Category: All Videos

Good friend and contributor to HVAC School Neil Comparetto made this video showing the way in which he creates access ports for static pressure and gas combustion analysis. As techs we find ourselves in the tough position of needing to drill access holes to take measurements but the drilling and sealing of the holes can sometimes create real and perceived issues with the equipment. Many techs use high temp RTV Silicone, Rectorseal Duct Seal compound or even tape. In some cases these sealants may be appropriate but Neil shows how he uses plugs to make a good permanent access point. Always make sure to leave any work is a well sealed and workmanlike condition.

You can find many of these items at Trutech tools HERE 

Measuring airflow is easy… measuring airflow accurately is quite a bit more difficult. In many cases when we as technicians measure airflow we are trying to get to the almighty CFM (Cubic Feet per Minute) volume measurement. You can take CFM readings fairly easily with a hood like the Testo 420 shown above, but even a hood has some limitations when the goal is to measure total system CFM vs. register / grille CFM.

In this series of videos Bill Spohn from Trutech tools demonstrates all of the tools you can use to measure airflow from hot wire and rotating vane anemometers, to flow hoods, to smart grids and pitot tubes, all the way down to using a GARBAGE BAG.

I had the privilege of seeing this presentation in person (I am the one behind the camera) and I wanted to share it with you. It is well worth your time.

— Bryan

I was about 13 years old the first time I bent EMT with my uncle. We were doing a renovation at a church, and watching him bend EMT and then getting to do it MYSELF was a truly religious experience.

There are a few things in the trade where workmanship really comes into play such as copper pipework, making up a panel or fabricating ductwork… bending EMT belongs on that list. While most commercial electricians do it every day, HVAC techs and installers only run into an application where we do it on a rare occasion. When that does happen its good to have a basic understanding of how it works. In this video Juan from the The Air Conditioning Guy channel goes over some quick basics on bending EMT

For more info you can read this great guide on bending from Klein

— Bryan

As a technician gains skill they will learn that regularly testing your tools is a huge part of success. It isn’t long in the field before techs find out that just because a meter or gauge gives a particular reading it doesn’t ALWAYS mean it is correct. Vacuum is one of these areas.

Everything in an air conditioning and refrigeration system leaks to some extent, our job isn’t to eliminate all leaks, our job is is to reduce the leakage rate to as low as possible. When using a sensitive micron gauge we find that isolating an assembly and checking the “decay” or standing leak rate is a great way to test and ensure that a system has minimal leaks and moisture. The challenge is that all of the connections in your rig leak and even the vacuum gauge itself leaks.

Some techs attempt to test the leak rate on micron gauge by connecting it to a core tool and then straight to the pump, evacuating the gauge down to very low level and then valving off. If you do this, you will find that every commercially available vacuum (micron) gauge shoots up pretty quickly. This is because the VOLUME of the gauge and coupler are so low that ANY leakage whatsoever has an enormous effect.

In this video Ulises Palacios shows us how to use an an empty recovery tank to better test the leak rate of a vacuum gauge rig.

It is certainly important to test all of your vacuum rig components, just remember that volume makes a huge difference when decay (standing vacuum) leak testing.

— Bryan

In this 60-second tech tip video by Brad Hicks with HVAC in SC. he shows us how and why to remove the weep port plugs on a condensing fan motor. I know from experience that motors can fail prematurely when this practice isn’t followed. Remember that motor orientation dictates which are removed. It (generally) the ports facing down that need to be removed and the ones face up stay in place.

Transcript

What’s going on guys here is a quick 60-second tech tip is on changing condenser fan motors. Whenever you’re changing them, most all condenser fan motors have plugs that are supposed to be removed depending on the orientation of the motor. Since this shaft is facing down into the unit these need to be removed and basically what they do is, they open the weep holes so any condensation or moisture that can get into the motor doesn’t stay in there to corrode the windings and in turn prematurely make the motor fail. So make sure you take those plugs out, if you don’t, like that motor over there you’ll be back within a couple years to replace it again. Just a quick tip make sure you take those plugs out like I said this motor is oriented this way so you want to take the plugs out of the bottom like I just did and your motor will last much longer. There you go thanks for watching.
— Brad Hicks

 

I hear many techs complain about the finicky and ineffective nature of electronic leak detection. So much so that some claim that is is a waste of time altogether. we recently located a leak inside the fins of a ductless evaporator coil, pinpointed to an exact spot using an electronic leak detector. For demonstration purposes, we took that coil and performed a definitive test to locate it in the video below.

A leak detector can be tricky to use so here are some of our top tips –

  • Know your detector. Know it’s limitations, it’s sensitivity and what can cause false positives. For example some leak detectors will sound off on certain cleaners or even soap bubbles. My detector sounds off when jostled or when the tip is blocked.
  • Keep a reference bottle so you can check your detector every time before you use it.
  • Maintain your detector and replace the sensor as required. Most heated diode detectors require sensor replacement every 100 hrs or so.
  • Keep it out of moisture. Most detectors will be damaged by almost any amount of moisture.
  • Move slowly and steadily. Don’t jump around or get impatient.
  • Most refrigerant is heavier than air which means that starting from the top and working down is usually a more effective way to pinpoint.
  • Go back to the same point again and again to confirm a leak. Don’t condemn a component bases on one “hit”
  • Find the leak WITH BUBBLES whenever remotely possible, even after pinpointing with a detector.

— Bryan

The tech tip today is a video put out by my friend Brad Hicks from the HVAC in SC YouTube Channel. Thanks Brad!


