Puregas MHT Series User manual

Owners Manual
Refrigerated Air Dryer
MHT SERIES
IMPORTANT: READ THIS MANUAL
CAREFULLY. IT CONTAINS INFORMATION
ABOUT SAFETY AND THE SAFETY OF OTHERS.
ALSO BECOME FAMILAR WITH THE PROPER
INSTALLATION AND CONTROLS OF THE AIR
DRYER BEFORE OPERATING. ONLY QUALIFIED,
TRAINED AND LISCENSED PERSONAL SHOULD
SERVICE OR OPERATE THIS EQUIPMENT.
CAUTION:THIS MACHINE CONTAINS HIGH
PRESSURE GAS AND ELECTRICITY.
TABLE OF CONTENTS
INTRODUCTION, RECEIVING, DATA LABEL 2
HOW THE AIR DRYER WORKS 3
INSTALLATION 4
DRYER CONTROLS, START UP, INITIAL RUN
PROCEDURE 5
WEEKLY MAINTENANCE, SETTING DRAIN
TIMER, TECHNICAL DATA 6
ADJUSTING SUCTION PRESSURE/EVAP
TEMP, ELECT SCHEMATICS 7
NOTE:
If you need service on your dryer please have
the following information:
1. Model #__________________________
2. Serial #___________________________
3. Voltage___________________________
4. Name of distributor that dryer was pur-
chased from:
_________________________________
_________________________________
5. Description of the problem:

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INTRODUCTION
Thank you for selecting an MHT Series refrigerated air dryer from PUREGAS. The refrigerated air dryer is specifically designed
and manufactured for drying and purifying compressed air generated by an air compressor.
PLEASE READ THIS INSTRUCTION MANUAL CAREFULLY BEFORE USING THE DRYER.
Please pay attention to the precautions in transportation, installation and operation that are listed in this manual. Please use the dryer
according to our application guide and be sure to perform the proper preventative maintenance recommended in this manual. Failure
to perform the preventative maintenance will void the air dryer warranty. Refrigeration used in this air dryer is environmentally
friendly R134a and is available at local refrigeration wholesalers. Direct any question not covered in this manual to your distributor
or call PUREGAS at 1-800-521-5351. Before calling with any questions always have the air dryer model #, serial # and
pressure gauge readings. Service and maintenance can be obtained from your distributor. If you do not know your
distributor please contact the factory. Authorization # must be obtained from PUREGAS. before any parts or dryers are returned to
the factory. PUREGAS. will not be responsible for anything returned without authorization.
RECEIVING AND INSPECTION
1. The dryer cannot be tilted on its’ side or upside down during shipping.
2. Use forklift from the bottom of the dryer when installing and moving.
3. Dryers are shipped F.O.B. factory. Immediately upon arrival check the dryer for possible damage. If damage is found, report it to
the carrier and file a damage claim.
4. Check dryer data label to be sure you have the right dryer. Check the data labels voltage and amperage to be sure it is correct and
the one you ordered.
5. Check refrigeration gauges for pressure. If gauges read 0 PSIG STOP! Do not start dryer. Call yourdistributorforservice. This
could mean there is a leak and refrigerant has leaked out.
DATA LABEL
The data label is affixed to the outside of the cabinet. This label identifies the air dryer’s model and serial numbers and important
technical data. Before installing the dryer check all of the information on the data label for the correct model and voltage. If the
model number and voltage are incorrect do not install the dryer. Do not put power to the dryer. Call your local distributor.

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HOW THE AIR DRYER WORKS
MHT Series refrigerated compressed air dryers use refrigeration cooling to condense entrained moisture out of the compressed air
stream. Warm saturated air enters the air-to-air heat exchanger at the dryer inlet. In the air-to-air heat exchanger the inlet air is pre-
cooled by the outgoing cold air. The pre-cooled air then enters the air-to-refrigerant heat exchanger where it is cooled to its lowest
point by the refrigeration in the evaporator. As the air is cooled, moisture in the air changes from a vapor to a liquid. The liquid
condensate is removed from the airstream by the separator and discharged from the dryer by the automatic drain valve. The cold air
is reheated by incoming warm air as it passes back through the air-to-air heat exchanger. Pre-cooling the inlet air reduces the heat
load on the refrigerant compressor, permitting the use of a smaller refrigerant compressor. The outgoing cold air is reheated by the
incoming hot air. As a result the outlet air is warmed up as it leaves the dryer. This prevents the outlet pipe from sweating. The air
exits the dryer and is now clean and dry, ready for use.

