Knowledge Base:  

How does the Macurco HD-11 work?

Last Updated: 12/09/2013

The operation of the Macurco HD-11 Hydrogren Gas Detector is easy to understand. Important information is provided below.

1. Expect your HD-11 to "warm-up" for about 2 minutes when you first apply power; alarms are inhibited during this short period. The green LED light will blink on and off. After the warm-up, the green light will turn on continuously (ARMED), which indicates that the unit is operating normally.
2. A red LED (alarm) light will come on if gas is detected. The SPDT alarm relay activates to indicate the alarm condition.
3. As shipped from the factory, the HD-11 configuration is self-restoring. The red light turns off and the relay switches back to its normal state when the air clears of gas. To allow the unit to latch in upon alarm, a jumper wire on the circuit board can be clipped, which means that the power will need to be interrupted in order to unlatch the alarm condition. Conveniently, the HD-11's latching input can be modified before or after installation: Remove the cover and locate the jumper wire labeled "CLIP FOR LATCH IN" on the upper right hand side of the printed circuit board. Just clip or cut this jumper wire and separate the wire ends. Clipping the wire causes the unit to stay in alarm once gas has exceeded the pre-set threshold until the power is interrupted. Make sure the lights line up with their access holes as you replace the cover.
4. The product has a supervisory circuit of critical functions. A 'trouble condition' is activated by the failure of a non-reliable component. Both lights will switch on and off, as well as the normally closed trouble relay opening. In the case of a power failure, the trouble relay will also open.

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