Kärcher HDS4.0/22 Dealer's Manual

Also see for HDS 3.9/30: Operator's manual Operator's manual

Contents

18OperationsFor Tech Tip InstructionsCombustion efficiency in a natural draft pressurewasher is significantly influenced by the heat createdinside the coil, the design of the coil and flue and thelength and diameter of the exhaust stack. The tablebelow shows data included in the operator’s manual forflue and stack sizes and gas manifold pressuresettings. These sizes are critical for achieving propercombustion and acceptable emissions.Testing has shown that simply adding a 36” stackextension to the flue adapter on top of the pressurewasher can reduce the outlet temperature by 5-10°F.This occurs by inducing a higher pressure differential atthe exit of the coil and increasing the flow of air into thecombustion process and through the stack. Most or allof the lost outlet temperature can be recovered byinstalling and adjusting a damper in the stack. Howeverthis adjustment must only be performed by a trainedtechnician using a combustion analyzer. An adequatecombustion analyzer can be purchased for a little at$500 (Bacharach Fyrite Tech, Testo 310). The analyzermust determine percent oxygen and/or percent excessair as a minimum.The damper should be installed 24-36” above the flueadapter. The pressure washer can be operated safelywith the damper fully open but with the lower outlettemperature. If the damper is closed too far there willnot be enough oxygen to burn all of the fuel. This willcause higher and potentially dangerous levels of CO inthe flue gas emissions.To adjust the damper for proper combustion and effi-ciency perform the following:1. If there is no sample port for the analyzer probe,drill a hole slightly larger than the combustionanalyzer probe through the exhaust stack at a pointabout 18” above the flue adapter.2. Insert the probe of the combustion analyzer so thatthe tip is at the center of the stack.3. Open the damper to the fully open position.4. Start the pressure washer and allow it to heat upfor at least 20 minutes before making any adjust-ments.5. Note the values for% Excess Air and/or % Oxygen.6. Close the damper in small increments until %Excess Air is between 20-30% and/or % Oxygen is4-5%.This process can also be used when turning down thefiring rate for high altitude installations above 2000 ft.1. Adjust the gas pressure down 4% for every 1000 ftof elevation.Example: Recommended firing rate for a 4.8@3000 is4.2 wc-in. For an installation at 3500 feet reduce thispressure by 16% by setting the manifold pressure to4.2*.84 = 3.5 wc-in.A manometer capable of reading to at least the nearest0.1 wc-in will be required for this adjustment. These canbe found for less than $200 (Extech HD700).Follow steps 1-6 above to optimize the outlet tempera-ture of the pressure washer.Installations Above 2000 ft:Installation at altitudes greater than 2000 ft will requireadjustments to the gas manifold pressure.For installations above 2000 feet the firing rate shouldbe reduced by 4% per 1000 feet. Example: Recom-mended firing rate for a 4.8@3000 is 4.2 wc-in. For aninstallation at 3500 feet reduce this pressure by 16% bysetting the manifold pressure to 4.2*.84 = 3.5 wc-in.This adjustment should only be made by a properlytrained service technician. A manometer capable ofreading to the nearest 0.1 wc-in will be required for thisadjustment.In Canada, certification for installation at altitudes over4500 feet is the jurisdiction of local authorities.Gas Valve Replacement:If you replace your gas valve the manifold pressure forthe new valve will need to be adjusted to match thespecification plate for the machine. Follow the installa-tion and adjustment instructions provided with yourreplacement valve. A manometer capable of reading tothe nearest 0.1 wc-in will be required for this adjust-ment.NG LPModel Collar Stack wc-in kBTU-in wc-in kBTU-in3.5@2000 10" 8" 3.6 310 7.8 3103.9@3000 10" 8" 3.4 354 7.4 3544@2200 10" 8" 5.1 364 11.2 3644.8@3000 10" 10" 4.2 415 9.1 4155.0@2300 10" 10" 4.7 437 9.5 4396.3@3200 12" 10" 4.3 507 7.4 5078@3200 12" 12" 3.1 658 7.0 6589.5@3000 12" 12" 5.4 816 10.0 775Karcher Liberty HDS Stationary Dealer’s Manual 9.801-508.0 - AY