In the HVACR world, it is not impossible that the designers of a walk-in cooler/freezer to mistakenly chose the wrong FPI (fins per inch) selection for the application you are servicing. Here is a table to reference when you are looking at possible causes of an iced-up coil. With fin spacing too close, frost can easily bridge the gap and quickly reduce air flow through the evaporator.
The proper selection of fins per inch plays a role in maintaining proper humidity levels in the conditioned space as well. The bottom line is this: don’t always assume that the application engineer can’t make a mistake in the selection process. Always look at this factor when troubleshooting your HVACR evaporator problems.
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I just can’t say enough about an app that has become an essential part of my life and the overall operation of our HVACR service team.
I am talking about EVERNOTE. It is one of the best ways to assemble, organize and present information that I have ever seen. Now you may be thinking that I am compensated for endorsing this product but you are wrong. I am compensated by using the product. I use it for training purposes as well. It has a great presentation mode that I use instead of powerpoint slides.
I use it many times per day. It is extremely useful when we have our weekly service huddle meeting.
Below is a screenshot sampling one of our huddle meeting frameworks.
You can easily hyperlink the topics to other notes that have been organized into specific Notebooks.
We also have the essential Notebooks shared with all the service techs. It is feature-rich and the beauty is that it syncs across just about all platforms.
An example list of our company shared Notebooks contain the following topics: Work Data, Parts Information, Site Information, Memos, Policies, Training, etc. In these Notebooks are contained over 500 notes and training presentations. It is easily searchable for specific notes inside these Notebooks.
As we go throughout the week and run across some useful topic to discuss or encounter a recurring issue, we add it to the list for “Monday” and we keep the team informed. It helps us to maintain a near-paperless approach to our day to day business practices. For all our larger digital files that contain operation manuals and other manufacturer information, we use Box, which contains over 12GB of technical information for our team to access.
My wife and I both have the premium version and use it for all our financial paperwork and household business. Click here to for a free trial of Evernote.
The final factor in evaluating the air distribution in a space is the comfort of the occupants. In general, a person is thermally comfortable when body heat loss equals body heat production. What most people call a “draft” is simply a slight movement of air that results in a local feeling of “coolness.” It has been determined that a velocity change of 15 ft/min has about the same effect on comfort as a 1°F of temperature change. KEEP READING BELOW…..
A typical room air distribution system with local air velocities of less than 40 to 80 ft/min will satisfy 80% of occupants. Localized air temperatures should be less than 2°F below the general room temperature. The temperature near the floor should be less than 4°F below that at about shoulder height. For heating, local air velocities generally are below 40 ft/min. For cooling, local air velocities should be between 40 and 80 ft/min.
A defective expansion valve, refrigerant overcharge, or extremely low load may permit liquid refrigerant to reach the compressor from the evaporator. Because liquids are not compressible, the pistons and valves can suffer damage from such “slugs” of liquid.
To prevent this, you can put a suction accumulator in the suction line between evaporator and compressor. Trapped oil may build up in the bottom of the accumulator after the refrigerant evaporates. Accumulators therefore have an oil return line leading from the bottom of the trap.
This figure shows a cross section of a typical suction-line accumulator. It has a U-tube for passage of refrigerant vapor back to the compressor. The metering port at the bottom of the tube allows oil to return back to the compressor. The metering port is small enough that any liquid refrigerant entering should be boiled off before it reaches the compressor. EXCERPT FROM THE” TECHNICAL INSTITUTE MANUALS “AVAILABLE AT THE ONLINE STORE AT RSES.ORG.
Rigid connections at the compressor are prone to crack or break from vibration and stress. The cause may be discharge gas pulsation or compressor movement because of high torque.
There is a simple way to prevent line breakage from these causes. Install vibration eliminators in both the suction and discharge lines. They should be the same size as the lines. Install the vibration eliminators parallel with the drive shaft on the compressor. It should only be clamped on one end.
A typical vibration eliminator has rigid copper ends to connect to the compressor and the system. Between the ends is a length of flexible tubing. It is covered with woven brass or stainless steel mesh for strength.
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There is a lot going on in the world of Refrigeration. Electronics, alternative refrigerants and new ways to service equipment. One way to keep ahead of these changes and grow your business is to sign up for Refrigeration Contractor Weekly.