This video demonstrates how to use the Testo 410i and 605i to verify airflow and delivered capacity on a Mitsubishi ductless heat pump.
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.
When evacuating, the FASTEST way is to use two large diameter hoses connected to two core removal tools and the cores removed. These hoses are then connected to the pump using a tee or evacuation “tree”.
However, when you only have one large hose another acceptable method is to connect the large hose to the suction side and the vacuum gauge to the liquid side alone.
Brad Hicks from HVAC in SC made a nice little video showing how he does this with just one hose. He uses a core tool with the vacuum gauge on the liquid line to ensure that there aren’t and issues with depressing the core, which happens often with certain cores and gauge couplers. The other reason is so that he can valve off the vacuum gauge when he releases the charge or charges the unit to prevent refrigerant and oil from potentially entering his vacuum gauge.
The disadvantage of this setup is that the vacuum must all pull through the metering device which can add time to the process. In the case of a “hard shut off” TXV this method may not work.
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 dry bulb 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 –
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 –
We cover all of this and more in this video –
There are many acceptable methods for making a wire splice and you need to consider many different factors when making a splice. Here are a few considerations.
Here are a few options for splicing wires depending on application –
Splicing any high voltage conductor in an “open” manner or in way that is not specifically rated. In most cases get a UL rated connector and make the connection inside a UL / NEMA rated rated box or assembly.
Making a splice by just twisting wires together and putting electrical tape on top. Just don’t.
Using wire nuts and creating a big ball of wires and running electrical tape over them until it looks like a giant blob of tape.
Use wire nuts on low voltage or control wire in dry and accessible conditions but twist them so the wires stay neat and lay half of the conductors in one direction and the other half in the other direction and tape up in a neat fashion.
The same type of configuration with 3M Scotchlok crimp connectors for better moisture resistance than wire nuts.
In some mildly damp conditions you may be able to use self fusing silicone tape for a more water resistant layer than electrical tape.
Use butt end connectors on stranded wire or if using small gauge single conductor wire (like 18ga stat wire) you can double the end of the wire over before making a crimp. When making a crimp ensure that that the actual crimp is made on the side of the connector OPPOSITE the seam. Once you make a butt end connector pull HARD on it totect and ensure that no bare wire is exposed outside of the insulator.
Use heat shrink butt connectors and stagger the connections to reduce the bulge. Heat the connectors to seal them, then run a piece heat shrink over them all. I found this 4:1 shrink ratio, marine grade heat shrink that should do a great job or water proofing. Heat shrink can be a real life saver and you can use a heat gun or a small butane torch to heat it up. Coincidentally they also make little, portable butane soldering irons as well.
When making a soldered splice make sure to use rosin core solder and wipe off the rosin flux before covering the splice to help prevent corrosion. Remember to run the heat shrink over the cable and the individual conductors BEFORE you start making the splices to prevent sadness and yelling.
The best options are to just run a new wire or make the connections inside of a rate box with proper connectors. Sometimes the best way is the simplest way.