Module 10: Piping and Tubing

Pressure DropPRESSURE DROP = working pressure differential b/t the gas meter outlet to the appliance regulator inlet

Maximum allowable pressure dropsNatural GasSupply pressure of 14 w.c.= manuf.'s instructionsPropaneSupply pressure of14 w.c.= manuf.'s instructions

High Pressure Tests: before appliances are installed

-performed after piping system installed and before appliances have been connected*if anything connected to system isn't rated for testing pressure, then it needs to be isolated or removed (to prevent damage)*must isolate system from the meter

Procedure1) Isolate piping system being tested2) cap/plug all open ends3) insert pressure gauge at one end4) pressurize system w/ air/inert gas to the specified test pressure (in code book)

Three tests required by the code1) High pressure test: prior to connecting appliances2) Working pressure test/Dial test: connect appliances and see if any gas leaks out w/out burners firing(testing for leaks from the gas meter outlet to the gas valve inlet of the appliance)3) Soap test: to check working pressure of the final connection(ensures that all components on valve train are pressure tight)(checking for leaks after appliance gas valve)

-another way of testing for leaks (for systems to the ground -> to the control module*the control module detects a DC voltage, which proves that the flame is litTHERE IS MORE IF INTERESTED

Blower Motor-if the filter is clogged, the amperage draw will decrease*b/c it is doing less work (b/c there is less air resistance meeting it when it spins)

Module 13: Building as a System

Gas technicians must be aware of:1) building envelope2) external environment3) actions of mechanical systems4) actions of occupants

Building Envelope

-building envelope = separates the inside of the building fromt he outside*comprises:-foundation and floor slabs-walls-roof-windows and doors*many different components:1) skin: (the outside) made of wood, bricks, concrete-protects underlying materials-maintains building integrity-reduces heat loss and heat gain2) vapour barriers: plastics sheets laid on the inside/warm side of insulation-retard the flow of moisture in vapour form to outside= will maintain proper lvls of humidity inside the house-if vapour barrier not continuous = relative humidity will decrease in winter= 6mm plastic installed on warm side3) insulation: usually made of fibreglass or rock-poor conductor of heat, so will retard flow of heat from inside to outside-poorly insulated house will increase heating fuel consumption

Types of Building Construction

-three types of building construction in ON:1) Balloon Frame: a continuous wall cavity from the ground floor to the attic-fibre insulation usually added by vlowing it into attic or wall cavity2) Double/solid Brick: uses a double layer of brick instead of stud framing and brick sin-insulation is usually rigid boards of fibreglass3) Platform: (most common now) each floor built as separate platform-tendency for air leakage at the headers

-several factors that impact upon Building as a System:-occupant lifestyle-mechanical systems-external environment

Occupant Lifestyle:-people/animals/plants w/in building-when occupant load increases => relative humidity w/in building increases-actions that affect building systems:-cooking and food prep.-smoking-contaminants generated by occupants (CO, perspiration, breathing, exercise)-bathingMechanical Impact:-all equipment and appliances in the building-water heaters-dryers-motors-fireplaces-wood stoves-air cleaners-central vacs-refridgerators-lighting-natural draft appliances-air changers (HRVs, ERVs)-impact from mechanical equip. can be severe: gas tech.s must take combustion and ventilation air into accountExternal Environment:-building location matters:-if home is in path of strong prevailing winds = cooling effect in the winter-shade trees can have same effect in summer-exposure to solar radiation can have same effect in summer and winter

Minimizing negative impact:-above factors will impact on quantity and quality of:-heat-moisture-air flow-heat/moisture will always flow from area of high concentration to low concentration-buildings are constructed to keep conditioned area from escaping to the outside= helps keep energy costs to a minimum= helps keep occupant comfort at a maximum-need appropriate amount of moisture-enough moisture for benefit of occupants, furniture, and building construction-too much moisture = moulds and mildew*reasons for excess moisture:-new construction materials-open sump pits-poor air barriers-too little moisture will cause:-wood to dry and crack-make air dry and might lead to respiratory illnesses-exfiltration: movement of air from inside to outside-infiltration: movement of air from outside to inside

Sources of Heat Loss:-buildings must be insulated to retard flow of heat and moisture-airflow can increase heat loss up to 30%-heat loss sources:-walls (where majority of heat loss is from)-basements-floors-windows and doors-attic-heat gain sources:-windows-doors-walls-most effective ways to reduce heat loss = seal air leaks-around windows, doors, baseplats and headers, foundations, electrical outlets and ceiling lights

Relative Humidity-relative humidity = ratio of actual amount of water vapour pressure in air compared to what vapour pressure would be if the air was totally saturatedsaturation = point at which condensation occurs

