HVAC field guides

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External static pressure, CFM, duct leakage, charging, balancing, and commissioning notes.

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Field GuideRetro-commissioning existing buildings field guideWhat retro-commissioning is, why tuning the building you already have beats replacing it, how to find the drift with trend data and functional tests, and how to keep the savings from drifting back.Retro-CommissioningExisting Building CommissioningBuilding Drift Jun 29, 202621 min read Field GuidePredictive maintenance and condition monitoring field guideHow to read a machine's own condition and fix it before it fails: the ladder, the P-F window, the techniques, criticality ranking, and the record that turns a finding into a work order.Predictive MaintenanceCondition MonitoringP-F Curve Jun 29, 202621 min read Field GuideIndoor air quality monitoring and sensors field guide for HVACWhat continuous IAQ monitoring is, what to measure, why CO2 is the ventilation proxy, how to place and calibrate sensors, and why the value is the response, not the sensor.Indoor Air QualityIAQ MonitoringCO2 Sensors Jun 29, 202621 min read Field GuideConstruction closeout and warranty management field guideStart closeout on day one, hand the owner a building they can operate with the records and warranties, then run the warranty year so the relationship and the reputation survive it.CloseoutSubstantial CompletionWarranty Management Jun 29, 202621 min read Field GuideHVAC warranty reserve and callback cost management field guideThe callbacks land after you booked the profit: what the warranty obligation costs, what a callback really runs, sizing a reserve from your own history, and killing the root cause so the same call does not come back.Warranty ReserveCallback CostRoot Cause Jun 28, 202621 min read Field GuideValue engineering in construction field guideWhat value engineering actually is, why it is not cost-cutting, the function analysis at its heart, the SAVE job plan, life-cycle cost, timing, the VECP, and how to keep value while lowering cost.Value EngineeringFunction AnalysisLife-Cycle Cost Jun 28, 202621 min read Field GuideService truck inventory and van stock field guide for HVACStock each truck for the first-time fix without burying cash or losing parts off the ticket: the stock list, par levels, restock from the work order, cycle counts, and the metrics.Truck InventoryVan StockPar Levels Jun 28, 202621 min read Field GuideService dispatch and technician scheduling field guide for HVACMatch the right tech to the right job at the right time with the right parts, keep the board live all day, and bill more hours doing it.Service DispatchTechnician SchedulingDispatch Board Jun 28, 202621 min read Field GuideHVAC service agreements and recurring revenue field guideWhat a service agreement is, why recurring revenue makes the business worth more, how to price the tiers for profit, schedule the visits, and convert one-off customers into members.Service AgreementsRecurring RevenueMaintenance Contracts Jun 28, 202621 min read Field GuideRespiratory protection program field guide (OSHA 1910.134)Why a dust mask off the shelf is not compliance, how the OSHA program fits together, and the parts crews skip that get cited: medical evaluation, fit test, and a cartridge change schedule.Respiratory ProtectionOSHA 1910.134Fit Test Jun 28, 202621 min read Field GuideRefrigerant oil return field guide for long and vertical line setsKeep the velocity high enough to sweep the compressor's oil home, trap and double-riser the verticals, and design for minimum load, not just the nameplate day.Oil ReturnSuction RiserDouble Riser Jun 28, 202621 min read Field GuideHVAC overhead recovery, markup vs margin, and bid pricing strategy field guideRecover overhead and a real profit in every bid: what overhead is, the markup-versus-margin trap, the divide-don't-multiply math, burdened labor, break-even, contingency, and walking the jobs that lose money.Overhead RecoveryMarkup vs MarginBid Pricing Jun 28, 202621 min read Field GuideNatatorium and indoor pool dehumidification field guide for HVACRemove the evaporation load and hold the dew point below the cold surfaces, keep the room negative and exhaust the chloramines at the deck, and build it all from corrosion-resistant materials behind a warm-side vapor barrier.NatatoriumPool DehumidificationDew Point Control Jun 28, 202621 min read Field GuideMold remediation and IAQ field guide: fix the water, contain, remove, verifyMold is a water problem first. Fix the moisture, contain the work under negative pressure, physically remove the mold, and verify with a third-party professional instead of spraying biocide and painting over it.Mold RemediationIICRC S520Indoor Air Quality Jun 28, 202621 min read Field GuideLaboratory fume hood and exhaust ventilation field guide for HVACHold the face velocity, keep the lab exhaust dedicated and corrosion-resistant, disperse the plume above the roof, and keep the room negative with enough makeup air.Fume HoodLaboratory VentilationANSI AIHA Z9.5 Jun 28, 202621 min read Field GuideJobsite logistics and site planning field guideLay out where material lands, how trucks get in and out, where the crane sits, and how the public stays clear, then update the plan as the building eats the site.Site LogisticsLaydown and StagingCrane Planning Jun 28, 202621 min read Field GuideIndoor air quality investigation and testing field guide for HVACStart with the people and the building, check carbon monoxide first, find the