Greenheck MPX-H14 Installation Manual
®
®
Part #472695
Model MPX
Installation, Operation and Maintenance Manual
Please read and save these instructions for future reference. Read carefully before attempting to assemble,
install, operate or maintain the product described. Protect yourself and others by observing all safety
information. Failure to comply with instructions could result in personal injury and/or property damage!
Model MPX
General Safety Information
Only qualied personnel should install and maintain
this system. Personnel should have a clear
understanding of these instructions and should
be aware of general safety precautions. Improper
installation can result in electric shock, possible injury
due to coming in contact with moving parts, as well as
other potential hazards. Other considerations may be
required if high winds or seismic activity are present.
If more information is needed, contact a licensed
professional engineer before moving forward.
1. Follow all local electrical and safety codes, as
well as the National Electrical Code (NEC), the
National Fire Protection Agency (NFPA), where
applicable. Follow the Canadian Electric Code
(CEC) in Canada.
2. All moving parts must be free to rotate without
striking or rubbing any stationary objects.
3. Unit must be securely and adequately grounded.
4. Do not spin wheel faster than maximum
cataloged fan RPM. Adjustments to fan speed
signicantly affect motor load. If the fan RPM is
changed, the motor current should be checked
to make sure it is not exceeding the motor
nameplate amps.
5. Verify that the power source is compatible with
the equipment.
6. Never open access doors to the unit while it is
running.
DANGER
• Always disconnect power before working on or
near this equipment. Lock and tag the disconnect
switch or breaker to prevent accidental power up.
• If this unit is equipped with optional gas
accessories, turn off gas supply whenever power
is disconnected.
CAUTION
This unit is equipped with a compressed refrigerant
system. If a leak in the system should occur,
immediately evacuate and ventilate the area. An
EPA Certified Technician must be engaged to make
repairs or corrections. Refrigerant leaks may also
cause bodily harm.
CAUTION
When servicing the unit, the internal components
may be hot enough to cause pain or injury. Allow
time for cooling before servicing.
Model MPX Make-Up Air Unit
1
Receiving
®
Upon receiving the product, check to make sure all
items are accounted for by referencing the Bill of
Lading to ensure all items were received. Inspect
each crate for shipping damage before accepting
delivery. Notify the carrier if any damage is noticed.
The carrier will make notication on the delivery
receipt acknowledging any damage to the product.
All damage should be noted on all copies of the Bill
of Lading which is countersigned by the delivering
carrier. A Carrier Inspection Report should be lled
out by the carrier upon arrival and led with the
Trafc Department. If damaged upon arrival, le
claim with the carrier. Any physical damage to the
unit after acceptance is not the responsibility of the
manufacturer.
Unpacking
Verify that all required parts and the correct quantity
of each item have been received. If any items are
missing, report shortages to your local representative
to arrange for obtaining missing parts. Sometimes it
is not possible that all items for the unit be shipped
together due to availability of transportation and truck
space. Conrmation of shipment(s) must be limited to
only items on the Bill of Lading.
Handling
Units are to be rigged and moved by the lifting
brackets provided. This model is not designed for
forklifting. Location and number of lifting brackets
varies by model and size and all provided lifting
brackets must be used to properly support the unit
during handling. Handle each unit in such a way as
to keep from scratching or chipping the coating.
Damaged nish may reduce the ability of the unit
to resist corrosion. See also Installation / Handling
Concerns / Lifting in this manual.
should be given to touch-up or repainting. Units with
special coatings may require special techniques for
touch-up or repair.
Machined parts coated with rust preventative should
be restored to good condition promptly if signs of
rust occur. Immediately remove the original rust
preventative coating with petroleum solvent and clean
with lint-free cloths. Polish any remaining rust from the
surface with crocus cloth or ne emery paper and oil.
Do not destroy the continuity of the surfaces. Wipe
clean thoroughly with Tectyl® 506 (Ashland, Inc.) or
the equivalent. For hard to reach internal surfaces or
for occasional use, consider using Tectyl® 511M Rust
Preventative or WD-40
® or the equivalent.
Models and Capacities
The make-up air unit with packaged heating and
cooling is manufactured in four different platform
sizes, each of which has four different output tonnage
options. Examine shipping documents to verify
correct model as received and highlight the model and
tonnage as shown below.
Platform Tonnage
MPX-H14 5, 6, 8, 10
MPX-H24 11, 13, 16, 18
MPX-H34 20, 23, 26, 30
MPX-H34 (two furnaces) 20, 23, 26, 30
Serial Number
A metal plate with a unit serial number is located on
the door to the control center. Record the unit serial
number here:
Storage
Units are protected against damage during shipment.
