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  1. #1
    Seasoned Camper KirbyRVA's Avatar
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    384GK, furnace cold air return location

    The pics of the 384GK on Grand Design's website show a large grill under the desk which I would think is the cold air return for the LP furnace. I have no such grill. I've looked every where and can find no specific cold air return. My heat air flow seems a bit lazy so I went into the utility area and checked all the duct work for any disconnections, leaks or kinks and found none. So I suspect some restriction on return air may be an issue.

    Can any of you with a 384GK tell me where your cold air return is? The bottom shelf in the pantry is basically a box. The front of that box stops about 1 1/2" above the floor so that may be GD's intended cold air return since the furnace is near that location. However, I wonder if they intended to cut an opening in the front of that box and install a grill but just forgot to do it during the build. Based on other things I've seen with this rig, it would not surprise me.
    2019 Solitude 384GKR
    Stored, used at Myrtle Beach, SC
    [SIGPIC][/SIGPIC]

  2. #2
    Seasoned Camper
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    Our 375RES has the box in the pantry with the gap above the floor, it's the cold air return for the furnace.

  3. #3
    Fireside Member mntbikejack's Avatar
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    It is under the steps. They are completely open to the basement.
    2019 Ford F-350 Limited
    2019 Grand Design Solitude 384GK


  4. #4
    Seasoned Camper KirbyRVA's Avatar
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    Quote Originally Posted by mntbikejack View Post
    It is under the steps. They are completely open to the basement.
    I am aware of the opening under the steps but that would not qualify as a cold air return from a heated area to a furnace. When the furnace is running, cold air from the basement is sucked into the living area from under the steps. In cooling season, warm air is also sucked into the living area when the AC is running. I have blocked off that opening since it makes no sense to me to have it and it reduces the effectiveness of both cooling and heating. In a properly set up HVAC system, there should be a return from the heated space to the intake of the furnace.

    As has been noted by others, I suspect the open space below the box in the bottom of the pantry is the intended cold air return. The furnace is just a few feet directly behind that pantry.
    2019 Solitude 384GKR
    Stored, used at Myrtle Beach, SC
    [SIGPIC][/SIGPIC]

  5. #5
    Fireside Member mntbikejack's Avatar
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    Quote Originally Posted by KirbyRVA View Post
    I have blocked off that opening since it makes no sense to me to have it and it reduces the effectiveness of both cooling and heating. In a properly set up HVAC system, there should be a return from the heated space to the intake of the furnace.

    \
    That is exactly why the heating isn't functioning properly. The stairs are designed to be the cold air return. If you don't believe me call Grand Design.
    2019 Ford F-350 Limited
    2019 Grand Design Solitude 384GK


  6. #6
    Commercial Member huntr70's Avatar
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    Do you have the drawer under the steps or the open space?

    The early models had a drawer, and those models had the grate under the desk.

    Later models got the open space and the vent grate went away.

    Old model...
    Attached Thumbnails Attached Thumbnails gallery-384gk-kitchenhutch.jpg  
    Steve- Inventory Manager at Tom Schaeffer's RV, Shoemakersville, PA www.tomschaeffers.com
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    2011 RAM 3500 SRW Outdoorsman Edition 4X4, 6.7 Cummins--TWEAKED!
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    Commercial Member huntr70's Avatar
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    New model....
    Attached Thumbnails Attached Thumbnails Solitude384GK_B2F-jh-web.jpg  
    Steve- Inventory Manager at Tom Schaeffer's RV, Shoemakersville, PA www.tomschaeffers.com
    [email protected]
    2011 RAM 3500 SRW Outdoorsman Edition 4X4, 6.7 Cummins--TWEAKED!
    2021 Reflection 310RLS

  8. #8
    Seasoned Camper KirbyRVA's Avatar
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    Quote Originally Posted by mntbikejack View Post
    That is exactly why the heating isn't functioning properly. The stairs are designed to be the cold air return. If you don't believe me call Grand Design.
    I did call Grand Design last year during heating season and asked about the open space under the stairs. I was getting cold air coming into the living area right below the wall T stat. IMO that was causing the furnace to run longer and the area near the entry door and desk was cold. The Grand Design person never claimed that was a return for the furnace. He said it was open 'to prevent heat build up in the basement area.' When I noted to him that even though there was a small heat opening in the top of the basement storage area, the air coming from under the steps into the heated living space was much colder than desired, he just fumbled and never really gave me a satisfactory answer. I suggested to him that if the furnace had a properly sized cold air return from the living area, overheating should not be a problem.

    Think about it. To properly heat your living space you install a cold air return low in the living area which allows the furnace to pull cooler air thru its intake. That air crosses the heated plenum and goes out the ducts back into your living areas (and other spaces you want to heat). Why would you also leave an opening between you living space and another space that is either cold or poorly heated and dilute your heated air with colder air? That would be like punching a hole in your wall between your living room and your unheated garage and allow your furnace air handler to pull cold air into the living room. Also, if the opening under the stairs was a 'return' for the furnace, air would move from the living area into the basement....in the direction of the furnace intake. It does not....the colder air moves into the living area so it cannot be considered a 'return' air space.

    Perhaps Grand Design feels that the opening under the steps aids in the circulation of air in the basement storage area.....preventing pressure build up?? If that is the case, they could merely have installed a small vent to the outside. In any case, their design makes it more difficult to heat and cool these things and they are already poorly designed for optimum heating and cooling.

    On another forum, someone shared a proprietary drawing of our floorplan and it clearly shows Grand Design intends for the space in the pantry to be the cold air return for the furnace.

    In two discussion I've had with Grand Design....one about wiring/conduit and one about HVAC, it was clear to me that they have little real technical knowledge of electrical and HVAC.
    Last edited by KirbyRVA; 11-26-2019 at 11:45 AM.
    2019 Solitude 384GKR
    Stored, used at Myrtle Beach, SC
    [SIGPIC][/SIGPIC]

  9. #9
    Fireside Member mntbikejack's Avatar
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    The basement is considered part of heated living area. The furnace sucks air directly from the basement so if you isolate the basement by blocking the steps you are defeating the system in the 384GK. If you put a return in the pantry and blocking the return in the steps you are just moving it a few feet to the left.
    2019 Ford F-350 Limited
    2019 Grand Design Solitude 384GK


  10. #10
    Seasoned Camper KirbyRVA's Avatar
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    Quote Originally Posted by mntbikejack View Post
    The basement is considered part of heated living area. The furnace sucks air directly from the basement so if you isolate the basement by blocking the steps you are defeating the system in the 384GK. If you put a return in the pantry and blocking the return in the steps you are just moving it a few feet to the left.
    Grand Design says the return in my 384GK is under the box in the bottom of the pantry. I agree that the furnace is also pulling air from the basement via the space under the steps but am suggesting that is not necessary if there is a properly sized return for the furnace in the living area. Have you used your rig in cold temps? If so, have you measured the temp of the air coming into your rig from under the steps? It is much colder than the living area. If you are satisfied with that, that works for you. I am not satisfied with that set up.

    I would like to have someone from Grand Design with either an engineering or HVAC/mechanical background explain to me their logic for the set up. I am now suspecting it is due to their decision not to put a real ducted return somewhere in the living area.....basically a cheap and easy route.
    2019 Solitude 384GKR
    Stored, used at Myrtle Beach, SC
    [SIGPIC][/SIGPIC]

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