Humidity balance:RemovalSourceventilationshowersexhaust fansplantsfurnace operationcookingnatural air changeseasonal storagedrying firewoodwet basementconstruction moisture-warm air holds more water vapour than cold air (takes more water vapour to saturate the same amount of air*so: relative humidity decreases when air is heated (e.g. by a furnace)(b/c amt of water is the same, but air molecules are further spaced apart)-cold air = molecules are more dense-heated air = molecules less dense = more room for water vapour-methods of decreasing relative humidity-A/C dehumidifies conditioned air-increase air flow through building-use HRV to exhaust warm moist air + bring in cooler, drier air-in winter, if vapour barrier is continuous, then relative humidity should stay the same

Ventilation-ventilation air: fresh air required by all building occupants= introduction of outside air to replace exhausted air or to dilute indoor air-older houses made of looser construction satisfied ventilation req.s w/out any specific measures(fresh air entered house through cracks in building envelope)-newer houses are tighter = so they require a specific amount of air to be introduced by mechanical ventilation-ventilation also the best way to remove odours from a house

Heat Recovery Ventilators-HRVs = mechanical heat exchangers-warm moist air exhausted from inside of building is cycled out while cooler, dry, fresh air is cycled in-heat exchanger in the HRV transfers heat from inside exhausting air to the cooler incoming air (reduces cost of supplying ventilation air and re-heating it in the furnace-usually have two speeds:1) low speed for continuous ventil.2) high speed for exhausting inside air when it is outside of comfort range*this speed controlled by humidistat-if humidity level climbs above comfort range, high speed option will become energized-can have their own dedicated ductwork, or can be hooked into return air side of furnace ducting

Filtration-regular filters: purposes is to protect, furnace components, heat exchangers, and A/C coils from effect of heavy particle pollution= arrestance-dust spot efficiency = measurement of filter's efficiency at picking particles of dust at various size ranges-filters clean air w/ three methods:1) Impingement:-dust particles strike filter media and are stopped2) Straining:-dust particles stopped if they are larger than space between the fibres3) Electrostatic Precipitation:-dust particles given an electrical charge which is opposite to that of the filter material= dust particles are attracted to filter media

Building Pressure-air flows from area of high pressure to low pressure-when air is heated in winter by furnace = it will expand= will put building under positive pressure-air will flow through openings and cracks-building under negative pressure: cause outside air to be drawn into structure-a building can experience both positive and negative pressure at the same timee.g. mechanical ventil. system may be oversupplying one area of the house, while lack of make-up air in basement can cause a negative pressure-several means by which building pressure is changed:1) Stack Effect:-warm air rises in a building, finding its way through cracks in the building envelope-may cause negative pressure in basement and starve gas-fired appliances located in the area2) Mechanical or Natural Ventilation Effect:-exhausting building air can lead to negative pressure w/in building-air will enter building to equalize the pressure: it will do this through path of least resistance= in many cases: venting system of appliances: will disrupt these appliances from venting properly*mechanical ventilation = most common cause of negative pressure in a house3) Duct Effect:-improperly designed or installed HVAC systems can cause air to leak out of ducts and short cycle= can lead to poor occupant comfort and removal of combustion air from appliance rooms4) Wind Effect:-positive pressure building up on windward side-negative pressure building up on leeward side5) Flue Effect:-venting systems are usually easiest way for air to enter and exit a building

Spillage-natural draft systems can be susceptible to spillage of flue gases into house-most common cause of spillage = negative pressure in building created by mechanical exhaust systems*caused by downdraft down chimney-causes of downdraft:1) improper vent locations2) negative air pressure condition w/in house3) strong prevailing winds-causes of spillage:1) blocked vent2) down draft3) negative pressure in house

Combustion Air Sizing-gas tech. must consider several things when installing a gas-fired appliance:1) BTU input2) Construction type: tight or loose3) method of venting flue products: draft controlled or no draft controlled-for inputs greater than 400 000 BTU: appliances must use outside air for combustion and ventilation