ventilation or moisture cause, and fix the source instead of selling a purifier.Indoor Air QualityIAQ InvestigationSick Building Syndrome Jun 28, 202621 min read Field GuideHydronic balancing valves and circuit setters field guide for HVACSet and verify the water flow to every coil and terminal so close loads do not hog the flow and far loads do not starve, then record the set gpm in the balance report.Hydronic BalancingCircuit SetterPICV Jun 28, 202621 min read Field GuideHVAC service maintenance agreement field guide for contractorsTurn one-off repair calls into recurring revenue: the agreement types, the tiers, pricing from the true visit cost, the scope, the auto-renewal and escalation, and the pull-through work.Maintenance AgreementService ContractRecurring Revenue Jun 28, 202621 min read Field GuideHiring and onboarding field technicians for HVACFind, hire, onboard, and keep skilled techs when labor is the limit: the channels, the job ad, the ride-along, the first 90 days, the pay, and the path.Technician HiringTech RetentionOnboarding Jun 28, 202621 min read Field GuideHealthcare and hospital HVAC ventilation field guide (ASHRAE 170)Hold the room pressure relationship, deliver the air changes and filtration each space needs, keep humidity in range, and monitor and validate it all to a clinical standard.Healthcare HVACASHRAE 170FGI Guidelines Jun 28, 202621 min read Field GuideFire and smoke damage restoration and odor removal field guideBeat the acidic-residue clock, dry-clean the soot before you wet it, match the chemistry to the residue, and pull the odor out at the source instead of masking it.Fire Damage RestorationSmoke Odor RemovalIICRC S700 Jun 28, 202621 min read Field GuidePortable fire extinguisher field guide: classes, PASS, and fight-or-fleeMatch the extinguisher class to the fuel, decide fast whether to fight or get out, use PASS, and keep the units inspected and recharged so the one you grab actually works.Fire ExtinguisherFire ClassesPASS Technique Jun 28, 202621 min read Field GuideHVAC customer financing options field guide for contractorsOffer the homeowner a monthly payment so the replacement and the better system become affordable: how the dealer program works, the dealer fee, deferred interest, qualifying in the field, compliance, and the metrics.Customer FinancingDealer FeeDeferred Interest Jun 28, 202621 min read Field GuideContractor succession and exit planning field guideWhat succession and exit planning is, the exit options, how a contracting business is valued, what makes it sellable, reducing owner dependence, deal structures, and the timeline to prepare.Exit PlanningBusiness ValuationSuccession Planning Jun 28, 202621 min read Field GuideCommercial refrigeration field guide for walk-in and rack systemsWalk-in coolers and freezers, reach-ins, and supermarket racks: match the temp, set up defrost, charge it right, seal the box, and handle the refrigerant transition.Commercial RefrigerationWalk-In CoolerDefrost Jun 28, 202621 min read Field GuideCommercial kitchen equipment installation field guideThe install is coordination: land the gas, electric, water, drain, and ventilation where the equipment goes, restrain the gas, air-gap the drain, balance the hood and makeup air, and meet NSF.Commercial KitchenKitchen Equipment InstallGas Connector Jun 28, 202621 min read Field GuideCommercial ice machine field guide: installation and serviceThe refrigeration is the easy part. The water side, the filtration that fights scale, the air-gapped drain, the sizing derate, and the cleaning that keeps mold out are what make or break an ice machine.Ice MachineWater FiltrationNSF Sanitation Jun 28, 202621 min read Field GuideCombustion analysis and flue-gas tuning field guidePut a calibrated analyzer in the flue, read oxygen, carbon monoxide, temperature, and draft, and prove the appliance burns clean, safe, and efficient instead of guessing.Combustion AnalysisFlue Gas AnalyzerCarbon Monoxide Jun 28, 202621 min read Field GuideCold storage and refrigerated warehouse design field guideScaling a walk-in to a warehouse: heat the sub-floor or the freezer heaves, keep the inward vapor barrier continuous or ice fills the panels, manage the ammonia with PSM, and pull the building down slowly.Cold StorageRefrigerated WarehouseFreezer Floor Heave Jun 28, 202621 min read Field GuideCleanroom HVAC and contamination control field guideDesign to the ISO class, push HEPA-filtered air at the right rate and pattern, hold the pressure cascade clean to dirty, and certify by particle count and filter-integrity scan.Cleanroom HVACISO 14644HEPA Filtration Jun 28, 202621 min read Field GuideChiller plant sequencing and optimization field guideStage the chillers to the real load at their efficient part-load point, reset the chilled-water and condenser-water setpoints to cut the lift, fix low delta-T, and trend the plant so the bad sequence shows up in the data before it shows up on the bill.Chiller Plant SequencingChilled Water ResetkW per Ton Jun 28, 202621 min read Field GuideHVAC change order management and scope control field guideStop giving away the extras: what a change order is, what triggers one, how to price it, getting it signed before the work, the scope baseline, the log, and billing the change so it never disappears into the final.Change OrderScope ControlScope Creep Jun 28, 202621 min read Field GuideCentrifugal chiller surge: causes, control, and how to stop itWhat surge is, why high lift drives it, how the compressor map and surge line work, and what to clean, purge, and check before a surging machine eats its