You're viewing our full library of technical Q&As. You can also view them broken down into the categories of Commercial HVACR, Residential HVACR, or General HVACR . You can also ask a question of your own.

Full Technical Q&A Library

Tiki bars and big screen TVs in the pool area
Before construction is started pool area design conflicts need to be resolved Read it.

Avoiding condensation inside of indoor pool walls
Special software or an engineering review is required Read it.

Indoor pools are out of Manual J's league
Indoor pools require Manual N design practices Read it.

Indoor pool HVAC system design values
Many pool designvalues are based on how the pool is used and operated. Read it.

When to Vent
Make sure your condensate drains are working properly Read it.

QI Charging Documentation Requirements
Know what is needed to properly document a system is properly charged Read it.

Geo-thermal Heat Pump Information
Where to find geo-thermal heat pump information Read it.

How do you know if a bladder expansion tank is working properly?
A thump with the knuckle as you pass by can save callbacks Read it.

What is a VAV?
How VAV's work in brief Read it.

What is a proportional air Balance?
Proportional air balance defined Read it.

Flow-Hoods are not always accurate
Using an AMD for measuring airflow at the diffusers accurately Read it.

Code requirements for room operating temperatures or temperature differentials between rooms
When homeowners adjust the thermostat, they expect to walk away and forget it, knowing the entire living space will be reasonably close to the desired temperature. ACCA Manuals provide HVAC contractors with the guidance needed to make that happen. Read it.

Code requirements for adjusting gas burners for high altitude locations
National Fuel Gas Code (NFGC) ANSI Z223.1 recommendations Read it.

Calculating air density at high altitudes
Formula and table for calculating air density. Read it.

Something to check out on retrofits with bypass ducts
Old Manual D designs are obsolete when it comes to bypass ducts. Read it.

High Static pressure now what?
Advice on what to do when a duct has a high static pressure measurement. Read it.

Updated flex duct friction rate chart
The new Manual D provides the information you will need to evaluate duct. Read it.

R-410A system space requirements
Unanticipated installation expenses can be minimized by first determining if the required clearance is available. Read it.

Existing R-22 indoor coils and R-410A
It is recommended that contractors proceed with caution because many older coils were not designed for the R-410A equipment’s higher operating pressures. Read it.

Drop in Refrigerant
Contractors are encouraged to not use any refrigerant unless it is endorsed by the compressor or equipment manufacturer for use in the specified equipment. Read it.

Refrigerant KDD5?
A new drop in refrigerant for R-22 systems Read it.

Can't pull a vacuum
Vacuum gauge leak problem Read it.

Federal Regs on Upgrading Older HVAC Systems
Mismatched heat pumps and upgrading older model HVAC systems. Read it.

J8 Fireplace
The fireplace calculation in Manual J 8th edition explained. Read it.

# on my J Speedsheet
Common user problems with the J speedsheet Read it.

Thermal Mass
Calculating thermal mass in a Manual J procedure. Read it.

Sensible Heat Ratio (SHR)
The default sensible heat ratio is not always the right one. Read it.

CT Formula a N Mystery
Calculating cavity temperature (CT) values. Read it.

Using the N-5 AE Speedsheet
Solving a frequent issue with the ACCA Manual N speedsheet. Read it.

Using Manual N Abridged Edition
ACCA's Manual N 5th edition includes an "abridged edition" procedure that can only be used under certain circumstances. Read it.

What load calculation software should I purchase?
Find the tool you need to use all of the Manual J8 applications. Read it.

Blown in Foam R Value
Design guidance for structures with blown in foam insulation Read it.

Manual J for Replacements
Q&A for Consumers: explains the importance of Manual J heating and cooling load calculations. Read it.

Bypass Duct Design
It's time to update your bypass duct designs. Here's guidance on variable air volume (VAV) duct designs. Read it.

Flex Duct Friction Loss Calculations
How to calculate friction loss on already installed flex systems. Read it.

Intermittent Burned Wire
Looking for an intermittent electrical problem in the compressor start / run circuit. Read it.

High Duct Static Pressure Found
What to check and do when the duct static pressure is running higher than the design value. Read it.

A1/A2, and Slope in Manual D Group 12 Transitions
An explanation of terms used in Manual D fittings Read it.

Balancing Registers
Advice on adjusting room supply registers. Read it.

Combustion Testing Equipment
A list of combustion testing equipment that is available. Read it.

Traversing to Measure Airflow
Brief description of what traversing is and how it is used to determine airflow Read it.

Pressure Matching Method
Brief description of pressure matching method for testing duct leakage. Read it.

Line Sets for 410A Systems
Replacing line sets when replacing R-22 systems with R-410A. Read it.

Avoid an Oil Crisis When Changing Refrigerant Types
A brief discussion of oil differences in R-22 and R-410A systems. Read it.

Converting R-22 Systems to R410A
Converting from R-22 to R-410A is not a simple matter. Read it.

The Future of R-22
R-22 is not banned, but production and availability will continue to decrease. Read it.

Manual D Duct Troubleshooting
Manual D duct troubleshooting for "losing air or supply air temperature drop /increase in the duct”. Read it.

Just Say No to Pan Joists
Use of pan joists for return ducts is not recommended. Read it.

