This video is a really basic look at how to check total external static pressure and why it matters when we're talking about total external static pressure. We are talking about the total static pressure that the equipment is seeing. The air handler or fan coil is seeing external to the unit design so step one. We need to make sure that everything is perfectly clean before we do this.

This is mostly really useful. This test on brand new equipment, but it's also fine if the equipment is in like new condition, so the blower wheels clean evaporator is clean filters clean all that if any of this is off, it's going to be kind of inaccurate to measure total external static pressure Step two: we want to run the system in cool or heat mode, depending on whether we're measuring our total external static pressure for cool or heat. So you can do it in either, but they're not going to necessarily be the same for both. So don't assume that they'll be the same.

Most units will run a different fan, speed in both cooling and heating. So if you're doing it in heating, that is your heating total external static and if you're doing it in cooling, that is your cooling total external static. But make sure that it stays running at high stage generally, if it's a multi-stage piece of equipment when you are doing this measurement first step is going to be to zero out a dual port or equivalent manometer here we're showing the job link probes, the job link, Manometers from field piece which operate very similar to a dual port because you have more than one of them, but you want to make sure that they're zeroed to atmosphere before you insert them into the ductwork. It's very important that you do that.

If this is a fan coil, you want to install your negative port if it's a dual port or just one of your single ports, if it's one of the joblink probes underneath the evaporator coil, but on top of the filter. Now again, your filter needs to be clean. In most cases, the filter is not included in the factory specifications. If you have a factory filter, sometimes it may be.

So you want to look at your factory specs on that, but in most cases you want to put it directly under the evaporator coil on a fan coil and then directly above the blower on a gas furnace. It's kind of the same thing, but keep in mind that your blower is going to be first, so you want to put your negative manometer in with the blower underneath the blower, and then you want to put your positive manometer in between the top of the gas Furnace and the cased or uncased evaporator coil, because that is not part of what comes in the box so on a furnace, you have to put it in between the furnace and the evaporator coil, which can be tricky. Generally speaking, there are some spaces that you can drill in order to get a manometer in place, but you definitely want to refer to the information on your particular system and pay close attention to make sure you don't drill into the coil or damage anything when you Do this, if you do drill a furnace or a fan coil in any way, you want to make sure to use some appropriate plugs to make sure that you're completely air sealed when you're done do a nice job with that, don't just go drilling things and leaving Them wide open another thing when you are putting your supply duct in place on a fan coil make sure that you're putting it into the center of a straight run of duct. So that way you don't have turbulence.

Most manufacturers are going to recommend that you use a static pressure. Probe pointed opposite of the airflow direction, so pointed into the airstream in order to get the best reading. But we also find that using things like ball needles, or even just a straight probe on residential equipment, generally works just fine. What you're trying to avoid is getting air right into the end of the probe if you have an open end and that will lead to velocity pressure affecting your measurement.

You want to put your return air probe into a laminar air drop for best probe location, but what that basically means is you want to put it into a place where there's not going to be very much turbulence? You don't want to put it in a corner or any place that the air could be turning or moving, especially in a backwards direction. If you put it into a corner a lot of cases, you get this sort of reverse airflow, where you have turbulence so avoid that put it into a straight portion as best you can, in many cases, you're going to be left just kind of sticking it above. The air filter on the return side, again like we mentioned before, make sure that your probe is perpendicular to the duct walls. Don't allow your probe to go sideways where that velocity pressure can impact your static pressure probe.

This measurement should be measuring the difference between your positive and negative pressures, as examples shown here. If you had a negative return static of 0.15 and a positive supply static of 0.15, you would have a total external static of 0.3 equipment is generally designed for external static somewhere between 0.8 and 0.2. Depending on the equipment. We are going to see that with equipment.

That's designed under the new sear 2 standard that they're going to be designed for 0.5 or more, in most cases, 0.5 kind of being the standard. But nowadays you will find a lot of equipment, especially fan coils that are rated all the way down to 0.2, and so you have to design your ductwork appropriately for the equipment based on the static pressure that it can handle. If you do have a high negative return static, that may mean a dirty filter or an undersized return. Duct.

Those would be some of the most common causes or a system that's set with too high airflow to begin with, which that would cause both of these to be high. If you have a high supply static same thing, if the whole system is producing too much airflow that could cause high static, but also undersized supply. Ductwork kinked supply, duct work, supply, duct work, that's improperly strap, maybe a bunch of vents that are shut. Those are all things that can cause a high positive static pressure, and so these are good things to look at combined to come up with a total external static pressure number but individually.

They can also tell you whether or not you have more of a problem on your return or your supply, depending on which one is the higher number and then finally make your appropriate adjustments. Make sure that everything is cleaned. If you find anything, that's dirty, strap, duct work, adjust air flow, look at your rated total external static pressure for your equipment and make sure you're in that range for optimum system operation. So it's just that simple.

The main thing to know here is here on step. Three that furnaces and fan coils are different and where you position your probes, make sure you are familiar with those probes make sure that you are putting plugs in place and make sure that you are zeroing your manometer before you place it into the system. In the first place, this is some of the most common mistakes that i see made. Also don't assume that a high static number is due to a problem uh with the ductwork.

It could be due to a system that is producing too much airflow, so pay attention to that as well on your settings for your equipment. Hopefully that was helpful thanks for watching we'll catch you on the next video 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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