Converting 12v fridge to dual 120v/12v

[Ralph163]

Looking for some input. Converting the 12v fridge on my 2006 Marlin to dual 12v/120v. Using a relay, it will switch over to 120v when I am connected to shore power and then automatically goes to 12v when shore power is disconnected. I am using a 10a 12v power supply (PU) and a 12v 30a relay. Everything seems to work well, but the relay seems to generate a lot of heat. Doesn't seem excessive, but it concerns me. Would a resistor between the hot leg and the trigger help?

I am starting to think a manual on/off/on switch might be a safer choice than a relay..

 

[DennisG01]

I think the problem is that it's a cheapie relay and not designed for constant duty.

I'd have to do some homework and digging and spend some time researching to give you a suggestion, but look for a continuous duty relay (and a better brand) and I think you'll be happier.

 

[Hookup1]

No resistor needed. It will be fine. Here is my version.

Converting refrigerator from dc to ac/dc

How difficult is it to convert refrigerator from 12vdc to 110vac/12vdc. I have a 2007 marlin I run the refrigerator all summer. While at the dock I am plugged in and would rather not have battery charger on 24/7

www.greatgrady.com

 

[Ralph163]

No resistor needed. It will be fine. Here is my version.

Converting refrigerator from dc to ac/dc

How difficult is it to convert refrigerator from 12vdc to 110vac/12vdc. I have a 2007 marlin I run the refrigerator all summer. While at the dock I am plugged in and would rather not have battery charger on 24/7

www.greatgrady.com

Yes. The same setup as mine. I even purchased the same relay. What concerns me is the heat generated by the "trigger" coil on the relay. The "trigger" is activated when 120v is supplied to the PSU (when I am on shore power) and provides 12v to the trigger.

When I bench tested the system, the metal plate underneath the coil on the relay, gets VERY hot. That concerns me leaving it like that for weeks at a time unattended.

 

[Ralph163]

I think the problem is that it's a cheapie relay and not designed for constant duty.

I'd have to do some homework and digging and spend some time researching to give you a suggestion, but look for a continuous duty relay (and a better brand) and I think you'll be happier.

Yes, I would be curious to find another relay rated for continuous duty. Or a relay that "flips" a selector switch, I forget what those are called (as opposed to a relay that provides continuous power to the "trigger" when activated)

EDIT: Okay, I remember, it's called a continuous duty solenoid relay. I had them on my anchor winch (and they failed once!). Basically, applying power "flips" and A/B selector switch. I don't think they come in DT versions. So, it would require two. And that would get a bit pricy.

SPDT CONTINUOUS DUTY 12V PVC COATED 6STUD

SPDT CONTINUOUS DUTY 12V PVC COATED 6STUD

www.elecdirect.com

I think I need to find a DPDT switch instead and manually select input power source. Preferably a rotary switch. The thought of a relay burning up or failing troubles me. Even if it's a remote chance.

https://www.newark.com/carling-technologies/rv26d2dc0cb-k4c/rotary-switch-dpdt-12vdc-20a/dp/64X9562

 

[Hookup1]

Eliminate the relay and use the breaker. I eliminated water heater and microwave on my boat and freed up two breakers.

Could also try a different brand of the DPDT relay to see if it runs cooler. No idea how hot mine runs - its behind the fridge. Shoot with IR temp gun.

.

 

[Ralph163]

Eliminate the relay and use the breaker. Could also try a different brand of the DPDT relay to see if it runs cooler. No idea how hot mine runs-it behind the fridge.

Yes, that's is where I am at right now. Separate breaker for 120v PSU. I will use an on/off/on selector switch to choose between the 12v and the 120v options. This way I can't accidentally have the breakers for both on at the same time. Seems like the easiest solution for my concerns regarding the relay.

 

[Hookup1]

I suppose the switch will work for you but having it automatic is what I wanted. Couple of last minute suggestions.

No specs on relay coil resistance which would affect heat output but trying another manufacturers relay may work.

Also that relay has a metal frame and could be screw mounted on the back of the refrigerator. Use the back plate as a heat sink.