Detailed Procedures for Inspecting Heating Systems InspectAPedia® -
How to Inspect Heating Systems - as An Approach to the Forensic Inspection of Any Complex System
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Detailed Sequence of Step by Step Gnspection of heating boilers & furnaces for operating & safety defects
Heating system step by step detailed inspection procedure
How to understand & report the significance of findings during a heating system inspection
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This document presents the detailed sequence of steps to use when inspecting residential heating systems with focus on heating boilers and furnaces, on assuring
completeness, accuracy, and on maximum heating system defect detection. The heating system inspection methodology involved is intended to be generalized to
the forensic diagnostic inspection of any complex system in order to have the highest probability of detecting
important safety or operating defects.
This sounds fancier than intended. Our object is to use an organized
procedure for inspecting for defects, without losing the ability to discover unexpected problems as well.
Detailed Steps in the Sequence of Examination of Oil-Fired Hot Water Boilers
Viewpoint #4--Detailed close scrutiny of the equipment, after a few "sanity checks" ASHI 9.1.A.1 The inspector shall observe ... heating equipment
Inspect before operating the boiler
What are we looking at? Form a working Definition: A system
which heats the house. A steel, copper, or cast iron "box"
of hot water, connected to a loop of pipe (and radiators or baseboards)
which runs around through the living area. The same physical water
stays in the boiler and is circulated by a pump so that heat is delivered
to the living area. Burning oil makes hot gases which are used to
heat the water before being exhausted outside. Pumps move fluids.
Safety controls at various points protect against a number of potential
hazards.
We include links to detailed heating system articles that explain how boiler or furnace parts and components work, how to inspect or repair them, and description of common problems that occur with each heating system component.
Look at the temperature/pressure gauge: normal operating values?
Look for leaks in the boiler itself (Cast iron is more resistant to death by leaks than steel. Older cast iron systems without
tankless coils, if shut off in summer, may be at risk of leakage and hidden damage. Steel rusts through. Cast iron cracks or leaks at joints.)
Look for leaks at controls now and again in the sequence below
Leaks at valves or fittings which drip into the jacket of a steel boiler or onto controls or zone valves risk failure and
loss of heat.
Is there a tankless coil? If so, address both topics, looking at heating first, DHW second.
Examine components in the sequence of operation
Training in proper operation sequence of the equipment and in the
function of its controls is a step towards technical correctness. If you do not understand how a mechanical system works you cannot
reliably expect to observe missing or defective components. This discussion is an exercise using sequence of operation to work
for completeness. It is not technically exhaustive, it focuses on
a specific example: oil-fired hot water, zoned, heating system.
Examine the accessible parts of the system. Let your eye travel
from component to component in the sequence of operation. Apply the
inspection logic discussed earlier, at each step. Consider the implications
should each component be missing, damaged, inoperative, leaky, noisy,
sooty, repaired by an amateur, etc. Think through the operating sequence as you examine each component in that
order.
The following are the steps in one common set-up. This list is lengthy
and detailed. The actual visual examination may take only a few minutes.
The following 39 steps in a heating boiler operating sequence are discussed in more detail at BOILER OPERATION DETAILS. Similar information is provided for warm air heating systems at FURNACE OPERATION DETAILS.
Room temperature drops,
room thermostat switches "on" ASHI 9.1.A.2 normal operating controls - see THERMOSTATS
[zone valve opens and] circulator [starts] [except in Canada where circulators may be set up to run continuously and where the thermostat directly turns on the oil burner] [Circulator usually located on cooler return-side of the distribution piping loop-longer life.] - Zone Valves
boiler temperature and pressure are indicated on the TP gauge and should show increase not to exceed normal operating limits (200 deg F or less and less than 30 psi) - Gauges on Heating Equipment
hot heating water leaves boiler passing by the ...
