For newcomers to the custom channel, either as fledgling system designers or installers, integrating automation controllers with HVAC can be the most intimidating new discipline to master. While it isn't overly complex, it's far enough removed from the audio and video that's near and dear to us all to seem like a whole different world.

While a thorough overview of HVAC, which refers to Heating, Ventilation, and Air Conditioning Systems, and its integration is a little beyond the scope of this column, for integrator who are just beginning to tackle controlling their client's HVAC systems, here are some bits of sage advice to help smooth out the learning curve.

Study, Study, Study!

The fact that HVAC isn't really that complex means that with some applied effort, it's possible to become an expert on the subject. In addition to the necessity of knowing how HVAC works in order to be able to know how to control it, being able to effectively communicate the automation's requirements will go a long way to smooth out the integrator's professional relationship with the mechanical contractor.

In addition to vendor specific training, as well as CEDIA's invaluable course on HVAC integration (ESD322: Subsystems HVAC in the CEDIA course guide), there are a plethora of free online resources that offer, at the very least, a good grounding in the basics of how HVAC systems work. HVAC For Beginners is one good introduction to the subject.

Memorize the Small but Important Details

While it's typical that either the electrician or the mechanical guy will drop the lines for the home's thermostats and temperature sensors, on a home automation project, it's entirely probable that the integrators' installers will be the ones doing so. The standard on-wall height for mounting thermostats and temperature sensors is 60-inches (150 centimetres) from the floor. There are two reasons why: first, higher or lower mountings will give less accurate temperature readings. Second, a thermostat that is higher or lower won't be as convenient for people of average height to read and adjust.

Another important detail is the proper location to install slab sensors for in-floor heating. In the case of in-floor heating that's encased in concrete slab, the mechanical contractor installs metal conduit into the slab for the placement of the sensors. That way, if one fails (and they sometimes do), it can be easily fished out and replaced without needing a jackhammer. In that instance, sensor location has already been decided for the integrator.

In the case of sub floor heating, where the heating pipes are run beneath the floor boards, integrators need to run their lines to the heating location, and mount the slab sensor equidistant from the heating pipes. Too close to a pipe, and the temperature reading will be inaccurately high.

Know the Resistance of Your Temperature Sensors

Ideally, the integrator should be specifying both the thermostats and the temperature sensors that their automation vendor either sells or recommends. Never, under any circumstance, mix and match units from two different brands unless you know their complete specifications and have tested them together in the office.

The reason why is that temperature sensors are electrical devices and have resistance, and that can vary from brand to brand. Many readily available temperature sensors have a resistance of 10 kΩ, while others can be as much as 15 kΩ or as little as 100 Ω. Automation thermostats with inputs for remote sensors are calibrated based on a known, fixed resistance. Input from a sensor with resistance that's as much as 10 times greater or lesser will mean grossly inadequate readings, and an HVAC system that doesn't work.

Understand Airflow

An important part of designing a killer cinema or media room is allowing for adequate airflow. A room full of people watching football means greater occupation density than an average room, and can create a close, overly warm, uncomfortable atmosphere. In order to get the HVAC needs met from the mechanical contractor, integrators need to speak their language. That means they need to be conversant with CFM (cubic feet-per-minute), BTU's (British Thermal Units) and Tons of Cooling. HVAC installers will generally want to know how many Tons of Cooling are needed, so after calculating the total heat load in BTUs in the room, it needs to be expressed in Tons of Cooling. The easy part is that 1 Ton of Cooling = 12,000 BTU. Fortunately, there are plenty of online reference sites to help determine total BTUs. One good calculator is this one from the Association of Home Appliance Manufacturers.

HVAC integration isn't rocket science. In fact, it's akin to baking bread: if you don't know how, it's mystifying. If you do know, it's so simple, it becomes second nature. There's nothing to fear about HVAC. Put in some solid time studying the fundamentals, and it will become just one more area of mastery for your integration company.

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