hoshizaki technical support tech -tips - Hoshizaki America, Inc.

HOSHIZAKI TECHNICAL SUPPORTTECH -TIPS____________________________________________________________________________________________________Rodd Burger Hoshizaki America, Inc. Volume 202Writer/Editor 618 Hwy. 74 South May 26, 2003Peachtree City, GA 30269Ph: (800) 233-1940 Fax: (800) 843-1056 E-mail: techsupport@hoshizaki.com____________________________________________________________________________________________________WHATS THE BIG DEAL WITH WATERFLOW? By Frank Neely: That is a very goodquestion. Much of an ice machine’s performancedepends on proper water quality, volume and flow.This is especially true of Hoshizaki KM cubermachines so let us spend some time together andfigure out “the big deal”.that we only bring water in during the harvest cycle,we must be able to supply the machine, at the veryleast, 7 to 8 gallons of water in less than five minutes.Therefore; proper water volume and flow becomescritical in assuring that the unit has enough water for afull batch of ice and is achieving maximumperformance.Let’s start with why water volume and flow is such acritical component for proper ice making. First,Hoshizaki cubers utilize a batch weight system. Theterm “batch weight” means that we bring in all of thewater needed to make a complete batch of ice at onetime. This water comes in during the harvest ordefrost cycle and no additional water is fed in duringthe ice making cycle. This is one of the reasons thatwater volume and flow are so critical. A goodmethod to determine if we have proper water flow isto time how long it takes to fill a dry sump/reservoir tooverflowing. As a rule of thumb, on the KM-1800/2000/2400, the sump should start to overflowand drain water within 90 to 120 seconds. For allother machines the sump should fill to overflowing in60-90 seconds. If you can pass this test, you can feelreasonably sure that you have adequate water flow tothe unit.Here is an example that should demonstrate whygood water volume and flow is a must for the batchweight system. Consider the KM-2400SRH3 whichhas a sump that holds over 6.0 gallons of water. Theaverage harvest cycle for this machine will run from 2minutes minimum to approximately 5 minutes. (Itcould run longer in cold water areas or if the defrostcompletion timer is adjusted longer.) Keeping in mindNow let’s take a look at the second reason whywater volume and flow are so critical. Hoshizaki KMmachines use a hot gas defrost system with waterassist. Now don’t let the word assist fool you, wateris just as important, if not more important, than the hotgas in achieving a proper harvest cycle. The reasonthat water flow is so critical for our harvest cycle isthat we depend on that water to help with heattransfer. Let’s break it down a little. Hoshizaki usesa stainless steel evaporator which gives us a verydurable and smooth surface to produce our crescentshaped cubes. Not only is a stainless steelevaporator a great feature for its durability but itallows us to use very strong chemical ice machinecleaners to clean the evaporator plates, reducingpreventative maintenance time.Due to the slower heat transfer and freezing rates ofstainless, we are able to produce and harvestindividual clear, hard cubes. This slower heat transferin turn, makes it necessary to have water assistedharvest. We bring in our potable water throughdistribution tubes and down the center of the twostainless steel plates. As the water falls through themiddle of the plates and around the evaporator “ribs”,it washes over the copper serpentine picking up theheat from the hot gas and distributing it evenly to all

areas of the stainless steel plates. This method of heattransfer allows the individual cubes to fall off theplates properly with minimum melting.But what if we don’t maintain proper water volumeand flow? What effect will that have on the machine?Well, I’m glad you asked that question. Really thereare two main concerns to look at here. First, lowwater volume and flow reduces harvest efficiencybecause the unit depends on that volume of water tohelp transfer the heat from the hot gas. If the adequateamount of water is not provided, some cubes maystick to the plate which will ultimately wind up causingthe dreaded freeze up of the evaporator!Second, the lack of water volume and flow coulddecrease the length of defrost too much. How youask? Without the water removing the heat from thecopper serpentine the temperature will rise too fast atthe suction line were the thermister is mounted andcause the defrost completion timer on the board toinitiate prematurely. This could leave ice on theevaporator which will again ultimately wind up causingthe dreaded freeze up of the evaporator. Déjà Vu allover again.Lastly, there is a possibility of less than a full reservoirat the end of the harvest cycle. This would causeshorter cycles resulting in a low batch weight, andpoor efficiency / production.Hopefully the information above has helped you tounderstand the importance of water volume and flow.Also it is very important for you to keep thisinformation in mind when sizing water filters, watertreatment systems, and water lines. Below you willfind water line size and flow rate charts also found inthe Technicians pocket guideWATER LINE SIZEMODEL Line Size Fitting SizeKM-150B - KM-250B 3/8” OD 3/8” FlareKM-280 – KM-900 3/8” OD 1/2” FPTKM-1300 – KM-2400 1/2” OD 1/2” FPTAll Flakers/DCM’s 3/8” OD 1/2” FPTFLOW RATESKM-150/250/280/All FlakersKM-500KM-630/900/All DCM’sKM-1300/1600KM-2000/24001.05 GPM1.58 GPM2.11 GPM3.96 GPM4.23 GPMINTRODUCING THE AM-100 AND AM150In the October 2002 Vol. of Tech Tips weintroduced the AM-50BAE ice maker. We are nowproud to introduce two additional models in thesmaller AM style machines. The AM-100BAE usesR-134a and produces approximately 105 pounds ofice with 44 pounds of storage and the AM150BAFuses R-404a with 150 pounds of production with 88pounds of storage. These models will complementour already extensive line of cubers and allow moreversatility when working with your customers uniqueapplications. These new smaller ice machines willalso open up many new markets that were notavailable in the past.The sequence of operation for the AM-100 and AM-150 is basically the same as we discussed in theOctober 2002 issue with just some minor timingchanges. For more information and availability ofthese units, contact your local distributor. To viewspec sheets and service manuals access our web siteat www.hoshizaki.com.AS ALWAYS…If you have any comments or suggestions for TechTips please send them to:Techsupport@hoshizaki.com orFax to 1-800-843-1056 ATTN: Tech Tip editorCOMING NEXT MONTH…1. Reach In Freeze upsVolume 202 page 2