Module 14: Domestic and Non-Vented Appliances

Ranges-use flexible metal connectors: allows appliance to be moved for cleaning and servicing w/out disconnecting the gas supply-conditions for using them:1) must not exceed 6ft2) when used to connect appliance to rigid piping, a shutoff valve must be installed in the piping immediately upstream of the flexible connectorHeat Transfer Methods1) Convection: heat transfer through a fluid (air or water)-two methods of convection heating in ovens:1) natural convection:-warm air rises and cool air descends-in standard, natural convection oven: hottest area is at top of the oven, no matter where burner is located2) forced convection oven:-heat produced by burner is circulated evenly throughout the oven by a fan2) Conduction: heat transfer from particle to particle (through direct contact)eg. pot of water on the stove3) Radiation: heat transfer by means of heat rays emitted from a heat sourcee.g. an overhead broiler burnerIgnition:1) Standing Pilot = has a continuously lit pilot-three designs:-one pilot for each burner-one pilot for two burners-one pilot for all four burners-Flash tube:= runs from top burner ignition port to the pilot flame to provide a direct path for ignition flame-when burner valve is turned on, gas flows through burner ignition port, through the flash tube (which draws in air behind it and mixes with the gas)-pilot sets of the air gas mixture, which flashes back to the burner and ignites all the burner ports-improper ignition:-too much air in mixture = when flash tube fails to light burner and there is no flame at the end of the burner-too little air in the mixture/too much gas = if there is a flame at the end of the flash burner but the burneer will not light off the pilot2) Electrical igniter-uses a spark generation device

Domestic Clothes DryersMoisture Exhaust Ducts:-must be exhausted to the outdoors-must be non-combustible or certified-not to be connected into venting-don't use sheet metal screws (lint will get stuck) = use duct tape

Schematic:(page 14-10)

Ignition Systems:-three types:1) Constant pilot2) Glow-coil (an HSI; operates under 120V AC)3) Glo-sil (operates under 120V AC)

1) Constant pilot:-pilot remains on all the time2) Glow coil system:= resistance wire mounted on a ceramic block-mounted to a step-down transformer mounted to valve body-when power applied, it glows and produces enough heat to light the PILOT GAS-as soon as dryer timer is set to a heat setting, pilot valve is energized*the warp switch: (will de-energize pilot valve)-acts as a safety device to break circuit to the glow coil and pilot valve when a malfunction occurs:-main burner doesn't light due to interrupted gas supply-pilot fails to light-pilot flame is faulty and not generating enough heat to cause pilot switch to operate-composed of bimetal arm that bends when heated (heat comes from the resistance heaters)-if left in circuit, warm switch will open after three or four minutes-normally: pilot ignites and pilot switch swings to other circuit, removing resistance heater from the circuit before the warp switch can react3) Glo-sil burner= designed to be hotter and much faster-run on 120V

BBQsBriquettes and lava rock:-gas flame heats surface of the lava rocks, which radiate heat to cook the food-too many lava rocks = may cause premature burner burn-out

Lamps-lamps are equipped with mantles that provide light*purpose = convert bunsen flame to luminous flame and thus give more light-two basic types of mantles:1) soft mantles2) pre-formed hard mantles

Module 15: Gas Metres, Pressure Regulators and Relief Valves

Natural Gas and Propane Regulators

Functions of a Gas Regulator1) reduce and maintain constant downstream pressure2) provide a means by which pressure to the appliance can be adjusted3) provide a more smooth, even flow (e.g. w/ a zone or appliance regulator)

Operating Forces of a Gas Regulator1) Measuring element (DIAPHRAGM): measures the downstream/outlet pressure= measures downstream/outlet pressure2) Restricting element (ORIFICE): increases or decreases gas flow= restricts flow of gas into regulator3) Loading element (SPRING): used to set the operating pressure= determines operating pressure

*closing force = the downstream/outlet gas pressure

Components1) Orifice: THE RESTRICTING ELEMENT-controls the volume of gas entering the chamber2) Spring: THE LOADING ELEMENT; OPENING FORCE*two jobs:1) sets working pressure2) opening force = overcomes pressure on gas side to open seat-can adjust in order to set different working pressures3) Diaphragm: THE MEASURING ELEMENT-separates the bottom part from the top4) Vent: allows gas to escape in case of overpressure downstream of the regulator-allows top of the diaphragm to breath-all regulator vents have to be facing downFunctions:-allow for displacement of air above measuring element (diaphragm) so it can operate-allows gas to escape in case of diaphragm rupture or downstream overpressure-allow for installation of a leak-limiting orifice in some regulators5) Leak Limiting Orifices:-vent limiting orifice:-normally a #78 drill size-will allow one cubic foot of gas per hour to pass6) Surge Limiting Device:(for when too much gas enters the regulator)-used in special applications that require regulator to be slow opening-position of the ball restricts flow of air from top of chamber

-static pressure = lock-up pressure = shut-off pressure= the regulator shuts off at this pressure-the pressure under which downstream pressure will stabilize after the burner shuts down(should not exceed 20% of operating pressure)

TerminologyService regulator: regulator at end of utility's pipeline that reduces supply pressure to working pressure(may also describe second stage regulator in a propane system)

Appliance regulator: reduces building line pressure to the manifold pressure of the appliance

System regulator / low-pressure regulator / zone regulator: the regulator b/t the service and the appliance regulator

First stage regulator / high-pressure regulator: reduces tank pressure down to supply line pressure on a propane system (0-375 PSIG down to 10PSIG)