own thrust bearing.Centrifugal ChillerChiller SurgeInlet Guide Vanes Jun 28, 202621 min read Field GuideBuilding automation fault detection and diagnostics field guideWhat fault detection and diagnostics is, the trend-data and tagging layer underneath it, the faults it finds, how it prioritizes and diagnoses, and the detect-diagnose-dispatch-verify loop that closes the fix.Fault DetectionBuilding AnalyticsFDD Jun 28, 202621 min read Field GuideHVAC bid, proposal, and closing the sale field guideTurn the estimate into a clear proposal and walk the customer to yes: good-better-best options, the value story, financing, presenting in person, and the follow-up that closes the job.Sales ProposalGood Better BestClosing the Sale Jun 28, 202621 min read Field GuideHVAC apprenticeship and training program field guideBuild techs you cannot hire: the OJT hours, the related instruction, the mentor, the competency milestones, and the license-and-pay path that turns a helper into a journeyman.ApprenticeshipGrow Your OwnCompetency Tracking Jun 28, 202621 min read Field GuideAir-side economizer fault detection field guide for HVACFind the broken economizer that runs mechanical cooling unseen: stuck dampers, dead actuators, bad sensors, the wrong changeover, the FDD logic, and the functional test that proves it.Air-Side EconomizerFault DetectionEconomizer FDD Jun 28, 202621 min read Field GuideWaterside economizer and free cooling field guideHow the cooling tower makes chilled water with the chiller off when the wet-bulb drops, the plate heat exchanger that keeps the loop clean, integrated control, and the freeze protection that keeps it from killing the plant in winter.Waterside EconomizerFree CoolingPlate Heat Exchanger Jun 27, 202621 min read Field GuideVAV vs CAV air distribution systems field guide for HVACWhat separates constant air volume from variable air volume, how each one controls a zone, where the energy goes, and which system belongs on the building in front of you.VAV vs CAVVariable Air VolumeConstant Air Volume Jun 27, 202621 min read Field GuideThermostat types, wiring, and smart controls field guideWhat a thermostat does, why it has to match the equipment, the type ladder from mechanical to communicating, the terminal letters and the C-wire, heat pump and staging setup, and how to install and troubleshoot one.ThermostatsSmart ThermostatC-Wire Jun 27, 202621 min read Field GuideSteam pressure reducing valve station field guide for HVACHow a steam PRV station drops high-pressure distribution steam to the pressure the equipment needs: the valve, the strainer, the separator and drip trap, the safety relief, the gauges, and the bypass.Steam PRVPressure Reducing ValveSafety Relief Valve Jun 27, 202621 min read Field GuideSteam heating system fundamentals field guide for HVAC crewsHow a steam system actually moves heat: the boiler makes steam, the steam rides its own pressure to the terminals and condenses, and the condensate finds its way home.Steam HeatingLatent HeatOne-Pipe Steam Jun 27, 202621 min read Field GuideSnow melt system field guide: hydronic and electricPick hydronic or electric, size the high melt load, fill the loop with glycol, insulate under the slab, and let an automatic snow sensor run it only when it is snowing and cold.Snow MeltHydronic Snow MeltElectric Snow Melt Jun 27, 202621 min read Field GuideRefrigeration cycle field guide: how the vapor-compression cycle worksCooling moves heat, it does not make cold. Read the four-part loop, the phase change that carries the load, the high and low side, and the saturation numbers that tell you what the system is doing.Refrigeration CycleVapor CompressionEvaporator and Condenser Jun 27, 202621 min read Field GuideRefrigeration accessories field guide: filter-drier and sight glassWhat every refrigerant-line accessory does, why the filter-drier matters most, and how to install, size, and read them without killing the compressor.Filter-DrierSight GlassSuction Accumulator Jun 27, 202621 min read Field GuideRefrigerant types and the A2L transition field guideWhy refrigerants keep changing, what A2L means under ASHRAE 34, which low-GWP refrigerants replace R-410A, and how to handle a mildly flammable charge safely in the field.A2L RefrigerantR-454BASHRAE 34 Jun 27, 202621 min read Field GuideRefrigerant metering devices field guide: TXV, orifice, and EEVKnow which device is on the system, why a TXV holds superheat and an orifice does not, when you need an external equalizer, and how to read a starved valve from a starved line.Metering DevicesTXVFixed Orifice Jun 27, 202621 min read Field GuideRefrigerant line brazing and nitrogen purge field guideBraze copper refrigerant joints while a trickle of dry nitrogen flows through the line, so the heat never forms the oxide scale that plugs the metering device and kills the compressor.BrazingNitrogen PurgeCopper Oxide Scale Jun 27, 202621 min read Field GuideRefrigerant evacuation field guide: pulling a deep vacuumPull air and moisture out of the system with a deep vacuum, read it in microns on a micron gauge, prove it dry and tight with a decay test, and record what the system held before you charge it.EvacuationDeep VacuumMicron Gauge Jun 27, 202621 min read Field GuideRadiant floor hydronic heating design field guidePick the install method, size the tubing and loops, hold the loops equal, drop the water to a low supply temperature, insulate under the heat, and start it without trapping air.Radiant Floor HeatingHydronic RadiantPEX Tubing Jun 27, 202621 min read Field GuidePump cavitation and NPSH diagnosis field guide for