Qmark MSPH User Manual

PRH Series

Plenum Heaters

Installation & Maintenance Instructions

Dear Owner,

Congratulations! Thank you for purchasing this new heater manufactured by Marley Engineered Products. You have made a wise

investment selecting the highest quality product in the heating industry. Please carefully read the installation and maintenance

instructions shown in this manual. You should enjoy years of efficient heating comfort with this product from Marley Engineered

Products... the industry’s leader in design, manufacturing, quality and service.

... The Employees of Marley Engineered Products

WARNING

!

Read Carefully - These instructions are written to help
you prevent difficulties that might arise during installa­tion of heaters. Studying the instructions first may save
you considerable time and money later. Observe the
following procedures and cut your installation time to a
minimum.

TO REDUCE RISK OF FIRE OR ELECTRIC SHOCK:

1. Disconnect all power coming to the heater at main service
panel before wiring or servicing.

Note: More than one disconnect may be required.

2. All wiring must be in accordance with national and local
electric codes and the heater must be grounded.

3. Verify the power supply voltage coming to heater matches
the ratings printed on the heater nameplate before ener­gizing.

SAVE THESE INSTRUCTIONS

4. This heater is hot when in use. To avoid burns, do not let
bare skin touch hot surfaces.

5. Do not insert or allow foreign objects to enter any ventila­tion or exhaust opening as this may cause electric shock,
fire, or damage to heater.

6. Do not block air intakes or exhaust in any manner.

7. A heater has hot and arcing (sparking) parts inside. Do not
use in areas where gasoline, paint, or flammable liquids
are used or stored.

8. Use this heater only as described in this manual. Any other
use not recommended by the manufacturer may cause fire,
electric shock, or injury.

9. This heater is not approved for use in corrosive atmos­pheres such as marine, green house, or chemical storage
areas.

10. FOR DUCT CONNECTED HEATERS, rated at 0.20”

external static pressure.

ENERAL INFORMATION:

12” Small

11.64” Large

10”

Small

15.32”
Large

Electrical
Knocknot

Ground
Connection

Power
Connection

G

The PRH Series plenum heaters are design certified by ETL to
Standard for Heating and Cooling Equipment ANSI / UL 1995,
CAN/CSA C22.2 No. 236-05, third edition. The PRH Series
plenum heaters are unique application heaters approved for
installation in a concealed space, an area between a finished
ceiling and drop ceiling, a plenum space or inside a plenum.
These series of heaters may be installed in areas that are not

eadily accessible and may be installed with a duct system or

r
installed for free-air discharge. Always install units to operate
within the intended temperature rise, intended external static
pressure range and in the intended installation position (see
Figure 2 horizontal-right).

Figure 2

AIRFLOW DIRECTION

MOUNTING:

The PRH Series plenum heaters are intended to be mounted
in the horizontal-right installation position (see Figure 2) and in
a suspended manner. The unit can be rotated on its axis in
any position needed (can not be mounted vertically). Suspend
the unit from the building structure in a horizontal plane. Units
must be independently supported. Support channels or straps
are intended to be permanently attached to unit frame/housing.
Be careful not to obstruct access to control panel with support
channels or straps. DUCT CONNECTIONS / DUCTING:

The PRH Series plenum heaters may either be installed for
free-air discharge or with a duct system. The proper sizing of
warm air ducts is essential in providing satisfactory heating
operation. Ductwork should be in accordance with the latest
editions of NFPA-90B (Warm Air Heating and Air Conditioning

ystems) or Canadian equivalent. Every PRH model is

S
equipped with an inlet and outlet grille for free-air discharge.
Both grilles are intended to be removed when connecting to a
duct system. The inlet and outlet ends of the unit are
equipped with perforated flanges to aid in forming both inlet
and outlet duct flanges (see Figure 3).

These perforations will aid in forming a rectangular inlet and
outlet duct flange if they are desired for connection to the duct

ystem. The unit is designed for a rectangular flange duct con-

s
necting and the clear area around the flange is intended for
screw penetration. This feature aids in attaching the duct work
to the unit so that the ductwork may be fastened and sealed to
the unit.

CONTROL ACCESS:

The front door allows access to all the controls and compo­nents within the unit. The unit is design certified for 0” clear­ances however, while installing the unit, be careful not to
obstruct access to this control panel. This panel allows access
to the unit for making the power connection, the thermostat
connection and is intended to allow access to all the internal
components that make up the unit.

