Changing Coil Hand; Direct Expansion Coils; Chilled Water And Hot Water Coils; Steam Inner Distributing Tube Coils - Carrier Aero 39MN Series Installation, Start-Up And Service Instructions Manual

CHANNEL, HAT
Fig. 175 — Spacer (Hat Channel)

Changing Coil Hand

NOTE: Electric heat coil hand cannot be changed.
NOTE: The coil cover panel is not part of the coil. Remove
cover panel from end of unit. New holes must be cut in coil
cover panel. Original holes must be plugged and insulated.
New side panels may be necessary when changing coil
hand.
NUFIN COILS — The NuFin coil is airflow direction sensi-
tive, especially when used in dehumidifying applications.
Hydronic versions are counterflow circuited for full gravity
draining when installed level.
Correct installation will result in the typical bottom inlet on
leaving air face and top outlet on entering air face of coil, a
self-venting design. This will ensure cold air contact with cold
water, and warm air with hot water.
Coil repositioning for opposite hand application will com-
promise one or more of these characteristics. However, there
will be those situations where this may prove acceptable.
As a general rule, a change from counterflow circuiting to
parallel flow for sensible heating and cooling applications will
result in a 5% drop in net capacity per row of coil. In one and
two row heating coils, the actual drop may not be measurable,
thus of insignificant consequence.
It is important that the airflow direction of the NuFin coil be
adhered to when latent cooling is possible. Significant moisture
carryover from the face of the dehumidifying coil will result if
this rule is violated, even at very low face velocities. The same
result is often experienced if after-market fin coatings are
applied.
If a NuFin hydronic coil is installed with correct airflow, but
opposite piping hand, and counterflow is maintained, steps
must be taken to ensure that the coil is continuously vented,
and that the water velocity is maintained to prevent the coil
from air-binding.
Hot or cold areas of the coil face (or otherwise broad tem-
perature differences and stratification) are usually indications
that one or more circuits are air-locked internally. This can re-
sult in coil freeze-up (a condition NOT covered by warranty).
Refrigerant coils may be rotated for opposite hand applica-
tions, maintaining the proper airflow direction.
Do not reposition the distributor(s); they will perform equal-
ly well in upflow or downflow positions. When soldering ex-
pansion valves to up-feed distributors, use the minimum satis-
factory amount of solder to prevent damaging the valve or
plugging passages.
DIRECT EXPANSION COILS — Rotate the coil in vertical
plane and reinstall. Distributor must be on downstream side of
coil. (Refer to Fig. 176.)
ATTACH WITH 4 SCREWS
TO COIL CASING
a39-2921
CHILLED WATER AND HOT WATER COILS —
These coils can be rotated. If coil is rotated in vertical plane
and reinstalled with counterflow maintained, supply will be at
the top of the coil and return will be at the bottom. Ensure coil
is continuously vented and water velocity is maintained to pre-
vent air binding.

STEAM INNER DISTRIBUTING TUBE COILS

Rotate in horizontal plane and reinstall. See Fig. 176.
Chilled and hot water coils must not be rotated horizon-
tally. If coils are rotated horizontally, severe water blow-off
will result.
DX AND ALL
WATER COILS
STEAM COILS
ONLY
a39-2388
Fig. 176 — Coil Rotation
PIPING — Direct expansion, chilled water, and hot water
coils should always be piped for counterflow. (Fluid should en-
ter the coil at the leaving-air side.) Steam coils must have the
condensate connection at bottom of coil.
To determine intervals for cleaning coils in contaminated air
operations, pressure taps should be installed across the coils
and checked periodically. Abnormal air pressure drop will indi-
cate a need for cleaning the coils.
Annual maintenance should include:
1. Clean the line strainers.
2. Blow down the dirt leg.
3. Clean and check operation of steam traps.
4. Check operation of control valves.
5. Check the operation of check valves to prevent con-
densate flowback.
6. Check operation of thermostatic air vents, if used. A
float and thermostatic trap will contain a thermostatic
air vent. When the bellows is ruptured, it will fail
closed.
7. Check operation of vacuum breakers.
8. Check operation of the thermal protection devices used
for freeze-up protection.
9. Steam or condensate should not be allowed to remain
in the coil during the off season. This will prevent the
formation and build-up of acids.
There are additional precautions and control strategies, as
found in various catalogs and in the ASHRAE Fundamentals
Handbook and in the Carrier System Design Guide — Piping
189
CAUTION
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