Second stage regulator / medium pressure regulator: reduces supply line pressure to building line pressure

Twin stage regulator: regulator that combines a first stage and second stage in one

-example where system regulators are handy:-if need 300' of gas pipe to feed 3m BTUs at 14 w.c. => requires 4 pipe*but at 5PSIG => requires only 1.5 pipe= so run pipe at 5PSIG and introduce a service regulator just upstream of the appliances

Two Stage Propane Regulators-required on all permanent installations-max. first stage pressure = 10PSIG-first stage regulator eliminates fluctuating supply pressure (b/c pressure in the tank changes w/ temperature)-allows for small supply lines b/t tank and building

Creeping regulator = gas being passed at regulator valve seat when leak test being done w/ manometer

Converting Natural Gas to L.P.G Regulator1) change orifice2) change spring3) set manifold pressure4) change rating plate

Gas MetersTypes:1) Bellows:domestic and commercial installations2) Rotary-type:used for commercial and industrial applications3) Orifice-type:used to measure large volumes4) Turbine:used to measure large volumes

Meter Construction:-castings can be made from: tin, pressed steel, cast iron, aluminum-interior parts are often synthetic or plastic-bellows meters don't require lubrication-some rotary meters require lube

Domestic Bellows Meter:-outlets come in different sizes:1 outlet= 225 000 BTU output max1.25 outlet= 400 000 BTU output max1.5 outlet= 800 000 BTU output max-anything above 800 000BTU = need a new meter-max. allowable pressure drop = 1/2 w.c.

1) positive displacement meter-measures actual volume of gas-force that operates the meter = diff. b/t the pressure of the gas at the meter inlet and the pressure at the outlet acting upon the diaphragms or chambers2) temperature compensated (means they are for outside use)

Functions of a Gas Meter:1) measure consumption2) leak test a piping system3) measure input to an appliance (clocking the meter)Metric:(3600) x (dial #) x (35.31) x (# BTUs per cycle)# of sec.s per revolution

Imperial(3600) x (dial #) x (# BTUs per cycle)# of sec.s per revolutionPropane Containers

CylinderTankStandard set by:Transport CanadaBoiler and Pressure Vessels Act (TSSA)

Re-inspection:10 years from date ofmanuf.

Capacity:Pounds of waterUS water gallons

Relief Valve Pressure:375 PSIG250PSIG

-largest propane cylinders manufactured = 1000lb.s-cylinders stamped w/ date of manuf. on collar-on construction sites: 3 N.G. cylinders can be manifolded together-propane containers on mobile vehicles: have to be mounted on the A-frame

Module 16: Domestic Gas Fired Refridgerators

Principles of Absorption-gas fired refridgerators and A/C units based on principle of absorption*this depends on principle of two chemicals have an affinity/attraction for each other-refridgerant is attracted to the absorbent*this forces refridgerant to move throughout the absorption system(sometimes pumps or gravity are used to do this)

Main Elements of an Absorption System1) Evaporator= where the refrigerant evaporates from a liquid to a vapour...thus taking heat from the surrounding area and cooling it2) Absorber= where the absorbent is found-attached to evaporator by piping-absorbent attracts refrigerant from evaporator and mixes w/ it3) Generator (12V DC or 120V AC or propane)= where absorbent/refrigerant mixture is separate

-as refridgerant/absorbent mixture becomes stronger, absorber can't attract as much refridgerant-to finish cooling process, refrigerant has to be separated from absorbent-heat via a gas burner is added in the generator-refrigerant is distilled out of the solution and moves to the condenser-absorbent returns to absorber in a weaker solution that can attract more refrigerant4) Condenser= refrigerant condenses back to a liquid-heat is given off-refrigerant travels back to the evaporator where process begins again

Capacity Control of Absorption Systems1) capacity of an absorption system can be regulated by controlling operation of the heat source in the generator2) regulating strength of absorbent/refrigerant solution => control ability of absorbent to attract refrigerant vapour out of evaporator3) rate of evaporation of refrigerant = determines the amount of refrigeration that occurs

Sequence of Operation of a Gas-Fired Domestic Refrigerator(where absorbent is water and refrigerant is ammonia+hydrogen [R717])

GENERATOR1) heat applied to cooling unit at the GENERATORFROM THE GENERATOR:-ammonia vapour and weak ammonia liquid solution (which contains water)2) ammonia vapour rises through vapour pipe and into CONDENSER3) weak ammonia solution (containing water) is diverted to the top of the ABSORBER COILS4) any small amount of weak ammonia solution that enters vapour pipe flows into ammonia pipe via gravity (it is lower)IN CONDENSER5) ammonia in CONDENSER is cooled into a liquid6) ammonia liquid enters evaporator that contains hydrogen vapour7) as liquid ammonia contacts the hydrogen => ammonia begins to vapourize8) ammonia and hydrogen flow down to return pipeIN ABSORBER9) hydrogen and ammonia separated in ABSORBER in conjunction w/ weak ammonia solution present in the weak ammonia pipe10) ammonia vapour attracted into the ammonia hydroxide solution in ABSORBER11) hydrogen rises into EVAPORATOR

