Tuesday, July 31, 2012 at 11:29AM The Samsa Success Blog is an area on our website that will be updated frequently with information about interesting projects done by Samsa Mechanical Service. Thanks for visiting and enjoy!
Friday, July 27, 2012 at 4:15PM 
This McQuay WHR150 chiller was giving our customer issues for years. After many failed attempts at correcting the issues they were referred to Samsa Mechanical Service by one of our other satisfied customers.
This is a 150 ton chiller with four copeland reciprocating compressors, two 75 ton refrigeration circuits and 8 stages of unloading including hot gas bypass.
We arrived at the customers facility to check the operation of the chiller and found many issues. First, the chiller is starting in a fully loaded state running 7-15 minutes depending on load and shutting off without unloading. Next we find a 3/8' copper line with valves on both ends connected to each refrigeration circuits lead compressor's oil sump (we were informed that in low loads the refrigeration circuits 
would lose oil to each other), obvious problems.
While checking out the actual operation of the refrigeration circuits we found the expansion valves so far out of adjustment that the compressors were constantly failing on low oil pressure which we corrected by adjusting the expansion valves to maintain proper superheats.
A few days later we returned to find that the unit was indeed losing refrigerant/oil from one circuit to the other. One circuit would fail and cause the running curcuit to pull refrigerant from the circuit not running (higher pressure because its not running) because of what I assume is a circuit to circuit leak in the evaporator (only common spot on the system after we removed the connection between the two 
Before - Notice all the arrows pointing to reset buttonscompressors). The evaporator is common on the system and is divided by a plate with two gaskets at both ends of the heat exchanger one of which had to be leaking.
This chiller was oversized compared to building loads so we proposed pumping down the second circuit on the chiller and only running one circuit to get through the summer and minimize the leaking, at fall shutdown we would remove the heads and replace the gaskets. Once the gaskets were replaced we would do standing vaccum tests individually to verify the system was tight.
We further suggested, based on the current on/off operation, that we upgrade the chiller control system to a MCS Magnum micro processor with the addition of electronic expansion valves. This proposal was accepted and these repairs/upgrades were performed in the fall of 2011.
Before - ControlsThe system has been running ever since with no problems. The most common complaint in the building is now that people are too cold.
Leaking evaporator divider - Notice dark spots where leaking was taking place
After - Controls
After - Controller
