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Bulletin A-20-HHT
®
Series HHT Hazardous Area Humidity/Temperature Transmitter
Specications - Installation and Operating Instructions
4-9/32
[108.74]
13-23/32 [347.98]
1/2 NPT
3-29/32
[99.22]
4-15/32 [113.51]
1/2 NPT
2-23/32
[69.06]
1/2 NPT
The Series HHT Hazardous Area Humidity/Temperature Transmitter takes
accurate measurements in the harshest of environments. The transmitter is offered
in explosion-proof and intrinsically-safe versions depending on the applications
requirements. The explosion-proof model is offered with 4 to 20 mA outputs for humidity
only. The intrinsically-safe version is offered with 4 to 20 mA output for humidity and
temperature. Both versions have an optional two line alphanumeric display to show the
current humidity and temperature.
The Series HHT humidity/temperature transmitter is excellent for offshore HVAC
applications, dust and grain applications.
MODEL CHART
Model Protection Description Display
HHT-EU
HHT-IU
HHT-IT
HHT-EU-LCD
HHT-IT-LCD
Explosion-Proof
Intrinsically Safe
Intrinsically Safe
Explosion-Proof
Intrinsically Safe
Humidity
Humidity
Humidity/Temperature
Humidity
Humidity/Temperature
No
No
No
Yes
Yes
SPECIFICATIONS
Relative Humidity Range: 0 to 100% RH.
Temperature Range: -40 to 140°F (-40 to 60°C).
Accuracy: ±2% 10-90% RH, ±0.9°F at 72°F (±0.3°C at 25°C).
Hysteresis: ±1%.
Repeatability: ±0.1% typical.
Temperature Limits: -40 to 140°F (-40 to 60°C).
Storage Temperature: -40 to 176°F (-40 to 80°C).
Compensated Temperature: -40 to 140°F (-40 to 60°C).
Power Requirements: For intrinsically safe models HHT-IX, 9.5 to 28 VDC. For
explosion-proof models HHT-EX, 16.5 to 28 VDC.
Output Signal: 4 to 20 mA, 2 channels for humidity/temperature models (loop
power on RH).
Response Time: 15 s.
Electrical Connections: Screw terminal block.
Conduit Connection: 1/2 female NPT.
Drift: <1% RH/year.
RH Sensor: Capacitance polymer.
Temperature Sensor: Solid state band gap.
Housing Material: Aluminum.
Display: Optional 2 line alpha numeric, 8 characters/line. Temperature display is
°F/°C selectable.
Display Resolution: RH: 0.1%: Temperature 0.1°F (0.1°C).
Weight: 2 lb 8 oz (1134 g).
Agency Approvals: FM Approved to: XP-IS / I / 1 / BCD / T5 Ta = -40°C to 60°C,
DIP / II, III / T5 Ta = -40°C to 60°C; TYPE 4X, IP66; IS / I, II, III / 1 / ABCDEFG / T4
Ta = -40°C to 60°C - 03-001467-00; ENTITY; TYPE 4X, IP 66; I / 0 / AEx ia / IIC / T4
Ta = -40°C to 60°C - 03-001467-00; ENTITY; TYPE 4X, IP 66, CE.
DWYER INSTRUMENTS, INC.
P.O. BOX 373 • MICHIGAN CITY, INDIANA 46360, U.S.A.
Phone: 219/879-8000
Fax: 219/872-9057
www.dwyer-inst.com
e-mail: info@dwyermail.com
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Wiring Diagram – Humidity Only
NON-HAZARDOUS SIDEHAZARDOUS SIDE
GROUND THIS SIDE OF CABLE ONLY
MODEL
INTRINSICALL
EXAMPLE USING PEPPERL
BARRIER SYSTEM
HAZARDOUS SIDE
NON-HAZARDOUS SIDE
MODEL HHT-IU, RH ONLY
INTRINSICALL
EXAMPLE USING MTL
SYSTEM
Explosion Proof Installation Notes:
1 . Install in accordance with any applicable national electric code.
2. Plug unused conduit openings. Plug must engage a minimum of 5 threads.
3. Use conduit seal within 18 inches of conduit entry.
4. Disconnect power before servicing.
5. Control equipment voltage on hazardous side is 250 Vrms/DC maximum.
6. Do not substitute any components. The intrinsic safety of the sensor may be
compromised.
7. Shielded cable for 4 to 20 mA loop is necessary to meet CE requirements or
when used in electrically noisy environments.
Wiring Diagram – Humidity and Temperature
Intrinsically Safe Installation Notes:
1. Remove power from the instrument before carrying out any servicing.
2. Use only FM approved Associated Apparatus. When installing the Associated
Apparatus, the manufacturer’s instructions must be followed.
