There are many pieces of advice offered, on a regular basis, to homeowners regarding the desire to prolong the life of HVAC units. Though simple, many of these tips do have merit can be very helpful in minimizing the strain, or the load put on older HVAC systems. For instance, it is often recommended that a homeowner:

• Have the system inspected annually
• Regularly clean air ducts
• Adjusting thermostat settings on peak hot and cold days to reduce run time
• Install insulation and window coverings to better trap heating and cooling

They do often mention room temperature control. However, while thermostat settings can be a contributing factor to HVAC systems being run harder than they need to be, there is another control method not often mentioned — relative humidity.
Relative humidity is the misunderstood cousin of dry bulb temperature or ambient temperature. Relative humidity and is often over looked in residential settings. However, controlling units to maintain the desired relative humidity and the desired ambient temperatures is truly the very best way to maximize the efficiency of a residential HVAC system. It is also a great way to ensure the system is not being overworked, thereby extending its lifespan.

On those hot muggy days, when relative humidity is in the upper 70s outdoors, air-conditioned spaces can feel cold and clammy. This cold clammy feeling is a result of the air being supplied to the space. Not only is it conditioned and cold, it is also laden with water. How can this be avoided? In some models there is a function for controlling relative humidity. This can be used to set back the condensing unit, while speeding up the fan of the indoor unit. This causes more air to pass over the cooling coil, and therefore dries the air before it is supplied to the spaces. Some units actually have re-heat or hot gas bypass functions that allow the air being cooled to be heated up slightly, to further dry it before it is supplied to the space. This level of control minimizes wear and tear on HVAC system, lowers energy bills, and ensures a more comfortable indoor environment.

What is needed for this level of control? A relative humidity sensor. If your system is not already outfitted with such a control, they can often be retrofitted. The folks at SRP controls offer a wide variety of duct mounted relative humidity sensors that can be installed on existing systems.