- Tech Tips
Adolfo Wurts from Arbiter Incorporated, designer of the UEI WRS line of Bluetooth scales comes on the podcast and we talk about scales including.
You can find these scales for sale at TruTech Tools by going HERE
And don’t forget to use the coupon code “getschooled” for an 8% discount at Trutechtools.com
Find out more about the WRS line by visiting the UEI website
I’ve had a change of heart.
Back in the early 2000’s during the big construction boom I did a lot of system startups on residential units for a large company I worked for.
When installers were running the linesets prior to startup they weren’t always very careful to keep them clean and dry and many times we would end up with a restriction in the piston or TXV.
These new residential systems come with a precharged with refrigerant in the condenser. So after my vacuum was complete I would “release” the charge by slowly opening the liquid line service and watching to see if my suction pressure would steadily rise.
I did this so if there was anything in the liquid line it would hit the screen or drier before the metering device instead of possibly running the other way and clogging the TXV or orifice.
Many times I would know that there was a restriction before I even started the system because I got used to watching that suction needle rise. While I did this for a good reason that reason is in the past.
When we install systems we take great care to make sure the lineset stays clean and dry and we flow nitrogen while brazing with the line drier installed near the indoor coil.
It’s a new day and I’m giving up my old sins.
It is not likely that you will lose enough compressor oil to cause any damage by opening the liquid line slowly, but any oil the compressor does lose has a long journey before it gets back to the compressor. The other issue is that oil loss in those first few moments in the life of a new system can have long lasting effects on the operation and longevity of that compressor.
Have you ever taken a liquid line hose off after a new system install and gotten oil all over?
The reason for that is often due to opening the liquid line first and the compressor losing oil to the discharge line and then to the liquid line.
When you open the suction side slowly first and oil loss from the compressor will enter the suction line. Once the compressor begins running no it will pull that oil back into the compressor.
When doing it this way you would attach your micron gauge to the liquid line core remover side port with the schrader in place in the side port. Once you completed your vacuum and proved you had no leaks or moisture by valving off the VCT’s and watching your decay rate. You would then attach your gauge manifold and slowly crack the suction side until you see a few psi on the liquid side. Now remove the vacuum gauge to ensure it is not damaged by the system pressure.
Most micron gauges can handle some pressure, for example the Testo 552 can handle up to 72 PSIG(4.96 bar) and many can handle 400 psi(27.57 bar) or more. it never hurts to remove that expensive and sensitive micron gauge before you expose the sensor to high pressure, but never remove it BEFORE the system is under positive pressure or you will lose the entire vacuum.
You would then purge your manifold hoses and fully open the suction valve and then the liquid line valve.
When charging a system that has no charge (not running) weigh refrigerant into the liquid line first until both sides equalize in pressure to ensure that you are not introducing liquid refrigerant right into the compressor crankcase.
Also keep in mind that running the crankcase heater once the charge has been released and before the system is started is also a good practice to prevent flooded start on the compressor.
For those of you who follow the podcast you know how excited I am about the new MeasureQuick app and what it will do to help technicians make better measurements and diagnosis. The app is NOW AVAILABLE on Android and will be available within hours on IOS (Apple)
To find out more and to download just go to measurequick.com/downloadnow
Here is a video from Jim on the launch
And a video from Brad Hicks with HVAC in SC showing his system at home on the app
and you can hear the MeasureQuick launch podcast episode HERE
Big thanks to Jim Bergmann for bringing this excellent technology to the HVAC industry.
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.
I have seen MANY junior techs replace hoses just because the O-rings were leaking. Every decent hose manufacturer sells replacement O-rings so you can keep those hoses in service until the hoses themselves become damaged.
Here are some more tips to make it easy.
In this episode of the podcast Jim Bermann talks about the launch date of the measureQUICK (MQ) app, what it will do, why he made it, who it is for and why it’s different than anything else that came before.
You can find out more by going HERE
To start with I’m going to cut straight to the part that most of you want to know. This is based on calculations I have done personally based on typical Mastercool DOT tanks but feel free to come to your own conclusions based on your own calculations. I prefer to stay on the safe side.
30 lb(13.6kg) recovery tank – Fill with no more than 17lbs(7.7kg) of R410a or 21 lbs(9.5kg) of R22 – total tank weight will be about 35lbs(15.9kg) for R410a and 39lbs(17.7kg) for R22
50 lb(22.7kg) recovery tank – Fill with no more than 32lbs(14.5kg) of R410a or 39 lbs(17.7kg) of R22 – total tank weight will be about 60lbs(27.2kg) for R410a and 67lbs(30.4kg) for R22
Now for the details.
First, you should look for the Tare Weight of the tank. It will be stamped on the top rim of the tank or handle with TW- and then the # like shown below on a common propane tank
Tare weight is simply the empty weight of the tank and must be factored for whenever you are weighing the total weight of the tank.
Next look for a stamp that says WC(PA), this indicates the water capacity of the tank, the total weight in liquid water to fill the tank 100%.
You also need to consider a few more things before you start filling
There are a few different ways to do the math. Some use the specific gravity of the refrigerant but I just use cubic foot per pound at 130 degrees°F(54.4°C) to calculate just to be certain I am on the same side of the range.
Water has a volume of 62.42 pounds per cubic foot, R22 is 66.17 and R410a 54.70. You can find other refrigerants by looking up their data sheets.
a 30lb(13.6kg) Mastercool 400 PSI(27.57 bar) recovery tank has a water capacity of 26.2 lbs. Divide that by the water volume of 62.42 and you get 0.419 cubic ft of space in the tank (25.2 / 62.42 = 0.419)
If you are filling the tank with R410a you would then multiply the space in the tank (0.419 cubic ft) by the cubic feet per lb of liquid R410a at 130 degrees (54.70) and you get 22.95 lbs to completely fill the tank.
However you cannot completely fill the tank, you must only fill it to 80%, so you multiply the 100% full weight (22.95 lbs) by .80 which gives you 18.36 lbs rounded down to 18 lbs of total internal R410a weight (I go down to 17 just to be extra conservative).
If you then want to calculate the total weight of the tank + the refrigerant inside the tank you would need to add the tare weight. For this Mastercool 30lb tank, the TW = 17.99lbs for a total tank weight of 34.99 lbs
So in order to know for sure that you are not overfilling a tank, you must have the following –
For R22 and 410a I came up with some quick (conservative) cheat numbers to simplify the math a bit.
For R410a just multiply the WC(PA) by .65 to find a safe fill weight, for R22 multiply WC by .82
You would still need to add in the tare weight to calculate total tank weight and if you are using a different refrigerant you need to start the math from scratch.
When in doubt, err on the safe side… and for heavens sake… use a scale and read the information on your tank.
P.S. – Tech Daniel Green made a really cool spreadsheet calculator to get max fill for various refrigerants HERE
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.