HVAC Coil manufacturers can over emphasize the need to
designate left or right hand. The different reference points used can be
intimidating and confusing. Often times, it just doesn't matter.
Do you need to specify a left or right handed steam HVAC
coil?
Not generally. Most steam HVAC coils are universal. Steam
coils are normally 1 or 2 rows deep. This allows you to reverse the piping
connections. The supply connection must be on top and the return connection
must be on the bottom. Return connections on steam coils need to be as low as
possible for proper condensation removal. As long as you have the return
connection lower than the supply connection, it does not matter if you have a
right handed or left handed steam HVAC coil.
Do hot water HVAC coils need to be left or right handed?
Hot water and steam coils are almost identical since both
are typically only 1 or 2 rows deep. The major difference is the supply and
return feed. If possible, feed the bottom connection and return the top
connection. This helps promote the removal of air that can get trapped in the
HVAC coil.
Which HVAC coils require a 'hand' designation?
Cooling coils that are larger than 2 rows require a hand
designation. All coils except steam coils should be installed in a counter-flow
arrangement. This is particularly true for HVAC coils with three rows or more.
Counter-flow refers to the direction of the air across the fins relative to the
fluid in the tubes. A counter-flow arrangement will produce the most capacity.
Using a chilled water cooling coil as an example, the coldest water entering
the coil should be cooling the coldest air leaving the coil. See below for a
more detailed explanation of counter-flow.
A detailed explanation of counter-flow:
A HVAC coil is an air to fluid heat exchanger. Air is
traveling on the outside of the tubes and fluid is traveling on the inside of
the tubes. The most important principle in designing any heat exchanger is put
the air and the fluid in a counter-flow arrangement. This means that the air and
water travel in opposite directions through the heat exchanger. You always want
the water, refrigerant or steam entering on the side of the exchanger where the
air is leaving. This means that as the air goes from left to right, the fluid
is traveling from right to left. All coils are tested in counter-flow
arrangements and it provides maximum efficiency. You can lose 15% of the
capacity when a HVAC coil is piped backwards. This is the primary reason why
deeper HVAC coils are designated as right or left hand. Counter-flow has
negligible effect on 1-2 row coils.
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