What an Energy Recovery Wheel Does
A recovery wheel is a rotating core that passes heat and moisture between exhaust air and fresh air. Most houses use a fixed ERV core. Wheels show up on larger equipment.
Bringing outdoor air into a building costs energy, because you then have to heat or cool that air. A recovery wheel reduces the waste. It is a honeycomb rotor in a cassette. Half the wheel sits in the exhaust air, half in the fresh air. The wheel turns slowly. In winter it warms the incoming air with heat that was about to leave. If it is an enthalpy wheel, it moves moisture too, which is what keeps winter air from arriving bone dry or summer air from arriving fully loaded.
Houses versus larger equipment
A typical home ERV uses a fixed plastic or paper core, not a wheel. Wheels are common on commercial rooftop units, some large ventilators, and a few big residential products. If someone told you a standard furnace has a recovery wheel, they are usually pointing at the wrong part. The blower wheel moves air. It does not exchange heat with outdoor air.
What fails, and what not to do
Wheels seize, belts or drives fail, and the seals that separate the two air streams leak. A wheel that is not turning is just a blockage. A wheel that is caked does a poor job of transferring anything. Cleaning and drive work happen with the unit off, by someone who can get the cassette back in without wrecking the seals. Hosing a wheel in place floods the cabinet and can destroy the media.
If the question is really that the house feels stale, start with whether you have an ERV at all, and whether the furnace filter and the returns are doing their jobs. We sort that on a diagnosis instead of assuming a wheel is hiding in the furnace.
Common questions
Does my furnace have an energy recovery wheel?
Probably not. Home furnaces have a blower wheel, which only moves air. Recovery wheels are a ventilation device, more often on larger equipment.
Can I clean the wheel myself?
Do not hose it in place. If a wheel is present and dirty, it needs to be serviced with the unit off so the media and the seals survive.
Does a wheel replace the air conditioner?
No. It only reduces the penalty of ventilation air. The heating and cooling equipment still carries the house load.
