In this quick and simple video, we're going to show how to charge a system using the sub cooling method and analog tools, many of you have asked me to do that. We've done a lot of videos with probes and other things, but we're going to show with a basic analog manifold now. This method specifically works on systems that have a txv metering device that are specifically designed to be charged via the sub cooling method. You're going to want to use this in addition to using a scale, especially if you've just put the system into commission, you would use the length of the line set in order to calculate the amount of refrigerant.

So you'd want to use that as well. But when you are charging you want to be monitoring your sub cooling, i'm going to show you the basic way to do that. First, you identify your liquid line service valve, which we have here. You remove the cap.

I always check the seals inside the cap before i attach my gauges now. The way that i'm going to do this on the liquid line is i'm going to attach a core depressing tool and that quarter pressing tool allows you to control the flow of refrigerant coming out of the valve. So that way, you don't have a lot of refrigerant loss, and now you can depress or undepress the schrader core in order to allow or disallow flow. So we're going to go ahead and put our red hose, which goes to our high side gauge onto our liquid line service valve.

We're then going to put our blue hose, which goes to our low side manifold gauge on our suction line, without a core depressor, because it's low pressure you're not going to have the same losses here, we show how, when you turn the cord oppressor clockwise, that depresses The core pushes in the core allowing flow through the schrader port, allowing us to measure the pressure on the liquid side on the other side on the suction side, we're simply using the cord oppressor inside the hose end to depress the schrader. Next, we're going to go ahead and put a line: temperature clamp on the liquid line. Here we show a cooper atkins self-contained line temperature clamp. This is a tool that i've used for a really long time.

It's very effective and compact we're going to take a look at our data tag and we're going to identify where it shows 10 degrees of indoor txv sub cooling. Now the reason it says, indoor txv, sub cooling is because this is a heat pump system, and so they don't want to confuse that with heat mode sub cooling. So it's specifying the indoor txv, which is what is used in cooling mode. Now we're going to take a look carefully at our gauges.

It's really important that you notice that our pressures are this white scale on top and our temperatures are the pink scale on the bottom. So, as you can see right away, one of the challenge with analog gauges is that this is pointing at approximately 340 psi, which is approximately 105 degrees. But you can see it's kind of more 104 and a half. It's really hard to tell because of the width of the needle, and that is one of the challenges with analog gauges, to tell exactly what we've got but just just around and make it nice round numbers we're going to say 340 psi and we're going to say.

105 degrees is what that's relating to that is our saturation, our liquid saturation, now we're going to go over to our suction side, and now you can see that this is pointed at 40 degrees on our r410a scale, which is the equivalent to about 118 psi. Now, if you want to try to figure out how this works, even though this is 125., so this would be 120 and it's right about 118 and it's pointing across through to the r410a scale, which is our suction saturation scale. So we have a 40 degree, suction saturation, otherwise known as a 40 degree saturated evaporator temperature. We have 105 degree liquid saturation, which we also call our condensing temperature and that's what we're going to use to set our sub cooling.

So next we have to compare that 105 degree, liquid, saturated temperature to our physical liquid line temperature, and that's what we're clamped on to here with our cooper atkins clamp and we can see it's 100 degrees if we take 105, which is our liquid saturation or our Condensing temperature, we subtract our actual measured liquid line temperature. We see that we have 5 degrees of sub cooling, meaning that it's fully liquid. We are cooled 5 degrees below our liquid line temperature. So because, if we go back to our data tag, we can see that our target is 10 degrees and we only have 5 degrees.

That means that we need to add refrigerant in order to increase our sub cooling, so we're going to add refrigerant to increase our sub cooling. So that means we need to use an r410a refrigerant tank and immediately we're going to go ahead and use a charging adapter, and what this does is is it creates a pressure drop out of the tank preventing liquid refrigerant from making it down the suction line? If we charge the system, we just open up these valves and charge the system, we could potentially flood the compressor, because the refrigerant goes through the yellow hose through the manifold down the suction hose and then straight to the compressor which can cause compressor flooding. So this adapter that we put on the tank helps prevent that problem, so we're going to place that on the tank and then we're going to invert the tank and we invert the tank. Because r410a is a blend.

