Environmental Express HotBlock CAL 3300 - Manual (Page 18)

The temperature has overshot the set point and the audible alarm has sounded
.
The function of the fail-safe system is to cease heating of the HotBlock in the event of a set point overshoot of
15°C and to alert the technician of the incident. The HotBlock can be “fooled” into fail-safe mode if the set point
is manually changed to a value
≥
15° below your current temperature. However, the primary cause for the runaway
temperature is a faulty relay that has exceeded its useful life. You may troubleshoot the relay by following these
steps:
Caution: This procedure is a potential electrical hazard and should only be performed by qualified personnel.
1. Power off your HotBlock.
2. Remove the bottom panel of the HotBlock by unscrewing the rubber feet.
3. Power the HotBlock on and allow it to overshoot your set point temperature.
4. Locate the solid state relay mounted to the bottom panel.
5. Set your volt-meter to measure AC voltage.
6. Touch your red lead to (white wire) of the solid state relay and touch your black lead to a ground
source (e.g., the green/yellow wire from the power module or an empty terminal on the terminal board).
7. If your volt-meter reads 110V-122V, then the relay is stuck in the “closed” position and it must be replaced
(see parts list, page 10).
The HotBlock will not heat beyond ambient temperature.
A HotBlock that will not heat beyond ambient temperature typically has a failed relay, heater mat or
controller.
n Relay—To test the relay, the output voltage must be determined with a volt-meter.
Caution: This procedure is a potential electrical hazard and should only be performed by qualified personnel.
To measure the relay voltage, follow these steps:
1. Remove the bottom panel of your HotBlock by unscrewing the rubber feet.
2. Locate the solid state relay mounted to the bottom panel.
3. Set your volt-meter to measure AC voltage.
4. Touch your red lead to (white wire) of the solid state relay and touch your black lead to a ground
source (i.e., the green/yellow wire from the power module or an empty terminal on the terminal board).
5. If your volt-meter does not read 110V-122V, then the relay has stuck in the “open” position and it must be
replaced (see parts list, page 13).
n Heater Mat —To test the heater mat, the resistance (ohms) must be determined with a volt-meter. It is
recommended that your heater mat be replaced if it measures 25 ohms (W) or greater. It is also
recommended that the thermocouple and insulation be replaced as well, both are inexpensive parts that are
not easily accessible otherwise.
To measure your heater mat resistance, follow these steps:
1. Power off your HotBlock and remove the bottom panel of your HotBlock by unscrewing the rubber feet.
2. Locate and disconnect the white wire connected to the relay and an identical wire on terminal #2
Environmental Express • 17
Troubleshooting Guide
HotBlock Operation Guide
www.environmentalexpress.com