Refrigerator Problems – Troubleshooting Help -2
Today we are going to talk about refrigerator compressor start devices, two specific types, the TSD and the PTC start devices. We are going to unpack what these mean, what they are, how to identify them, how they fail so you'll have a better understanding of what you're dealing with when it's time to do a refrigerator repair with a bad compressor starter.
So we will start with some definitions, PTC, Positive Temperature Coefficient, this refers to, you have probably heard this term in regards to sensors and other things where the resistance increases with temperature, that’s what that means, Positive Temperature Coefficient, as opposed to a negative temperature coefficient where the resistance decreases as the temperature increases so they are inversely related
And a PTC, Positive Temperature Coefficient device, the resistance increases as the temperature increases, in the context of start devices, this refers to the metal oxide coated ceramic pill that is inside that start device are we are going to take a look inside PTC start devices here in just a minute, we are going to see what we are talking about here when we talk about the ceramic pill and so the point is as the resistance of that ceramic pill increases with temperature, it takes that start winding out of the circuit, this is how it works and I have talked about this in another presentation in the refrigeration course.
So initially, it is cool, it is closed, it has low resistance, both the start winding and the main winding are in the circuit, the pill quickly heats up, as it does, its resistance increases and it takes the start winding out of the circuit, this is how the PTCs work, the other type is the TSD, Time Starting Device and these rely on a small electronic board inside the TSD and we are going to look again at that board we are going to see them, it consists of a TRIAC and a couple of capacitors inside there, it does the same function as the PTC, that is it takes the start winding out of the circuit but instead of doing it by heating up and its resistance increasing, it does it based on time.
So the capacitors control the gating of the TRIAC and the TRIAC opens and takes the start winding out of the circuit, the whole idea behind TSDs was to eliminate that extra energy that is used to heat the PTC pill, I don’t know how much energy they are saving, I can’t imagine it is an incredibly significant amount but apparently it is enough that it made them want to come out with this device in their ever increasing attempts to comply with the increasingly stringing energy star requirements so they are just trying to shave off little milli-watts here and little milli-watts of energy there so this is one way of doing that.
Alright, so let’s take a look inside the PTC start device, I mentioned the pill, here we go right here, the PTC pill, this is what it is actually called in the industry so you know I am not just making this stuff up and it is, as I mentioned, a little ceramic disk that is coated with some metal oxide and I have talked about these in detail in another presentation in the refrigeration course and you will see that a common failure mode for them is to splinter, right here is part of that ceramic disk, there is another piece right there, another piece of it right there and here are some pieces inside the device here inside the casing of the start device.
These will actually, the ceramic disk will fracture from heat fatigue and give off and just splinter that’s why when you shake it a lot times, one of the failure modes indicates that it is bad, you shake it and it rattles, another thing that it will do is burn up, you will see them inside here, sometimes you will see the burn visibly on the outside and we are going to see that in just a second, sometimes, it will just give off a smell, so this is inside the PTC start device and how they work and the common way that they will present themselves in failure mode.
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