Hey this is Brian, with hvac school HVC, our school comm and the hvac school podcast. This video is about dry and wet contacts, and I'm using the Danfoss ERC 213 diagram as a way to demonstrate this, because it was just a really good example of this that I recently worked on. So a lot of a lot of experienced technicians may use the phrase dry contacts or wet contacts you're, especially going to hear the phrase dry contacts quite a bit and it's important to kind of understand what that means as well as why that is significant to you. In the field, so this is the ERC 213.

This is a kind of a basic pictorial diagram that shows, you know how it's connected, but first thing to just illustrate is that this is the compressor, so it's showing these are. This would be a compressor, and this is a set of normally open contacts, and then you have a line on a 20 volt line. This is a neutral side here and then you have two contacts here: five and six one seven is an unused terminal. So, first off just so you so you know which is which this would be considered a dry contact.

He says this is the one here on the left side do one that would be considered a dry contact and then terminals, five and six. So one and two would be considered set of dry contacts. Five and six would be wet contacts, and so five is used for either alarm or defrost. You can see this symbol here looks like a melting snowflake.

That means defrost. It can also be used for an alarm and then six is a fan. So here's how this works. This is a dry contact because there is no input, there's no automatic input on the control for one and two.

So, in order to power the compressor, you would have to apply power whatever you wanted: 240 volts or 120 volts, depending on the compressor control or the compressor itself. If you're directly driving the compressor out of this control, you would have to apply that power to Terminal two and then it would go out on Terminal one or vice versa. So you can apply it on Terminal one and that would go out on Terminal two. But it's dry because it's not taking any power, that's intrinsic to the control, it's not taking what you're, feeding the control with and passing that along, whereas these wet contacts there's only one terminal.

So it's five and six and it's fed from this three L so terminal number three is fed in and then that goes out to defrost. So you connect your defrost heaters to terminal number five. You connect your fan to terminal number six, but it's reliant on the powered voltage of the controller, so in this particular case the ERC to 13. A this one is a hundred twenty volt controller, and so this 120 volt controller is going to pass 120 volts.

It's used to power, the controller itself, 120 volts potential between line and neutral. It's going to pass that power through from terminal 3 to terminal 5 and terminal 6. So it's actually a shared power supply similar to the. If you think of the our terminal on your typical thermostat, your other terminals, your other feed terminals that go out to your different low voltage devices and an air conditioner, those are those are all wet terminals, so orange and yellow and green they're all wet, because they're All fed from the same, the same power supply that feeds the control itself, whereas this do one terminals 1 and 2.

They are dry because they don't have any voltage intrinsically applied, meaning within the controller itself. It's not it's not actually applying power to these terminals. So you have to then connect to either terminal 1 or 2 with a constant power supply and then feed it through to the device and so just to simplify it. This would be considered a wet, a dry contact.

These would both be considered wet contacts deal. One is dry: do to do. Three are wet. Another example of dry contacts would be.

You know the the contacts in a typical relay like a 93 forty or a typical compressor, contactor, those you have to feed power in you have to feed current in order for it to go out, it doesn't somehow you know, grab current from some other. Some other point: that's powering the device itself like like this is the case here. So hopefully that makes sense, dry and wet contacts as you. If you want a really nice Universal controller, that does a great job.

I would consider looking at the ERC 213 just installed. One the other day, I really liked it. It's a nice nice controller does a lot of different features, a lot of different functions, thanks for watching.