Delta HT01 User Manual

Installation, Operation &
Maintenance Instructions

Sentry Series

Models HP0* (Pressure Switches)
Models HD0* (Differential Pressure Switches)
Models HT0* (Temperature Switches)

IOM-SENTRY-Ex-A : OCT 2012

General

The unit is manufactured, checked and supplied in
accordance with our published specification, and
when installed and used in normal or prescribed
applications, with the lid in place and within the
parameters set for mechanical and electrical
performance, will not cause danger or hazard to life
or limb.

THE USERS ATTENTION IS DRAWN TO
THE FACT THAT, WHEN THE UNIT IS
‘LIVE’ WITH RESPECT TO ELECTRICAL
OR PRESSURE SUPPLIES, A HAZARD
MAY EXIST IF THE UNIT IS OPENED OR
DISMANTLED.

UNITS MUST BE SELECTED AND
INSTALLED BY SUITABLY TRAINED AND
QUALIFIED PERSONNEL IN
ACCORDANCE WITH APPROPRIATE
CODES OF PRACTICE SO THAT THE
POSSIBILITY OF FAILURE RESULTING IN
INJURY OR DAMAGE CAUSED BY
MISUSE OR MISAPPLICATION IS
AVOIDED.

Operating principles

Pressure Switch models P0* and Differential
Pressure Switch models D0* are diaphragm
operated switches.

These diaphragms generate a force proportional to
the applied pressure and are balanced by a user
adjustable control spring. When the force exceeds
that created by the control spring, the diaphragm
moves causing a push rod to actuate a snap-acting
micros-witch.

Temperature models T01 & T02 work in the same
way as the Pressure models with the exception that
the applied pressure comes from the expansion of a
vapour enclosed in either a rigid stem or semi-rigid
thermal system.

INSTALLATION

Mounting (All models)

The instruments are designed to be mounted
vertically with the process connection underneath.
However, mounting up to 45° from the vertical in any
plane is acceptable, although a small calibration shift

may occur. They can be mounted either direct to
process, or to a wall or panel using the mounting
holes provided. Select the mounting point so as to
avoid excessive shock, vibration or temperature
fluctuation. Instruments should be mounted to avoid
excessive heat transfer from the process lines or
adjacent plant. To avoid undue stresses being
imparted to the instrument when wall/panel
mounted, it is recommended that a short length of
flexible line be installed between the instrument and
process line. If sudden changes of pressure
(pulsations) are likely then we recommend that
snubbers are fitted between the process line and
instrument. Use a spanner to support the process
connection when fitting the instrument.

CHECK THE CONNECTION THREAD SIZE
AND SPECIFICATION ON THE UNIT TO
AVOID MIS-MATCHING WITH THE
PROCESS CONNECTION ADAPTOR. SEE
DIGIT 11 OF PRODUCT CODE.

Mounting (T01 - Rigid Stem)

Assemble the unit via a thermowell, using the
spanner facility provided and ensuring that:

a) the sensing bulb is fully immersed in the
process temperature
b) the sensing bulb does not bottom out in the
thermowell which could cause damage

Mounting (T02 - Capillary system)

Mount the sensing bulb so that the capillary end is
above the bulb and the bulb is level with, or no more
than 250mm below the base of the instrument. The
stem is fitted with a sliding compression gland to
accommodate different thermowells.

Wiring

DISCONNECT ALL SUPPLY CIRCUITS
BEFORE WIRING

WIRE IN ACCORDANCE WITH LOCAL
AND NATIONAL CODES. USE CABLES
NO LARGER THAN 2.5 MM 2 (14 AWG)

DO NOT EXCEED ELECTRICAL RATINGS
STATED IN LITERATURE AND ON
NAMEPLATES.

www.delta-controls.com

IOM-SENTRY-Ex-A : OCT 2012

Wiring (continued...)

1 or 2 electrical entries are provided, into which
cable glands can be assembled. The thread type
and size is marked on the enclosure, just below the
connection. Select a suitable cable gland which will
maintain the IP rating of the instrument.

USE ONLY SUITABLY ZONE 1 CERTIFIED
CABLE GLANDS OR STOPPING PLUGS.
CABLE TEMPERATURES MAY EXCEED 80°C.
USE ONLY CABLES WITH SUITABLE
OPERATING TEMPERATURE RANGE.

Use only certified adaptors for Zone 1/Div 1.
Unused entries are to be fitted with suitably certified
stopping plugs.

The three switch terminals are clearly marked
“NORMALLY CLOSED”, “NORMALLY OPEN” and
“COMMON”.

The following diagram can be used as a guide for
wiring.

OPERATION

Adjustments

Pressure and Temperature Switches are supplied
calibrated at the midpoint of their range and to a
falling pressure or temperature unless otherwise
specified.

To re-calibrate:

1. Isolate the instrument from the process and
power.

2. Slacken the set point lock screw.

3. Using a suitable spanner, rotate the range
adjuster clockwise to increase the set point and
counter-clockwise to decrease the set point.

4. Tighten the set point lock screw.

5. Close the instrument lid and tighten lid lock screw

Note: For accurate setting of Pressure and
Differential Pressure models, a suitable pressure
gauge must be used in conjunction with the above
procedure. Do not attempt to set the switch outside
the scale limits. For Temperature models a suitable
calibrated temperature source should be used.

Though the unit may be set anywhere within its
range, for optimum performance, it is good practice
to have a set point value between 25% and 75% of
span.

The striker screw and lock nut are factory set and
should not be adjusted. Should these parts be
accidentally loosened, please contact Delta for
assistance.

Each instrument if supplied with a label indicating
product description, product code, approvals, etc, as
shown in the example below.

Example label:

Insert bare wires fully into the terminal block and tighten
securely. Keep wiring tails to a minimum and check that
wires do not interfere with the operating mechanism. Use
the earthing / grounding points provided.

BEFORE CLOSING THE LID:

 ENSURE WIRE IS CLEAR OF ALL

MOVING PARTS.

 ENSURE THAT WIRES DO NOT

TOUCH THE LID AS IT IS CLOSED.

Close the lid, being careful not to trap any wires in
doing so. Securely tighten the M3 lid locking screw
set provided using a 1.5mm hex key.

MAINTENANCE

Inspections should be carried out at quarterly to
yearly intervals depending upon operating
conditions. Isolate the unit from process and power
and remove the lid. Check all terminals for
tightness. Check that cable tails are not fouled or
chafed. Check for internal condensation. Check
that the gasket is seated properly in the lid recess
and is not worn. Keep the enclosure and lid clear of
dust build up. It is recommended that instruments
used to provide an alarm are operated periodically to
ensure they are functioning correctly. If further
maintenance is required seek advice from DELTA
CONTROLS before attempting repair or
replacement of parts.

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