air scoop (not always present; avoids air-bound baseboards)
[air purge] (not always present; often leaky or sealed off)
[automatic] water feeder (normally the manual valve for water supply to boiler is "on", the automatic valve is closed unless the boiler pressure drops below 12-15 psi.This valve is often also a backflow-preventer.) - Water Feeder Valves, Hydronic Boiler
expansion tank (waterlogged, dumping relief valve)(attic? no r v?=some old equipment) - Expansion Tanks
[zone valve] (not always used, shorter life on the "hot" supply side of <->piping) - Zone Valves
distribution piping (watch for mineral salts indicating small clogged leaks)
baseboards - which warm the room and thus the ... ASHI 9.1.A.6 heat distribution systems including fans, pumps, ducts and piping with supports, dampers, insulation, air filters, registers, radiators, fan-coil units, convectors - RADIATORS and Air Bleeder Valves
room thermostat senses the heat increase. Water passes - THERMOSTATS
more distribution piping returning to boiler past
zone service drain and [flow balancing valves] (are they leaky?) - Zone Valves
[circulator pump] (if it's not a convection system used on older houses) - Circulator Pumps & Relays
back into the boiler.
temperature in the boiler drops as cooler water returns.
temperature sensor feels the temp drop and tells the ...
primary control or high-limit control, but nothing happens (in the U.S.) until ...
temperature drops 15 deg F below the HI setting on the primary control. Then the
primary control turns on the oil burner (any drip/leak damage onto the control?) (Canadian systems: thermostat may activate burner directly.) - Aquastat Functions
burner pumps oil from the tank through ... (did we see the tank? is there an oil filter?)
hot gases pass through tubes in steel or between sections in cast iron boiler, sending heat back into the heating water through the heat exchanger. (soot acts as insulation--boiler cleaned recently?)
hot gases are collected at top of boiler and sent out through exhaust flue ...
where the barometric damper assures proper and even draft; hot gases continue ..., up
up the chimney to outdoors. ASHI 9.1.A.4 chimneys, flues, and vents (is the chimney improperly shared or vented to multiple floors?) ASHI 9.1.A.5 solid fuel heating devices [e.g. wood and coal stoves]
boiler temperature rises up to the "HI" limit. (Thinking of High take a look for a pressure relief valve and look for defects there: leaking, corroded, not piped to floor, reduced diameter piping.) - RELIEF VALVES - TP Valves on Boilers
sensor informs Primary Control which turns off the burner-(sloppy shut down?) (Circulator is continuing to run)
the room is warm enough according to the thermostat so the ...
thermostat senses the temperature rise and opens its switch. (Special thermostat sophistication and functions excluded here)
Look closely at controls, peripherals, key components,
while going through the detailed sequence ASHI 9.1.A.3 automatic safety controls
Combination control - combining High Limit and "Low Limit" (which may or may not be in use depending on presence of a tankless coil). See BOILER CONTROLS & SWITCHES for details.
High Limit and Low Limit (if tankless coil) separate controls on older equipment - Limit Switches, Boilers
Flame sensing device: Cad Cell or Stack Relay (watch for sensitive relays and learn about the re-stepping lever) - Cad Cell Relay Switch Flame Sensors
Pressure and Temperature gauge--12 psi cold, less than 30 psi hot. Over 30 psi dumps relief valve.(Typical operating temperature
settings LO-120-160 HI-180-200 degF. Typical operating temperature observed at the gauge will be below the high, and can be as low as
nighttime room temperature in non-heating season if no tankless coil is in use. The temperature/pressure gauge may help in checking for
normal conditions before and during boiler operation. However the gauge can be wrong!) - Gauges on Heating Equipment
Tankless coil--leaks, missing mixing/tempering valve, relief valve (some jurisdictions). Risk of scalding water at the house sinks/tubs if there is no mixing valve. - TANKLESS COILS
Leaks and Corrosion - some implications
Surface rust--repairable. Clean when serviced and monitor
Exfoliation--very serious, possibly not repairable,
risks loss of boiler.
