OUTDOOR ENCLOSURES for BACKFLOW PREVENTION …

1 Most of us would probably agree t hat t he most import ant benef it of above ground backf low prevent er ENCLOSURES is t he eliminat ion of underground vault s or pit s whichare def ined by OSHA as conf ined spaces. In t he case of t he reduced pressure principle backf low prevent er, adequat e drainage is provided so t hat t he public wat er supply is prot ect ed. Worker saf et y is great ly improved because t he above ground enclosure is not a conf ined space as def ined by OSHA. There are, however, st ill some saf et y issues that have not been addressed unt il recent er s used f or f reeze prot ect ion in ENCLOSURES are powered by elect ricit y.

2 Becauseelect ricit y is so common in our everyday lives, it is of t en not t reated wit h t he respectthat it deserves. Current f low of 1/ 10 of an amp or 100 milliamps is enough t o st opthe heart and cause fibrillat ion. To put t his in perspect ive, one 1 2 wat t light bulb draws1/ 10 amp on a 120 volt circuit . It's easy t o underst and t hat a small amount of elect ricit y t hrough t he heart can dangerous as elect ricit y is in dry locat ions, damp and wet locat ions dramat icallyincrease the danger. We have all heard t he saying t hat wat er and elect ricit y do not American Societ y of Sanit ary Engineering ( ASSE) has recent ly made t he decision that the interiors of backf low prevent er ENCLOSURES are damp locat ions as def ined in Art icle 100 of the National Electrical Code.

3 The reason for this ruling is that water and ot her liquids can accumulat e in the int erior of an enclosure f rom several sources. So m e o f these are list ed below:1. Sprays of wat er f rom t est cocks during t est ing and/ or maint Leaks in t he piping or backf low Dischar g e f rom a reduced pressure principle backf low prevent er caused byline pressure f luct uat ions, f oreign mat erial in t he check valves, a rupt ured diaphragmin t he relief valve assembly or normal relief operat Condensat ion caused by t he piping and backf low assembly surf ace t emperat urebeing below t he dew point t emperat ure of t he surrounding Intrusion of rain wat er bet ween t he concret e slab and t he walls of t he enclosureand under and t hrough drain Dampness inherent in a concret e slab placed on t he ore, t o meet t he requirement s of t he Nat ional Elect rical Code f or damp locat ions,heat ers used in backf low prevent er ENCLOSURES must be constructed and installedaccording t o Art icle 424-12(b)

4 Of t he Nat ional Elect rical ENCLOSURES f or BACKFLOW PREVENT I ON A SSEMBLI ES a nd ELECRICA L HAZA RDSpage 1 Art icle 424-12(b) of the 1999 and 2002 Editions of the Nat ional Elect rical Code st at esthat: "Heaters and related equipment installed in damp or wet locat ions shall beapproved f or such locat ions and shall be constructed and installed so t hat wat er or ot her liquids cannot ent er or accumulat e in or on wired sect ions, elect rical component sor duct work."Drainage syst ems f or backf low prevent er ENCLOSURES are designed t o meet t he requirement s of ASSE St an d ar d # 1 0 6 0 , OUTDOOR ENCLOSURES f or BACKFLOW Prevent ionAssemblies.

5 This St andard st ates t hat : " The dept h of water within the enclosureshall not exceed 1 50 mm (6 inches) during f ull f low of t he backf low prevent er reliefdischarge, nor shall t he dept h of wat er exceed 8 mm ( 5 inches) af t er complet ionof f ull flow." See Figure 1 liquid levelallowable by ASSE 10606"Figure 1 Heat er s inst alled inside t he ENCLOSURES more t han six inches above t he f loor must be liquid t ight and suit able for use in damp or wet locat ions t o meet t he constructionrequirement s of Art icle 424-12( b) of t he Nat ional Elect rical can be seen t hat any heat er mount ed less t han six inches above t he f loor level of an enclosure can be submersed.

6 Submersion of t he heat er virt ually guarant ees t heent rance and accumulat ion of wat er or ot her liquids in or on wired sect ions and elect rical component s inside t he heat er. Theref ore, t o sat isf y t he installation requirement s of Art icle 424-12(b) heaters must be mounted more t han six inches above t he floor t o prevent t he ent rance of wat er or ot her liquids int o t he heat 2 CONCRET E SL A BFlo o r LevelArt icle 424-12(b) of the 1999 and 2002 Editions of the Nat ional Elect rical Code st at esthat: "Heaters and related equipment installed in damp or wet locat ions shall beapproved f or such locat ions and shall be constructed and installed so t hat wat er or ot her liquids cannot ent er or accumulat e in or on wired sect ions, elect rical component sor duct work.

7 "Drainage syst ems f or backf low prevent er ENCLOSURES are designed t o meet t he requirement s of ASSE St an d ar d # 1 0 6 0 , OUTDOOR ENCLOSURES f or BACKFLOW Prevent ionAssemblies. This St andard st ates t hat : " The dept h of water within the enclosureshall not exceed 1 50 mm (6 inches) during f ull f low of t he backf low prevent er reliefdischarge, nor shall t he dept h of wat er exceed 8 mm ( 5 inches) af t er complet ionof f ull flow." See Figure 1 liquid levelallowable by ASSE 10606"Figure 1 Heat er s t hat are suit able f or use in damp or wet locat ions have been t est ed by ETLor UL f or conditions f ound in t hose environment s.

8 The name plat e on t he heat erwill bear the stat ement "for use in damp or wet locations " and t he ETL or UL markand cont rol number. These heat ers are not t est ed f or or meant t o be immersed;theref ore, t hey should not be mount ed less t han six inches above t he f is also st rongly recommended t hat ground fault circuit int errupt ers are inst alledin t he heat er circuit s for addit ional prot ect ion. However, It should be warned t hat GFCI ' s d o not t ake t he place of t he requirement s of Art icle 424-12(b) of the National El e c t r i c a l Code. GFCI ' s a r e s u s cept ible t o damage by volt age surges f rom ut ilit y companies and light ning strikes and can cont inue t o deliver power when t hey no longer provide ground f ault prot ect ion.

9 According t o OSHA: " Due to the complexity of a GFCI, it is necessary to test the device on a regular basis. For permanent ly wired devices, a mont hly t est is recommended. GFCI ' s h a v e a built -in t est circuit which imposes an artificial ground fault on t he load circuit to assure that the ground f ault is st ill f unct ioning. Test and reset but t ons areprovided f or t est ing." Aside f rom being complex devices requiring frequent t est ing, no one can be assuredthat GFCI's will be installed in t he field. The Nat ional Elect rical Code only requires GFCI' s in bathrooms, kit chens and on roof t ops in commercial and indust rial buildings.

10 See Art icle (B) of the 2002 m e d e signers and owners consider t he heat er operat ion essent ial t o prevent f reezedamage t o t heir wat er supply, t heref ore, t hey prohibit t he inst allat ion of GFCI's in t he heat er circuit due t o nuisance t ripping. For t he same reason, GFCI' s are not used onrefrigerat ors and f ASSE, The Nat ional Elect rical Code, UL and ETL:Si n ce it s incept ion in 190 6, t he ASSE ( American Societ y of San it ar y Engineering) hasadopt ed the f undament al policy of " Prevent ion Rat her Than Cure" . This policy hasbeen used in t he f ormulat ion of programs t o educat e t he plumbing indust ry and t hepublic in the saf e and correct manuf act ure and inst allat ion of plumbing component ore, backf low prevent ion devices represent a large part of t he ASSE St andardsPr o g r am.