HVACRead the gravel sound, measure the suction, work out whether NPSH available fell below NPSH required, and fix the suction side before the impeller is gone.Pump CavitationNPSHSuction Pressure Jun 27, 202621 min read Field GuidePTAC and PTHP package terminal units: a field guideWhat a through-the-wall package unit is, PTAC versus PTHP, the standard sleeve and the pitch that keeps water out of the room, sizing, electrical, and the maintenance that keeps a property of them running.PTACPTHPWall Sleeve Jun 27, 202621 min read Field GuideReading the Psychrometric Chart: A Field GuideHow to read the psychrometric chart in the field: dry-bulb, wet-bulb, dew point, humidity ratio, enthalpy, and the process lines that explain what a coil is doing.PsychrometricsWet-BulbDew Point Jun 27, 202621 min read Field GuideKitchen exhaust and grease duct field guide (NFPA 96)What the exhaust system is, why the grease is a fire hazard, how NFPA 96 governs the welded duct, the clearances, the fan, and the cleaning that keeps it from burning.Grease DuctNFPA 96Kitchen Exhaust Jun 27, 202621 min read Field GuideHydronic expansion tank and air separator field guide for HVACAbsorb the thermal expansion, pump away from the tank, strip the air at the hot low-pressure point, set the pre-charge to fill pressure, and size the tank to the manufacturer's data.Expansion TankAir SeparatorPumping Away Jun 27, 202621 min read Field GuideHVAC zoning systems: dampers, thermostats, and controls field guideHow zoning splits one system into independently controlled areas, what the panel, dampers, and thermostats each do, and why the bypass-versus-modulating call decides whether the system runs quiet or roars.HVAC ZoningZone DampersZone Control Panel Jun 27, 202621 min read Field GuideHVAC vibration isolation and equipment mounting field guideIsolate the fan, pump, chiller, and AHU from the structure: pick the deflection to the equipment and the floor, break every rigid path with flexible connectors, and never let a bolt or a chunk of debris short the isolator out.Vibration IsolationEquipment MountingSpring Isolators Jun 27, 202621 min read Field GuideHVAC ventilation rate and outdoor air field guide (ASHRAE 62.1)Set the minimum outdoor air with the rate procedure, correct it for the zone and the system, modulate it with occupancy, and prove the air is actually delivered.Ventilation RateOutdoor AirASHRAE 62.1 Jun 27, 202621 min read Field GuideUnit heater field guide: gas, electric, and hydronic shop heatWhat a unit heater is, where it fits, the gas and electric and hydronic types, why separated combustion exists, and the combustion air, venting, and CO safety that keep it honest.Unit HeaterGas Unit HeaterSeparated Combustion Jun 27, 202621 min read Field GuideHVAC test instruments field guide: gauges and metersThe gauges and meters a tech reads to charge, evacuate, balance, and diagnose by the numbers, what each one measures, and why a wrong reading is a wrong diagnosis.Test InstrumentsManifold GaugesMicron Gauge Jun 27, 202621 min read Field GuideHVAC temperature split and delta-T diagnostics field guideTake the air-side split across the coil, read it against the indoor humidity, fix airflow before you touch the charge, and check the furnace rise against the nameplate.Temperature SplitDelta-TFurnace Temperature Rise Jun 27, 202621 min read Field GuideHVAC system types: a field guide to choosing a systemThe axes that sort every HVAC system, the families behind the labels, and how to match the system to the building before the bid locks it in.HVAC System TypesSystem SelectionVRF Jun 27, 202621 min read Field GuideHVAC preventive maintenance program field guideHow to run a real PM program: the schedule, the filter and coil work, the economizer nobody checks, the charge you do not top off, and the record that proves it.Preventive MaintenanceHVAC PM ProgramASHRAE 180 Jun 27, 202621 min read Field GuideInfrared radiant tube heater field guide for HVAC crewsWhy radiant beats forced air in big open space, the tube and luminous types, the clearance and venting that govern the install, and how to lay it out.Infrared Radiant HeaterTube HeaterClearance to Combustibles Jun 27, 202621 min read Field GuideHVAC fan array and fan wall systems field guideWhy the fan wall replaced the single big fan: redundancy, part-load efficiency, a short cabinet, even airflow, and the backdraft damper that has to be there.Fan ArrayFan WallPlenum Fans Jun 27, 202621 min read Field GuideHVAC estimating and bidding field guide for mechanical contractorsPrice the equipment, the sheet metal, the piping, and the labor, add overhead and profit, and turn the takeoff into a bid that holds and a proposal that becomes the contract.HVAC EstimatingSheet Metal TakeoffLabor Units Jun 27, 202621 min read Field GuideDuct insulation field guide: wrap vs liner for HVAC crewsPick external wrap or internal liner by the job, keep the vapor barrier sealed on the warm side, hold the code R-value, and seal the duct before any insulation hides the leaks.Duct InsulationDuct WrapDuct Liner Jun 27, 202621 min read Field GuideHVAC air duct cleaning and IAQ field guide: the NADCA source-removal methodWhen duct cleaning is actually warranted, how NADCA source removal cleans the whole system under negative air, and how to prove it worked instead of just paying for it.Air Duct CleaningNADCA ACRSource Removal Jun 27, 202621 min read Field GuideDesiccant dehumidification systems field guide for HVACPull moisture out by adsorbing it onto a desiccant instead of condensing it on a coil, reach the low dew points a coil