Carbolite HTMA Series - Manual (Page 6)

High Temperature Ovens
6
MF16 3.09
3.5 Variable Speed Fan Option (if fitted)
When this is ordered, a variable speed control is fitted in the fan circuit. Operation of the control is
self-explanatory.
Please note that there is a minimum setting at which the fan motor starts up when the oven is
switched on. Find this setting by experiment, and mark the position on the control or front panel.
It is unlikely that a control setting of less than 50% would be required, as there would be very little
air flow around the oven.
3.6 Exhaust Fan Option(if fitted)
Start the extraction unit using the amber switch on the control panel; this is only functional when
the instrument switch is on.
The amount of air exhaust can be controlled by adjusting the slider under the exhaust box.
When the exhaust fan is turned on, there may be a drop in internal temperature before the oven
recovers to the setpoint value.
When working near to the maximum temperature, the airflow should be small to reduce the
amount of energy wasted in heating air.
3.7 Stoving and Curing Option(if fitted)
The oven is fitted with an explosion relief panel and a powered exhaust fan. The exhaust fan is
physically similar to that described above.
With this option the fan runs all the time that the oven is switched on.
A pressure switch detects that there is sufficient air flow through the chamber, and prevents the
oven from heating if the exhaust fan is not working correctly. If the pressure switch does not detect
sufficient air flow, a fault light comes on and the oven is prevented from heating up.
At least 200mm free space must be left at the back and side of the oven to allow the explosion
relief panel to break out if there is a rapid build up of pressure inside the chamber.
3.8 HTMA - Manual Gas Control- Eurotherm 3216 Main controller Option (if fitted)
The two gas solenoid valves are controlled by a three position switch located on the front of the
oven.
When the switch is in the Purge position the gas flows through the Purge flow meter. This is a high
flow used to purge the chamber at the beginning of the cycle.
When the switch is in the Process position the gas flows through the Process flow meter. This is a
low flow used when the process is running.
When the switch is in the off position the no gas flows.
3.9 HTMA -Automatic Gas Control- Eurotherm 3508/Nanodac Main controller Option (if
fitted)
The two gas solenoid valves are controlled by program segment output relays in the main program
controller.
Program segment relay 1 controls the Purge flow. This is a high flow used to purge the chamber at
the beginning of the cycle. The purge time is set as a dwell period at ambient temperature.
Program segment relay 2 controls the Process flow. This is a low flow and should be on during the
heat and cool down stages of the cycle.
The program segment relay outputs are set to on or off when the controller is being programmed.
See controller handbook for details.