Module 17: Conversion Burners

Oil BurnersHow they work:-as liquid oil passes through orifice = oil vapourizes(how much oil is dispersed through orifice + the angle of spray is marked on orifice)-when converting: can remove fill pipe, but can't touch venting-oil chambers contain a ceramic chamber that heats up and radiates heat back out to ensure all oil droplets get burnt=> want to prevent liquid oil building up in bottom on chamber-by product of oil burning = soot-barometric dampers are used to adjust draft-placed downstream of chamber in the flue

Firing rates:1US gallon of #2 light oil = 140 000BTUs*so a nozzle size of 0.5 will produce (140k x 0.5) = 70 000BTUs

Type of Burners:1) Atmospheric burners:-operates on natural draft from chimney or venting system to receive enoug combustion air through unit-inshot vs. upshot:-inshot usually used w/ appliances converted from oil-fired-upshot burners usually used w/ appliances converted from coal

Combustion:Combustion triangle: oxygen (air) + fuel (gas) + ignition

Products of combustion:1) CO22) H203) Light4) Heat

Excess air:=> needed to ensure that all molecules of fuel are burned (they all need to contact air)-introduced as part of primary and secondary air (so a lot of excess air passes through combustion)-too much excess air = reduced efficiency (it just vents out the flue)-percentage of excess air can be measured in flue gas as unburned oxygen

Stoichiometric/Perfect Combustion:ultimate percentage of CO2 = the percentage of CO2 in the flue gases if perfect combustion takes place-assumes all oxygen in air supplied is used in burning gasOne cubic foot of oxygen will produceN.G.L.P.G....cubic feet of CO213...cubic feet of water vapour24...cubic feet of nitrogen818.5...ultimate CO211.9%13.9%

Recommended CO2 readings for oil to N.G. conversions:= 7 to 8.5%Recommended CO2 readings for oil to L.P.G. conversions:= 9 to 9.9%

Gross Stack Temperature-actual temp. of flue gases affected by:1) selection of burner2) burner adjustment design of furnace/boiler3) neutral pressure point4) firing rate of orifice5) manifold pressure6) GST has direct effect on efficiency

Net Stack Temp.= difference b/t gross stack temp. and ambiet temperature surrounding appliance

Draft Controls-double-acting barometric draft controls:= suitable for N.G. conversion burner installations-only barometric draft control suitable for oil = single-acting

Module 18: Water Heaters, Combo Systems, Potable Water Heating Systems

Water Heater ComponentsTemperature Control-uses rod and tube control (w/ copper as sensing element)-rod made of steel = low co-efficient of thermal expansion-tube made of copper = high co-efficient of thermal expansion-temp. dial settings:HOT= 160 degrees FNORMAL= 140 degrees FWARM= 120 degrees F

Unitrol (the large controller on the tank)= senses temperature-combines functions of:1) temp. control2) E.C.O (like a hi-limit)-located inside the rod and tube-if water gets too hot => will open permanently and has to be replaced3) main gas valve4) pilot gas valve5) gas regulator

Temperature and Pressure Relief Valve (T and P)-protects tank from excessive temp. + pressure-pressure valve is spring loaded and usually automatically self-resealing*if tank relieves on temp. -> fusible plug must be replaced-pressure relief valve set to relieve at 150PSI-fusible plug melts at 210 degrees F-relief opening => near top of tank*opening must be between 2 pipe diameters and 12' from floor

Dip Tube= entry tube for cold water refill-tube that goes from cold water inlet on top of tank and delivers water to bottom of tank-hot water exits through outlet pipe on top of tank

Anodes= sacrificial element which prevents interior of the tank from corroding-positive electrode which oxidizes-should be changed when 3/8 thick-change when water gets a rotten smell-lime forms in tanks b/c heated water is less dense and heavy minerals in it sink to bottom-to de-lime a tank = use muratic acid mixed w/ water-lime affects heat transfer-how to tell if tank is limed = popping, gurgling, crackling sound

Flammable Vapour Sensor= senses anything flammable around tank and shuts off the tank-works through resistance (so can't be bypassed)-placed near bottom of tank (so don't paint floor)

Mixing Valve-used on commercial water heats and automatic washers-used where more than one temp. of water is needed-allows cold water to be mixed with hot water to achieve a desired temp.