cannot, and plan for the warm dry air that comes back out.Desiccant DehumidificationDesiccant WheelLow Dew Point Jun 27, 202621 min read Field GuideHVAC coil types, cleaning, and maintenance field guideWhat each coil type does, why a dirty coil quietly steals capacity, how to clean one without wrecking the fins, and the freeze protection that keeps a water coil from bursting.HVAC CoilsCoil CleaningEvaporator Coil Jun 27, 202621 min read Field GuideHVAC building automation and DDC controls fundamentals field guideWhat a BAS and DDC system is, the control loop, the I/O, sensors, actuators and valves, the controllers, the sequence of operations, BACnet and Modbus, the front-end, and the point-to-point checkout that proves it works.Building AutomationDDC ControlsBACnet Jun 27, 202621 min read Field GuideAir distribution field guide: diffusers, grilles, and registersPick the supply device for the throw, set the pattern, balance in the duct and not at the face, and put the return where the air actually needs to go.Air DistributionDiffusersGrilles and Registers Jun 27, 202621 min read Field GuideHeat pump reversing valve and defrost field guideThe four-way valve that flips the cycle, the O versus B control that trips everyone, the defrost that runs cooling on purpose, and how to tell a stuck valve from a low charge.Reversing ValveDefrostHeat Pump Jun 27, 202621 min read Field GuideHeat pump fundamentals field guide: COP, balance point, and defrostMove heat, do not make it: how a heat pump heats and cools with one system, what COP and the balance point mean, and why defrost is normal.Heat PumpCOPDefrost Jun 27, 202621 min read Field GuideGas furnace operation and troubleshooting field guideHow a gas furnace fires in sequence, what every component proves before the next one runs, and how to read a no-heat call by where the sequence stops.Gas FurnaceFurnace TroubleshootingSequence of Operation Jun 27, 202621 min read Field GuideFire and smoke damper installation and testing field guidePut the right damper at the right rated barrier, install it exactly to the listing with the sleeve and the access door, and prove it closes on the schedule NFPA sets.Fire DampersSmoke DampersNFPA 80 Jun 27, 202621 min read Field GuideFan laws and affinity laws field guide for HVAC air systemsPredict what a speed change does to airflow, pressure, and power, read the fan against the system curve, and size the motor so the cube law never bites you.Fan LawsAffinity LawsFan Curve Jun 27, 202621 min read Field GuideFan belt, drive sheave, and V-belt alignment field guide for HVACSet the speed with the sheaves, tension the belt right, align the sheaves true, and stop throwing belts and killing bearings on belt-drive fans.Belt DriveSheave AlignmentBelt Tension Jun 27, 202621 min read Field GuideEvaporative cooling and swamp cooler systems field guideHow evaporative cooling actually works, why the wet-bulb is the floor it can never beat, why a swamp cooler dies in humid air, and how direct, indirect, and two-stage units really differ on the job.Evaporative CoolingSwamp CoolerWet-Bulb Jun 27, 202621 min read Field GuideDuctwork types field guide: sheet metal, flex, and ductboardPick the duct type that fits the pressure, the space, the budget, and the air quality, and put each one where it actually performs.Ductwork TypesSheet Metal DuctFlex Duct Jun 27, 202621 min read Field GuideDuct leakage testing and sealing field guide for HVAC crewsFind the leak class the spec calls for, seal the duct to the seal class before it is hidden, pressurize a section with a calibrated fan and orifice, and prove the leakage against the SMACNA allowable.Duct LeakageSMACNADuct Sealing Jun 27, 202621 min read Field GuideDedicated outdoor air system (DOAS) field guide for HVACDry the ventilation air to a low dewpoint, let a parallel system carry the room sensible load, recover the exhaust energy, and prove the supply dewpoint in the field.Dedicated Outdoor Air SystemDOASASHRAE 62.1 Jun 27, 202621 min read Field GuideCooling tower types and how they work field guideWhat a cooling tower does, why the wet-bulb is the floor it can never beat, and how open, closed-circuit, crossflow, counterflow, induced, and forced-draft towers actually differ on the job.Cooling TowerCondenser WaterEvaporative Cooling Jun 27, 202621 min read Field GuideCondensate neutralizer field guide for condensing appliancesCondensing appliances make acidic condensate, so a neutralizer raises the pH with media before the drain. Size it, install it downstream of the trap, check the outlet pH, and refill the media.Condensate NeutralizerAcidic CondensateCondensing Furnace Jun 27, 202621 min read Field GuideHVAC compressor types: scroll, screw, reciprocating, centrifugalHow the four compressor families work, where each fits by tonnage, how they hold part load, and the handful of mistakes that kill them.Compressor TypesScroll CompressorScrew Compressor Jun 27, 202621 min read Field GuideChiller types and selection: centrifugal, screw, scrollWhat a chiller is, the compressor families and how they reject heat, the efficiency each one buys you, and how to pick the machine the building actually wants.Chiller SelectionCentrifugal ChillerScrew Chiller Jun 27, 202621 min read Field GuideChilled water vs DX cooling comparison field guideThe two ways a commercial building makes cold air, what the choice costs you up front and over twenty years, and how to tell which one the building actually wants.Chilled WaterDX CoolingAir-Cooled Chiller Jun 27, 202621 min read Field GuideChilled water pumping: primary-secondary vs variable primary