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Q)
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What is an IP rating?
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A)
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This is a protection rating. Please see the FAQ section
entitled "general
topics" for further information
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Q)
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Can PTC and NTC probes be extended?
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A)
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PTC and NTC probes can be extended but a few precautions
should be observed as follows: (1) the maximum advisable
distance is approximately 100 metres. (2) always use
good quality low resistance cable with a large cross
sectional area. This will minimize any additional resistance
from being imparted, which could effect a controller's
accuracy.(3) on long runs, use screened cable and only
earth one end of the screen. (4) do not run probe cables
alongside power cables.
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Q)
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What is the main difference between PTC & NTC
probes?
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A)
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PTC - resistance increases as temperature increases.
NTC - resistance increases as temperature decreases.
NTC probes work at higher resistance values than PTC.
Typical sensor resistances at C are:
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-30°c
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-20°c
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-10°c
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0°c
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+10°c
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+20°c
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PTC Ohms
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617
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677
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740
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807
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877
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951
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NTC Ohms x 1000
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115
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70
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42
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27
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18
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12
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Q)
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Are there probes that are more accurate than PTC
or NTC?
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A)
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PT100 probes can be used for greater accuracy, but
only with a controller calibrated to accept this probe
type.
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Q)
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What if PTC or NTC probes do not cover the required
temperature range?
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A)
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Consider PT100, Ni100 or thermocouples type K, J or
S. Some of these can cover temperatures as wide as -70
to +500°c but you must use a suitable controller.
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Q)
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I want to control head pressure using a fan speed
or step control. Should I choose an instrument that
controls on pressure or temperature?
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A)
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Pressure sensing controls from Saginomiya are generally
more expensive but are more accurate and will respond
much faster. Temperature sensing controls from Dixell
or Eliwell are often less expensive but are less accurate
and will respond more slowly.
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Q)
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I need to control on a temperature averaged between
two points.
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A)
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It is necessary to arrange 4 probes (in 2 pairs) to
form a "Wheatstone Bridge". We can advise
on the exact wiring arrangements.
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Q)
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I have a number of systems and must avoid them defrosting
together. How do I ensure separation of defrosts?
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A)
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For up to 4 systems use controllers with built in interval
timers, with a parameter that delays the start of defrosts.
Typically, this parameter will be adjustable from 0
to 59 minutes, so with a maximum of 4 controllers, defrosts
could have a minimum guaranteed separation of 15 minutes.
The parameter's setting must be in non-volatile memory
to ensure that defrosts will remain separated even if
power is interrupted.
For more than 4 systems use controllers that have "Real
Time Clocks" built in. These allow you to set precise
times of day for defrost to occur so each controller
can have different defrost times. Alternatively consider
Centralized scheduling of defrosts using a temperature
monitoring & alarm system. These consist of a central
monitoring & alarm panel or PC, which is connected
to all the controllers by a network cable. A signal
from the central unit can initiate defrosts by individual
controllers to avoid simultaneous defrosting.
We can select the appropriate controllers on request.
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Q)
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I'm trying to adjust a parameter setting on an electronic
controller and it won't go beyond a certain value.
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A)
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Electronic controllers use logic programming which
prevents conflicts between parameters. Assuming that
the value you are trying to alter is not at the limit
of its adjustment, there is probably another parameter
setting that is in conflict. Consider which parameters
may conflict and check their settings. E.g. you are
trying to lower the Upper Set Point Limit to + 5°c
but it will not go lower than + 10°C. Check the
Set Point, if it is set at + 10°c the problem can
be fixed by lowering the set point before setting the
upper set point limit.
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Q)
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A controller is flashing an alarm message. What
does it mean?
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A)
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Typical alarm messages and their causes are as follows:
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Alarm Message
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Cause
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Action
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HA or HAL
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High temperature alarm
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Check & rectify reason for high temperature
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LA or LAL
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Low temperature alarm
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Check & rectify reason for low temperature
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P1 or E1
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Thermostat probe fault
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Check connections / replace probe if necessary
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OOO
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Thermostat probe open circuit
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Check connections / replace probe if necessary
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CCC
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Thermostat probe closed circuit
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Check connections / replace probe if necessary
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P2 or E2
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Evaporator probe fault
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Check connections / replace probe if necessary
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FF
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Fast freeze interrupted by power cut
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Restart fast freeze cycle
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rtC
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Real Time Clock settings lost. Usually due to
an interruption of power supply exceeding 7 hours
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Re-enter time clock settings and check reason
for loss of power
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EE or E3
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Data corruption
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Check for electrical spikes. Check all parameter
settings are correct. If problem persists, replace
controller and fit spike suppressor
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Q)
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Is there a multi-purpose control for use as a service
replacement?
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A)
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There are two such controllers in our range.
The Dixell Universal-R can be used to replace most
of the 32 x 74mm format panel mounted controls from
LAE, Carel, SAE, Eliwell, Intek, Every and Teddington.
It can function as a thermostat, thermostat with off-cycle
defrost, thermostat with time intiated and time or temperature
terminated defrost, or thermostat with time intiated
and time or temperature terminated defrost plus fan
delay. It also includes audible/visual high & low
temperature alarms and an alarm relay output.
It works with either 1 or 2 probes as required, and
is compatible with both PTC and NTC probes. It operates
on a 12v AC power supply.
Programming is quick and simple and the programming
guide for the Universal-R can be is available as a download
The specification of the Universal-R can also be downloaded
from this site.
To replace only thermometers, thermostats (cooling
or heating) and off-cycle defrost refrigeration controlers
the similar Universal-J is also available.
The specification of the Universal-J can be downloaded
from this site.
A list of some (but not all) of the controls that the
Universal-R and Universal-J can replace is also available
as a download.
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