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INSTALLATION AND LOCATION CONTINUED
VENTILATION– Install dryer only in a well-ventilated, clean, dry area and keep at least 3 feet between the dryer, other equipment
and the walls.
DRYER LOCATION– Make sure there is approximately 3 feet around the dryer for service and maintenance purposes. Do not
install the dryer outside. The air dryer must not be exposed to direct sunlight, rain or snow. Do not install the dryer in an environment
with fire, high temperature or low temperatures. Make sure the dryer is installed in an environment that is clean and dry. Dust and
dirt particles will clog the air-cooled condenser. A clogged and dirty condenser will reduce the performance of the dryer and will
eventually cause damage to it.
AMBIENT TEMPERATURES– Suitable ambient temperature for the refrigerant dryer is a MIN of 40°F to a Max of 110°F. The
performance of the dryer will be significantly decreased when the air dryer is subject to temperatures higher than 110°F. For
installations with ambient temperatures higher than 110°F it is recommended to use a water-cooled condenser on the dryer. Contact
your distributor for details.
SELECTING PROPER IN AND OUT PIPING AND PIPING DESIGN– Pipe diameter should be sized according to air flow
requirements. Do not mix the air inlet and outlet air flow. It is recommended that a vibration absorberbe installed on the dryerinlet
and outlet to eliminate vibration from the compressor. Do not use the inlet and outlet of the air dryer to support the weight of
the air piping.
3 VALVE BYPASS AND ISOLATION VALVES– Should be installed on the air dryer outlet and inlet ports to allow for
bypassing, depressurizing and proper maintenance and servicing of the air dryer.
CONDENSATE DRAINS– Condensate drains must be properly piped from the dryer to prevent moisture re-entrainment. The
dryer is equipped with an automatic drain valve that controls the discharge of the condensate and a manual valve to manually drain
condensate. The user must run a drain line to an environmentally approved condensate collection/disposal system.

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ELECTRICAL INSTALLATION– The dryer data label lists the electrical power requirements for the air dryer. The user must
confirm that the line voltage matches the voltage listed on the data label. (Warning– Operating the air dryer with improper line
voltage will void the warranty.) Provide the proper size wire, disconnect switches and fuses in accordance with applicable
codes. Field wiring must comply with local and national fire safety and electrical codes. Standard dryer’s enclosures and controls are
designed to meet NEMA 1 Type 1 electrical standards. All wiring is complete. Connect power leads as indicated in the electrical
schematic. Ground the frame properly. Once power is connected turn the power on to the dryer.
MAXIMUM WORKING PRESSURE - 232 psig.
CAUTION:
BREATHING AIR APPLICATIONS– This dryer has not been tested for breathing air applications. The owner is advised to do its
own testing and use for breathing air applications at own risk.
DRYER CONTROLS
1. On/Off switch– Turns the refrigerant compressor on/off.
2. Power On Light– Indicates there is power to the dryer.
3. Digital Dew-Point Temp. Indicator– indicates the approximate dew point temp of the compressed air.
4. Refrigerant Suction Pressure Gauge
5. Hot Gas Bypass Valve– Controls the evaporator pressure
6. Fan Cycling Switch– Cycles the condenser fan on and off based on the condensing pressure. (See Figure 1)
7. High Pressure Shutdown w/Manual reset– Cut Out 300 PSIG
8. Low Pressure Shutdown– Cut Out 10 psig / Cut In 25 psig
9. Programmable Electronic Auto-Drain Valve– Automatically controls the draining of liquid condensate removed by the dryer.
START UP
The following procedure must be followed to start your air dryer. Failure to follow this start up procedure will void your warranty. If
problems occur during start up, contact your distributor.
1. Turn off the On/Off switch.
2. Verify the main electrical supply voltage matches the voltage specified on the data label.
3. Do not turn the dryer on during this warm up period.
4. Check the proper connection and support of the compressed air lines to the dryer .
5. Check dryer bypass and isolation valve system.
6. Confirm that the inlet and ambient air temperature, pressure and flow to the dryer meet specified requirements.
7. Confirm that the condensate drain lines from the separator are properly piped to an environmentally approved disposal system.
INITIAL RUN PROCEDURE
After start up and checks are complete and after the main electrical power to the dryer has been turned on
1. Turn ON the dryer On/Off switch.
2. After 15 seconds observe the refrigerant suction pressure gauge. It should start to pull down immediately.
3. Let the dryer run for 15 minutes.
4. Check the refrigerant suction pressure gauge
Should Read: On R134a dryers ( 28 psig to 34 psig)
6. Check the DEWPOINT TEMP INDICATOR. After about 15 min it should read 35°F to 39°F.
7. Verify that the condenser fan motor is operating. The fan will cycle on and off.
8. Allow compressed air to flow through the dryer.
9. Confirm that condensate is discharging from the condensate drain. This may take 30-60 min.
10. Make sure bypass valves are closed and 100% of the air from the compressor is flowing through the dryer.