Direct Fire Water Heaters (Underfired Storage Tank)

= most common type of water heater-the flue acts as the heat exchanger-spiral baffle placed in flue to act as heat transfer-important components:ANODET and PMIXING VALVEDIP TUBE

Water Tank Principles

Two Types of Heat Transfer1) conduction via flue2) convection via heat at bottom moving up through the liquid (when burner is off)

-temp. of water in tank:150 degrees F at top140 degrees F at bottom

Legionnaire's Disease= bacterial growth in warm water-must keep tank water temp above 140 degrees F to kill off bacteria

Expansion Tanks-dip tube water can warm up and expand => wants to go up through cold water inlet-use expansion tanks to prevent this and buildup of pressure

Solder-only use lead free solder for potable water

Hissing sound when filling up water tank-when first filling up tank => lots of cold water-if the burner is turned on you might hear a hissing sound-this is condensing water falling onto the burner= normal; not a problem

Stack Effect-short draws of hot water caused by any hot water leak(tank will allow small drips of cold water to replace the hot water)= a little water drips down dip tube-so unitrol only on intermittently*result = cold at bottom, warm throughout

Instantaneous Water Heaters-cannot run out of hot water at their designed flow rate-require sufficient water supply for proper operation-important components:PUMPPUMP CONTROLCONTROL SWITCH T AND PLIMIT CONTROL

Twinned Water Heaters= two storage type tanks connected in parallel*requires inlet and outlet piping having equal resistance in order to draw equally from each tank

Types of Water Heater Systems1) Direct Vent-vents to outside + tanks combustion air from outside-can be used in a bathroom2) Power Vented Water Heater (not high efficiency)-exhaust fan starts and is proven before burner ignition3) High Efficiency Water Heaters(like a high efficiency furnace)-important componets:ECOT AND PANODEDIP TUBE-spiral heat exchanger-vents downwards (sometimes?)

Closed-loop Combination SystemSystem ComponentsCheck valves= used to prevent anti-syphoning (allows water to only flow in one direction)Mixing valve= used to bring hot water temp. down to 120 degrees FExpansion or Cushion tank= allows for thermal expansion in cold water line(so installed on cold water line)

Characteristics-ferrous metals not allowed in potable water application-max. allowable length of pipe for return and supply = 50'-can't use chemicals-three-way valve may be used as a diverter on a return line*are sized to match flow requirements of heating unit in the system-temp. sensors measure:-supply fluid temp.-return fluid temp.-mixed fluid temp.-indoor air-outdoor air

*are mounted:-in wells-directly to metal pipes-according to manuf.'s recommendations-fluid flow controlled by pressure bypass valve or shunt pump-max. allowable velocity of fluid in supply and return lines less than 2 = 4ft/sec.-min. size and type of water heater recommended for a combo. system= 40 gallon high recovery gas-fired water heater= 40 gallon high efficiency gas-fired water heater

Circulating PumpsPurpose= to overcome resistance in system caused by pipings and fittings, etc.Head pressure = ability of the pump to overcome resistance-how to size pump?= use head pressure and water flow rate

Module 19: Forced Warm Air Heating Systems

Condensing Furnaces-condensate lines run to open drains-average flue temp. = 80 to 120 degrees F-methods to determine if heat exchanger is cracked1) visual2) smoke bomb3) flue gas analyzer-High boy vs. Low boyHigh boy= supply air on top; return air on bottomLow boy= supply air on top; return air on top-temp rise = diff. in temp b/t supply and return air-have two heat exchangers: primary and secondary-type of heat transfer mainly used by forced warm air furnace = convection

Stage furnacesSingle-stage: all BTUs are fired at onceTwo-stage:have two stages of heat1) low fire:~2/3 of total BTU input2) high fire:all BTUs are fired*this is controlled by the circuit board

Modulating furnaces= contains a special modulating gas valve-operates in increments depending on what has to be heated(BTUs climb slowly)

Fan Control-two ways to control:1) Time on2) Time off= controlled by the circuit board

Random Stuff-avg. CFM/ton for an A/C= 400CFM-avg. CFM/ton for heat pump= 450CFM-if replacing an old inefficient (60%) furnace with a newer efficient one (80%), how to determine the size (BTU input)?= perform a heat loss calculation-vents must terminate at least 6' from a mechanical air supply

Types of Warm Air Furnaces1) Upflow (Highboy)-stands vertically-needs head room-return air at bottom; supply air at top-designed for first floor w/ ducts in attic OR basement w/ ductwork under first floor joists2) Downflow or Counterflow-return air through the top; supply air at bottom-ductwork may be in concrete floor or in crawlspace3) Horizontal-positioned horizontally on its side-installed in crawlspaces, attics, or suspended from floor joists-return air in one end; supply air out the other4) Low boy-approx. 4ft high-used primarily in basements w/ low headroom-ductwork under the first floor-both return and supply air at the top

