The effect of the inverter-driven mini-split ductless system has been profound; since its arrival on America’s shores decades ago, the mini-split inverter system has seen double-digit growth in all sectors.
Not only though, have the sales reflected the ease of installation and low capital cost afforded by these ductless (and ducted) systems, but indeed the homeowner, well-researched on the internet, has discovered that inverter systems are quiet and energy-efficient.
Challenge:
Mini-split systems don’t offer a solution
All mini-split (DFS) manufacturers use flare connections which can leak if not done properly
Good things for the HVAC industry, but the mini-splits don’t answer every question and frankly, for the vast number of homes with existing ductwork, they don’t offer a reasonable solution to heating and cooling with an inverter system.
And though a mini-split installation may generally involve less labor, not all goes flawlessly. All mini-split (DFS) manufacturers use flare connections which can leak if not done properly, and all use a 4-wire interconnecting wire to power the indoor units from the outdoor unit, also allowing communication between the indoor and outdoor units.
Communication error code
That DC communication is predicated upon an excellent ground; a DC circuit with a weak ground will not flow current easily and will create a “communication error” code.
Unbeknownst to an installer, neutrals and grounds can be mixed in the panel which can back feed voltage on a ground which, if used as a ground for the signal, can create a frustratingly difficult error to diagnose and remedy.
Inverter drive
Wouldn’t it be great if all of the benefits of an inverter system: the very soft start (no contactor; DC voltage is gradually fed to the condenser fan motor and compressor), quiet operation, energy efficiency, ability to load balance, and more…were manufactured in a system designed to be used with “standard” wiring and “regular” ductwork?
Well, such a product is indeed currently available and, though a brand can’t be mentioned specifically, the Big Three and others are producing what are essentially standard unitary systems, but with an inverter drive for the compressor.
Hybrid IDS system
The hybrid IDS system looks small like a regular outdoor condensing unit with a small condensing coil surface
At first appearance, the hybrid IDS system looks small, because it is. It looks like a regular outdoor condensing unit, but unlike the >16 SEER systems, the condensing coil surface is small, because the energy efficiency is found in reducing the running speed of the compressor (variable-speed DC compressors are used).
Manufacturers using fixed-speed compressors have no option to find SEER numbers, but to reduce compressor size (reduce running amperage) and increase heat transfer area (condenser coil/unit size).
Hybrid inverter system Benefits
Because it starts softly, the system avoids amperage inrush loads common to an “on-off” system. Additionally, the inverter driven ducted, the unitary system is consequently very quiet without the full-load hum of a compressor on the start or condenser fan motor at full speed.
There are other benefits of a hybrid inverter system too, besides the soft start and sound reduction. Because it is essentially a “unitary system”, the connections are common to braze connections made to a standard indoor, ducted coil (R410a rated).
Mini-split vs. hybrid connections
Mini-split inverter systems use mechanical connections because a standard filter-drier cannot be used (with the EEV in the outdoor unit, the liquid line becomes a low-pressure saturated liquid; a filter drier becomes a restriction).
In the hybrid system a standard TEV regulates the indoor coil during cooling, making the liquid line “standard” and in which a liquid line filter drier is used (bi flow for ht. pump).
Fewer ground issues, dual-fuel application
IDS system uses a standard 24v. control means any thermostat to be used and dual-fuel application can be done seamlessly
Not only is the piping distinctly different between the mini-split inverter and the ducted inverter system, but so is the wiring. A very traditional 240v. supplies the outdoor unit and a 24v. the circuit controls it (applicable to nearly all 24v. thermostats) making the ducted inverter system far less subject to ground issues at the panel.
And because the IDS system uses a standard 24v. control, unlike the DFS control circuit (DC communicating), which means not only can nearly any thermostat be used but used as a dual-fuel application can be done seamlessly with existing technology and existing duct systems.
Inverter technology
Users have access to this inverter technology and, while it may seem intimidating at first, understand that the hybrid systems offer that inverter technology without an investment in training. The same tools, muscle memory, knowledge, and comfort level a technician uses installing a fixed speed system are all that are employed when installing a hybrid system; same piping and brazing techniques, same familiar wiring and controls.
Inverter systems are the technology of the future for the HVAC industry providing very quiet, very energy-efficient systems that can be applied to a regular ducted system with regular tools and with regular wiring and thermostats.