flowPick how the water moves through the chillers and out to the coils: constant flow, primary-secondary with a decoupler, or variable primary flow with a minimum-flow bypass, and hold the delta-T.Chilled Water PumpingPrimary-SecondaryVariable Primary Flow Jun 27, 202621 min read Field GuideChilled water low delta-T syndrome field guideWhy the return water comes back too cold, what it costs in pump and chiller energy, how to find the bad coils and valves, and why the fix lives at the coil, not the plant.Low Delta-TChilled WaterCoil Selection Jun 27, 202621 min read Field GuideBuilding pressurization control and makeup air field guideRead the air balance, hold the building slightly positive, keep the negative-pressure failures out, and prove the pressure with a manometer instead of a guess.Building PressurizationMakeup AirStack Effect Jun 27, 202621 min read Field GuideBoiler water treatment, chemistry, and blowdown field guide for steam and hydronic systemsKeep the water in spec so the boiler does not scale, pit, or foul: control hardness, kill the oxygen, hold the pH, and blow down the solids, heavier on steam than on a closed loop.Boiler Water TreatmentBlowdownOxygen Scavenger Jun 27, 202621 min read Field GuideBoiler types field guide: fire-tube, water-tube, condensing, and how to chooseSort boilers by hot water or steam, fire-tube or water-tube, cast iron, and condensing or not, then match the type to the system so a condensing boiler actually condenses.Boiler TypesCondensing BoilerFire-Tube Boiler Jun 27, 202621 min read Field GuideAir handling unit (AHU) components and operation field guideWhat every section of an air handler does, in the order the air hits it: mixing box, filters, coils, condensate, fan, and the controls that tie it together.Air Handling UnitAHU ComponentsCooling Coil Jun 27, 202621 min read Field GuideAir curtain and door heater field guide for commercial HVACMatch the unit to the door width, mount it tight to the header, aim it slightly outward, wire the door switch, and prove the stream reaches the floor.Air CurtainsAir DoorsAMCA 220 Jun 27, 202621 min read Field GuideGeothermal heat pump field guide: loop, flow, and commissioningInstall and commission a ground-source heat pump: pick the loop, size it to the soil, fuse the pipe, purge the air, set the flow, and prove the numbers at startup.GeothermalGround Source Heat PumpWater Source Heat Pump Jun 26, 202621 min read Field GuideVRF and VRV system commissioning and startup field guideBraze under nitrogen, pull a deep vacuum, weigh in the calculated charge, auto-address the controls, run the test mode, and file the startup record the warranty needs.VRF CommissioningVRVRefrigerant Charge Jun 26, 202621 min read Field GuideVAV box commissioning and airflow field guide for HVACSet the min and max airflow, calibrate the flow sensor to the hood, prove the reheat sequence, and document the box the engineer accepts.VAV CommissioningAirflow SetpointsGuideline 36 Jun 26, 202621 min read Field GuideSteam heating and trap commissioning field guide for HVACUnderstand how a steam system moves heat, then commission and survey the steam traps that pass condensate, hold the steam, clear the air, and keep the system from waterlogging or hammering.Steam HeatingSteam TrapsCondensate Return Jun 26, 202621 min read Field GuideSplit-system AC and heat pump install field guideInstall a matched AHRI pair, braze the lineset under flowing nitrogen, pressure test and pull a deep vacuum, then weigh in and verify the charge by subcooling and superheat.Split SystemLineset InstallCondenser Jun 26, 202621 min read Field GuideSheet metal duct fabrication and installation field guideBuild the duct to its pressure class, pick the seam and the joint for the static, seal it to the seal class, support it on the SMACNA spacing, and prove the leakage in the field.Duct ConstructionSMACNAPressure Class Jun 26, 202621 min read Field GuideRooftop unit (RTU) installation and startup field guideSet the curb level and watertight, rig the unit, trap the condensate, check rotation, verify the charge and airflow, set the gas temperature rise, and commission it on paper.Rooftop UnitRTU StartupPackaged Unit Jun 26, 202621 min read Field GuideRefrigerant piping line sizing and design field guideSize the suction, liquid, and discharge lines for low pressure drop and enough velocity to return the oil, then trap and lift them so the compressor never runs dry.Refrigerant PipingLine SizingSuction Line Jun 26, 202621 min read Field GuideRefrigerant leak detection and recovery field guide for HVACFind the leak with a detector, bubbles, dye, or a nitrogen standing pressure test, recover the charge instead of venting it, braze under nitrogen, pull a deep vacuum, and document it the way 608 wants.Refrigerant LeakLeak DetectionRecovery Jun 26, 202621 min read Field GuideRefrigerant charging field guide: superheat and subcoolingCharge by superheat on a fixed orifice and by subcooling on a TXV, read both numbers together to diagnose the charge, and record what proves it.Refrigerant ChargingSuperheatSubcooling Jun 26, 202621 min read Field GuideMakeup air unit and commercial kitchen ventilation balanceReplace the hood exhaust, hold the kitchen slightly negative to the dining room, temper the supply, interlock the fans, and prove the balance with a gauge.Makeup Air UnitCommercial Kitchen VentilationIMC 508 Jun 26, 202621 min read Field GuideKitchen hood fire suppression semi-annual service guideInspect the wet-chemical system, replace the links, prove the nozzles still aim at the appliances, test actuation