Changing Coil Hand; Nufin Coils; Direct Expansion Coils; Chilled Water And Hot Water Coils - Carrier AERO 39MN Installation, Start-Up And Service Instructions Manual

CHANNEL, HAT
Fig. 126 — Spacer (Hat Channel)
15. Inspect the adhesive backed gasket applied to the lower
baffle, spanning the entire unit, on the surface that con-
tacts the coil (see Fig. 125). If damaged, remove the re-
mainder of the old gasket and replace.

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 mea-
surable, 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 veloc-
ities. 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
result in coil freeze-up (a condition NOT covered by warran-
ty).
Refrigerant coils may be rotated for opposite hand applica-
tions, maintaining the proper airflow direction.
Do not reposition the distributor(s), they will perform
equally well in upflow or downflow positions. When solder-
ing expansion valves to up-feed distributors, use the mini-
mum satisfactory amount of solder to prevent damaging the
valve or plugging passages.
ATTACH WITH 4 SCREWS
TO COIL CASING
a39-2921
DIRECT EXPANSION COILS — Rotate the coil in vertical
plane and reinstall. Distributor must be on downstream side
of coil. (Refer to Fig. 126.)
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 contin-
uously vented and water velocity is maintained to prevent air
binding.
STEAM INNER DISTRIBUTING TUBE COILS — Rotate
in horizontal plane and reinstall. See Fig. 127.
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. 127 — Coil Rotation
PIPING — Direct expansion, chilled water, and hot water
coils should always be piped for counterflow. (Fluid should
enter 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 indicate 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 conden-
sate 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 for-
mation and build-up of acids.
134
CAUTION