Installation and Service
THIS MANUAL IS THE PROPERTY OF THE OWNER. 
PLEASE BE SURE TO LEAVE IT WITH THE OWNER WHEN YOU LEAVE THE JOB. 
Inspection on Arrival
1. Inspect unit upon arrival. In case of damage, report it 
immediately to transportation company and your local 
Modine sales representative.
2. 
Check rating plate on unit to verify that power supply meets 
available electric power at the point of installation.
3.  Inspect unit upon arrival for conformance with description of 
product ordered (including specifications where applicable).
Table of Contents
Inspection on Arrival ................................. 1
Special Precautions ................................. 2
SI (Metric) Conversion Factors......................... 3
Before you Begin ................................... 3
Unit Location....................................... 4
  Combustible Material and Service Clearances ......... 4
 Unit Mounting .................................. 5
  Venting  ....................................... 6
 Gas Connections............................... 12
  High Altitude Accessory Kit . . . . . . . . . . . . . . . . . . . . . 13-14
 Electrical ...................................15-16
 Operation..................................... 17
Unit Components .................................. 18
Dimensions....................................... 19
Service/Troubleshooting............................. 20
Unit Wiring Diagram ................................ 21
Serial/Model Number/Replacement Parts  ............... 22
Commercial Warranty........................Back Cover
INSTALLATION AND SERVICE MANUAL
separated combustion gas-fired unit heaters 
model HDS and HDC
6-584.13
5H0800020000
October, 2019
All models approved for use in California by the CEC and 
in Massachusetts. Unit heater is certified for residential and 
commercial applications. These unit heaters are certifed 
as Utility heaters and are intended for the heating of non-
living spaces that are attached to, adjacent to, or part of a 
structure that contains space for family living quarters. They 
are not intended to be the primary source of heat in residential 
applications. 
  WARNING
1. Improper installation, adjustment, alteration, 
service or maintenance can cause property 
damage, injury or death, and could cause 
exposure to substances which have been 
determined by various state agencies to cause 
cancer, birth defects or other reproductive harm. 
Read the installation, operating and maintenance 
instructions thoroughly before installing or 
servicing this equipment.
2. Do not locate ANY gas-fired units in areas where 
chlorinated, halogenated, or acidic vapors are 
present in the atmosphere. These substances 
can cause premature heat exchanger failure due 
to corrosion, which can cause property damage, 
serious injury, or death.
FOR YOUR SAFETY
The use and storage of gasoline or other flammable 
vapors and liquids in open containers in the vicinity 
of this appliance is hazardous.
FOR YOUR SAFETY
WHAT TO DO IF YOU SMELL GAS:
1. Open windows.
2.  Do not try to light any appliance.
3.  Do not touch any electrical switch; do     
  not use any phone in your building.
4.  Immediately call your gas supplier     
  from a neighbor’s phone. Follow the gas    
  supplier’s instructions. If you can not reach   
  your gas supplier, call your fire department. 
IMPORTANT
The use of this manual is specifically intended 
for a qualified installation and service agency. All 
installation and service of these units must be 
performed by a qualified installation and service 
agency.










