In our previous HVAC lingo post, I discussed some of the more common types of equipment that our industry offers, this post we will continue to hit some key pieces of equipment that are common in our area and some of the components that are required to make them work. Last, I want to touch bases on ductwork and why it is so important but commonly not done correctly to save on cost but creates the most trouble for your system. Again, I will try and stay out of the weeds and straight to the point, but I have been doing this for the last 20+ years and kind of geek out once I get going. So, I apologize in advance.
Let’s get started.
Ductless (Mini-Spits)
Ductless systems heat and cool a space without using ductwork to move air. They are made up of two main components.
- Outdoor unit (Heat Pump/Condensing unit
- Indoor Unit (Head/Cassette)
The Indoor unit is essentially a compact air handler with a fan and coil that delivers heating and cooling directly into a room. Ductless indoor units typically come in several styles, including:
- Wall mounted cassette. Typically installed close to the ceiling between 8 to 10 feet from the floor. If you go too high up, they will not be as effective.
- Floor mounted cassette. Name can be confusing; the unit is mounted on the wall around 6 inches off the floor.
- Ceiling cassette – linear. Installed flush mount into a level ceiling area, cannot be installed in a vaulted ceiling. Typically installed closer to walls, away from the center of the room. With single direction, air-throw towards the center of the room.
- Ceiling cassette – 4 way. Installed flush mount into a level ceiling area, cannot be installed in a vaulted ceiling. Unit will throw air in 4 different directions. Typically installed in the center of a room.
All the units listed above will require refrigerant lines (line set), electrical/communication wire, and condensate drains to be run between the indoor and outdoor unit. The indoor and outdoor unit’s locations are partially determined by what allows the cleanest and most practical route.
If you are considering a ductless as your primary heat source, it is important to plan for colder conditions. Many environmental factors, especially freezing fog, can reduce heating capacity and make it harder to maintain your thermostat setpoint. Most ductless systems do not have built-in backup heat like a traditional air handler, so a separate backup heat source is recommended. Talk with your comfort advisor about the best option for your home.
Refrigerant pipe (Line Set)
This is copper tubing that connects the indoor and outdoor together, carrying refrigerant back and forth so the system can move heat.
- In heating mode (heat pump) it carries the refrigerant that has picked up heat from the outside air to the indoor unit to be transferred into the air inside your home.
- In cooling mode (air conditioner or heat pump) it carries the refrigerant that has picked up heat from inside your home to the outside, where the outdoor unit releases that heat outdoors.
Communication wire (thermostat wire/stat wire)
This wire carries control signals between the thermostat and HVAC equipment. It’s how the thermostat talks to each system component.
ERV (Energy Recovery Ventilator)
This system does 3 functions simultaneously. It removes stale air from your house, venting it to the outside, pulls fresh air from the outside, bringing it into your home at a balanced rate, preventing negative or positive pressure differences. That’s the ventilation side. The “energy recovery” part happens inside the ERV’s heat/energy exchanger core. The outgoing conditioned air passes through the core next to the incoming fresh air stream. The two air streams do not mix, but energy transfers between them. This helps pre-condition the incoming air, so your HVAC system doesn’t have to work as hard to heat or cool the fresh air you’re bringing in. You are also not wasting all the energy used to condition the air that’s being exhausted. In many situations, an ERV can also help us manage indoor humidity by transferring a portion of moisture along with heat energy, which can improve comfort and reduce energy waste.
HRV (Heat Recovery Ventilator)
HRV is very similar to an ERV in how it ventilates stale air out, fresh air in, with balanced airflow but it transfers heat only, not moisture. In our area, we typically recommend ERVs over HRVs because we’re often focused on maintaining comfortable indoor humidity and overall comfort while ventilating. HRVs can still be a valid option in certain homes and climates, but for most of our customers, an ERV is the better fit.
Whole home humidifier
Whole home Humidifiers can be a great add-on to your HVAC system. Humid air feels warmer, so many people can keep their home at lower temperatures and still feel comfortable. If you have hard wood floors or valuable wood furniture, this is a great way to protect them from our extremely dry High Desert air. They also can provide many health benefits with dry skin, excessive static, and respiratory comfort. Unlike portable units, whole home humidifiers can provide consistent humidity to a larger area.
There are two common Humidifiers that contractors will typically offer in our area:
- Bypass humidifier– usually has a lower upfront cost and a simple, proven design. It uses the HVAC system’s airflow to evaporate water across a replaceable water panel (pad).
