FRESH AIR - SmartZone Automatic Contrtol with RANCO ETC Outdoor Temperature Sensor

Fresh Air is important to indoor air quality (IAQ). All the way back to Benjamin Franklin’s “air baths” and even much earlier in history, we have had some at least vague understanding of the fact that “stale” indoor air can be bad for us and we need to get some fresh air at least once in a while.

In modern homes, windows, doors, insulation , house wraps, roofing and other materials have imporved drastically in the last 40 years and we how have homes and buildings that are getting tighter and tighter. This means that the air outside stays out and the air inside stays in... which is good for efficiency of heating and cooling systems, but not for air quality and overall health. This is why many parts of the world have “fresh air” requirements, meaning simply that they are required to bring in a prescribed amount of outside air in and mix it with the inside air. In the US, a standard callled ASHRAE 62.2 is followed as a guideline for how much outside air in CFM (Cubic Feet per Minute) needs to be brought in based on occupancy & square footage of the home/building. We are not here to discuss the efficacy of the 62.2 because it has some obvious flaws in its sheer simplicity, we just want to show how to apply this method of fresh air but with one additional VERY IMPORTANT feature. We want to simply disable the automatic intake of outside air WHEN the outside temperature is too high or too low. What is too high or too low? This is going to depend on your application including climate, hvac equipment type, home size, your comfort level etc.

NOW AVAILABLE - Ecojay custom Outdoor Temperature Controller

The use of the RANCO temperature controller is no longer necessary with the SmartZone. We now offer a custom outdoor temperature controller that provides MUCH more functionality specific to the SmartZone Fresh Air controls.

• High & Low Temperature Limits

• Enable/Disable Fresh Air

• “Demand” Fresh Air

• NEW: Temperature-based Economizer

For more info about this new and exiting product, take a look here:
https://zoningsupply.com/buy/outdoor-air-thermostat

If you are considering Fresh Air or Economizer with your SmartZone-4X, you will want this accessory!

The primary reason for this “ADVANCED FEATURE” is to prevent outside air that is extreemly hot or cold from coming into the house automatically. Use the instructions and diagrams below to install this RANCO ETC-212000 Temperature sensor and you will have the ability to control automatically the temperature range that Fresh Air is allowed to operate. For example , you could set the upper limit to 90 deg F and the lower limit to 30 deg F and then SmartZone will only operate fresh air when the outside temperature is between 30 and 90 deg.

Before this Outdoor Temperature Advanced Fresh Air Feature will work, the SmartZone-4X must be set up for FRESH AIR control. Click the button below to see an application note about basic fresh air. NOTE: Fresh-Air setup instructions can also be found in the SmartZone System Guide

Ashrae 62-2 Ventilation (Fresh Air) sizing & calculation

Many homes these days have such tight seals around doors, windows, and even closed-cell foam insulation... they are almost air-tight.  You can think of an old house like an antique metal or wooden ice box where modern homes are more like Yeti coolers.  While this is great for keeping temperatures steady inside the home, it also can trap moisture and toxic gases inside.  Fresh air ventilation is necessary to keep a healthy and efficient home.

But how much fresh air is needed?  If you bring in too much, you will make your HVAC equipment work too hard and loose efficiency.  If not enough fresh air is brought into the home, the air can become humid and allow mold growth or VOCs and other toxins can build up.  Luckily, the national organization ASHRAE has a specific recommendation for the amount of air based on occupancy and square footage of the home.  See table below.

Taken from SmartZone-4X Install Guide

However, this table should not be taken as gospel.  Just like other HVAC calculations and estimations, many factors are not really being taken into account with this rough estimate based on # of bedrooms (occupancy) and square footage.  Some adjustments may be needed based on factors such as climate, ceiling height, other air-leakage, etc.  To comply with 62-2 is the baseline & adjustments can be made in the field by setting run-time.

Learn more about how SmartZone-4X can control fresh air more efficiently than a separate fresh-air controller in the Install Guide