Seal boots to prevent raccoon leaks

Ok, so this has nothing to do with raccoons but I like that photo.

Whenever you are installing duct boxes (also called boots or cans) in an aftermarket application, make sure to place a bead of sealant like mastic or silicone on the flange so that as it presses against the substrate it will seal against leaks to and from the unconditioned space. When installing in a new construction environment where the boxes / boots / cans go in before the substrate you will either want to use boots that already have gaskets or you will want to add a gasket to the flange such as foam tape.  In these cases, it is still a good idea to seal the edge further from the inside once the drywall (or similar) is in place and before the grilles and registers are installed.

 

 

Video Transcript

What’s going on guys? here’s another 60-second tech tip, this is on supply and return grills and properly sealing them. As you can see this return grill that I have pulled down was not properly sealed. No silicone or mastic, so basically what’s happening you can see a little bit of wood here when the blower comes on it pulls air that’s pulling unconditioned air from between the sheetrock and the wood that’s framing this box out of the attic and into our Airstream. Since our air filter goes here as well most of this isn’t being filtered, it’s just passing right into the system. As you can see that return is fairly dirty so all of this should be sealed with mastic and usually we just silicone or you can mastic this as well. Same thing with supply grilles, so if you ever have customers that are dealing with dust issues or units getting dirty but the filters aren’t that dirty this could be your culprit. Make sure you’re paying attention to the supplier return grilles and look out for this kind of stuff so hope that helps thanks for watching.

When you first start checking your supply air with a thermo-hygrometer you may notice that the relative humidity is REALLY HIGH. Often the RH in a supply duct will be between 85% and 96% relative humidity on a system that is functioning as designed. The reason for this is fairly simple.

In order for dehumidification to occur the air must reach dew point, otherwise known as 100% relative humidity

Jim Bergmann explains it this way. Think of a sponge being like air and when it is fully expanded it is like the air in the return. When the sponge is fully saturated and can accept no more water it is at 100% RH and when it is completely dry it is at 0% RH. Let’s imagine that the sponge is 50% saturated and full size in the return. When that sponge (air) goes over the evaporator coil it is compressed, because colder air can hold less moisture. Once that air is compressed (cooled) enough it will begin to give up moisture. This point at which it starts to give up moisture is called dew point or 100% relative humidity. Once that air leaves the coil it still remains in approximately the same temperature state (compressed sponge) as it was when it went over the coil. This means that unless heat is added or removed from that air, it will remain at 100% relative humidity.

So why is it less that 100% RH in the supply?

There are several reasons why the air in the supply will be slightly below 100% in the supply. First is contact factor or bypass factor which are both terms used to demonstrate the efficiency of a coil at “contacting” the air. The greater the surface area of the coil and the longer the contact time of the air on the coil the more efficiently heat will be transferred from the air to the coil.

Because no coil is 100% efficient, there will always be some air molecules that leave the coil warmer than others, this causes the airstream to be warmer overall and decreases the RH of the air stream. You will notice when a system has a higher coil air velocity (speed) it will have a higher bypass factor (lower supply humidity). When you run lower coil air velocity the bypass factor will drop and the supply RH will increase.

There is also some heat added by the blower motor and possibly even the cabinet or supply ductwork. This added drybulb heat results in a warmer airstream and thus some additional moisture capacity. Imagine a slight expansion of the sponge due to heat from the duct walls and the blower motor.

Once that supply air exits the duct and mixes with the room air it is allowed to “expand” again and the relative humidity drops below what it was initially. This is why supply air has a high RH in cooling mode.

Here is a video we did on the topic –

— Bryan

 

Recovery is the removal of refrigerant from a system to either store and send in for recycling or to reintroduce back into the same system.

Here are some top tips –

  • Make sure your tank is empty and evacuated to 300 microns if you plan to return the refrigerant back into the system.
  • Never mix refrigerants.
  • Purge hoses before recovery.
  • Use a flare line drier on the inlet of the machine to increase the life of the machine and to filter and dry the refrigerant. These must be replaced regularly.
  • When recovering into a tank using the standard method invert the tank and pump into the vapor port on the tank.
  • Remove Schrader cores before recovery for faster recovery and a cooler tank.
  • Use larger gauge hoses with no core depressors for faster recovery.
  • Check Recovery machine inlet screens regularly and clean or replace as needed.
  • Some machines require oil to be run through the machine from time to time. Read manufacturer specifications.
  • If your tank becomes hot you can either place it in a bucket of water or run water over the tank.
  • Do not leave refrigerant in your machine during storage. If your machine has a purge mode make sure to purge the refrigerant out of the condenser (see manufacturers specs on your machine).
  • Most HVAC systems holding under 200 lbs of refrigerant are not required to be pulled into a vacuum during recovery. See this chart from the EPA.
  • Weigh the refrigerant out and do not fill the tank to more than 80% of the REFRIGERANT capacity, not just the water capacity.

We cover all of this and more in this video –

— Bryan

On occasion you will either find a furnace or be tasked with installing a furnace where the coil overlaps the edge of the furnace because the coil is wider. In the case of a Carrier CNPVP coil you need to ensure that you align the coil according to manufactures specs or you risk cutting off about 1/3 of the airflow.

The best case scenario is to use a coil that is a sizer match for the coil or to buy or make a  tapered metal transition between the furnace and the coil. The the case of the CNPVP the manufacturer allows the coil to be offset to the left.

In this video we illustrate replacing a leaking coil and reconfiguring it in the proper orientation.

— Bryan

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