If the unit cannot be installed and operated
immediately, precautions need to be taken to
prevent deterioration of the unit during storage.
The user assumes responsibility of the unit and
accessories during storage. The manufacturer will
not be responsible for damage during storage. These
suggestions are provided solely as a convenience to
the user.
Inspection and Maintenance During
Storage
While in storage, inspect units once per month. Keep
a record of inspection and maintenance performed. If
moisture or dirt accumulations are found on the parts,
the source should be located and eliminated. At each
inspection, rotate all moving parts by hand ten to
fteen revolutions to distribute lubricant on motor and
bearings. If paint deterioration begins, consideration
Model MPX Make-Up Air Unit
2
Table of Contents
®
General Safety Information . . . . . . . . . . . . . . 1
Receiving, Handling and Storage . . . . . . . . . . . 2
Models and Capacities . . . . . . . . . . . . . . . . 2
Serial Number . . . . . . . . . . . . . . . . . . . . . 2
Product Overview . . . . . . . . . . . . . . . . . . . 4
Supplemental Manuals . . . . . . . . . . . . . . . . 4
MPX Subassemblies
Blower . . . . . . . . . . . . . . . . . . . . . . . 4
Coils. . . . . . . . . . . . . . . . . . . . . . . . . 4
Dampers . . . . . . . . . . . . . . . . . . . . . . 4
DX System . . . . . . . . . . . . . . . . . . . . . 4
Electric Heater . . . . . . . . . . . . . . . . . . . 4
Filters . . . . . . . . . . . . . . . . . . . . . . . . 4
Indirect Gas-Fired Furnace . . . . . . . . . . . . 4
Unit Weights and Dimensions. . . . . . . . . . . . . 5
Clearances and Handling
Service Clearances . . . . . . . . . . . . . . . . . 6
Additional Clearances . . . . . . . . . . . . . . . 6
Handling Concerns . . . . . . . . . . . . . . . . . 6
Lifting . . . . . . . . . . . . . . . . . . . . . . . . 6
Rail and Roof Curb Mounting
Rail Mounting and Layout . . . . . . . . . . . . . 7
Roof Curb Mounting
Install Curb . . . . . . . . . . . . . . . . . . . . . 7
Install Ductwork . . . . . . . . . . . . . . . . . . 7
Set Unit . . . . . . . . . . . . . . . . . . . . . . . 7
Ductwork Connections . . . . . . . . . . . . . . . . 7
Vibration Isolators . . . . . . . . . . . . . . . . . . . 8
Plumbing / Piping Overview
Condensate Drain Trap . . . . . . . . . . . . . . . 8
Gas Connections . . . . . . . . . . . . . . . . . . 8
Typical Gas Supply Connection . . . . . . . . . . 8
Electrical Information
Field Power Connection . . . . . . . . . . . . . . 9
Voltage Supply . . . . . . . . . . . . . . . . . . . 9
Voltage Imbalance . . . . . . . . . . . . . . . . . 9
Low Voltage Controller Circuitry . . . . . . . . . . 9
Discharge Air Temperature Sensor . . . . . . . . . .10
Recommended Electrical and
Gas Connection Locations . . . . . . . . . . . . . .10
Discharge Air Temperature Sensor . . . . . . . . . .10
Control Centers
Main Control Center Components . . . . . . . . .11
Furnace Control Center Components . . . . . . .11
Control Center Components
DDC Control Package . . . . . . . . . . . . . . .12
Digital Scroll Compressor Controller . . . . . . .12
Fan Proving Switch. . . . . . . . . . . . . . . . .12
Variable Frequency Drives (VFD). . . . . . . . . .13
Phase Monitor . . . . . . . . . . . . . . . . . . .13
Typical Wiring Diagram . . . . . . . . . . . . . . 14-15
Controller Sequence of Operation . . . . . . . .16-17
Optional Controller Accessories . . . . . . . . . . .18
Refrigeration Schematic and
System Components . . . . . . . . . . . . . . .19-20
Digital Scroll Compressor
Refrigeration Modulation. . . . . . . . . . . . . .21
Compressor Cycling . . . . . . . . . . . . . . . .21
Conguration . . . . . . . . . . . . . . . . . . . .21
Electronic Control . . . . . . . . . . . . . . . . .22
Two Compressor Operation Concept . . . . . . .22
System Start-Up . . . . . . . . . . . . . . . . . .22
Troubleshooting
. . . . . . . . . . . . . . . . . .22
Pre Start-Up Checklist . . . . . . . . . . . . . . . .23
Start-Up Checklist . . . . . . . . . . . . . . . . . 23-24
Unit Start-Up
Fan . . . . . . . . . . . . . . . . . . . . . . . . .25
Supply Fan (Plenum Type) . . . . . . . . . . . . .25
Fan Performance Modications . . . . . . . . . .25