Components1) Gas Valve Train and Burner-gas valve (main, pilot, combo.)-regulators-pilots-thermocouples-burners2) Heat exchanger-proper airflow (temp. rise) is required*too much airflow = products of combustion will condense*too little airflow = stress on heat exchanger-normal temp. rise = 40 to 70 degrees F-poor combustion = corrosion of heat exchanger

Sensible Heat (cubic feet per minute)

CFM=BTU (output)1.1 x Temp. rise3) Fan switch-automatically turns blower off and on-delays blower fan operation to heat the heat exchanger and prevent nuisance drafts-delays blower fan termination to cool heat exchanger and dissipate heat-switch is temp. controlled or time delayed4) Limit switch-normally closed safety switch-when detects overheat situation = will open and de-energize main gas valve-can be in combo w/ fan limit switch

Module 20: Hydronic Heating Systems

-boilers must conform to the Biolers and Pressure Vessels Act (governed by TSSA)

Hydronic Heating Systems-use hot water and/or steam to provide heat*water is 10x more efficient than air in transferring heat-also reduces pollutants from being re-circulated w/in conditioned space-hilimits are set at 200 degrees F for hot water boilers-low flue gas temp.s = cause condensation-primary cause of sooting = incomplete combustion

Temperature and Pressure Ranges for Hot Water Boilers

Temp. RangePressureLow Pressure boilers170 to 250 degrees F7 = alkaline, the amt of heat required to melt 1 ton of ice (generally over 24hrs)

Vent Sizing-when inspecting venting look for:1) rotted parts2) screws3) correct size

-tables allow for two 90 degree elbows

TablesC1= Type B double wall vent-double wall vent connector-one appliance

C2= Type B double wall vent-single wall vent connector-one appliance

C3= Type B double wall vent connector-two or more appliances

C4= Type B single wall vent connector-two or more appliances

Chimneys-use tables C5, C6, C3, C4

-to find diameter of chimney liner => have to go to B-vent charts and reduce by 80%

Tee-Wyes-have to reduce B-vent tables by 10%

DuctsSupply Air-effect of making supply air smaller*air velocity increases*air volume decreases= noisy duct work-effect of making supply air larger*air velocity decreases*air volume decreases= will starve less proximate runs of air

Return Air-if make return air smaller*air velocity increases*air volume decreases*air will flow too fast over heat exchanger-not enough heat will be absorbed-heat exchanger will overheat-if return air is too small => can take off blower door

------------------------------------------------------------------VENTING PRACTICES

Module 23: Forced Air Add-On Devices

Air Filters and Cleaners*three possibilities for air filtration:1) Media filters (throw away)(also called mechanical filters)-made from fibreglass and positioned in air stream2) Electrostatic air filters-media filters that generate static charge from air flow-static charge attracts particles to the medium3) Electronic air cleaners-use an external power source to generate a charge-particles are attracted to charged plates rather than a media filter

1) Media filters-become efficient when 25% plugged-physically remove particles from air stream-two types:1) Hammock: surround fan; have a hammock shape2) Slab filters: consist of layers of filter material held together by cardboard frame-usually designed for one-time use-advantages: initial cost and upkeep is low-disadvantages: low efficiency on normal atmospheric dust

-replacing and cleaning filters-should be inspected every month and cleaned when required2) Electrostatic filters-may replace media filters when more filtration is necessary-most are washable and reusable-adv.s: no electricity required and more efficient than media filters-disadv.s: less efficient than electronic air cleaners3) Electronic air cleaners-have four main sections:1) pre-filter: screens large particles2) charging section: contains small-diameter wire through which high DC voltage is passed from power pack (6 to 25 kV)-this creates an electrostatic field-as airborne particles pass through field they become positively or negatively charged3) collecting section: contains a series of parallel plates-plates are alternately positively charged with direct current voltage of 4-10kV-uncharged plates are grounded-charged particles are attracted to the plates4) power pack or voltage section:-consists of step-up transformer and rectifierA stage: step-up transformer increases 120V AC to 3000-3500V AC at collector cells-B stage: rectifier circuit converts this to 7500-8500V DC at charging cells-usually installed in return air plenum-must filter entire return air stream-should be installed upstream of any humidifier: don't want moisture from humidifier to cause mineral and salt buildup in EACWiring:-EACs function only when blower is operating and air is in motion-should be interlocked w/ blower circuit (so it only operates when blower operates)Ozone production:-properly-functioning EACs will produce small amount of ozone-strong ozone odour can indicate continuous arcing (caused by too-large EAC being put in plenum -> some of it is not getting air)-activated carbon filter must be installed downstream of EAC

Humidifiers-humidifiers = add water vapour to air in a building (to increase relative humidity)*warm air holds more water than cold air, so relative humidity changes w/ the temp.

