Help selecting a timer relay

[Ian_Edwards]

I'm re-wiring the bow thruster control this winter. The thruster is a Lewmar unit with a semiconductor based controller in the cockpit, which in tern controls MOSFET switches in the bow thruster compartment, and these fire the contractors on the thruster, which is nominally 5kW at 12volts, with a 500amp maim fuse.
The MOSFET switches have failed yet again, the 4th time in the 12 years I've owned the boat.
I plan to replace both the cockpit controller and the MOSFET switches with momentarily switches in the cockpit and relays in the bow thruster compartment. A straight forward modification.
However, I want to put a timer relay on the supply to the relays, to prevent accidentally operation of the bow thruster.
A simple timer relay will do this, but I'm having difficulty finding an appropriate unit. I want the power to be enabled for a minimum of, say 3mins and a maximum of, say 10mins. I want a simple plug-in relay that I can carry spares for and swap over in the event of a failure.
The only one I can find is a rear window heater relay on 12v planet, which would do, but is rated at 16amps, much to big, 2amps would be more than adequate.
Any ideas on where I can source low power (2 amps 'ish) timer switches which mount in a relay socket. I don't want any exposed PCB's, just something simple and robust.

 

[wrr]

A rear window heater timer relay should be fine, just because it can handle 16a does not mean that it will not operate switching a lesser current. I use one for a cooling fan which is rated far below the relay maximum switched current.

 

[Ian_Edwards]

It's not the max rating I'm concerned about, it's the physical size.
Perhaps I should have made that clearer.

 

[Graham_Wright]

Why not just use a biassed to centre two way switch?

 

[PaulRainbow]

I'm re-wiring the bow thruster control this winter. The thruster is a Lewmar unit with a semiconductor based controller in the cockpit, which in tern controls MOSFET switches in the bow thruster compartment, and these fire the contractors on the thruster, which is nominally 5kW at 12volts, with a 500amp maim fuse.
The MOSFET switches have failed yet again, the 4th time in the 12 years I've owned the boat.
I plan to replace both the cockpit controller and the MOSFET switches with momentarily switches in the cockpit and relays in the bow thruster compartment. A straight forward modification.
However, I want to put a timer relay on the supply to the relays, to prevent accidentally operation of the bow thruster.
A simple timer relay will do this, but I'm having difficulty finding an appropriate unit. I want the power to be enabled for a minimum of, say 3mins and a maximum of, say 10mins. I want a simple plug-in relay that I can carry spares for and swap over in the event of a failure.
The only one I can find is a rear window heater relay on 12v planet, which would do, but is rated at 16amps, much to big, 2amps would be more than adequate.
Any ideas on where I can source low power (2 amps 'ish) timer switches which mount in a relay socket. I don't want any exposed PCB's, just something simple and robust.

If you wire the timer relay to the supply to the momentary switch you can keep the relay somewhere nice and dry. This is a good quality timer relay that should do as you want (no need for a min and max time, just a max):

LMMT 12-230V AC/DC | Broyce Control DIN Rail Mount Timer Relay, 24 → 230 V ac/12 → 230V dc, 1-Contact, 0.1 s → 100h, | RS

 

[Alex_Blackwood]

I'm re-wiring the bow thruster control this winter. The thruster is a Lewmar unit with a semiconductor based controller in the cockpit, which in tern controls MOSFET switches in the bow thruster compartment, and these fire the contractors on the thruster, which is nominally 5kW at 12volts, with a 500amp maim fuse.
The MOSFET switches have failed yet again, the 4th time in the 12 years I've owned the boat.
I plan to replace both the cockpit controller and the MOSFET switches with momentarily switches in the cockpit and relays in the bow thruster compartment. A straight forward modification.
However, I want to put a timer relay on the supply to the relays, to prevent accidentally operation of the bow thruster.
A simple timer relay will do this, but I'm having difficulty finding an appropriate unit. I want the power to be enabled for a minimum of, say 3mins and a maximum of, say 10mins. I want a simple plug-in relay that I can carry spares for and swap over in the event of a failure.
The only one I can find is a rear window heater relay on 12v planet, which would do, but is rated at 16amps, much to big, 2amps would be more than adequate.
Any ideas on where I can source low power (2 amps 'ish) timer switches which mount in a relay socket. I don't want any exposed PCB's, just something simple and robust.

Why not fit a key switch in a suitable position for the control circuit. Loads available via the usual search engine.
Edit. Wire in series with the supply to the momentary switch.