Fan Belt Drives . . . . . . . . . . . . . . . . . . .25
Belt Drive Installation. . . . . . . . . . . . . . . .25
Fan Wheel Rotation Direction . . . . . . . . . . .26
Fan RPM . . . . . . . . . . . . . . . . . . . . . .26
Vibration . . . . . . . . . . . . . . . . . . . . . .26
Spring Vibration Isolators . . . . . . . . . . . . .26
Coils. . . . . . . . . . . . . . . . . . . . . . . . .26
Condensate Drain . . . . . . . . . . . . . . . . .26
Troubleshooting
Airow. . . . . . . . . . . . . . . . . . . . . . . .27
Alarms . . . . . . . . . . . . . . . . . . . . . . .28
Unit . . . . . . . . . . . . . . . . . . . . . . . 29-30
Refrigeration System . . . . . . . . . . . . . . 31-35
Routine Maintenance
Monthly / Semi-Annually / Annually . . . . . . . .36
Units with Packaged DX . . . . . . . . . . . . . .36
Lubrication . . . . . . . . . . . . . . . . . . . . .36
Dampers . . . . . . . . . . . . . . . . . . . . . .36
Fan Belts . . . . . . . . . . . . . . . . . . . .36-37
Fan Motors . . . . . . . . . . . . . . . . . . . . .37
Fan Wheel and Fasteners . . . . . . . . . . . . .37
Fan Bearings . . . . . . . . . . . . . . . . . . . .37
Internal Filter Maintenance. . . . . . . . . . . . .38
External Filter Maintenance . . . . . . . . . . . .38
Coil Maintenance . . . . . . . . . . . . . . . . . .38
Maintenance Log
. . . . . . . . . . . . . . . . . . .39
Warranty . . . . . . . . . . . . . . . . . . . . . . . .40
Model MPX Make-Up Air Unit
3
Product Overview
®
MPX Subassemblies
This model is a horizontally congured make-up
air unit designed for outdoor installations. It has
an integral DX package for cooling and optionally
contains either an electric heater or one or two highly
efcient indirect gas-red furnace(s) to provide a
primary heat source for the building or to simply
temper the air that is supplied to the building. The unit
is designed to provide sufcient air to replace air that
is exhausted from the building and also heat and cool
as needed. The make-up air volume produced by the
unit is constant, but can be optionally modulated to
provide a variable volume (VAV).
The DX system comes fully charged with R-410A
refrigerant from the factory and is ready for operation
upon arrival.
All units are equipped with two compressors as
standard. The smallest units may have only one
compressor. If the digital scroll compressor option
was selected, the lead circuit will have a digital
scroll compressor and if a second compressor is
present, that one will be a standard xed scroll type.
All units with multiple compressors allow for staging
of compressors to meet a wider range of outdoor
air loads while reducing the number of cycles per
compressor.
Compressed Refrigerant
All of these make-up air models are charged with
environmentally-friendly R-410A compressed
refrigerant. Do not use tools or parts designed for
other refrigerants on this unit.
Airflow Arrangement
This model is designed for 100% outdoor air and
can be combined with a Variable Air Volume (VAV)
capability for greater exibility in response to building
air handling needs. The optional VAV function involves
a Variable Frequency Drive (VFD) controller for the
blower motor.
Safety Listing
The models are listed per ANSI/UL 1995, Heating and
Cooling Equipment and are ETL Certied.
Supplemental Installation, Operation and
Maintenance Manuals
Refer to the following Installation, Operation and
Maintenance manuals for additional information:
• Plenum and Plug
• Indirect Gas-Fired Furnace, Model PVF
• PCO3 Controller
Blower
Each unit has just one backward curved blower
(centrifugal fan). For further information refer to the
Plenum and Plug IOM.
Coils
Every unit is supplied with a single DX evaporator coil.
If there is only one cooling circuit, then the DX coil
is not divided. If two cooling circuits are specied,
then the DX coil will be an interlaced design. A reheat
coil may be optionally installed in the unit and is
connected to the lead compressor. Multiple condenser
coils are attached to the exterior of the model.
Dampers
There is only one damper that may be found in the
unit. It is an optional low-leakage motorized damper
located inside the cabinet in the intake airstream, near
the air intake weatherhood.
