Carrier 31MC User Manual
Electronic and Mechanical Air Cleaner
|—8i"-4
31MC
UNIT
31MC,MP114
31MP214; ^
31MC,MM,MP220
Fig. 1 — Dimensions, Electronic and Mechanical Air Cleaners
GENERAL
The Carrier 31MP plate-type and 31 MM mediatype electronic air cleaners and the 31MC highefficiency mechanical air filters, all shown in Fig.
1, are designed for use with residential and light
commercial forced-air heating and/or cooling sys
tems. They can be installed vertically or horizont^lji in. the ductwoi;ic„9r at the furnace. The
units are easily converted in the field from right to
left hand by removing the air cleaning components
and reassembling them in reverse order. Cabinets
will support a weight of 400 lb when installed
beneath a vertical furnace or air-handling unit.
Package Contents — The 31MP and 31 MM elec
tronic air cleaner packages and the 31MC highefficiency filter package consist of:
1. One31MP, 31MMor31MCunit.
2. Two base angle air baffles.
3. A template for preparing the furnace opening.
4. A bag of hardware consisting of 6 no. 8B x
1/4-in. long screws, 6 no. 8 speed nuts and a
small bag containing wire nuts for making
electrical connections.
5. A coil of foam tape.
6. Package of replacement media (31MM Models
only).
7. An installer’s packet.
SIMM
A (in.)
21’/4
28V,
31MP
When unpacking the unit, if any in-transit
damage is observed, file a claim with the trans
portation agency. Since the air cleaner components
are packed in a single carton, be sure to inspect
all packing materials before discarding.
Application — Install the electronic air cleaner
where all of the air circulated by the system will
pass thru it. The best location is in the return air
duct close to the blower compartment. This
location provides the most even air flow distribu
tion across the face of the electronic cells or
mechanical filter element and also allows the air
cleaner to keep the blower and motor clean. In a
cooling system, the air cleaner keeps the evap
orator coil clean.
When it is not possible or economically feasible
to mount the air cleaner in the return air duct,
consider installing the unit in the air discharge
duct. However, give special consideration to the
following factors when planning such an
installation.
1. Even air flow distribution across the face of the
electronic cells may be difficult to achieve. Use
turning vanes and transitions where necessary.
2. Put the air cleaner upstream from the coil in a
cooling system, if possible. The electronic air
cleaner or mechanical filter will help keep the
© Carrier Corporation 1975
Form 31MP-2SI
coil clean, reducing maintenance costs. Also, air
coming from the coil will frequently be near
100% relative humidity.
3. The air flow temperature thru the air cleaner
must be within 40 F to 125 F.
Location — Because air-handling systems vary
greatly in arrangement and style, factors such as
accessibility, ambient temperature ratings, tran
sitions, and other requirements must be carefully
considered.
In crawl space or attic installations (uncondi
tioned space), air cleaner must be insulated the
same as ductwork.
The unit must be readily accessible for periodic
inspection and cleaning of the prefilter and elec
tronic cells to maintain maximum efficiency and
trouble-free operation. A minimum of 30 in. of
clear area should be left in front of the air cleaner
for cell and prefilter removal.
The air cleaner must be installed where the
temperature will be within a 40 F to 125 F range.
Humidifiers — Location of the system humidifier is
important to the operation of the electronic air
cleaner or mechanical filter.
When an evaporative-type humidifier is used, it
may be installed between the furnace warm air
duct and the return air duct without affecting the
electronic air cleaner.
An atomizing-type humidifier must be installed
downstream from the air cleaner. If the atomizingtype humidifier is installed upstream, high
humidity, salts and minerals will decrease the
efficiency of the electronic cell and cause service
problems or damage the high-efficiency filter
element in the mechanical air filter.
Outdoor Air — When outdoor air is added to the
return air duct, sufficient heat must be added to
maintain the return air temperature at 40 F mini
mum. Lower temperatures can cause ionizer wire
failure under certain conditions. Two methods are
recommended:
1. Mixing baffles or vanes. When outdoor air is
added, make certain that it is far enough ahead
of the air cleaner to be mixed and warmed
properly. If not, baffles must be installed to
force mixing of the air.
2. Preheat coil. If a large amount of outdoor air is
used, it must be heated. A thermostat should be
used to control the heater. (A strip heater or
hot water coil are typical heaters.)
INSTALLATION PROCEDURE
Remove Filter and Clean Blower Compartment
Before Starting Installation.
1. Remove and discard the old filter if one is used.
2. Thoroughly clean the blower compartment.
The air cleaner cannot remove (firt from the
blower compartment or distribution ducts.
Installation of 31MP Plate-Type or SIMM MediaType Air Cleaner
1. Remove power door by turning fastener knob.
Fig. 2, item 5, counterclockwise until power
door is free. Slide out prefilter and air cleaner
cells.
1 — Cabinet
2 - Collector Cell (31 MP)
3 — Prefilter
4 — Power Door
5 — Fastener Knob
6 — Test Button
Fig. 2 — Electronic Air Cleaner Components,
Model 31 MP
7 — Indicator Light
8 - ON-OFF Switch
9 — Ceramic Insulators
10 — Opening for Power Supply
11 — Junction Box Cover
2. Unit can be installed with air flow thru the
cabinet in either direction. No changes to the
cabinet are necessary when reversing the air
flow direction thru air cleaner. See Fig. 3.
