Bard QW2S1 Installation Instructions Manual

Bard QW2S1 Installation Instructions Manual Manual pdf 35 page image

Manual 2100-532BPage 35 of 46WATER CORROSIONTwo concerns will immediately come to light whenconsidering a water source heat pump, whether forground water or for a closed loop application: Willthere be enough water? And, how will the water qualityaffect the system?Water quantity is an important consideration and onewhich is easily determined. The well driller mustperform a pump down test on the well according tomethods described by the Nation Well WaterAssociation. This test, if performed correctly, willprovide information on the rate of low and on thecapacity of the well. It is important to consider theoverall capacity of the well when thinking about a watersource heat pump because the heat pump may berequired to run for extended periods of time.The second concern, about water quality, is equallyimportant. Generally speaking, if the water is notoffensive for drinking purposes, it should pose noproblem for the heat pump. The well driller or localwater softening company can perform tests which willdetermine the chemical properties of the well water.Water quality problems will show up in the heat pumpin one of more of the following ways:1. Decrease in water flow through the unit.2. Decreased heat transfer of the water coil (entering toleaving water temperature difference is less).There are four main water quality problems associatedwith ground water. These are:1. Biological Growth. This is the growth ofmicroscopic organisms in the water and will showup as a slimy deposit throughout the water system.Shock treatment of the well is usually required andthis is best left up to the well driller. The treatmentconsists of injecting chlorine into the well casingand flushing the system until all growth is removed.2. Suspended Particles in the Water. Filteringwill usually remove most suspended particles (finesand, small gravel) from the water. The problemwith suspended particles in the water is that it willerode metal parts, pumps, heat transfer coils, etc. Solong as the filter is cleaned and periodicallymaintained, suspended particles should pose noserious problem. Consult with your well driller.3. Corrosion of Metal. Corrosion of metal partsresults from either highly corrosive water (acidwater, generally not the case with ground water) ofgalvanic reaction between dissimilar metals in thepresence of water. By using plastic plumbing ordielectric unions galvanic reaction is eliminated.The use of corrosion resistant materials (such as theCupronickel coil) through the water system willreduce corrosion problems significantly.4. Scale Formation. Of all the water problems, theformation of scale by ground water is by far the mostcommon. Usually this scale is due to the formationof calcium carbonate, but magnesium carbonate orcalcium sulfate may also be present. Carbon dioxidegas (CO2), the carbonate of calcium and magnesiumcarbonate, is very soluble in water. It will remaindissolved in the water until some outside factorupsets the balance. This outside influence may be alarge change in water temperature or pressure.When this happens, enough carbon dioxide gascombines with dissolved calcium or magnesium inthe water and falls out of solution until a newbalance is reached. The change in temperature thatthis heat pump produces is usually not high enoughto cause the dissolved gas to fall out of solution.Likewise, if pressure drops are kept to a reasonablelevel, no precipitation of carbon dioxide shouldoccur.REMEDIES OF WATER PROBLEMSWater Treatment. Water treatment can usually beeconomically justified for close loop systems.However, because of the large amounts of waterinvolved with a ground water heat pump, watertreatment is generally too expensive.Acid Cleaning the Water Coil or Heat PumpRecovery Unit. If scaling of the coil is stronglysuspected, the coil can be cleaned up with a solution ofPhosphoric Acid (food grade acid). Follow themanufacturer’s directions for mixing, use, etc. Refer tothe “Cleaning Water Coil”, Figure 24. The acidsolution can be introduced into the heat pump coilthrough the hose bib A. Be sure the isolation valves areclosed to prevent contamination of the rest of the systemby the coil. The acid should be pumped from a bucketinto the hose bib and returned to the bucket through theother hose bib B. Follow the manufacturer’s directionsfor the product used as to how long the solution is to becirculated, but it is usually circulated for a period ofseveral hours.