What happens if positive and negative are reversed, and which model has reverse polarity protection?
The HCT402 has reverse polarity protection: connected wrongly it draws no current, and connected correctly it comes online with an audible confirmation. The HCT400 does not have this protection and a reversed connection will damage the motor. This is the most critical installation difference between the two models.
In field installations, mixing up positive and negative is the most common cause of permanent damage. The two models differ on this point.
HCT400: there is no reverse polarity protection. If the supply is connected in reverse the motor is damaged. So check the connection twice before applying power, verify wire ends with a meter rather than by color, and make the first power-up through a fuse.
HCT402: it is reverse polarity protected. Connected wrongly, the circuit draws no current — it stays silent. Connected correctly, the system comes online with an audible confirmation. In practice this lets you tell immediately, during installation, the difference between a seemingly faulty device and a wrong connection: if there is no sound, check the polarity first.
On both models, the second most common cause of permanent damage is a loose negative connection. Connect the negative line to clean metal or directly to the battery terminal, not to painted sheet metal. The HCT402 can be connected directly to 12V and 24V systems; the HCT400 is for 12V systems and its full performance range is 10-18V.
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