BoatHowTo · video

What this video covers

Jan Attenstedt and Nigel Calder discuss the feasibility of paralleling two 250-amp relays to manage the high current draw of a 6-kilowatt, 24-volt bow thruster.0:41 The owner reports repeated relay failure, likely caused by electrical arcing that melts the contact points shut during operation.0:02 Calder confirms that paralleling two relays effectively reduces the current load per unit and mitigates the risk of contact welding.1:33 He notes that high-current DC circuits inherently produce arcs during make-and-break cycles, which degrades the relay points over time.1:48 Calder emphasizes that if an emergency battery isolation switch is used to break a high-amperage circuit during a short or a stuck-relay event, the switch sustains internal damage and requires immediate replacement.2:47 These switches are rated for carrying high loads but not for interrupting them under load.3:21 Paralleling relays provides a viable solution for systems experiencing premature contact failure due to high current demands.1:07

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