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dude99

Yet another furnace age question, Old Airco

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I always hate to see that done because it cuts the filter surface area in half (less than half). If they're using a pleated filter with fine media in it, that reduction in surface area can throw up a high static pressure across the filter and cause the furnace to run hot.

Jim, you are right, of course, but when this model was going through certification, the 12" x 16" x 1" filter was within a few square inches of the requirements for airflow. Because it was a downflow and air conditioning was so sparse up here, the supplied filter was only designed for the heat-only application. The manufacturer at the time could have upgraded the filter to a washable foam variant that on paper showed a greater airflow capacity than the fibreglass filter but was in reality denser and more restrictive. They/we chose to go with the custom-made filter plus the side filter in order to meet the rules.

In the field, we regularly changed the filter to the single 12x16 fibreglass and have seldom (read, never) seen them plugging up between annual checkups. We monitor the temperature rise and find no issues with the filter change whatsoever. Even dirty filters are not putting the furnace anywhere near its limit point. The reduced filter size has had no negative effects for our customers.

Those pleated filters, however, were never certified for use in any furnace back in 80's and 90's. I doubt if they are now. Unless they are watched closely and changed often, they will kill a perfectly good furnace. Hopefully, the furnace airflow is balanced with a dirty pleated filter in place. Ideally, the filter system is replaced with a wider version, complete with a bigger and better filter flame.

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The WBS2 is a reliable furnace with quality parts and a good design. It is a "standard efficiency" model with a rated AFUE (Annual Fuel Utilization Efficiency) of 55%. However, if the furnace is in a dedicated furnace room off the garage, as many are here in the Lower Mainland, the off-time losses are considerably reduced. This furnace is one worth keeping until the heat exchanger shows signs of rusting and pitting at the top of the clamshells.

Thank you very much for your detailed response. I had the furnace cleaned and they couldn't tell me there where two filters.

What we are looking to do is to move the furnace from the closet in the house to mount it horizontally in the crawl space. It is a small house and we need the room. I will get someone to take a look for the pitting/rust that you mentioned to see if it would be worth moving this furnace or buying a new one. I estimate this one to be around 26 years old.

Much appreciated.

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What we are looking to do is to move the furnace from the closet in the house to mount it horizontally in the crawl space. It is a small house and we need the room. I will get someone to take a look for the pitting/rust that you mentioned to see if it would be worth moving this furnace or buying a new one. I estimate this one to be around 26 years old.

The Airco/Olsen WBS2 is a naturally-aspirated, downflow gas furnace. It is only approved for an upright installation in the orientation that it is currently working; that is, with the blower at the top. There is no way that it can be mounted horizontally. Besides being contrary to the specifications on the Rating Plate, it would be extremely dangerous.

The WBS2 is an old furnace design with no other installation options.

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I have a question about a WBS2-90 furnace apparently installed new in a condo completed in 1990.  During the installation a custom sheet metal flue was constructed from the top of the furnace via a 180 degree turn to the floor where fresh enters through from more custom sheet metal in the crawl space to intake grills in the house.  Whatever filter arrangement there was in the original furnace design is provided now in a single 18" x 12" x 1" slot at the top of the  custom sheet metal flue just as it turns 180 degrees into the furnace intake.  I have not been able to find filters to fit the slot.  I am using a 12' x 16" filter now but there a lot of leakage around the filter.  Suggestions please?

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