and the gas trip, and tag what you found.Hood SuppressionWet ChemicalUL 300 Jun 26, 202621 min read Field GuideHydronic system balancing field guide for HVACSet the flow at every coil to design GPM, balance the circuits proportionally, trim the pump, hold the delta-T, and write the report the engineer signs.Hydronic BalancingChilled WaterBalancing Valve Jun 26, 202621 min read Field GuideHydronic pump installation and replacement field guide for HVACSize the pump to the duty point, set the suction piping so it does not cavitate, align the coupling, flush the loop before it runs, prove rotation, and start it without wiping the seal.Hydronic PumpCirculatorNPSH Jun 26, 202621 min read Field GuideHydronic make-up water and glycol treatment field guide for HVACFeed the loop without corroding it, get the air out, give the water room to expand, set the glycol for the cold, and treat the water so the system lasts.Hydronic Water TreatmentGlycolExpansion Tank Jun 26, 202621 min read Field GuideHumidification and dehumidification control field guide for HVACControl dew point instead of relative humidity, pick the right humidifier and dehumidifier, stop the CRACs from fighting, and commission the loop so it holds the band without burning energy.Humidity ControlDew PointASHRAE TC 9.9 Jun 26, 202621 min read Field GuideFan coil unit (FCU) installation and commissioning field guide for HVACHang the FCU, flush and balance the water, set the airflow, prove the condensate drain and overflow, stroke the valve, and write the start-up report.Fan Coil UnitFCU CommissioningCondensate Drain Jun 26, 202621 min read Field GuideEnergy recovery ventilator (ERV) commissioning field guide for HVACBalance the outdoor and exhaust airflows, set the frost and economizer bypass, measure the temperatures across the device, and prove the effectiveness against the AHRI 1060 rating.Energy Recovery VentilatorERV CommissioningAHRI 1060 Jun 26, 202621 min read Field GuideEconomizer and demand-control ventilation commissioning field guide for HVACDrive the economizer through its modes, set the high-limit and minimum outside air, calibrate the sensors, and commission DCV so the free cooling actually saves energy.Air-Side EconomizerDemand-Control VentilationASHRAE 90.1 Jun 26, 202621 min read Field GuideDuctless mini-split and multi-zone heat pump install field guideSet the indoor heads, run and flare the lineset to torque, evacuate deep, add charge for the line over the factory length, and prove every zone drains and runs.Mini-SplitDuctlessMulti-Zone Jun 26, 202621 min read Field GuideDuct design and friction rate field guide with ACCA Manual DRun Manual J to S to D in order, set the friction rate from available static and total effective length, size every trunk and branch to it, and verify the airflow in the field.Manual DFriction RateDuct Design Jun 26, 202621 min read Field GuideCooling tower commissioning and water treatment field guideProve the tower makes its approach to the wet-bulb, hold the cycles of concentration, and stand up the water management plan that keeps it from scaling and from growing Legionella.Cooling TowerWater TreatmentASHRAE 188 Jun 26, 202621 min read Field GuideCooling and heating load calculation field guide with ACCA Manual JRun a room-by-room Manual J load before you pick equipment, use the 1 percent and 99 percent design conditions, keep sensible and latent separate, and size to the answer instead of the square-feet-per-ton habit.Manual JLoad CalculationSensible and Latent Jun 26, 202621 min read Field GuideCondensate drain and trap management field guide for HVACTrap the drain to beat the static, slope the line, protect the space with a secondary pan and float, pump where gravity will not, keep the line clear, and dispose of the water by code.Condensate DrainCondensate TrapDrain Pan Float Switch Jun 26, 202621 min read Field GuideCommercial exhaust fan and ventilation field guide for HVACSet the code exhaust rate, give the air a way back in, pick the right fan, terminate it away from the intake, and prove the pressure with a gauge.Exhaust VentilationParking Garage VentilationASHRAE 62.1 Jun 26, 202621 min read Field GuideChiller plant startup and commissioning field guideGet the water, power, and controls ready, let the factory tech make the first start the warranty requires, then prove the chiller makes its tons and its kW per ton at design conditions.Chiller CommissioningChilled Water PlantFactory Startup Jun 26, 202621 min read Field GuideChilled beam commissioning field guide: active and passiveActive and passive beams, the warm-water dew point margin, the DOAS pairing, and the condensation test that proves the coil stays dry.Chilled BeamsActive Chilled BeamCommissioning Jun 26, 202621 min read Field GuideBoiler startup and commissioning field guideGet the water side clean and treated, fire the burner and tune the combustion, then prove the limits, the low-water cutoff, and the relief valve before the boiler ever runs unattended.Boiler CommissioningLow Water CutoffCombustion Tuning Jun 26, 202621 min read Field GuideAir filtration, MERV ratings, and indoor air quality field guide for HVACMatch the MERV to the application, check the static before you upsize, seal the filter against bypass, and change it on the pressure drop instead of the calendar.MERV RatingAir FiltrationIndoor Air Quality Jun 26, 202621 min read Field GuideAir balancing and TAB report field guide for HVACRun the TAB sequence in order, set total air first, balance the branches proportionally, prove building pressure, and write the report the engineer signs.Air BalancingTest Adjust BalanceTAB Report Jun 26, 202621 min read Direct AnswerExternal static pressure field guide for HVAC techniciansMeasure total external static pressure, read it against the blower table, split supply from return to find the restriction, and record the airflow that proves the fix.External Static PressureTotal External Static PressureAirflow Jun 26, 202620 min read

