I am building a load bank and wanted advice on wiring it. I have 4 4ohm 1000 watt resistors. I want to switch from 4 to 8 ohms. I am thinking of a nice rotary switch.
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Given the high currents in a 4R 1kW resistor, you need very chunky switches capable of at least 15A - I've not personally seen a rotary switch capable of that, but a quick search revealed Ohmite Power Tap switches might fit the bill - no idea how expensive though.
Labs use binding posts for connections, making it easy to series or parallel loads.
https://audioxpress.com/article/you-can-diy-build-an-audio-dummy-load
https://audioxpress.com/article/you-can-diy-build-an-audio-dummy-load
I also only found the Ohmite switches, Mouser stock them, but I chose instead to use 4 mm sockets and plugs to select the resistance. A switch would be nice but the price put me off.
RS Components list a 12 position rotary switch from NSF rated for 6 A but it didn't look that impressive and is only somewhat cheaper. I guess that there isn't much demand for high current low voltage rotary switches. Possibly the load could use toggle switches. I am not sure how easy a high current low voltage toggle switch is to find.
I used nine 1 ohm '50W' resistors and nine 0.1 ohm '25W' resistors on a large heatsink to provide 0 to 9.9 ohms in 0.1 ohm steps with the 4 mm sockets arranged like a rotary switch.
RS Components list a 12 position rotary switch from NSF rated for 6 A but it didn't look that impressive and is only somewhat cheaper. I guess that there isn't much demand for high current low voltage rotary switches. Possibly the load could use toggle switches. I am not sure how easy a high current low voltage toggle switch is to find.
I used nine 1 ohm '50W' resistors and nine 0.1 ohm '25W' resistors on a large heatsink to provide 0 to 9.9 ohms in 0.1 ohm steps with the 4 mm sockets arranged like a rotary switch.
Light switches are an alternative and rated for 15A in the US. Kind of odd in this application but you can get DPDT light switches (expensive) or straight toggle switches https://www.amazon.com/Gardner-Bend...d=1731954334&sprefix=dpdt,aps,170&sr=8-6&th=1
There are several variations on these which are good for 20A: https://www.amazon.com/Changeover-P...1954585&sprefix=rotary+switch,aps,159&sr=8-21 The connection diagram is confusing at first but pretty flexible.
There are several variations on these which are good for 20A: https://www.amazon.com/Changeover-P...1954585&sprefix=rotary+switch,aps,159&sr=8-21 The connection diagram is confusing at first but pretty flexible.
It seems like you only need a ON-OFF switch to select 4Ω or 8Ω.
For single channel connection, when the switch is in OFF position it provide a 2000W 8Ω load or 4000W 4Ω load if the switch is in ON position.
For dual channel connection, when the switch is in OFF position it provide a 2000W 8Ω load or 1000W 4Ω load if the switch is in ON position.
The switch should be able to switching minimum of 15.8 amp @ 127 volt.
For toggle switch, my suggestion is 30A rated or higher.
Leviton-MS302-DS-Disconnect-Industrial-Non-Grounding/dp/B002MPQ51O?
For changeover switch, my suggestion is 32A rated or higher.
Changeover Selector Switch, Power Transfer Switch, 2 Positions 8 Terminals, LW26-32 C04/2 440V 32A
For single channel connection, when the switch is in OFF position it provide a 2000W 8Ω load or 4000W 4Ω load if the switch is in ON position.
For dual channel connection, when the switch is in OFF position it provide a 2000W 8Ω load or 1000W 4Ω load if the switch is in ON position.
The switch should be able to switching minimum of 15.8 amp @ 127 volt.
For toggle switch, my suggestion is 30A rated or higher.
Leviton-MS302-DS-Disconnect-Industrial-Non-Grounding/dp/B002MPQ51O?
For changeover switch, my suggestion is 32A rated or higher.
Changeover Selector Switch, Power Transfer Switch, 2 Positions 8 Terminals, LW26-32 C04/2 440V 32A