3. The earth terminal on the housing must be wired to a local earth ground in the
hazardous area.
4. Refer to FM control drawing, Dwyer number 03-001467-00.
5. For Model HHT-IT, use ONLY Pepperl + Fuchs KFDØ-SCS-Ex1.55 Galvanically
Isolated Barriers.
SHOWN TRANSPARENT
FOR CLARITY
Entity Parameters:
Vmax = 28 VDC
Imax = 100 mA
Ci = 62 nF
Li = 7.7 µH
Pi = 651 mW
HHT-IT, RH AND TEMP.
Y SAFE WIRING
250 OHMS
CONVERSION RESISTOR
IF SHIELDED CABLE IS USED FOR
4-20 mA LOOP, GROUND THIS SIDE
OF CABLE ONLY
Figure 1 Figure 2
4-20 mA
LOOP
SUPPLY
SHOWN TRANSPARENT
FOR CLARITY
MODEL HHT-IT
Y SAFE WIRING
HAZARDOUS SIDE NON-HAZARDOUS SIDE
SHOWN TRANSPARENT
FOR CLARITY
+ FUCHS
BARRIER
NOTE! THE PEPPERL +
FUCH KFD0-SCS-Ex1.55
BARRIERS ARE
GALVANICALLY ISOLATED,
SO GROUNDING IS NOT
REQUIRED.
IF SHIELDED CABLE IS USED
KFD0-SCS-Ex1.55
KFD0-SCS-Ex1.55
I.S GROUND
4-20 mA
LOOP SUPPLY
RH
RECEIVER
TEMP.
RECEIVER
4-20 mA
LOOP SUPPLY
MODEL HHT-IU
MTL7787+
IF SHIELDED CABLE IS USED,
GROUND THIS SIDE OF CABLE ONLY
Figure 3
I.S GROUND
RH
RECEIVER
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Power Supply Requirements:
The maximum DC Power Supply is 28 VDC. The minimum required DC Power Supply
required is based upon the following:
1. Minimum DC voltage requirement of the Model HHT.
2. Total load resistance.
3. Total leadwire resistance.
4. Zener barrier voltage drop ( Model HHT-IX only).
The formula for calculating the DC Power Supply is:
VDC = VHHT + VLOAD + VLEADWIRE + VBARRIER
Where VHHT = 9.5 V for Models HHT-IX and 16.5 V for Models HHT-EX.
VLOAD = Total load resistance X 20 mA
VLEADWIRE = Total leadwire resistance X 20 mA
VBARRIER = 8.1 V
(Typical zener barrier voltage drop for this application)
Example 1. Calculate minimum DC Power Supply for Model HHT-EX (Explosion
Proof)
Step 1. VHHT = Minimum voltage required by Model HHT-EX = 16.5 V
Step 2. Calculate VLOAD. Using the industry standard 250 OHM conversion resistor,
VLOAD = 250 X 20 mA = 5 V.
Step 3. Calculate VLEADWIRE. For this example assume a leadwire resistance of 10
OHMS. VLEADWIRE = 10 X 20 mA = 0.2 V
Step 4. VDC = VHHT + VLOAD + VLEADWIRE = 16.5 + 5 + 0.2 = 21.2 V
Example 2. Calculate minimum DC Power Supply for Model HHT-IU (Intrinsically
Safe)
Step 1. VHHT = Minimum voltage required by Model HHT-IX = 9.5 V
Step 2. Calculate VLOAD. Using the industry standard 250 OHM conversion resistor,
VLOAD = 250 X 20 mA = 5 V.
Step 3. Calculate VLEADWIRE. For this example assume a leadwire resistance of 10
OHMS. VLEADWIRE = 10 X 20 mA = 0.2 V
Step 4. VBARRIER = 8.1 V
Step 5. VDC = VHHT + VLOAD + VLEADWIRE + VBARRIER = 9.5 + 5 + 0.2 +8.1 =
22.8 V
For Model HHT-IT, follow instructions with Pepperl + Fuchs KFDØ-SCS-Ex1.55 Barrier.
INSTALLATION
Location: Select a location where the ambient temperature is between -40 to +140°F
(-40 to +60°C)
Position: The transmitter is not position sensitive. Units with the optional display
should be mounted for ease of viewing the display.
Caution: Use electrostatic discharge precautions (e.g. use of wrist straps) during
installation and wiring to prevent equipment damage.
Avoid locations where severe shock or vibration, excessive moisture or corrosive
fumes are present.
Do not exceed ratings of this device. Permanent damage not covered by the warranty
may result.
