod_cat=0&prod_mfg=3&prod_sub_cat=0&prod_id=25

 

[asnatlas]

Check out this thread...

Large Tank IN a Basement-Ventilation Suggestoin Please oh brethern of the mamoth tank