Downsides: It may require space for a bypass duct; it’s output is more limited than steam; it typically runs best when the system is operating in heating; many styles use more water because some water flows to the drain while running. Pads also need regular replacement (commonly each heating season, depending on water quality). - Steam humidifier – Steam humidifiers have a higher upfront cost. Part of that cost can be running dedicated electrical power to the unit. Some models use 120V; we typically recommend 240V for greater steam output. A major advantage is control. Many steam humidifiers can call for the blower to run even without a heat call, which can provide steadier humidity. They also typically use only the water needed to make steam to maintain your humidity setpoint, instead of a constant flow-to-drain operation.
Humidifiers can be a great add-on when conditions are right, but anytime we’re adding water to a system, proper installation and water management matters. A comfort consultant should discuss these risks with you and do a thorough inspection of your system to make sure your application is a good fit for your system.
Ok this covers most of the common system lingo, now let’s talk ductwork.
I personally feel that proper sized ductwork is the most important part of an HVAC system and is commonly overlooked in today’s market. I would love to vent all my frustration and tell you why I feel homes are being built with poorly designed ductwork, or equipment is being replaced without any consideration of the existing duct size and how private equity groups are buying up all the heating companies in the area and are more concerned about cost per man hour and maximizing revenue than providing quality work. Also, new codes are being passed that are doing nothing to prevent this from happening. They are more concerned with net 0 homes than requiring properly sized ductwork, that would in truth, save more energy and reduce waste than improperly sized ductwork in a conditioned space will ever save. No, I refuse to vent, even though it’s the V in HVAC. I promised to stay out of the weeds so let’s stick to the lingo.
If you a looking to replace your system and speak to a comfort consultant, they should ask you how your previous system has been working for you, this is us trying to find out if there may be issues with your duct system. If everything has been great and you have no issues and your system is 15+ years old with minimal problems, there are no red flags and wouldn’t normally bring up your ducting. If your system is 6 years old, never worked well, and have comfort concerns in rooms, then we will probably want to explore your ducting a little more.
Here are a couple of tell-tail signs you may have ducting problems.
- Hot or cold rooms. If you have a room that is more than 3 degrees off from your thermostat set point.
- Noisy. If you have replaced your filter and you still hear air moving through the ducts or your indoor unit sounds like it about to lift off.
- High energy bills.
- High maintenance costs.
Here is some Lingo that we would use referring to your ductwork.
Manual D – Industry-standard method for designing residential duct systems. Used to size ducts so the equipment is running at manufactures suggested static pressures and that each room in the house is getting the required BTU’s to maintain set temperature.
Manual J – The industry-standard method for calculating a home’s heating and cooling load (how many BTUs it needs). It accounts for things like square footage, insulation, windows, air leakage, orientation, and local design temperatures so equipment can be sized correctly to your home.
There are two common methods of doing a manual J on a home.
- Block load – Just using total square footage. This is typically done when ductwork is existing and there are no red flags that ducting may be sized incorrectly.
- Room by room – This should be done on all new construction project or existing homes with comfort issues. We size every room in the house, looking at windows, ceiling heights, walls exposed to outside and many other things. This will tell us equipment size and how many BTU’s each room needs. This must be done before manual D can be completed.
Manual S – Equipment selection/sizing uses the Manual J load to choose a system that meets the BTU needs and specifies the airflow (CFM) required for proper performance.
Static Pressure – this is like getting your blood pressure taken at the doctor’s office, it tells us if the ductwork is restrictive. Too high and something will fail eventually. High static pressure will increase energy consumption, reduce system capacity and create excessive duct noise.
Friction Rate – A calculated value used to size ducts—basically how much pressure loss per length of duct is allowed.
Total Effective Length – The equivalent length of a duct run after adding the extra resistance of fittings like elbows and transitions.
CFM – (Cubic feet per minute) A measurement of airflow. How much air your system’s blower moves
Velocity – How fast air moves through a duct. Too high can be noisy, too low can reduce mixing and comfort.
Supply duct – Ductwork that delivers conditioned air to rooms.
Return duct -Ductwork that pulls air back to the HVAC equipment to be filtered and reconditioned.
Plenum – the duct box right at the equipment that distributes air into the duct system.
Trunk line/main trunk – the big main duct that feeds branches.
Branch runs – smaller ducts that feed individual rooms.
Supply vents/supply registers – where heated/cooled air comes out into the room.
Return vents/return grilles – where air is pulled back into the system to be filtered and re-heated or re-cooled. Typically, the biggest grille in your home in a hallway. Well, this is the end of my HVAC blog about our lingo, I apologize if I missed something, there are just so many things to cover. I tried my best with grammar and punctuation; the truth is I am much better at HVAC than I am writing a blog. I have no plans to quit my day job to pursue this, so there is no reason to critique me. Hopefully this will help someone feel a little more informed about our industry when needing to make a decision.