Browse every HVAC question, answered

HVAC calculators

ACH to CFM calculatorFind the airflow for a target air change rate: CFM = room volume x ACH / 60, from floor area and ceiling height.Ventilation rate calculatorFind the breathing-zone outdoor air a space needs: Vbz = Rp x Pz + Ra x Az.Tons to BTU calculatorConvert a cooling load to tons of refrigeration: tons = BTU per hour divided by 12,000.Dew point calculatorFind the dew point from air temperature and relative humidity, and the surface temperature condensation forms at.Duct equivalent diameterConvert a rectangular duct to its equal-friction round diameter: De = 1.30 x (a x b)^0.625 / (a + b)^0.250.Affinity laws calculatorScale fan or pump flow, pressure, and power for a speed change using the affinity laws: flow with speed, pressure with the square, power with the cube.Duct airflow calculatorSolve duct airflow and velocity from the duct size using continuity (Q = V x A): enter a round or rectangular duct and either the CFM or the velocity, and get the other.Hydronic load calculatorFind the heat load of a hydronic loop from flow and temperature difference: BTU/hr = GPM x 500 x delta-T, and tons = GPM x delta-T / 24.Mixed air temp calculatorFind the mixed air temperature from the outdoor and return temps and the outdoor-air percentage.NPSH available calculatorFind the net positive suction head available to a pump: NPSHa = atmospheric + static - vapor pressure - friction head.Pump BHP calculatorFind pump brake horsepower from flow and head: BHP = (gpm x head x specific gravity) / (3960 x efficiency).Sensible heat calculatorFind the sensible heat an airstream carries: BTU/hr = 1.08 x CFM x the temperature difference.

HVAC readiness checks

Cold storage readinessA 2 minute check on whether your refrigerated warehouse handles the floor heave, vapor drive, and ammonia risk a walk-in never faces, before the slab cracks or a leak shuts you down.Succession & exit readinessA 2 minute check on whether your business is built to transfer for real value, before the day you want out arrives and you find out it is worth less than you hoped.EPA 608 practice testTen questions across the Core section and all four certification types, the way the real EPA 608 exam splits the work.HVAC Cx readinessA 2 minute check on whether an HVAC system will actually pass commissioning and run as designed, before the Cx agent and the owner find the problems.IAQ monitoring readinessA 2 minute check on whether your IAQ monitoring uses good sensors, watches the right things, and triggers a real response, or just shows numbers.NFPA 96 grease exhaust readinessA 2-minute check on whether the grease path, its fire protection, and the records are actually ready before the fire marshal walks it.Predictive maintenance checkA 2 minute check on whether your maintenance catches failures developing on the critical equipment, or just reacts after they break.Brazing and evacuation readinessA two-minute check that catches the setup gaps that seed scale, hide leaks, and leave moisture in the system.Retro-commissioning readinessA 2 minute check on whether your existing building is tuned to work as intended, or quietly drifting and wasting energy.RTU startup readinessA 2-minute check that catches the curb, trap, rotation, airflow, charge, and rise gaps before you sign the startup sheet.Warranty management readinessA 2 minute check on whether you track warranties, catch defects before they expire, and triage callbacks, or let the warranty year drift.

Compare HVAC options

Air-side vs water-side economizerAir-side economizer vs Water-side economizer Centrifugal vs ScrewCentrifugal chiller vs Screw chiller Chilled water vs DXChilled water vs DX (direct expansion)Ducted vs mini-splitDucted system vs Ductless mini-split Fire-tube vs water-tubeFire-tube boiler vs Water-tube boiler Gas vs electric furnaceGas furnace vs Electric furnace

HVAC field tools

BlowerCFMAirflow and commissioning checks for HVAC work.GaugeGate DCDuct gauge, leakage, layout, and balance records.Hood Suppression PacketWet-chemical kitchen-hood semi-annual packets with nozzle maps, link clocks, cylinder date checks, signatures, and AHJ exports.ChargeRightOffline superheat and subcooling calculator giving HVAC/R techs a charge PASS, ADD, or RECOVER verdict.Dryer Airflow TestMeasures commercial dryer airflow, static pressure, and lint restriction and prints a condition report.DryPlan S500Sizes air movers and dehumidifiers for water-damage restoration with S500-derived room-by-room math.Walk-In Cooler Gasket FinderMeasures and matches cooler and oven door gaskets and exports a clean parts-desk order list.FryerStat Manometer LogLogs fryer, range, and oven gas manifold WC readings against targets with a before/after proof sheet.LoopWright Radiant DesignerOffline hydronic radiant design from room heat loss to loop lengths, GPM, and circulator match.ShaftLine DCTurns dial readings and machine dimensions into shim and slide moves for millwright shaft alignment.StaticDoctorField app for residential and light-commercial HVAC airside service and install.TitrateSuite DCConverts drops to ppm, sizes loops and pumps, and charges chilled-water loops for water-treatment techs.