Cleaning Up HFC-POE Systems
The forum’s intent was to discuss cleanups in new (HFC-POE) systems, built-up systems, and large systems; issues pertaining to burnouts, contaminations, recurrent situations, and unusual situations; and to see if there is a need for new tools or procedures.
Take, for example, the case of the engineer who specified a component for a transport refrigeration system. His company purchased a specific type of liquid-line filter-drier, which lost its desiccant in the system. “We’ve had to clean [the desiccant] from the system,” he said. (Note: ASHRAE forums cannot be reported in the trade press in such a way that identifies the speakers.)
One component manufacturer asked whether the desiccant had gotten into the expansion device. The engineer couldn’t say. “How small will [the desiccant] get?” he asked.
CATCH CONTAMINANTS EARLYA manufacturer pointed out that the servicer’s best bet would be to take the expansion valve out, clean it, possibly replace it, then put in a suction line strainer. This would help catch the contaminant as early as possible. “Get it out of the system before the expansion valve starts working with the desiccant,” the manufacturer advised.
Another engineer wondered if there are diagnostic tools to detect particulate in lubricant. A manufacturer replied in the affirmative. The servicer collects a sample and sends it to the lab for analysis. The report includes contaminants, acids, and moisture levels.
He added that “It can’t sample accurately downstream from the compressor” — the contaminant is broken down and compressed.
Another engineer said, “Once you get it to the lab, you can test for magnetic and nonmagnetic particles and silicates.” It’s a good bet that silicates would be found in that transport system, commented another engineer.
This all led to the intriguing question of, “How clean is clean?” Systems can contain particulates, acids, and moisture; during a cleanup, what levels of purity do you need to safely put the system back in service?
A manufacturer commented, “Of course, ARI 700 levels are preferred” for refrigerants, but reaching this level is not always practical in the field.
A consultant stated that for new systems, “If you know the lubricant’s acidity initially, you can monitor it regularly to see if it’s changing.” On large systems, it’s a good idea to use lab services.
An engineer asked if there are current products for flushing out HFC-POE systems. There are, replied a manufacturer. “You have to disconnect some lines to isolate components first.” The product flushes out sludge.
A manufacturer then asked, “How small is small? What is an acceptable-size particle that will not damage the compressor? Water and acid are bad, but at what levels?”
“Particulates on their own may not be bad,” said another manufacturer. “Wax may not be bad. Together they’re not so good.” ASHRAE may want to study combinations of contaminants in HFC-POE systems.
“I don’t know if you can define how clean ‘clean’ is,” said a component manufacturer. “Manufacturers need to do a better job of telling people what not to do — like flushing systems with water.”
A manufacturer advised contacting the equipment manufacturer when contaminant levels are known, asking whether it could be deleterious to the system.
An outspoken engineer commented that the answer you get “depends on whether the system is in warranty or out. If it’s out of warranty, you might get an intelligent answer.”
AVOIDING RECONTAMINATIONA refrigerant manufacturer said that while there are solvents to clean to oem levels, the problem is that you can’t see what’s left behind after the cleaning.
“Just because the solvent comes out clean, doesn’t mean there aren’t contaminants left in the system,” said an engineer. “They can be compacted or stuck somewhere. Sometimes all you can do is do the best you can, and pray,” he said, adding, “This works quite often.”
Then there is the problem of recontamination after burnouts. “How many times has the guy changed out the motor and filter-drier, but neglected to change the oil filter?” asked an engineer. This can result in recontamination of the system.
And on multiple-compressor systems, like refrigeration systems, “If there’s one burnout, you should check out the filter-driers on the other compressors.”
Publication date: 03/11/2002