Common Heating System Leak Locations
Coil mounting plate - see rust stains below and around plate
Pipe fittings at face of coil plate - mineral salts
Leaks around bolt openings - suspect hidden damage
Examples of understanding function and implications:
Leaks are never acceptable, anywhere on a heating system. Leaking relief valves
need immediate attention and repair (Leaking relief valve could be
due to water-logged expansion tank, improper control settings (temp
too high), improper automatic water feeder operation (pressure too
high), or defective valve (leaky). True, you only have to report the
valve. Did you miss problems at the other components?) Corroded relief
valves also need test and repair/replacement
Do not touch the relief valve- it may open and fail to shut
down.
Do not pick at corrosion as you may start a catastrophic, un-stoppable leak requiring total system shut-down.
Different water pressure/flow observed in the kitchen:
hot water pressure significantly less than cold--is a tankless
coil installed? is a water softener installed? is there "hard"
water--have mineral deposits clogged the coil? Are there "cleanout"
plumbing fittings on the coil piping? Does this suggest a history
of clogging and acid-flush treatments? Can a clogged coil be repaired
or replaced? How severe was that rust you observed at the coil mounting
plate?
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Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair
Our recommended books about building design, inspection, and repair, and about indoor environment testing, diagnosis, and cleanup are at the InspectAPedia Bookstore.
Domestic and Commercial Oil Burners, Charles H. Burkhardt, McGraw Hill Book Company, New York 3rd Ed 1969.
National Fuel Gas Code (Z223.1) $16.00 and National Fuel Gas Code Handbook (Z223.2) $47.00 American Gas Association (A.G.A.),
1515 Wilson Boulevard, Arlington, VA 22209 also available from National Fire Protection Association, Batterymarch Park, Quincy, MA 02269.
Fundamentals of Gas Appliance Venting and Ventilation, 1985, American Gas Association Laboratories, Engineering Services Department. American
Gas Association, 1515 Wilson Boulevard, Arlington, VA 22209. Catalog #XHO585. Reprinted 1989.
The Steam Book, 1984, Training and Education Department, Fluid Handling Division, ITT [probably out of print, possibly available from several home inspection supply companies] Fuel Oil and Oil Heat Magazine, October 1990, offers an update,
Principles of Steam Heating, $13.25 includes postage. Fuel oil & Oil Heat Magazine, 389 Passaic Ave., Fairfield, NJ 07004.
The Lost Art of Steam Heating, Dan Holohan, 516-579-3046 FAX
Principles of Steam Heating, Dan Holohan, technical editor of Fuel Oil and Oil Heat magazine, 389 Passaic Ave., Fairfield, NJ 07004 ($12.+1.25 postage/handling).
CT 06801 800/227-1663 [home inspection training material] 1987
"Residential Hydronic (circulating hot water) Heating Systems", Instructional Technologies Institute, Inc., 145 "D" Grassy Plain St., Bethel, CT 06801 800/227-1663 [home inspection training material] 1987
"Warm Air Heating Systems". Instructional Technologies Institute, Inc., 145 "D" Grassy Plain St., Bethel, CT 06801 800/227-1663 [home inspection training material] 1987
Heating, Ventilating, and Air Conditioning Volume I, Heating Fundamentals,
Boilers, Boiler Conversions, James E. Brumbaugh, ISBN 0-672-23389-4 (v. 1) Volume II, Oil, Gas, and Coal Burners, Controls, Ducts, Piping,
Valves, James E. Brumbaugh, ISBN 0-672-23390-7 (v. 2) Volume III, Radiant Heating, Water Heaters, Ventilation, Air Conditioning, Heat
Pumps, Air Cleaners, James E. Brumbaugh, ISBN 0-672-23383-5 (v. 3) or ISBN 0-672-23380-0 (set) Special Sales Director, Macmillan Publishing
Co., 866 Third Ave., New York, NY 10022. Macmillan Publishing Co., NY
Installation Guide for Residential Hydronic Heating Systems and
Installation Guide #200, The Hydronics Institute, 35 Russo Place, Berkeley Heights, NJ 07922
The ABC's of Retention Head Oil Burners, National Association of Oil Heat Service Managers, TM 115, National Old Timers' Association of the Energy Industry, PO Box 168, Mineola, NY 11501. (Excellent tips on spotting problems on oil-fired heating equipment. Booklet.)
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