Page 1 of 2 12 LastLast
Results 1 to 13 of 18
  1. #1

    Confused Thoughts On A Fresh Air Intake?

    I'm about to move forward with upgrading my original furnace/air with the Carrier Infinity Hybrid System Heat Pump / 96% Gas Furnace, on my 20 year old spec ranch. There is a finished area of the basement that will house a moderately sized (180g) saltwater fish tank, with a supply and return plumbed into the room. It was advised to put in a bath fan (approx 80-100cfm) because of excess humidity. Along with this it was advised to add a Fresh Air Intake into the main return trunk/plenum of the HVAC to avoid any negative pressure from the bath fan running. The bath fan will be on a de-humidistat so it's running time is unknown at this point. Could be consistant dependant on the humidity.

    What's everyones thoughts on a fresh air intake in this application? It will be on an adjustable damper, but will it add significantly to the load of the system?

    I really like the idea of fresh air in the house/system but wanted opinion before moving forward....

  2. #2
    Join Date
    Jul 2008
    Location
    Poestenkill, NY
    Posts
    769
    One option is a little heat recovery ventilator - providing constant exhaust from the fishy room and supplying fresh air to the return of the furnace.

    That's the most "elegant" answer. Honestly - a 80-100 cfm fan producing "negative pressure" in your house? It's not that tight - trust me.

    Or - less synically - don't worry about it - especially if this little fan runs on a humidistat. You don't see mechanical make up air in houses but once in a blue moon. We're talking one air change per "really long time" here.

  3. #3
    Quote Originally Posted by larobj63 View Post
    One option is a little heat recovery ventilator - providing constant exhaust from the fishy room and supplying fresh air to the return of the furnace.

    That's the most "elegant" answer. Honestly - a 80-100 cfm fan producing "negative pressure" in your house? It's not that tight - trust me.

    Or - less synically - don't worry about it - especially if this little fan runs on a humidistat. You don't see mechanical make up air in houses but once in a blue moon. We're talking one air change per "really long time" here.
    That makes sense, thanks. I was originally going to go with a large 190 CFM fan at first. I was talked out of it due to the negative pressure issue. Would it make a difference with a high powered fan like this?

  4. #4
    Join Date
    Jul 2008
    Location
    Poestenkill, NY
    Posts
    769
    Quote Originally Posted by drummereef View Post
    That makes sense, thanks. I was originally going to go with a large 190 CFM fan at first. I was talked out of it due to the negative pressure issue. Would it make a difference with a high powered fan like this?
    I doubt it. Depending on how big the room with the fish tank is - it's a general rule of thumb to remove 6 airchanges per hour (IIRC) to do the trick - so size the fan that way.

    Is it really that humid in the room? I would think with the air intake and return in the room from the main system you would be OK - from an armchair point of view... The humidity would be removed during the cooling season and welcome during the heating season - but the shoulder seasons... Anyway, I think you're over thinking this...

  5. #5
    Quote Originally Posted by larobj63 View Post
    I doubt it. Depending on how big the room with the fish tank is - it's a general rule of thumb to remove 6 airchanges per hour (IIRC) to do the trick - so size the fan that way.

    Is it really that humid in the room? I would think with the air intake and return in the room from the main system you would be OK - from an armchair point of view... The humidity would be removed during the cooling season and welcome during the heating season - but the shoulder seasons... Anyway, I think you're over thinking this...

    I probably am over-thinking/over-building this room. It's in my nature I guess... I would presume, as well, the Infinity Control will really help to keep the humidity within reason. Some of these larger "tank room" setups are known to have relatively high humidity with 250+ gallons at 80F water temp. Probably 60-70+% consistantly. This is of course without HVAC etc. I'm just wanting to cover myself so I don't back myself into a corner.

  6. #6
    Join Date
    Jun 2008
    Posts
    128
    How large is the room? How well sealed is it from the rest of the house? I would suggest an HRV of some sort, but cost wise just a slow speed fan will do the trick to keep humidity under control. Panasonic makes some very nice, quiet fans that are designed to run 24x7. I think the whisper green line is what you are looking for.

  7. #7
    I'm in the same boat. Currently setting up a frag tank with a 70g sump in my laundry/furnace room and I'm also concerned about the humidity level. My 15 old York system is slowly dying and I'm looking to replace it with something that will control humidity better. My nearest duct register is in the rec room approx 20' away and air return panel is also about 18' away in a different room. I'm considering installing an additional register in the laundry/furnace room where my tank is going to be located.

