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Geothermal heat pump filter slot


Brandon Whitmore
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I just got done inspecting a geothermal heat pump installed in a high rise condo. http://www.climatemaster.com/index/res_ ... ity27_page

The heat pump is the tranquility 20.

The heat pump is located in the laundry room while the return air is located in the hallway outside this room.

Question: does it matter that the filter slot is wide open, and that some of the return air is being pulled from the laundry room? The way they installed these systems, there is about a 1" gap between the filter and return air duct. Picture a return air duct run to a furnace, but being partially open on 2 of the 4 sides.

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Yes, it matters. The return air will take the least path of resistance, and that would be along the sides with no filter. Either the filter is too small or the opening for the filter is too big. Either way it is not proper. Unfiltered air will be entering the system and will increase the dust/dirt that collects on the coil.

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Originally posted by Brandon Whitmore

. . . Question: does it matter that the filter slot is wide open, and that some of the return air is being pulled from the laundry room? The way they installed these systems, there is about a 1" gap between the filter and return air duct. Picture a return air duct run to a furnace, but being partially open on 2 of the 4 sides.

I looks like they just neglected to fashion a cover for the filter opening. Or someone lost the cover.

The small return air opening in the laundry room isn't really a problem. If it were a big opening, then M1602.2(3) might apply. It says that you can't have a return air opening in a room the volume of which is less than 25% of the entire volume served by the system. But there's an exception if the return air opening isn't bigger than the supply air opening to the room.

I really don't see it as a problem.

- Jim Katen, Oregon

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Hi Jim,

I read that section-- problem is that there is no heat register in that room.

There is no cover on the back or front side-- it really is a decent sized opening. It just seems like it will screw with the design-- I would guess close to half of the air will end up coming from the laundry room, but I could be wrong.

I have been told that all of the units throughout the high rise are this way (new high rise adjacent to the new OHSU building).

Here's the code:

- M1602.2 Prohibited sources. Outdoor and return air for a forced-air heating or cooling system shall not be taken from the following locations:

- - 1. Closer than 10 feet (3048 mm) to an appliance vent outlet, a vent opening from a plumbing drainage system or the discharge outlet of an exhaust fan, unless the outlet is 3 feet (914 mm) above the outside air inlet.

- - 2. Where flammable vapors are present; or where located less than 10 feet (3048 mm) above the surface of any abutting public way or driveway; or where located at grade level by a sidewalk, street, alley or driveway.

- - 3. A room or space, the volume of which is less than 25 percent of the entire volume served by such system. Where connected by a permanent opening having an area sized in accordance with ACCA Manual D, adjoining rooms or spaces shall be considered as a single room or space

for the purpose of determining the volume of such rooms or spaces.

- - - Exception: The minimum volume requirement shall not apply where the amount of return air taken from a room or space is less than or equal to the amount of supply air delivered to such room or space.

- - 4. A closet, bathroom, toilet room, kitchen, garage, mechanical room, furnace room or other dwelling unit.

- - 5. A room or space containing a fuel-burning appliance where such room or space serves as the sole source of return air.

- - Exceptions:

- - - 1. The fuel-burning appliance is a direct-vent appliance or an appliance not requiring a vent in accordance with Section M1801.1 or Chapter 24.

- - - 2. The room or space complies with the following requirements:

- - - - 2.1. The return air shall be taken from a room or space having a volume exceeding 1 cubic foot for each 10 Btu/h (9.6 L/W) of combined input rating of all fuel-burning appliances therein.

- - - - 2.2. The volume of supply air discharged back into the same space shall be approximately equal to the volume of return air taken from the space.

- - - - 2.3. Return-air inlets shall not be located within 10 feet (3048 mm) of any appliance firebox or draft hood in the same room or space.

- - - - 3. Rooms or spaces containing solid-fuel burning appliances, provided that return-air inlets are located not less than 10 feet (3048 mm) from the firebox of such appliances.

Thanks for the replies all,

My vacation awaits..............

