Ultraviolet Light

Very high levels of UV break down free chlorine. UV is a constant treatment process, regardless of the bather load. It cannot be overdosed.

With the use of UV, the frequency of super-chlorination of the pool is reduced; this is the only quantifiable chlorine savings that can be attributed to the use of UV.

The elimination of combined chlorine by a UV system will significantly reduce the amount of corrosion of ferrous materials exposed to the pool environment.

When sizing a system, manufacturers look at the flow rate, the transmission, and how much energy is supplied.  Chlorine use in the pool may be reduced between 10% and 15% because disinfection is occurring as well, and free chlorine has less work to do.

The distinction between amalgam (low-pressure/high output) UV and medium pressure UV is defined by the internal gas pressure of the lamp when they are manufactured.  Low-pressure lamps have more of a vacuum than medium pressure lamps.  The UV wavelengths emitted from these two lamps differ based on the internal gas pressure and the amount of electricity supplied to the lamp.

UV can destroy chlorine.  Hanovia clips the wavelength that destroys chlorine.  It is very important when you are examining other UV manufacturers that this issue is addressed.

Benefits of UV

  1. Low chloramines are the primary benefit of UV technology.  High chloramine levels result in a corrosive off-gassing which dramatically increases the risk of corrosion to the deck equipment, HVAC, and the internal structure.  Chloramines are also responsible for the odor and irritation experienced by athletes, patrons and staff.
  2. UV has also been shown to be highly effective against chlorine resistant pathogens like Cryptosporidium and Giardia; as well as the vast majority of bacteria, viruses, yeast, and mold.
  3. Indoor air quality will improve from the reduction of combine chlorine. However, the mechanical engineer should consult and follow the recommendations of the latest ASHRAE standard for acceptable ventilation rates for the space.
  4. Athletic asthma is more common on competitive swimmers.  Greatly reducing the chloramines in the water, before they off-gas and provide a vapor blanket over the pool, can only improve swimmer’s health and potentially their performance.
  5. UV does NOT eliminate the need for super chlorination.  Super chlorination is required as a response to a fecal accident.

There are considerable savings on maintenance, personnel, and other chemicals.  A new bulb is required approximately every year and a quartz sleeve is required every two or three years.  CH recommends that owners should anticipate approximately $1,000 per year in maintenance costs ($500 - $800 for a new bulb and around $400 for a new quartz sleeve).  UV is a passive system that requires little monitoring and/or maintenance.  Most maintenance issues can be handled by a competent pool operator.

UV is currently CH’s first choice for secondary sanitation in a natatorium.

CH details that UV system should be placed after the filter and prior to the heat loop.

For retrofits or when space in mechanical room is an issue, the UV system may be placed after the heat loop and always prior to the chemical feed injection.

Ultraviolet light has been around since the early 80s.  It has been used successfully in the water treatment industry in the past.  Just until recently has UV begun to get the support in the industry for swimming pools.  Hanovia/PurAqua has teamed up with Paddock.

ETS is NSF listed for medium pressure UV.  It is listed under ATG Willand.  The ATG Willand emblem can be found on the UL label and the NSF label inside the panel door.  ETS is distributing the ATG Willand system and allegedly will begin to manufacture under the joint name under license.  Their problem was that NSF wanted to charge twice for testing the same unit if they were listed under both names (similar situation for Hanovia / PurAqua).  ETS has the technology, references, support, as well as the required NSF & UL listings.

ETS requires 480 V for all UV model sizes.  Smaller Hanovia units only need 120 V.  Siemens Barrier units operate on 208, 240, or 480 V depending upon the size.

Hanovia units are not capable of being mounted vertically.  However, with ETS units you can.  If an ETS unit is installed vertically though, the flow of the water should go up.  If flow goes down in a vertical mount, there’s possibility that air can get in the line and overheat a lamp.

Triogen is UL listed, NSF approved, medium pressure system manufactured in Scotland.  Their first unit was installed in 1997.  The system uses an inductive ballast rather than a transformer.  Hanovia is the only manufacturer using transformer.  Triogen previously lost the bulk of their reps to ETS but is currently working to get distribution in all 50 states.  Bulb life warranty 2000 prorated to 8,000 hours.  Hanovia is prorated to 4,000 hours.

Astral has recently introduced an NSF-listed UV system that Acapulco seems to be providing.  It was reported by Tim Warren that the system guarantees combined chloramines to be held below 0.4 ppm.  There are 55 currently installed worldwide and none so far in the United States (January 2008).  The units cost between $13,000 and $30,000 and come with a five-year warranty.  The bulb is rated for 4000 hours and is recommended to be changed at 50% effectiveness.  The cost for a replacement bulb is between $500 and $800.

For UV systems that utilize multiple bulbs, when any one of the lamps fails, the system is basically ineffective because the loss of only one bulb results in an exponential loss of dosage inside the cell.

The UV system will provide a UV “dose” of 60mJ/cm2 at the end of lamp life which is the minimum for chloramine destruction.  A dose of 30 mJ/cm2 is the minimum for effective destruction of pathogens.

Chloramines reduction: < 0.2ppm.  CH’s spec requires UV manufacturers to guarantee the unit will maintain chloramines below 0.3ppm.  This give the manufacturers a little room above what the unit should be capable of and still meets the PoolPak warranty requirement to protect the equipment.  Hanovia is willing to guarantee this on all units which is why they are the basis for design.  Other manufacturers have made similar claims, but may give push back when asked to “guarantee” the performance of their unit.

Disinfection: > 99.99% for Cryptosporidium and E. coli.

Siemens has over 500 units installed dating back to 2003.  Counsilman -Hunsaker specifies the Siemens Barrier M ultraviolet system and details are based upon this unit.  Electrical coordination of the Barrier M unit is included in the MEP Coordination document.

The Siemens Barrier M system shall be designed to deliver a Reduction Equivalent Dose (RED) of 600 mJ/cm2 for indoor pools and 400 mJ/cm2 for outdoor pools based on the end of lamp lifetime (70% of specified new lamp output according to NSF).

Counsilman-Hunsaker specifies units to have automatic wiper to clean the quartz sleeve.  This is critical with medium pressure UV units because the high operating temperature can require cleaning of the sleeve several times per day.  The smallest unit from Siemens (model M35) does not have automatic wiper and should not be specified or accepted.

The heat discharged from UV system to the mechanical room space should be calculated at 10% of the full system load.  Taking two ETS units as examples:

  • ECF225-10 = 2x2.5 kW * 0.10 = 0.5 kW Heal Loss
  • ECF215-6 = 2x1.5 kW = 3.0 kW * 0.10 = 0.3 kW Heat Loss

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