DX System
The DX system in the model is a complete, sealed
unit with compressed R-410A refrigerant. It consists
of one or two compressors (digital scroll optional),
evaporator and condenser coils and the following
integral components:
• expansion valves
• liquid line lter driers
• service / charging valves
• moisture indicating sight glass
• hot gas bypass (not present on optional digital
scroll compressors)
• crankcase heater on each compressor
Each DX system incorporates the following:
• high pressure manual reset cutout
• low pressure auto-reset cutout
• time delays for compressor protection
Electric Heater
An electric heater is optionally available for the model
and is used for tempering of the make-up air.
Filters
Each unit is optionally equipped with washable metal
lters in the outdoor air intake and with pleated
papers lters in the air intake stream. Paper lters may
be MERV 8 only, or the MERV 8 lters may be installed
as pre-lters for the optional MERV 13 paper lters or
optional MERV 15 lters.
Indirect Gas-Fired Furnace
The model may optionally include as many as two
indirect gas-red furnaces. See also Indirect GasFired Furnace, Model PVF Installation, Operation and
Maintenance Manual.
Model MPX Make-Up Air Unit
4
Unit Weights and Dimensions - dimensions are in inches
SUPPLY
AIR IINTAKE
COMPRESSOR
ACCESS DOOR
SUPPLY AIR
WEATHERHOOD
ACCESS
DOOR
CONDENSING
COIL
67.2
58.1
36.4
96.7
48.0
30.0
ELEVATION
CONTROL
CENTER
SUPPLY AIR
FILTERS
2-INCH
FILTERS
HGRH
COIL
DX
COIL
BI BLOWER
ASSEMBLY
SUPPLY AIR
DAMPER
IG HEATER
ELECTRIC HEAT
4-INCH
FILTERS
F
G
H
I
SUPPLY
AIR IINTAKE
COMPRESSOR
ACCESS DOOR
SUPPLY AIR
WEATHERHOOD
ACCESS
DOOR
CONDENSING
COIL
CONDENSING
COIL
RECOMMENDED
DUCT SIZE
39.0
11.4
39.0
6.0
DUCT SIZE
36.0
10.5
29.0
10.0
END
TOP VIEW
67.9
67.2
58.1
36.4
96.7
48.0
30.0
67.2
58.1
36.4
96.7
SUPPLY AIR
WEATHERHOOD
2 INCH SUPPLY
AIR FILTERS
SUPPLY AIR
DAMPER
2 INCH
FILTERS
4INCH
FILTERS
DX
COIL
HGRH
COIL
CONTROL
CENTER
BLOWER
ASSEMBLY
COMPRESSORS
IG HEATERS
ELECTRIC HEAT
F
G
H
I
I
®
MPX-H14, MPX-H24
G
F
SUPPLY AIR
WEATHERHOOD
2 INCH SUPPLY
AIR FILTERS
COMPRESSOR
MPX-H34
G
F
SUPPLY AIR
WEATHERHOOD
2-INCH SUPPLY
AIR FILTERS
2-INCH
FILTERS
SUPPLY AIR
DAMPER
SUPPLY
AIR
DAMPER
2 INCH
FILERS
4-INCH
FILTERS
DX
COIL
4-INCH
FILTERS
DX
REHEAT
COIL
COIL
I
ELEVATION
CONTROL
CENTER
REHEAT
COIL
CONTROL
CENTER
BLOWER
ASSEMBLY
BLOWER
ASSEMBLY
COMPRESSORS
IG HEATER
H
TOP VIEW
IG HEATERS
H
Single Furnace
I
Double Furnace
ELEVATION
Unit Size
MPX-H14 MPX-H24 MPX-H34 MPX-H34
Dimensions
Furnaces Single Furnace
A 54.3 67.2 72.2 76.2
B 86.6 96.7 97.7 97.7
C 34.0 36.4 33.2 33.2
D 48.1 58.1 72.7 72.7
E 62.6 67.9 70.8 70.8
F 21.6 27.7 38.8 38.8
G 23.5 30.5 37.0 37.0
H 54.3 67.2 76.2 76.2
I 132.4 150.8 148.0 182.7
Nominal
weight
(lbs)*
3194 3575 4831 5635
*Actual weights will vary based on the unit configuration.
Refer to the submittal for exact unit weight.