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Originally posted by Brandon Whitmore

Hi Jim,

I read that section-- problem is that there is no heat register in that room.

There is no cover on the back or front side-- it really is a decent sized opening. It just seems like it will screw with the design-- I would guess close to half of the air will end up coming from the laundry room, but I could be wrong.

I have been told that all of the units throughout the high rise are this way (new high rise adjacent to the new OHSU building).

Here's the code:

- M1602.2 Prohibited sources. Outdoor and return air for a forced-air heating or cooling system shall not be taken from the following locations:

- - 1. Closer than 10 feet (3048 mm) to an appliance vent outlet, a vent opening from a plumbing drainage system or the discharge outlet of an exhaust fan, unless the outlet is 3 feet (914 mm) above the outside air inlet.

- - 2. Where flammable vapors are present; or where located less than 10 feet (3048 mm) above the surface of any abutting public way or driveway; or where located at grade level by a sidewalk, street, alley or driveway.

- - 3. A room or space, the volume of which is less than 25 percent of the entire volume served by such system. Where connected by a permanent opening having an area sized in accordance with ACCA Manual D, adjoining rooms or spaces shall be considered as a single room or space

for the purpose of determining the volume of such rooms or spaces.

- - - Exception: The minimum volume requirement shall not apply where the amount of return air taken from a room or space is less than or equal to the amount of supply air delivered to such room or space.

- - 4. A closet, bathroom, toilet room, kitchen, garage, mechanical room, furnace room or other dwelling unit.

- - 5. A room or space containing a fuel-burning appliance where such room or space serves as the sole source of return air.

- - Exceptions:

- - - 1. The fuel-burning appliance is a direct-vent appliance or an appliance not requiring a vent in accordance with Section M1801.1 or Chapter 24.

- - - 2. The room or space complies with the following requirements:

- - - - 2.1. The return air shall be taken from a room or space having a volume exceeding 1 cubic foot for each 10 Btu/h (9.6 L/W) of combined input rating of all fuel-burning appliances therein.

- - - - 2.2. The volume of supply air discharged back into the same space shall be approximately equal to the volume of return air taken from the space.

- - - - 2.3. Return-air inlets shall not be located within 10 feet (3048 mm) of any appliance firebox or draft hood in the same room or space.

- - - - 3. Rooms or spaces containing solid-fuel burning appliances, provided that return-air inlets are located not less than 10 feet (3048 mm) from the firebox of such appliances.

Thanks for the replies all,

My vacation awaits..............

Hi,

I guess I don't understand why you're fixated on this when it's not a fossil fuel burning appliance. The stuff you've quoted above is meant to prevent someone asphyxiating themselves by installing a fuel-burning appliance improperly or in the wrong location. I doubt that would apply to an electric heat pump.

I should think a roll of self-adhesive foil tape and a razor knife on the shelf next to that unit is all that's needed to open and reseal that filter slot satisfactorily; either that are have a sheetmetal fella make a new cover.

ONE TEAM - ONE FIGHT!!!

Mike

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Originally posted by hausdok

Hi,

I guess I don't understand why you're fixated on this when it's not a fossil fuel burning appliance. The stuff you've quoted above is meant to prevent someone asphyxiating themselves by installing a fuel-burning appliance improperly or in the wrong location. I doubt that would apply to an electric heat pump.

The provisions of M1602.2, 1-4 apply to all ducted HVAC systems, not just fuel burning systems. Return air openings in small rooms can reduce the efficiency of the heat pump. They'll also create significant negative pressure in the small room while simultaneously creating signficant positive pressure in the rest of the house. That can cause all sorts of other problems. It's not just a back drafting issue.

I should think a roll of self-adhesive foil tape and a razor knife on the shelf next to that unit is all that's needed to open and reseal that filter slot satisfactorily; either that are have a sheetmetal fella make a new cover.

ONE TEAM - ONE FIGHT!!!

Mike

A sheet metal cover is the less bogus approach.

- Jim Katen, Oregon

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