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WEELKY MAINTENANCE
• Clean air cooled condenser coils– Blow off all dust and dirt that is on the condenser fins with a compressed air maintenance gun.
• While cleaning condenser fins take caution to no damage the fins.
WARNING: DRYER FAILURE DUE TO A DIRTY CONDENSER IS NOT COVORED UNDER WARRANTY
HOW TO SET THE CONDENSATE DRAIN OPEN & CLOSED TIME
(LOCATE DRAIN VALVE)
1. The OPEN (ON) time is adjustable from 0.5 sec to 10 sec. Drains are set at factory to open for 6 sec. When drain opens the on
light will light.
2. The CLOSED (OFF) time is adjustable 0.5 min to 45 min. Drains are set at factory to stay closed for 10 min. When drain is
closed the off light will light.
You may increase or decrease this based on moisture levels in the air.
Push the TEST button to manually open the drain valve.
TECHNICAL
SPECIFICATIONS DRYER MODEL
MHT40 MHT60 MHT100 MHT130
RATED CAPACITY IN SCFM 40 60 100 130
PRESSURE DROP (PSID) 1.4 1.6 1.75 1.8
MIN/MAX INLET PRESSURE 20 PSIG / 230 PSIG
MAX INLET TEMP 120F
MIN/MAX AMBIENT TEMP 45 F / 110 F
VOLTAGE 115-1-60 230-1-60
VOLTAGE RANGE 126-103 253-187
REF COMPRESSOR HP 1/3 1/2 3/4 1
RLA: RUN LOAD AMPS 5.82 9.5 13.7 7
LRA: LOCK ROTOR AMPS 32 48 69 41
MAX FUSE SIZE 20 20 30 15
MIN. CIRCUIT CAPACITY 11.54 12.4 18.5 9.9
REFRIGERANT TYPE R134a
REFRIGERANTE AMOUNT SEE DATA LABEL
REFRIG. SUCTION PRESSURE 28 PSIG
SHIPPING WGT (LBS) 180 195 205 250
MHT25
25
1.2
1/3
5.82
32
20
11.54
115
TECHNICAL DATA

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HOW TO MAKE MINOR REFRIGERANT SUCTION PRESSURE (EVAP TEMP) ADJUSTMENTS
1. Keep dryer running under a no load by turning off or bypassing the compressed air.
2. Remove dryer top and locate the Hot Gas Bypass Valve.
3. Remove cap on Hot Gas Bypass Valve and using an Allen wrench turn valve counter clockwise to decrease the suction pressure
and clockwise to increase the suction pressure. Make 1/2 turn adjustments and wait 2 to 3 minutes for suction pressure to
stabilize. Make more adjustments if needed.
MHT130 MHT75 & MHT100 MHT25 & MHT40
ELECTRICALSCHEMATICS

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PUREGAS, LLC
226A Commerce St.
Broomfield, CO 80020
1-800-521-5351
www.airdryers.com