Inkbird cooling won’t work

[hotbeer]

Yes you add up your continuous amperages if they are all connected to the same power cord. And that appears to be the 3.8 + 7.2 = 11 amps.

LRA is not quite the same as starting amperage though the two can be about the same value. LRA will likely always be a higher number. Both will only be a momentary increase in demand for a very brief time. I think starting amperage is a older term defined differently.

You don't have to have a device that is built for 30 amps of draw. It just has to be built to briefly handle that amount of current. You'd be okay if you found a device rated at over the 11 amps your refrigerator continuously draws when cooling. And typically the next step up is 15 amps. Then your only concern is how much momentary draw the device can handle.

Not all or even many sold for us as untrained in electrical knowledge will have that specification. But many are built to handle expected overloads due to surges and starting of stuff. But the amount they can handle varies on what the designer or engineer thought it should be for that devices expected use.

And take the above with the understanding that I don't have the training to even state that. Other than maybe for a what if discussion at the Pub with a round of beers going to all. So if someone knows more or needs to set me straight on that, then please do so.

Cheers!

 

[Deadalus]

This is very telling. The steady state operating current is 11 A (unless there are separate cords for the lights and compressor), and I believe most InkBird 308 type controllers are rated at 10 A. But the real killer is the LRA of 29.0 A. The Locked Rotor Amperage (LRA) is the start up current required by the compressor motor. This is what is killing the cooling relays in the InkBirds.

Brew on

I was wondering what that was. And @hotbeer suggests it is the starting amperage which I am only slightly familiar with. As I said earlier, I've seen that estimated at about 3x the steady state amperage and that might just be a rough guess. It's kind of built in to household wiring to handle that because it is brief? This refrigerator has a regular 115V plug in order to go in the Inkbird. That means a 15 amp circuit is ok for it as the manufacturer wouldn't put that plug on it otherwise. What is likely affecting the Inkbird relay more, the LRA or the steady state amperage? Should relays be sized more for the steady state or the LRA or both even?

 

[doug293cz]

I was wondering what that was. And @hotbeer suggests it is the starting amperage which I am only slightly familiar with. As I said earlier, I've seen that estimated at about 3x the steady state amperage and that might just be a rough guess. It's kind of built in to household wiring to handle that because it is brief? This refrigerator has a regular 115V plug in order to go in the Inkbird. That means a 15 amp circuit is ok for it as the manufacturer wouldn't put that plug on it otherwise. What is likely affecting the Inkbird relay more, the LRA or the steady state amperage? Should relays be sized more for the steady state or the LRA or both even?

Yes, household wiring takes motor startup into consideration. Most circuit breakers operate in a way that short overloads don't trip them. The shorter the overload, the more over-current it takes to trip them. If interested, there are characteristic curves published that quantify trip current verse time.

With mechanical contact relays, it is the current on make and break, and the associated arcing which eventually causes them to fail, unless they are way overloaded steady state, and overheat due to resistive heating. The higher the make/break current, the more energy in the arcs, and eventually, the arcing damages the contact points.

Brew on