Display: The temperature indicated on the display, if equipped with the LCD option,
is eld selectable via a jumper located on the circuit board just above the display. To
change the jumper position, remove the housing cover and position the jumper for °F
or °C according to Figure 4.
Figure 4
MAINTENANCE
Upon nal installation of the Series HHT Hazardous Area Humidity / Temperature
Transmitter, a periodic check of system calibration is recommended. The Series HHT
is not eld serviceable and should be returned if repair is needed (eld repair should
not be attempted and may void warranty). Be sure to include a brief description of the
problem plus any relevant application notes. Contact customer service to receive a
return goods authorization number before shipping.
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03-001467-00
03-001467-00
1
FM APPROVED
ASSOCIATED APPARATUS
2
NON-HAZARDOUS LOCATION
GROUND CONNECTION
G
2
1
GROUND CONNECTION
G
I.S. SAFETY GROUND
3
+
COM
HHT SERIES
TRANSMITTER
CATALOG NUMBERS:
HHT-IU AND HHT-IT
4
-
RH
m
Vmax=28VDC
Imax=100mA
Ci = 62nF
Li = 7.7 H
Pi = 651mW
-
TEMPERATURE
3
HAZARDOUS (CLASSIFIED) LOCATION
INTRINSICALLY SAFE FOR:
CLASS I DIV. 1 GROUPS A, B, C, D
4
OPTIONAL SHIELD
VI
IV
IV
CLASS II DIV. 1 GROUPS E, F, G
CLASS III DIV. 1
T4 Ta = -40°C TO 60°C TYPE 4X, IP 66
OR
T4 Ta = -40°C TO 60°C TYPE 4X, IP 66
CLASS I, ZONE 0, GROUPS IIC
VI
VI
FM CONTROL DRAWING
THIS LINE IS
NEMA 4X IP66
HOUSING ABOVE
DWYER INSTRUMENTS, INC.
P.O. BOX 373 • MICHIGAN CITY, INDIANA 46360, U.S.A.
Voc OR Uo OR Vt Vmax, Isc OR Io OR It Imax, Ca OR Co Ci + Ccable, La OR Lo Li + Lcable, Po Pi
DEVICES WITH ENTITY PARAMETERS NOT SPECIFICALLY EXAMINED IN COMBINATION AS A SYSTEM WHEN:
ZONE 0 HAZARDOUS LOCATIONS MUST BE IN ACCORDANCE WITH THE NATIONAL ELECTRICAL CODE NFPA 70, ARTICLE 505. ALL INSTALLATIONS MUST BE
3. DIVISION 1 HAZARDOUS (CLASSIFIED) LOCATIONS INSTALLATIONS MUST BE IN ACCORDANCE WITH THE NATIONAL ELECTRICAL CODE NFPA 70, ARTICLE 504;
2. EQUIPMENT CONNECTED TO THE ASSOCIATED APPARATUS MUST NOT USE OR GENERATE MORE THAN 250 Vrms OR VDC
IN ACCORDANCE WITH ISA RP-12.6.
1. THE INTRINSIC SAFETY ENTITY CONCEPT ALLOWS THE INTERCONNECTION OF TWO FM APPROVED INTRINSICALLY SAFE
IP66
IS NOT
NEMA 4X
UP TO LINE
PROBE TUBE
Printed in U.S.A. 9/19 FR# 443603-00 Rev. 8©Copyright 2019 Dwyer Instruments, Inc.
Phone: 219/879-8000
Fax: 219/872-9057
IRON/STEEL TO PREVENT IGNITION CAPABLE SPARKS.
6. DUST TIGHT CONDUIT SEAL MUST BE USED IN CLASS II AND CLASS III ENVIRONMENTS.
4. NO REVISIONS WITHOUT PRIOR APPROVAL FROM FM RESEARCH.
5. THE ASSOCIATED APPARATUS MANUFACTURERS INSTALLATION INSTRUCTIONS MUST BE FOLLOWED WHEN INSTALLING THIS EQUIPMENT.
9. ADDITIONAL SUFFIX LCD (LCD DISPLAY) DOES NOT IMPAIR INTRINSIC SAFETY.
7. WARNING - ENCLOSURE PARTS ARE CONSTRUCTED OF ALUMINUM. ENCLOSURE MUST BE PROTECTED FROM MECHANICAL FRICTION AND IMPACT WITH
8. SUBSTITUTION OF PARTS MAY IMPAIR INTRINSIC SAFETY. RETURN TO MANUFACTURER FOR ANY REPAIRS.
www.dwyer-inst.com
e-mail: info@dwyermail.com
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