Temperature Difference Between Rooms
Temperature differences between rooms in a dwelling. Read it.

Coil Cleaning Procedures
Advice for cleaning indoor and outdoor coils. Read it.

Cracked Heat Exchangers
What to do when a cracked heat exchanger is discovered, and why it matters. Read it.

Latest EPA Leakage Rates
Find and use the latest EPA leakage rates under Section 608. Read it.

Commercial Kitchen Hoods in a Home
Design considerations for the level of exhaust ventilation must be addressed. Read it.

Handling Used HVACR Oils
Removing or changing refrigerant oils. Read it.

Fresh air make up
Installation requirements for fresh air dampers on commercial buildings are a local issue. Read it.

Evaporator Freeze Up
Causes for residential and commercial evaporator coil freeze ups and some remedies. Read it.

Carbon Credits for HVAC
There currently is no way for an HVAC contractor to trade carbon credits for profit. Read it.

Caution! Shipping Refrigeration
Caution requirements for shipping refrigeration materials. Read it.

Shutting Off Unsafe Equipment
Shutting off unsafe equipment and the legal issues that arise. Read it.

Removing or Adding Load
Sizing the correct unit when customers raise questions about costs. Read it.

Heat Pump Troubleshooting
Newly installed heat pump system in an attic shows excessive sweating of the air handler. Read it.

Leaking Vacuum Gauges
Read it.

Alternative Drain Lines
Bearing the costs of stolen materials, are there any alternatives. Read it.

Heater Troubleshooting
Troubleshooting a unit heater with no visible signs of damage. Read it.

Evaporator Problems in High Humidity
An evaporator coil freezes up every time there is high humidity. Read it.

Suspected Burned Out Compressors
What to do when a compressor won't start. Read it.

CFM Levels and Installations
Applying correct level of CFM's when installing equipment. Read it.

Matching SEER Requirements
Matching SEER requirements when replacing indoor/outdoor equipment. Read it.

One System, Multiple Zone Levels
Requirements when two zone levels are being supplied by one system. Read it.

Refrigerant Replacement
What to do when replacing an unknown refrigerant when the data tag calls for another. Read it.

Kitchen Hood Considerations
Design considerations to be taken to overcome different levels of ventilation. Read it.

Brazing a Refrigeration Line
Setting the regulator pressure for the nitrogen purge when brazing a refrigeration line. Read it.

Charging Blended Refrigerants
How to charge and transfer the new blended refrigerants without altering their composition. Read it.

Fireplaces and Manual J
Fireplaces have considerable impact on heating, but not mch on cooling. Read it.

True Duct Design
Even with a true duct design, technicians must concern themselves with the return side of the system. Read it.

Clean Condenser Coils
The importance of clean coils and how to clean them. Read it.

Nitrogen Sweeps When Brazing
Nitrogen sweeps prevent copper piping from oxidizing. Read it.

EPA Rules Regarding Leak Repairs and Refrigerant Venting
The EPA hasn't changed the rules, just clarified them. Read it.

Diagnosing System Restrictions
Mistaking a restricted system for an undercharged one is common but can be prevented. Read it.

Frost on the Suction Line
Although frost may be normal in some low-temperature systems, it's best to make sure it's not a malfunction. Read it.

Suction Line Accumulators
These devices protect the compressor. Read it.

Crankcase Heaters
Heating the compressor crankcase reduces refrigerant migration and dilution. Read it.

Filter Driers
How to know when a filter drier needs to be changed. Read it.

TXVs for Different Systems
Low- and medium-temperature systems have different TXV requirements from A/C and heat pump applications. Read it.

Evaporator Size
Under- or over-sizing and evaporator can have serious consequences. Read it.

Finding Small Leaks
Small leaks can be frustrating; here's method for finding them. Read it.

Lubricants
Today's refrigerants require different oils from the ones most technicians are familiar with. Read it.

Crankcase Pressure Regulators
In the HVAC business, CPR doesn't mean cardio-pulmonary resuscitation. Read it.

Evaporator Pressure Regulators
EPRs are particularly valuable in refrigeration and in multiple-evaporator systems. Read it.

An Overzealous Salesperson
People are trying to sell customers all kinds of gadgets and fluids they say will improve performance, but they may void the manufacturer's warranty. Read it.

Refrigerant Leaks
Refrigerant leaks must be fixed, but EPA rules allow some time to come up with a solution. Read it.

Using a Sight Glass to Check Charging
Sight glasses on TXV-equipment are useful, but there are other things the technician must do to ensure proper charging. Read it.

The Significance of Subcooling
What subcooling is, how to measure it, and what it tells you about a system. Read it.

Determining the Proper Charge
Use instrumentation to make sure a system is operating properly. Read it.

TXVs
Thermostatic expansion valves are superior feed devices, but costly. Read it.

Customer-Installed Systems
EPA rules allow customers to buy and install HVAC equipment themselves. Read it.

Troubleshooting Mold
A member asks for help diagnosing a mold issue on three registers of a 16-register system. Read it.

You're viewing our full library of technical Q&As. You can also view them broken down into the categories of Commercial HVACR, Residential HVACR, or General HVACR . You can also ask a question of your own.