I
Double
Furnace
TOP VIEW
B
SUPPLY AIR
(HORIZONTAL
E
SUPPLY
A
DISCHARGE OPTION)
C
CONDENSING
COIL
D
5
Model MPX Make-Up Air Unit
Service Clearances
®
The units require minimum clearances for access on
all sides for routine maintenance. Filter replacement,
drain pan inspection and cleaning, fan bearing
lubrication and belt adjustment are examples of
routine maintenance that must be performed. Blower
and motor assemblies, coil and lter sections are
always provided with a service door or panel for
proper component access. Clearances for component
removal may be greater than the service clearances,
refer to drawings for these dimensions.
66 inches
42 inches
CONDENSER
FANS
36 inches
42 inches
CONDENSING COIL
IG FURNACE
Lifting
1. Before lifting, be sure that all shipping material
has been removed from unit.
2. To assist in determining rigging requirements,
weights are provided in the Unit Weights &
Dimensions section on page 5.
3. Unit must be lifted by all lifting lugs provided at
the top of the unit.
4. Rigger to use suitable mating hardware to attach
to unit lifting lugs.
5. Spreader bar(s) must span the unit to prevent
damage to the cabinet by the lift cables.
Additional clearances for units with
Packaged DX
Clearances must be maintained on all sides of
this model. This especially is true with the top of
this unit. Hot air is being discharged through the
condensing fans during operation, and the more
clearance available, the better the chance of avoiding
recirculation or coil starvation. This unit should never
be placed under an overhang or inside a building. A
minimum of 48 inches over the condensing fans is
recommended.
Handling Concerns for Units with
Packaged DX
While this unit was constructed with quality and
dependability in mind, damage still may occur during
handling of the unit for installation. Exercise extreme
caution to prevent any damage from occurring to the
refrigerant system. This unit contains a system that
is pressurized with refrigerant and if it is damaged,
the refrigerant could leak into the atmosphere or
cause bodily harm due to the extreme cold nature of
expanding refrigerant. Use protective equipment such
as gloves and safety glasses to minimize or prevent
injury in case of a system leak during installation.
6. Always test-lift the unit to check for proper
balance and rigging before hoisting to desired
location.
7. Never lift units by weatherhoods.
8. Never lift units in windy conditions.
9. Preparation of curb and roof openings should be
completed prior to lifting unit to the roof.
10. Check to be sure that gasketing has been
applied to the curb prior to lifting the unit and
setting on curb.
11. Do not use fork lifts for handling unit.
Model MPX Make-Up Air Unit
6
Rail and Roof Curb Mounting
®
Ductwork Connections
Rail Mounting and Layout
• The unit may be installed on rails provided and
installed by others. Ensure that rails are designed
to handle the weight of the unit and provide proper
load distribution on building supports.
• Make sure that rail positioning does not interfere
with the supply air discharge opening on the unit.
• Rails should run the width of the unit and extend
beyond the unit a minimum of 12 inches on each
side.
• Set unit on rails.
Roof Curb Mounting
Roof curb details, including duct location dimensions,
are available on the model’s roof curb assembly
instructions.
Rooftop units require curbs to be mounted rst. The
duct connections must be located so they will be clear
of structural members of the building.
1. Factory Supplied Roof Curbs
Roof curbs are model GKD which are shipped
in a knockdown kit (includes duct adapter) and
require eld assembly (by others). Assembly
instructions are included with the curb.
2. Install Curb
Locate curb over roof opening and fasten in
place. (Refer to Recommended Roof Openings).
Check that the diagonal dimensions are within
±1/8 inch of each other and adjust as necessary.
For proper coil drainage and unit operation, it is
important that the installation be level. Shim as
required to level.
3. Install Ductwork
Installation of all ducts should be done
in accordance with SMACNA and AMCA
guidelines. Duct adapter provided to support
ducts prior to setting the unit.
4. Set the Unit
Lift unit to a point directly
above the curb and
duct openings.
Guide
unit while
lowering
to align
with duct
openings.
Roof curbs
t inside the
unit base.
Make sure
the unit is
properly
seated on
the curb
and is level.
The supply fan in this unit is a plenum-type fan. The
discharge opening dimensions are provided in the
chart below. For proper fan performance, match the
duct size to the dimensions indicated. Installation
of all ducts should be done in accordance with Best
Practices and SMACNA.
Supply Air Duct Opening Dimensions
(height x width; inches)
Downblast Discharge Horizontal Discharge
Model
MPX-H14 28.9 x 25.9 24.9 x 25.9 28.5 x 27.5 28.5 x 27.5
MPX-H24 33.9 x 25.9 33.9 x 25.9 38 x 38 35.9 x 27
MPX-H34 33.9 x 25.9 36.3 x 28.9 38 x 38 39 x 40
Indirect
Gas
Electric
Heat
Indirect
Gas
Electric
Heat
NOTE
Downblast Discharge Ductwork - whenever
downblast discharge is used, the ductwork directly
beneath the unit must be connected with either a “T”
or an “L” configuration and the area directly beneath
the heat source must not have any openings such
as louvers or grates.
