Hermetic- Can be reciprocating, scroll and rotary compressor(s)
Semi-hermetic- Can be reciprocating, rotary or rotary screw, centrifugal
Open Drive- Can be reciprocating, centrifugal
Compression Ratio: How and why it is so important?
Our goal as mechanics is to achieve “the work” with the lowest compression ration
Compression ratio: Air Conditioning
Discharge pressure + 1 atmosphere (roughly 15 psi) 300+15=315
Suction pressure + 1 atmosphere 72+15=87
= Compression ratio =3.62 Comp Ratio
Compression ratio: Low Temp Refrigeration
Discharge pressure + 1 atmosphere 300+15=315
Suction pressure + 1 atmosphere 7+15=22
= Compression ratio =14.31 Comp ratio
Why is this important? It is a metric to use to see actual throughput of your work. If you are NOT using compression ratio’s as comparison of work, you should be. What other tools should you be using?
Always log your starting point:
Find the answer:
You have a low temp rack (R-22 with a C/I of 12psig and a C/O of 4 psig)
That rack is fitted with a 2-stage mechanical sub cooler and you are delivering 40 liquid temperature liquid to the 5-door frozen case. You have an expansion valve rated a 1 ton of capacitance, what is its corrected capacity?
Mechanical subcooling on a Package RTU?
Mechanical subcooling on a water-cooled chiller?
Mechanical subcooling on your home split system? HUH?
Sectional Steam Boilers-Vacuum Pump, Tank, and Trap survey replacements
We diagnosed a boiler issue a couple weeks ago for a customer in downtown Kansas City, as is the time of the year, boiler issues are critical, so a quick and correct assessment is needed. Our President, Jim Rogers, and a new PM went to attack this customer critical issue and came up with the solution below:
When a customer called and reported a boiler room issue, we came running. The steam sectional boiler is an ancient art quickly being replaced by hot water and electric boilers in new construction. However, downtown Kansas City is redeveloping many of its historic buildings to fuel the reemergence of its urban lifestyle and business hub. As this trend continues, and as space for new buildings remains minimal (and expensive), the steam boilers of the past will continue to serve as the single heat source for older buildings. Many mechanical contractors lack the knowledge or experience to manage these issues. At Martin, we continue to dedicate our time and effort to learning both new and old techniques. We pride ourselves on repairing and maintaining historic boilers while also sizing, updating, and installing contemporary boiler systems designed for the twenty-first century.
This is a common issue building owners face when running an old steam boiler, in a vacuum style system, with changing and untrained personnel, this style of systems will never be properly diagnosed or properly fixed. Martin Mechanical had the extensive knowledge and properly trained employees who saw the issues and were able to correctly fix each part of the problem.
At this specific building, originally built in 1909 and currently running a 1980s Smithville boiler, we faced a rotting vacuum and feed water tank. To make the situation worse, the lack of system maintenance and past “quick fixes” led to an inefficient workload and strain on the boiler and pumps. After a few minutes of examining the equipment and piping, as well as asking the maintenance staff about run times and upkeep, we realized the built-to-run vacuum system was operating incorrectly: running unnecessary loads on the system, wasting thousands of gallons of water, and draining costly utilities due to the incorrect sizing of pumps and traps. By replacing the rotted tanks for proper sizing, reconfiguring the piping layout, and bringing the low-pressure steam boiler back into the proper vacuum, we found a solution to run the system efficiently and effectively. As a result of this fix, the vacuum pump pulls air from the system, allowing for a smoother, more rapid heat build-up.
Refrigeration 101 – w/video and Fill in the blank matching test
Last week we held our monthly class at the Martin offices in our training room. This months focus was on the refrigeration cycle, parts, and components which make up the system for a building. Attached below are the slides from the class, a link to our youtube channel for the video, and a short matching “fill-in-the-blank” quiz over common parts and materials installed in a refrigeration system. Much was discussed outside the pictures, captions, and prompts on the power point, but some of the best highlights of the 2.5hour long training from our in-house expert, John Maske, follow;
“R410a refrigerant, because of its near Azeotropic properties, is the best balance of both worlds for temperatures, with both gases and liquids…”
“Parallel Metering Devices, will help a system fight against Room temperatures…”
“The thermostatic expansion valve (TEV) controls the flow of liquid refrigerant entering the direct expansion (DX) evaporator by maintaining a constant superheat of the refrigerant vapor at the outlet of the evaporator…”
Compression Ratios: Air Conditioning and Low Temp Refrigeration
Discharge pressure + 1 atmosphere (aka 14.7 or 15psi basically)/Suction pressure + 1 atmosphere
“Higher Pressures = Best possible heat transfer”
“…A good stewart of customers would do yearly tube analysis on chillers, via pneumatic probe and dry run, prevent maintenance is good maintenance…”
Refrigeration 101 specialties Quiz (link with above post)
Name the following specialty items
(Answers: Top down, left to right)