We have to charge it in the liquid phase because it r410a is a blend, it's a mix of r32 and r125, so we have to invert it and charge it by liquid. So that way, those two constituent refrigerants mix together before it goes into the system and we have to place it onto a scale. Once i get the yellow hose connected to our tank here, we're going to open it just a little bit to allow some vapor to escape and then we're just going to purge the hose at the gauge in order to get any air out of the hose you're Going to notice that i didn't show purging the other two hoses and that's because it varies quite a bit on the process, the process you would follow, depending on what type of adapters you have at the end of your hoses in this particular case, the way that We showed it before. You would generally just crack these hoses here, but a lot of you are going to have ball valves or quick disconnects on your hoses, and so that's going to slightly change your process.

We invert the tank onto a scale. We make sure that the scale is zeroed out so that way we can see exactly how much refrigerant we're adding to the system. We then open our manifold handle or valve by turning it counterclockwise, which allows refrigerant to flow up the yellow hose down through the blue hose and into our suction line, which is the low pressure side. Our tank pressure is going to be higher than our suction gauge and lower than our liquid gauge, which means that, while the system is running, we cannot add refrigerant into our liquid side or really at all.

If the system already has refrigerant the only time you can add refrigerant to a system when it's off is when it has no refrigerant and is under vacuum in this particular case, because we're just adding some refrigerant, this is a running system. We're going to open up our suction gauge, we're going to allow refrigerant to go through our yellow, hose down our blue hose and into our suction line. Now again, we don't want to put it in too fast because we don't want to slug the compressor, but because we have that charge adapter on there. That risk is greatly reduced.

So now we're going to watch as refrigerant slowly goes into the system. Generally speaking, we're only going to add you know something like half a pound, maybe a little bit more at a time before we shut off and we allow the system to stabilize and we recheck our readings now in real life, you're going to slowly kind of watch. Your sub cooling come up which is going to be generally a combination of your liquid temperature going down and your head pressure or liquid pressure going up on your gauge. So you're going to watch the temperature increase on your saturated scale on the high side gauge and then you're generally going to watch your liquid line.

Temperature either go down or stay pretty steady, but we've added 12 ounces of refrigerant and now we're going to let it stabilize and see what we've got. You can see that our liquid line temperature went down to 97 degrees from 100 degrees, and now we go up and look at our liquid line, saturated temperature. We can see that it went up to 107 degrees so now, because our pressure is up at 350, 107 degrees, liquid line saturation or condensing temperature minus 97 degree measured liquid line temperature. That means that we have this charge set in exactly as we should now.

We showed this very quickly in real life. This is going to be a slow process, you're going to add it in slowly shut it off, keep watching it until you hit that target number, while checking your other system operations such as compressor, amperage, suction pressure, superheat. All the other types of things, but again here we're just showing sub cooling. Once we get done we're going to reverse the process, we're going to shut off the tank, then we're also going to purge our refrigerant back through from the liquid side back to the suction side.

So we open up both of our valves that allows any liquid refrigerant that was trapped in our red hose to travel back and to be fed back into the suction side. So that way we don't waste refrigerant. Now we close both of our valves and now we can remove everything because we've backed off our quarter pressure, we don't have any risk of there being leakage out of our port move our quarter pressure tool, replace our caps, making sure that there are seals back in The caps and then we can go ahead and put our tools away now. Obviously this was a very simplified process showing how to charge using an analog manifold.

You do need to make sure that you purge your hoses properly to make sure you don't get air on the system. There's some things in there that you know some of you are going to point out in terms of this 3d model on that front. But the main thing here is showing how to utilize the analog manifold to safely charge the system with refrigerant, using a scale and taking an accurate measurement of the liquid line temperature and the liquid line pressure, converting that to a condensing temperature, otherwise known as our saturated Liquid temperature and taking the difference the amount that the liquid line measured is below our liquid saturation. That tells us our sub cool if the number is too low, we add refrigerant in order to hit our target while monitoring all of our other readings and measurements.

On our system, we're going to show some future videos of how to do it with probes and digital manifolds, similar to what we've done before we're also going to show superheat and other diagnostics. This is a basic look at charging: an air conditioning or heat pump system with refrigerant using the sub cooling method. Hopefully, you found that helpful thanks for watching our video if you enjoyed it and got something out of it, if you wouldn't mind hitting the thumbs up button to like the video subscribe to the channel and click, the notifications bell to be notified when new videos come Out hvac school is far more than a youtube channel. You can find out more by going to hvacrschool.com, which is our website and hub for all of our content, including tech tips, videos, podcasts and so much more.

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