No openings directly beneath the unit discharge.
Model MPX Make-Up Air Unit
7
Vibration Isolators
Intermediate
Shipping Rail
(typical)
®
Plumbing / Piping Overview
NOTE
Many motor / blower assemblies include optional
spring vibration isolation devices. When these
isolation springs are used, the motor / blower
assembly is secured for shipment by compressing
the springs and securing the assembly to
intermediate rails (see photo).
Spring Isolation
Device
Motor / Blower Assembly
in Shipping Position
After the unit is set in its nal location, visually inspect
motor / blower assembly to verify presence of spring
isolation devices. If they are present, carefully remove
shipping restraints to allow for free movement of the
assembly.
NOTE
These assemblies are shipped with the springs in
a compressed state and when shipping restraints
are removed, the assembly will bounce upward.
Do not position hands or fingers where they may
be pinched or injured by sudden movement of the
assembly.
The method of compressing and restraining the
motor/blower assembly varies with each product.
If sheet metal screws or bolts are used, they are
installed with an equal number on both the front and
the rear of each assembly. Screws or bolts used on
the rear rail are difcult to see. It is recommended
that the rear screws or bolts be removed before the
front ones in order to reduce the chance of injury. If
restraining bands are used instead of screws or bolts,
carefully cut and remove the bands.
The only piping connections required are the
condensate drain trap and gas connections for the
optional gas furnace(s).
Condensate Drain Trap
This unit is equipped with a stainless steel condensate
pan with a stainless steel drain connection. It is
important that the drain connection be tted with a
P trap to ensure proper drainage while maintaining
internal static pressures and to prevent migration of
sewer gas back into the unit. A P trap assembly (kit)
is supplied with the unit and is to be assembled and
installed as local conditions require and according to
the assembly instructions provided with the P trap. If
local and area building codes permit, the condensate
may be drained from the P trap onto the roof, but a
drip pad should be provided beneath the outlet. If
local and area codes require a permanent drain line, it
should be fabricated and installed in accordance with
Best Practices and all codes.
In some climates it will be necessary to provide freeze
protection for the P trap and
drain line. The P trap should
be kept lled with water or
glycol solution at all times and
it should be protected from
freezing to protect the P trap
from damage. If severe weather
conditions occur, it may be
necessary to fabricate a P trap
and drain line of metal and
install a heat tape to prevent freezing.
Gas Connections
If the model is equipped with an indirect gas-red
furnace, connection to an appropriate gas supply
line will be required. For complete information on
installation procedures for the optional gas furnace(s),
refer to Indirect Gas-Fired Furnace, Model PVF.
Typical Gas Supply Connection
Gas Cock
Ground
Joint
Union
Gas to
Controls
8
Model MPX Make-Up Air Unit
From Gas Supply
Bleeder Valve or
1/8 in Plugged Tap
8 in. Trap
Electrical Information
®
The unit must be electrically grounded in accordance
with the current National Electrical Code, ANSI/NFPA
70. In Canada, use the current CSA Standard C22.1,
Canadian Electrical Code, Part 1. In addition, the
installer should be aware of any local ordinances or
electrical company requirements that might apply.
System power wiring must be properly fused and
conform to the local and national electrical codes.
System power wiring is to the unit main disconnect
(door interlocking disconnect switch standard on most
units) or distribution block and must be compatible
with the ratings on the nameplate: supply power
voltage, phase and amperage (Minimum Circuit
Amps - MCA; Maximum Overcurrent Protection MOP). All wiring beyond this point has been done by
the manufacturer and cannot be modied without
affecting the unit’s agency / safety certication. If
eld installing an additional disconnect switch, it
is recommended that there is at least four feet of
service room between the switch and system access
panels. When providing or replacing fuses in a fusible
disconnect, use dual element time delay fuses and
size according to the rating plate.
Field Power Connection
All power and control connections should be run
through the floor or side panel of the unit.
WARNING
The roof lining contains high voltage wiring. To
prevent electrocution, do not puncture the interior or
exterior panels of the roof.
If power supply is desired through bottom of unit, run
the wiring through the curb, cut a hole in the cabinet
bottom and run wires to the disconnect switch. Seal
the penetration in cabinet bottom to prevent leakage.
The electric supply to the unit must meet stringent
requirements for the system to operate properly.