3. Apply template, supplied in package, to side of
furnace and prepare the opening in side of
furnace according to instructions on template.
4. Prepare return air duct for installation of unit.
Allow a minimum of 30-in. clearance in front
of power door for servicing.
5. Return air duct should use full cabinet open
ing. Run duct straight into unit. Use an elbow
with turning vanes if duct takes a sharp turn
close to air cleaner inlet. Do not baffle off any
portion of entering air side of air cleaner
When it is necessary to change duct size close
to the air cleaner, use gradual transitions to
reduce turbulence. See Fig. 4.
Fig. 3 — Left- and Right-Hand Assemblies
-------
L.
RETURN
AIR
DUCT
Fig. 4 — Transition from Smaller Ducts
6. When installing unit at bottom return opening
of an upflow furnace;
a. Center furnace on air cleaner cabinet and
remove components from cabinet.
b. Field-fabricated support not required on
Carrier furnaces.
c. When the furnace is larger or smaller than
the air cleaner, baffle off any mismatch
between furnace and air cleaner with
baffles, included with unit. Additional
support, such as support legs, is recom
mended when furnace overhangs the air
cleaner.
9. Slide prefilter and air cleaner cells into cabinet.
Units are shipped for right-hand installation.
To convert from a right- to a left-hand unit,
reverse the position of the prefilter and the air
cleaner cells in the cabinet as indicated in Fig.
3. Be sure the air flow arrows are pointing to
the direction of air flow thru unit, and the
ionizer wires in the cell are adjacent to the
prefilter. The 31MC220 high-efficiency me
chanical filter does not have a prefilter or
electronic cell. Simply reverse position of filter
element to change from right- to left-hand. An
air flow direction arrow is stamped on the
filter element.
10. Remove junction box cover on 31 MM and MP
units only. Fig. 5, item 1, located below
receptacle, item 2, on top inside of cabinet.
Install strain relief in opening for 120-volt
input supply, Fig. 2, item 10, in top of
cabinet. Connect 120-volt supply pigtails in
junction box with wire nuts provided, and
connect ground wire to green pigtail provided.
Wire supply voltage from fan circuit of system
to have air cleaner operating only when unit
fan is running. See Fig. 6, 7, 8 and 9 for
typical furnace wiring diagrams. All wiring
must comply with applicable local and
national codes.
prevefit » cormt fr««» atsl
7. If a filter flag is used to indicate a clogged
filter, install it downstream of cleaner, follow
ing instructions furnished with the filter flag.
8. Seal all joints on downstream side of air
cleaner.
11. Replace power door. Turn fastener knob
clockwise until power door is securely
fastened, thus ensuring good electrical contact
between power door and unit components.
Diverse installations are shown in Fig. 12.
12. Check over the installation for correct sheet
metal and electrical work.
C
3 — Top Guide 6 — Screw for Holding Top Guide
NOTE: The 2-cell unit (-220) shown; the 1-cell units (-114, 214)
have one contactor in the door
Fig. 5 — Junction Box and Top Guide
CONNECTIONS
Fig. 6 — Typical Furnace Wiring with Single-Speed
Fan Motor
THERMOSTAT
CONNECTIONS
Fig. 7 — Typical Furnace Wiring with Multispeed
Fan Motor and Air Cleaner Relay
THERMOSTAT
CONNECTIONS
Fig. 8 — Typical Furnace Wiring with Multispeed
Fan Motor and Sail Switch
115V HUMIDIFIER
!
---------
I DIRECT DRIVE WIRING
F| F2 12 5 ^
-IH
fan I 41 MED LO
SWITCH
115V HUMIDISTAT
HUI ,
3 ! 6
________
—((^ H ; H -------------
—il
24V HUMIDISTAT 24 V HUMIDIFIER
*Ar
LIMIT
m
____
LIMIT
]J
VAL2
--------------
■ —
--------
HAF VALVE
(WHEN USED)
---
CHWO
<2^>0-<2)
CONTACTOR IN REMOTE \
CONDENSING UNIT
-<f{^>-------------------'
BLOWER RELAY
Fig. 9 — Electronic Air Cleaner Wired into
58ES or 58GA Furnace Wiring
GAS
-----
-------------
1
LEGEND for Fig. 6, 7, 8, 9,10 and 11
31 MM or MP wiring FS
ACR — Air Cleaner Relay
FR — Fan Relay SS
(Location of ACR LS
is optional ) PS
(FR may be installed Trans
in furnace ) V
HAF
HR
— Fan Switch
— Heat Assist Fan Switch
— Humidifier Relay
— Limit Switch
— Pilot Switch
— Sail Switch
— Transformer
— Gas Valve
NOTES for Fig. 10 and 11
1 Transformer must be used on 208-230 V supply Exceptions:
a) 208-3 Phase wye
b) 208/230-1 Phase with reliable ground
2 Dashed lines indicate wiring for:
a) 208-3 Phase wye
b) 208/230-1 Phase with reliable ground
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