ELECTRICAL CONNECTIONS:

All field wiring must comply with NEC and local codes.

NNOOTTEE:: SSEEEE PPAAGGEE 33 && 44 FFOORR WWIIRRIINNGG DDIIAAGGRRAAMMSS

All units are designed for a single point connection to supply
power to the fan and electric heater. The PRH series plenum
heaters are shipped standard with a 80 amp 3-pole disconnect
switch. Field power connections are made to the line side of
this disconnect switch (see Figure 4).

Each unit is equipped with a grounding lug for ground connec-

Figure 4

Figure 3

tion. The unit must be properly grounded to comply with NEC
and local codes. Before making the power connection, insure
that the line voltage to the unit matches the ratings located on
the nameplate of the unit. All units should have copper wire
sized for 125% of nameplate amperage. Disconnect the power
supply before wiring the unit and insure the disconnect switch
is in the OFF position while making power connections or ser­vicing the unit. The unit cabinet has a 7/8” electrical knockout
for routing power supply to the disconnect switch (see
Specifications section for knockout location). Should the unit
require a larger electrical conduit connection, this electrical
knockout is intended to serve as the pilot hole in order to field
convert to larger electrical connections.

2

ONTROL CONNECTIONS:

C

The PRH Series plenum heaters are designed to operate from
a 24VAC thermostat. Model TH5220D1003 24V 2 stage ther­mostat is recommended to be used with the PRH Series
heaters. Thermostat connections are made to the thermostat
board located inside the unit. The thermostat label indicates
which connections are (RGCW) for making these thermostat
connections. The unit cabinet has a 3/8” knockout for routing

hermostat wiring to the units thermostat board (see

t
Specifications section for knockout location). Instructions for
wiring the thermostat are packed with the thermostat. The unit
is intended to operate with heat (W) and fan (G). If the unit is
intended for cooling signals from the thermostat, make the Y
connection from the thermostat to the G connection on the
unitʼs thermostat board.

UNIT OPERATION:

The PRH Series plenum heaters are intended to be operated
from a 24V thermostat. (Model TH5220D1003)

HEATING OPERATION

When there is a demand for heat, the thermostat sends a sig­nal to the unit for this demand for heat. The unitʼs thermostat
board will send power to the unit controls to initiate the heating
operation. The call for heat makes the connection on the ther­mostat board by powering “W” with “R”. Upon this demand for
heat, the heating element starts heating and the fan on delay
will power the fan within 60 seconds from the call for heat.
The fan delay ensures that there will not be a cold blast of air
to ensure comfort heating. When the heat demand has been
met, the thermostat will send the signal back to the unitʼs ther­mostat board to stop the heating operation. This breaks the
power connection between “R” to “W” and the heating element

tops heating immediately. The fan off delay allows the fan to

s
continue running to remove all residual heat from the heating
element and will turn the fan off within 60 seconds. Should
there be any abnormal conditions to cause the units limit to
open during the call for heat, the units heat will turn off immedi­ately but the fan will go through its normal off delay. During
this open limit period, the power to the thermostat will be inter­rupted until the limit closes. This helps in determining abnor­malities during heating operation by way of interrupting power

o the thermostat.

t

FAN OPERATION

When there is a demand for fan, the thermostat sends a signal
to the unit for this demand for fan. The unitʼs thermostat will
send power to the unit controls to initiate the fan operation.
The call for fan makes the connection on the thermostat board
by powering “G” with “R”. The fan will immediately come on
and continue to run until the demand for fan has ended. When
the fans demand has been met, the fan will immediately turn
off. This breaks the power connection between “R” to “G”.

HEATING OPERATION + FAN OPERATION

When there is a demand for both heat and fan at the same
time, the heating element will come on immediately as well as
the fan. The fan on delay will be bypassed. Upon completion
of the demand for both heat and fan, the heating element will
turn off immediately. However, the off delay will work the same
as during the heating operation.

COOLING OPERATION

Should the unit be used for cooling, the “Y” connection from
the thermostat should be connected to the “G” on the thermo­stat board. The cooling operation will operate like the fan
operation above.

WIRING DIAGRAMS

Single Phase - Single Element

Three Phase - Single Element 480V

3