Voltage supply and voltage imbalance between
phases should be within the following tolerances.
If the power is not within these voltage tolerances,
contact the power company prior to operating the
system.
Voltage Supply
See Voltage Use Range on the rating plate. Measure
and record each supply leg voltage at all line
disconnect switches. Readings must fall within the
allowable range on the rating plate.
Voltage Imbalance
In a 3-phase system, excessive voltage imbalance
between phases will cause motors to overheat and
eventually fail. Maximum allowable imbalance is 2%.
To determine voltage imbalance, use recorded voltage
measurements in this formula.
Key: V1, V2, V3 = line voltages as measured
VA (average) = (V1 + V2 + V3) / 3
VD = Line voltage (V1, V2 or V3) that
deviates farthest from average (VA)
Formula: % Voltage Imbalance = [100 x (VA-VD)] / VA
CAUTION
If any of the original wire as supplied with the unit
must be replaced, it must be replaced with wiring
material having a temperature rating of at least
105ºC.
WARNING
To prevent injury or death due to electrocution or
contact with moving parts, lock disconnect switch
open.
For units with a gas furnace, if you turn off the
power supply, turn off the gas.
Low Voltage Controller Circuitry
Manufacturer recommends that all low voltage
wiring be run in conduit wherever it may be
exposed to the weather.
Most factory-supplied electrical components are
pre-wired. To determine what electrical accessories
require additional eld wiring, refer to the unit-specic
wiring diagram located on the inside of the control
center access door.
Field Control Wiring Length/Gauge
Total
Wire Length
125 ft. 18
200 ft. 16
300 ft. 14
450 ft. 12
The low voltage control circuit is 24 VAC and control
wiring should not exceed 0.75 ohms.
Refer to Field Control Wiring Length/Gauge table for
wire length maximums for a given wire gauge.
Control wires should not be run inside the same
conduit as that carrying the supply power. Make sure
that eld-supplied conduit does not interfere with
access panel operation. All low voltage wiring should
be run in conduit wherever it may be exposed to the
weather.
If wire resistance exceeds 0.75 ohms, an industrialstyle, plug-in relay should be added to the unit
control center and wired in place of the remote
switch (typically between terminal blocks R and G
on the terminal strip (refer to Typical Control Center
Components). The relay must be rated for at least 5
amps and have a 24 VAC coil. Failure to comply with
these guidelines may cause motor starters to “chatter”
or not pull in which can cause contactor failures and/
or motor failures.
Minimum
Wire Gauge
Model MPX Make-Up Air Unit
9
Discharge Air Temperature Sensor
®
All units are supplied with a Discharge Air Temperature
Sensor that is to be eld-installed prior to unit startup. The sensor is to be installed at least three duct
diameters downstream of the
heat exchanger, or where good
mixed average temperature
occurs. The sensor must be
connected directly to the DDC
controller. All other sensors
and low voltage devices are
to be connected to the low
voltage terminal strip in the
control center. The discharge
air temperature sensor is
shipped loose and can be
found in the unit’s control
center. See the unit-specic
wiring diagram for connection
locations.
Typical Discharge Air
Temperature Sensor
Recommended Electrical and Gas Connection Locations
Installation requires penetrations into the cabinet for
high voltage electrical supply, low voltage controller
circuitry and for gas supply.
WARNING
Do not make penetrations in the roof of the MPX for
any reason. High voltage wiring is located between
the inner and outer shells of the roof. Damage to the
roof wiring circuitry could result in serious bodily
harm.
Gas supply connections are made through the
side of each unit in the factory-provided openings.
Penetrations for electrical connections are to be made
in the eld as job conditions may require. High voltage
supply wiring and low voltage controller circuitry
access may be made either through the side of the
unit or through the bottom. See illustrations below.
Recommended side access.
Control Center Door
Electrical Input
Access Side
Electric Heater Power Input Connection
Access Side
HIGH
VOLTS
LOW
VOLTS
Furnace 1
Gas Input
Furnace 2
Gas Input
Recommended locations for access through the base
of the cabinet are as shown.
Electrical Input
Base Access
Model MPX Make-Up Air Unit
10
Electric Heater
Power Input Connection
Base Access
Control Centers
®
Each model has a main control center where high
voltage supply wiring and low voltage controller
circuitry is terminated. In addition, if the electric heat
option was selected, there will be a separate control
center for the electric heater where the dedicated high
voltage supply is terminated. If the optional indirect
gas-red furnace option was selected, there will be a
furnace control center for each furnace.
