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An Important Note Regarding Return Duct Location and Sizing:
Careful return air duct sizing and take-off location is critical to proper stage-2 hybrid
operation. Overly restrictive return air configurations will result in very high (and
inefficient!) air deltas during stage-2 operation, and could cause the furnace or Well-
Connect to trip their high-limit safety switches during stage-2 run time. While this can be
an issue with any furnace and Well-Connect combination, it is most pronounced in
situations where a 2.5 ton Well-Connect is paired with a furnace of 80,000 btus or more,
and where the Well-Connect return duct has been tied in very close to the furnace intake
in a section of borderline-sized return duct. The photos below in Figure 13 show three
such systems, all experiencing high deltas causing furnace hi-limit faults or Well-Connect
hi-pressure lock-outs.
Figure 13
In the first photo, the section of return duct feeding the furnace where the Well-Connect
return duct is attached is only 10" x 24", which is just large enough to provide enough air
for the 125K BTU furnace on high fire (a furnace needs 2 sq.in of return duct per 1000
BTU). When the Well-Connect and the furnace are both running there is simply not
enough air available in that section of duct, so both units are starved for air resulting in
high temperature rise in both. In all three photos, the Well-Connect returns are tied into a
vertical return duct very close to the inlet of the furnace itself; this should be avoided.
Such vertical returns generally connect to trunk ducts that provide appropriate connection
points for the WC return duct. In extreme cases where the entire existing return duct
configuration is undersized it may be necessary to provide a separate return duct serving
just the Well-Connect.
Alternately, if the return is not ducted at all, make sure there is an unobstructed return air
path from the household supply registers back to the Well-Connect. Air can't move
through closed doors!
*Note* the air filter flange is made of four separate pieces, each held in place by two
screws. This is so you can remove the air filter from the top or either side, depending on
which direction is easiest to access for a given application.
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