DIY Heat Recovery Ventilator ?
 

I don't really need a HRV in the true sense for what they are designed for. I need something to deal with the possible humidity problems from a large tank.

This is my idea...

First my canopy will be sealed off from the air in the room in which it sits. Heat from my lights is dealt with in sump. So I am looking for a way to pull the hot, humid air from inside the canopy to the outside of my house.

I can easily punch a hole in the wall behind the tank, it's sits partially on a outside wall.

The only concern is replacing the air in the canopy as it's being pulled outside.

I could put a vent in the opposite end of my canopy and allow the air to be drawn in from the room but this is basically pumping my expensively heated air outside, not very energy efficient.

So I was thinking about having the air drawn in from outside as well as vented outside, of course in the winter this is going to be way too cold.

So.....

Why couldn't a person connect a pile of dry vent hose together (because they are fairly cheap) and snake them all over the ceiling in the basement thus allowing the new air time to warm from the house temperature? A person could even have the hose coiled up in numerous places to create even more "acclimation" time.

Thoughts???

So your concern is the humidity? What about some type of small de-humidifier built into the canopy? Not sure if there are any small enough to fit into a canopy, but might be worth the look. Who knows...maybe the rescued water from the dehumidifier can be filtered and fed back into the sump as your top-off water.

Either way, you're still paying to heat that air. The air you draw from outside will take a specific amount of energy to heat to room temperature, and that energy will come from your furnance/fireplace/heat pump/cookstove... whatever. Another minor problem is that it will take more fan than you think to push much air volume through any amount of dryer hose -- that stuff is fairly resistant to air-flow with all it's ridges and bends.

Matt's right. Any cold air brought inside and heated is consuming energy.

Well there ya go then, won't work properly. Thanks everyone, time to re-think.

As well as humidity control I would like fresh air circulating above the water.

How much air you talking of moving?

If your talking to move the moisture evapourated would think you could get by with a reality low CFM. Just do what your thinking (vent hole opposite to let in the room air in) and could use a small in-line fan such Princess Auto carries to boost furnace ducts or fab something up with a small muffin fan.

That is exactly what I am talking about, almost a whisper of air would do it I think.

There are two general ways to remove mosture from air.
1) Use a dessicant dehumidifier
This uses a mosture absorbant silica gel to trap moisture from air
2) A (direct Expansion) DX Dehumidifier.
This has a refrigeration cycle that cools a heat exchanger below the dewpoint temperature of the air passing through it. The mosture will condense on the surface (like water condesning on a cold pint of beer) and drop out of the air.

Using a dehumidifier is probably the best way to reduce humidity without having to worry about heating transfered air from the outside. If you wanted to build something from scratch, you can build a glycol run around loop to run during the cooler days, however it wouldn't be effective during the summer (but your air transfer from outside idea might work in in its place)

If this is on an outside wall could you not run a 2" pvc pipe from inside your canopy throu the wall and out side. this would not allow any air into your house and alow the humiditty to go out. all it would need is a small fan for coaxing the humid air outside, and some sort of valve (butterfly/ball) to close this up in the winter.

Yes that is pretty much how I envisioned it, it won't need much movement at all.

I am not as concerned about removing the moisture from the air as I am in removing the moist air all together, moving it outside. I have thought about a coil, still might do something like that too.

Little cost/benefit needs to be done also to guide your solution.

Pushing out a little air with a low wattage fan and the energy cost to heat makeup air compared to the cost of a HRV unit or running a dehumidifier etc.

When my MH are on, I use a muffin fan to blow air up from the basement through my canopy (upstairs) then it just vents to the room (no worries about moisture and have a system volume of ~200g). Figure it probably costs something less than 10 bucks a year.

Electrical cost calculator.

Exactly right. Turn down your furnace humidifer and distribute throughout your house during winter.

If you are refering to my pvc pipe thougt there would be no need to run your furnace period. you said this would be an air tight system right? the fans from your lights might even be enough to move the air out!!!!!!!

