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www.fueloilnews.com | FUEL OIL NEWS | FEBRUARY 2014 37 Combustion For atmospheric systems, check for any blockage of combustion air openings. "Think how easy it would be for a janitor to unknow- ingly tape cardboard or stuff insulation into combustion air entry points to prevent cold air in the boiler room! That's sure to cause problems in a hurry," said Joan Mishou, customer service manager for Laars Heating Systems Company. "Check the free flow of air into atmospherically-fired boiler rooms at least every six months," she added. "For ducted combustion units, check for blockages routinely." Also, clean and check filters every six months, or at least once a year. Check gas pressures while at peak load or on the coldest day of the year if possible to determine if there is a measurable reduction during peak operation. This would help to answer any questions about a boiler's ability to meet heat demand, and quality of combustion. Warren pointed out that gas line pressure can be a real nuisance in certain parts of the country. Areas that rely on older gas lines may not be able to supply sufficient pressure during peak demand. Inadequate gas pressure can cause rough light-off and lock-outs. Also, it's often misdiagnosed as faulty igniters, ignition controls or gas valves. Proper sizing of the gas piping between the boiler and the gas meter should always be confirmed before assuming the problem is caused by something out in the street. Typical gas pressure required by older commercial boilers is 4+ inches W.C. (4 inches and up water column). If there's any doubt about the pressure available to the system, you may need to put in a call to the gas company to see if line pressure can be increased. oil supply piping & Filtration Clean or replace fuel-line filters on oil boilers at least once a year, or every six months if the tanks are older and likely to contain sedi- ment or sludge that's sure to drift into the line. If this is the case, it's always helpful to take the boiler off line for a few hours during and after fuel deliveries. Water Quality & piping Any evidence of corrosive activity on piping should be addressed immediately and could be evidence of air infiltration. All visible piping should be checked for signs of deterioration during each scheduled maintenance visit. Check the boiler's relief valve to assure that it's not leaking. Is there proper pressure in the system? Many newer boiler designs use stainless steel or aluminum in their heat exchangers. The manufacturer may have requirements for water quality (pH, hardness, etc.). Be sure you know what these requirements are, and test for them when the boiler is inspected. eleCtriCal Wiring, DiagnostiCs & Controls Check all wiring in the system for overheating. Hardening or melting of insulation will certainly cause problems. Among other things, this can incapacitate or otherwise influence diagnostic systems, disabling safety (boiler-off) checks that would turn off the boiler in the event of problems. Check to be sure that the boiler shuts down on high limit and at low water cutoff. Check operation of the aquastat to be sure that the boiler shuts down at the set-point temperature. According to Warren, a service tech should also check the flow switch to assure that the boiler shuts off under no-flow conditions. Also, be sure to test the igniter for OHM resistance or micro amp sig- nal (depending on type) to assure that readings are within acceptable guidelines. ignition If an igniter fails, the many possible causes include condensation, venting or lack of proper combustion air. If condensation was dripping from the heat exchanger onto the igniter, it could be caused by suboptimal return water temperatures entering the boiler. This could be a piping issue, or a system issue where a by- pass loop need to be installed to mix supply and return water. Imagine that, as we look closer, this may be a strong possibility. Stating the obvious, then – one should always check the installation and operations manual to see what the manufacturer recommends. Typically, cast iron boilers recommend minimum return temperatures of 140°F degrees; copper atmospherics are often 110°F. Sealed combus- tion copper is usually 120-130°F. Naturally, to eliminate premature igniter failures with this condition one must bring the temperatures up or the problem will continue. Let's say we rule-out the possibility of condensation interfering with ignition. Other contributors to premature igniter failure would be improper venting or poor combustion air – either of which could lead to fouling of the heat exchanger; which would over-heat the combus- tion chamber. This isn't often a challenge with sealed combustion units, but is rather common with atmospheric units. If these are ruled-out, there's the possibility of low gas pressure. If the installation is done properly, most of these problems will never be seen. Another key facet to identifying and solving problems in the field is having the right tools on hand. A combustion analyzer, gas manometer and voltmeter are essential. A combustion analyzer delivers information quickly, telling you if it's a combustion problem and can then lead you to check venting or combustion air. As you move progressively through the diagnostics, this may lead to use of a gas manometer to check the gas pressure. • First Step – gas pressure • Second Step – combustion test • Third Step – visual check of heat exchange surface The key to preventing maintenance nightmares starts with a careful and deliberate startup of the equipment, and routine monitoring – more frequent, initially, and then at least on a six-month basis when the foundation for reliable boiler service and operation is set, and stable. If maintenance is scheduled and performed systematically, with problems addressed as they arise, the boiler and hydronic system will serve you, and your customers, well. HVAC/ HydroniCs By GreG Jannone, President, William Jannone & son, inc., Bound Brook, nJ l F o n