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  1. #1
    Join Date
    Apr 2012
    Location
    Princeton NJ
    Posts
    125

    "line of sight" basement return

    Hi, thanks for the previous help. My hvac fellow suggested a return in the finished and zoned basement (he's doing other things also). I've searched this forum, and sort of concluded that as long as it isn't “line of sight” to my hot water heater it is ok. Well the walls are drywall and insulated, but above the ceiling tile there are definitely connecting spaces to the equipment area, not big, but i'm sure air could flow. If I shined a flashlight i'm sure i would see light through it basically.

    What is line of sight? Would my situation be considered safe? (Although it is zone and as supply ducts, the zone rarely calls)

    Thanks Steve

  2. #2
    Join Date
    Dec 2002
    Location
    in a house, Appomattox, Va.
    Posts
    3,283
    line if sight, to me, means two things-

    a straight section of duct will transmit sound, wheras several ells will dampen noises from the equipment

    or visual line of sight in elec code means the disconnect for equipment must be line of sight and under 50' from equipment.

    since you're talking about a water heater, I assume its gas? in that csae its space depressurization that's the concern. YOU CANNOT DRAW FREE RETURN FROM A SPACE WITH GRAVTIY VENTING, it could suck fumes out the appliance into the room.
    Col 3:23


    questions asked, answers received, ignorance abated

  3. #3
    Join Date
    May 2008
    Location
    Missouri
    Posts
    3,483
    Never have heard anything about "line of sight" in reference to a return. Can you give us more information?? You don't now have a return in your finished basement? Why was it not put in when basement finished? Are you concerned with creating a negative pressure in basement? If you have discharge registers in your basement and add a return, you'll not create a negative pressure.

  4. #4
    Join Date
    Apr 2012
    Location
    Princeton NJ
    Posts
    125
    thanks for the comment billygoat

    wahoo--- it is a three zone system, with older trol-a-temp automatic dampers. There are supplies in the basement, but no return. The basement zone is rarely activated, yet the return would be active at all times. So, I am worried about negative pressure. However, i do know that my ducts in the basement leak, and that the older dampers really don't seal off completely---I still feel a tiny bit of air out of the supplies even when the zone isn't calling.

    A natural gas water heater is in the equipment room, sealed with a door (but as I said the upper most walls certainly aren't air tight). The furnace is direct vent/pvc pipe so i'm not concerned with it.

    I want to do it to balance the temp in the basement, plus I'm adding a 10inch round return upstairs. If I add another 10 inch in the basement it would give enough return for my (incorrectly sized/oversized) heater in second stage.

    What do you think?
    Thanks
    Steve

  5. #5
    Join Date
    Jul 2010
    Location
    nebraska
    Posts
    1,629
    Is there a door at the top of the stairs? If so then you'll want those basement dampers open at all times or have grills in the door so the basement can't go negative pressure.

  6. #6
    Join Date
    Apr 2012
    Location
    Princeton NJ
    Posts
    125
    martyinlincoln--thanks. The return would run through the dead space of the staircase and be on the floor (ceiling supplies). The door has a 1 inch botton cut off w/the slate floor. Still need a grill? Steve

  7. #7
    Join Date
    Jul 2010
    Location
    nebraska
    Posts
    1,629
    They can test with a manometer. If the basement goes into a negative pressure then the grill is needed. Doubt a 1" under cut door will be enough to balance the suction from a 10" return, at least not while the blower is running.

  8. #8
    Join Date
    Dec 2002
    Location
    in a house, Appomattox, Va.
    Posts
    3,283
    agree, seen louvered doors at top of stairs still get negative in bssement.
    Col 3:23


    questions asked, answers received, ignorance abated

  9. #9
    Join Date
    Aug 2012
    Location
    Silver Creek, Ny
    Posts
    94
    New Jersey,
    It is my humble opinion that since you already have the natural vented hot water heater tucked away in a closed off room, the only thing left to do is cut in a make-up air duct into the baesement inside this room for the hot water heater, then your free to pursue anything else you want in the rest of the basement, not worrying about creating a negative pressure, causing a backfeed of exhaust.
    Perfect Practice Makes Perfect

  10. #10
    Join Date
    Aug 2007
    Location
    Northern VA 38 degrees N by 76 degrees W
    Posts
    5,060
    Quote Originally Posted by central nj View Post
    thanks for the comment billygoat

    wahoo--- it is a three zone system, with older trol-a-temp automatic dampers. There are supplies in the basement, but no return. The basement zone is rarely activated, yet the return would be active at all times. So, I am worried about negative pressure. However, i do know that my ducts in the basement leak, and that the older dampers really don't seal off completely---I still feel a tiny bit of air out of the supplies even when the zone isn't calling.

    A natural gas water heater is in the equipment room, sealed with a door (but as I said the upper most walls certainly aren't air tight). The furnace is direct vent/pvc pipe so i'm not concerned with it.

    I want to do it to balance the temp in the basement, plus I'm adding a 10inch round return upstairs. If I add another 10 inch in the basement it would give enough return for my (incorrectly sized/oversized) heater in second stage.

    What do you think?
    Thanks
    Steve
    The equipment room when enclosed by walls and door should have consideration for combustion air for the water heater either through a high and low duct communicating with the outdoors or the inside basement. Depending on the cubic footage of the equipment room to btu ratio of the hot water heater it may be fine as is.

    In reference to adding more return to the over sized unit, without increasing the supply you will not accomplish anything. Adding the return to the basement should not effect the performance of the water heater unless the entire basement is sealed air tight, and the chances of that are highly improbable.

  11. #11
    Join Date
    Apr 2012
    Location
    Princeton NJ
    Posts
    125
    Thank you all. I profoundly appreciate it.

    The room is enormous--at least 600 sq ft. There are actually 2 50 gallon hot water heaters in it. The outside/garage connecting door is a good 36 inches wide. Has about a 1 inch gap at the floor, and air comings in all around the door--no weather stripping.

    I very stupidly sealed these gaps because cold air came it in winter (I am removing the sweep and weather stripping immediately/tonight).

    Maybe enough make-up air?

    Steve

  12. #12
    Join Date
    Aug 2007
    Location
    Northern VA 38 degrees N by 76 degrees W
    Posts
    5,060
    Quote Originally Posted by central nj View Post
    Thank you all. I profoundly appreciate it.

    The room is enormous--at least 600 sq ft. There are actually 2 50 gallon hot water heaters in it. The outside/garage connecting door is a good 36 inches wide. Has about a 1 inch gap at the floor, and air comings in all around the door--no weather stripping.

    I very stupidly sealed these gaps because cold air came it in winter (I am removing the sweep and weather stripping immediately/tonight).

    Maybe enough make-up air?

    Steve
    Do not remove the seal to the garage, you do not want infiltration air from the garage unless it is not used as a garage or yard equipment such as lawn mower, gas can, weed whacker, etc.

  13. #13
    Join Date
    Apr 2012
    Location
    Princeton NJ
    Posts
    125
    Second opinion (and others) THANK YOU, believe me.

    I was in a pinch yesterday, had to leave the fellow instructions for today's work. I had him put in the 10 inch return in the basement (but with a manual damper).

    My unit was on my running at 1600 cfm, and the basement return was working. I placed a small candle next to the hot water heater vent pipe (next to the small space near the 6 inch or so cap). Blew out the candle. The smoke absolutely went up the flue, it wasn't pushed out into the room. Just the pilot light was on the heater.

    I'm thinking that this is fine, sort of positive pressure in the room. Can I stop worrying about it?

    Steve

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