  8. #8
    Join Date
    Jun 2003
    Location
    Madison, WI/Cape Coral, FL
    Posts
    6,062
    Using outside air is great when the outside air is dry. In green grass climates, the outside air is wet and makes the inside space wet. 50-100 cfm of fresh air is good to purge indoor pollutants. During cold, dry weather, 50-100 cfm will also keep the space dry. When the outdoor dew point is +55^F, a 90 pint dehumidifier is the best bet. A high eff. dehumidifier will pay for itself in a short period because of the heavy loads.
    Actually during winter weather, leaky homes may need the moisture from the fish tanks to humidifiy the 50-100 cfm of natural fresh air ventilation. If so, the benefit of the HRV is eliminated. Monitor the %RH in your home. <50%RH during spring, summer, and fall. Dry enough to avoid moisture condensation on the inside of the windows during cold winter weather. Regards TB
    Bear Rules: Keep our home <50% RH summer, controls mites/mold and very comfortable.
    Provide 60-100 cfm of fresh air when occupied to purge indoor pollutants and keep window dry during cold weather. T-stat setup/setback +8 hrs. saves energy
    Use +Merv 10 air filter. -Don't forget the "Golden Rule"

  9. #9
    Join Date
    Jun 2008
    Posts
    128
    I think it would be best to seal the space as much as possible and ventilate it directly. This is a fish tank we are talking about (salt water at that) producing the moisture. I have experience with large salt water tanks, and this is not the kind of situation where you want that air circulating around the house. Outside moisture amounts will be nothing compared to the moisture from 18 sq ft of 80 degree salt water, probably with high wattage halide bulbs beaming down on it and lots of surface action. I'm also going to guess there is a protein skimmer in the mix forcing even more air/water interaction.

  10. #10
    Great thoughts guys! The room is approx 72 sq/ft. There will be a supply and return to the HVAC, along with a Panasonic 80CFM bath fan. I'm still voting for the fresh air intake on the system since it is adjustable. I can shut it down on very humid days and let the Infinity system do it's job. I also have a dehumidifyer that I can run if humidity gets out of hand.

    The Panasonic fan I'm looking into is the 80CFM Wisper Green that has a DC motor. Runs extremely quiet with only 11.3 watts of power. Rated for continuous run if needed.

    The saltwater tank is 180g with a 75g sump and 40g refugium. So approx 250+ gallons of circulation. Water temp will be 80F with metal halide lighting. Yes, there will be a protein skimmer on the system. I plan on drywalling with green board and also painting with an alkyd primer and waterborne epoxy paint as a topcoat. The room will be fairly "sealed" except for leakage under the door.

  11. #11
    Join Date
    Jun 2008
    Posts
    128
    I might think about putting a vent on the return that you could close. You might find that just pushig supply into the room and then pulling exhaust out the fan will do the trick. 80 CFM will be more than enough for you to keep the temps and humidity down. I'm going to guess you'll have over 1000 watts of light on that tank, heat load will be big in that room.

  12. #12
    Join Date
    Jul 2008
    Location
    Poestenkill, NY
    Posts
    769
    Well - if you do exhaust the room 24/7 - a HRV (sensible only - distinct from an ERV) might not be a bad idea. You would get constant fresh air - and it would be pre-conditioned. Just running direct exhaust will pull air in through the cracks - which I still think is no big deal at these cfm levels, but, hey if you plan on exhausting the room constantly, a 75 cfm HRV would be the most elegant solution (like I said in my first reponse ).

    I do not know if the salt content in the air would eventually foul a plate heat exchanger - I suppose it might over time, and I don't think they're very "cleanable"...

  13. #13
    Join Date
    Jun 2008
    Posts
    128
    I would bet the exchanger would get clogged with salt crust in a month. The HRV would be the most efficient for sure if it would stay working. I'm just thinking that the heat load from the pumps/water/lights would be many times higher than pulling in hot air in the summer time. In the winter the cold air would be a benefit.

    Will there be a chiller on the tank?? Need to figure the exhaust from that thin into the equation as well.

Page 1 of 2 12 LastLast

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
Comfortech Show Promo Image

Related Forums

Plumbing Talks | Contractor Magazine
Forums | Electrical Construction & Maintenance (EC&M) Magazine
Comfortech365 Virtual Event