The following Q&A session is from a webinar presented by Dan Krupp, director of sales and engineering at Universal Air Filters and hosted by Solar Power World on March 12, 2014.
Solar Power World: How often do air filters for PV inverters and other equipment need to be replaced?
Dan Krupp, director of sales and engineering at Universal Air Filter
Dan Krupp: That’s a good question, and it’s very popular question. As an air filter manufacturer, distributor and supplier, we react to customer behavior and preventive maintenance programs and processes. Most popularly, we are getting requests from the solar farm and solar system industry twice a year. So we’ll see a spike in replacement filter delivery activity in the spring and also in the fall. Filter replacement truly is equipment and environment specific, but most popularly our customers and their recommendations are asking end-users and maintenance teams to clean or replace filters every three to six months.
SPW: Are air filters rated to NEMA 3R, NEMA 4, NEMA 12 and IP54?
DK: These enclosure ratings such as NEMA and IP and even the inverter standards 1741, these are end item device specifications, and they apply to the electrical and the electronics enclosures that employ components such as air filters and EMI shielding. The direct answer to your question is “no.” There are no ratings to NEMA and IP applicable directly to the air filter. Compliant air filters that are flame retardant and have a performance specifications that are inline with UL standards support end-customer enclosure designers in meeting the NEMA and IP standards.
SPW: Is there a general rule or guideline that applies to the power level of inverters and when air filter solutions might become less than desirable?
DK: We are aware that the liquid cooling comes into play and does help with providing thermal management for larger, more thermally challenging systems. It is inconvenient to have fans and blowers and filters in systems, because fans fail if filters get dirty, and they need attention. They are, in many cases, a necessary component of thermal management, and therefore forced-air cooling with filtration is used very popularly in all types of systems.
When liquid cooling is introduced, it can be a replacement for forced-air cooling and fresh air systems. We’ve seen many outdoor enclosures and shelters that are a cooled by closed systems, closed air-to-air heat exchanges that do not require filtration. At the same time, we also see a combination of liquid cooling and forced-air cooling in a single system, which includes less filtration to protect heat sinks and other thermal management liquid cooling components that need to have cooling air brought across them to allow the system to be thermally competent.
SPW: Is it popular/possible to retrofit existing equipment deployed in harsh environments with air filters to provide equipment protection?
DK: That’s a very good question, and that’s a very popular question we get from field engineers, field service technicians who have equipment deployed in their power-gen facilities that arise from OEM manufacture without any filtration option included with it. Sometimes, equipment is designed for indoor use or mild environmental conditions, and when you put them into a solar farm or a power-gen facility which tends to be much harsher environments, then after a time in the field the requirement for filtration creates itself. We get many request from fuel techs looking for retrofit opportunities to improve the equipment protection qualities of the systems. We regularly come up with quick retrofit designs to keep these systems up and running.
SPW: Are there risks associated with form/fit/function cleanable air filter replacements to displace OEM provided disposable air filters ?
DK: Yes, there are. I think the risk is deviating or straying from the custom specifications that were required during the design of the original equipment. Quadrafoam can be specifically configured for the individual applications for airflow and dust protection. What we see regularly with aftermarket replacement applications is field techs will purchase a filter off the shelf or find the filter that’s readily available and not required to be OEM approved, and they tend to fail on the side of too restrictive and too much pressure drop. We’ll get complaints from the field that filters are blocking off all the airflow, and it’s because they’re not OEM approved, and the original designs specifications were not considered with replacements. As we emphasize in the presentation, be sure to use only OEM approved air filters, because of the risk of equipment barrier definitely multiplying when you stray from OEM approved.
For more detailed information watch the full webinar here.