Main Control Center Components
(locations vary by model)
High Voltage Side
1. Lockable Main
Disconnect
(terminate high
voltage supply
here)
2. Power
Distribution
Blocks
3. Fuse Holders
4. Compressor
Motor
Contactors
5. Condensing
Fan Motor
Contactors
6. Supply Fan
Motor Starter
7. Digital
Compressor
Controller
(optional)
8. Indirect Gas
Furnace
Transformer
(optional)
9. Fuse Blocks
10. Step-Down
Transformers
(number varies)
Low Voltage Side
11. DDC Controller
12. Relays
13. Fan Proving Switch/Dirty Filter Switch
(on side wall)
14. Low Voltage Terminal Strip
15. Hot Gas Reheat Controller (optional)
NOT SHOWN: Phase Monitor (see page 13)
In all cases, refer to the unit-specic wiring diagram
located on the control center door.
Furnace Control Center Components
(component locations will vary)
Components shown are for a typical 4:1 turndown
conguration.
High Voltage Side
1. Power Distribution Block
2. Inducer Relay (controls combustion fan)
3. Combustion Blower
Low Voltage Side
4. Input Converter
5. FX05 Controller (modulates heat and switches
entire unit on/off
6. Spark Generator (also has high voltage present)
6A. Spark Igniter
7. 24 volt Terminal Strip
Control Sensors
8. Hi Temp Sensor (auto reset)
9. Air Flow Switches
10. Flame Sensor
Gas Train
11. Combination Valve
12. EXA Valve
13. Burner Manifold
14. Collector Box
Model MPX Make-Up Air Unit
11
Control Center Components
®
DDC Control Package
Typical DDC Controller
Each unit is equipped with a microprocessor controller
commonly called a DDC, located in the main control
center. Depending on settings put in by the user and
the optional sensors ordered with the unit, the DDC
will control the operation of the unit and respond to
changing ambient conditions. The DDC will sense
outdoor air temperature and room temperature
(optional) and then regulate both heating and cooling.
It will switch from heating mode to cooling mode, as
needed. If an optional dehumidistat is ordered, the
DDC will also sense humidity levels in the space and
will adjust operation of the reheat coil during cooling
mode operation. All needed settings for the unit are
entered directly into the controller by means of push
buttons and both settings and operating conditions
can be easily viewed on the large LCD screen. An
optional remote interface panel is also available to
allow set points and other controller settings to be
adjusted from a remote location (see also Optional
Field-Installed Control Sensor. Microprocessor (DDC
Remote Interface. For further information on the
DDC controller, refer to the control catalog and the
Installation, Operation and Maintenance manual
provided with the controller.
Digital Scroll Compressor Controller
If the optional digital
scroll compressor
was ordered, the
main control center is
also equipped with a
dedicated controller
that monitors and
controls the operation
of the digital scroll
compressor. The
controller has LED
indicator lights to verify
correct operation and also various alarm conditions.
Typical Digital Scroll
Compressor Controller
(optional)
Fan Proving Switch
The unit uses a pressure switch to prove fan operation
before operating any heating or cooling sequence. It
does this by verifying a difference in air pressure on
both sides of the air supply fan. While the operation
of the switch is veried at the factory, the pressure
switch should be adjusted to meet eld conditions.
To adjust the switch, the supply fan must be running
with all of the access doors closed in order to
maintain normal operating pressures within the unit.
The control center door may be left open to access
the proving switch (see Proving Switch Location,
Electrical Information / Control Center Components).
The adjusting screw is located on the top of the
switch. Turning the screw clockwise will increase
the amount of pressure difference required to pull
the switch in, and turning it counterclockwise will
decrease the pressure difference required. Adjustment
to the switch is made while viewing the Supply Fan
Status screen on the DDC. Consult the DDC unit
control manual on how to view the Fan Proving
screen. While viewing the Fan Input Proving screen,
adjust the pressure switch so that the fan status
changes from “Open” to “Closed” or from “Closed” to
“Open”. Slightly decrease the set point by turning the
adjustment screw counterclockwise three rotations
to allow for pressure uctuations and air density
changes. The supply fan alarm may require resetting
before the unit can operate normally.
Setscrew (on front of switch)
must be manually adjusted after
the system is in operation.
Negative pressure connection
is toward the ‘front or top’ of
the switch. Senses pressure on
the blower side of filters.
Positive pressure connection is toward the ‘back
or bottom’ of the switch. Senses pressure at air inlet
side of filters.
Note that similar pressure switches may be found as
part of optional devices such as a dirty lter sensor.
Model MPX Make-Up Air Unit
12
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