Humidistats-an electric switch that controls operation of humidifer-should be placed by the thermostat-are run on 24V-run off 24V side of circuit boardOR-run off 120V side w/ a step-down transformer

Types of Humidistats1) Duct-mounted drum humidifiers / Power Humidifiers-contain 24V ac motor and wheel or drum covered in foam-when humidistat calls for humidity drum rotates through a water reservoir to saturate the foam-supply air travels across/through foam and picks up moisture

2) Spray humidifiers/Flow-Through Humidifiers (newer ones)-use sprayed steam of water to wet the medium-humidistat opens a solenoid, which opens a water valve-allows water to flow through a nozel where it is sprayed on the medium-then air travels over it

3) Plate humidifier-essentially a plate of water in the return air w/ a float to regulate water input*has no control mechanism

Testing Relative Humidity-sling psychrometer measures air temp. using two thermometers: a wet bulb and a dry bulb*as psychrometer is rotated quickly in air, moisture is evaporated from wet bulb-when the temperature stabilizes on the two thermometers, readings are taken-the readings are then compared to tables supplied w/ the device

A/CCooling coils-measuring pressure drop across coil*one way of checking system= measured using a magnehelic gauge or manometer

Module 24: Air Handling Systems

-residential systems are considered low-pressure systems

Duct SystemFunctions of a Duct System= supply conditioned air to parts of the house-operates as a loopSupply (discharge) air= under positive pressure-several different ways in which the system can be designed:1) extended plenum2) reducing plenum3) perimeter loop4) radial systemReturn air side= under negative pressure-two types of returns:1) central return: one return air grille is installed on each floor in a central location (like a hallway)2) individual return: have a return air grille in every room except kitchens, bathrooms, or rooms w/out air supply

Duct Liners= used to reduce sound and minimize heat transfer-if installed inside duct => meant to reduce noise-if installed outside duct => meant to reduce heat transfer

Flexible Duct connectors/Canvas Connectors= used to reduce noise-noise is transmitted through duct work from fans and blowers-flexible connectors absorb vibration-installed on both discharge and intake sides

Air Pressure Readings1) Gauge pressure:-amount by which pressure of air/fluid exceeds ambient atmospheric pressure-used to express pressures inside a closed system-expressed in PSIG (PSI gauge)2) Absolute pressure:-the level of pressure above a perfect vacuum-is equal to gauge pressure + atmospheric pressure-expressed in PSIA (PSI absolute)14.7PSIA = 0PSIG3) Static pressure (resistance to airflow):= air pressure in a duct at right angles to the direction of flow-as air moves along a duct, a static charge develops b/t surface of duct and surface of air= slows the airflow*residential static pressure should be 0.5w.c.=> must take all these into account b/c when designing a duct system you want to ensure that you get a certain volume and velocity of aird4) external static pressure:= resistance from outside the furnace casing (supply outlet) to the factory supplied filter in an air-handling device-you want the range at: 0.2w.c. to 0.5w.c.5) internal static pressure:= resistance to airflow inside the furnace casing (from return inlet to supply outlet)

Air flow and System EfficiencyCooling Systems-rule of thumb for cooling systems: for every ton of cooling, 400CFM of airflow is requirede.g.: a two ton cooling system requires 800CFM of air flow*but: heat pumps require 450CFM per ton

Blower Motors-direct-drive blower: blower motors are mounted inside the blower and are linked directly to the squirrel cage-belt-drive blower: belt drive motors are connected to the blower motor via a belt-contain four bearings: two on the fan shaft and two on the motor-drive pulley = motor pulley (is adjustable)-driven pulley = blower pulley (is fixed)

Propeller Fans= usually mounted over an outlet in the wall-used for general ventilation in areas where large quantities of air need to be moved against low static pressures

Centrifugal Blowers-air is moved perpendicular to the shaft-air enters through side casing and exits through a rectangular outlet-can move large quantities of air at relatively high static pressure

Blower Speed, CFM, Horsepower, and Static Pressure-direct relationship b/t speed of the blower and volume of air that it moves-blower speed can be changed by changing the drive pulley-some blower motors are equipped w/ adjustable pulleys*adjusting these will modify the blower speed and therefore the volume of air that is moved-increasing the diameter of the pulley = more amperage draw-decreasing the diameter of the pulley = less amperage draw

Drive ratio-in belt-driven blowers, the drive ratio = relationship b/t the motor pulley size and blower pulley size

(Drive pulley size) x (Drive RPM) = (Driven pulley size) x (Driven RPM)