Well I don't have any fans on my lights. I prefer to deal with the heat in my sump in the basement, seems easier to me. So all I would have in there is just lights, no ballast or anything. That is another reason I would like a little air movement in there, that and I am strong believer in keeping fresh air circulating over the surface of the water at all times.

I was picturing some sort of pipe, either a pce of PVC with a little 12 volt computer fan built in line or a inline duct fan but I think that would over kill. One computer fan should do it. I don't think it will take much but that is the reason for this post, I really don't know for sure.

i cant see it needing more power than that. also not sure but angleing the pipe may help warmer humid air "UP AND OUT?"

It is impossible to make your hood completely sealed because you would always need an access to feed and add corals etc. so you will have air venting into your canopy and going out side so it would seem pointless to even try and seal the canopy at all!!!

The canopy I have now is sealed off, when it's closed. I anticipate air flow through when it's open. I can shut the fan off if it became an issue.

IMO,
If you live in a cold climate and not on the coast, save yourself a headache and install an HRV. If you search them on here, you will find a couple of dandy threads on them and all the happy aquarists that installed one.

Of course if one lives in an older leaky house then its another story but if the house is well sealed, it requires ventilation.

I,m not sure, how running a dehimidifier is cost effective, esp. when compared with an HRV. They must be one of the most non cost effective ways of removing humidity, although, yes, they work good.

I do know of several aquarists who vent their hoods outside. Some in colder climates have dampers on them to redirect heat into the house on cold days but not sure how that removes the moisture, unless its not a problem. I think if vented out as you described, just some form of air replacement into the room that can be dampered is fine.

Still say in the long run, a HRV is the best way to remove humid stale air and bring fresh air back, {in a cost efficient manner} into a house, in the cold season. With central air, no problems in the hot season.

You are probably right. I do live in a older home that is far from sealed but I intend to remedy that soon.

It will be a little while before I get to the HRV step so I still have lots of questions to ask and things to learn.

If I know me I will just bite the bullet and buy one when the times comes, I like sleeping at night. LOL I am just poking around to see if any one has come up with a cheaper solution.

If your climate is warm enough there to just vent, which is basically an air exchanger, {w/no heat recovery}, some of the west coast guys with large systems had some really good venting designs with pics. And if you're interested in some good HRV threads, I believe I mentioned we had a few dandys. :smile:

How cold do the winters get over there?

During the winter, the humidity may not even be an issue unless you are having condensation at your windows. In this case reducing outside air to a minimum is usually desired as it generally means more heating dollars for your wallet. For typical residential homes, the combination of outside air introduced from your furnace and the inflitration from the building envelope is sufficient for code required ouside air ventilation rates.

For many aquarium keepers that don't run carbon all the time, elevated tank odors, which become more prominant with higher humidity (I'd guess above 50%Relative Humidity) can be exhausted outside from the house.

This creates an issue with beneficial heat lost from the house. Moist air will have a higher heat capacity and exhausting this heat entirely becomes a huge energy waste as the air exhausted outside will be replaced with cold -30degree air entering your house which will need to be heated by your furnace.

Enter the HRV. The Heat recovery ventilator is designed to recoup some of this otherwise lost heat energy by crossing (counterflow) the exhausted and replacement airflows with eachother. During the summer, your temperatures in the house will typically be hotter than outside unless you have inhome air conditioning. This makes the HRV useless, thats why there is a bypass to prevent the two airstreams from crossing during these conditions.

So why the long winded text?

If odours (interior air quality) is your only concern than you have two choices run carbon or exhaust the odor. If you are going to exhaust, then you will benefit from an HRV during the winter but likely not in the summer as you'd probably have to run it in bypass.

If humidity is your only concern, get a dehumidifier for the summer use, and check if mosture is even a concern during winter. Unless you are getting condensation or frosting inside your windows or walls (usually occurs at RH greater than 25-30%) you don't have to run the dehumidifer during winter.

Hope this helps

Reggie