Heating and Heat Disbribution

Installation

The location of the furnace should take into account ease of access for future maintenance and eventual replacement at some date. A more central location makes for moving air through shorter duct runs to all areas of the house.

Duct runs should be in accordance with the design and completed as smooth as possible with minimum use of elbows and fitting. Each 90-degree elbow adds as much resistance to airflow as 10 feet of straight duct.

It is a good idea to seal all ductwork joints with paint on duct sealer or foil type tape. Note that "duct tape" (the gray material type) is not a very good product for sealing heating ducts. Over time, under heat, the solvents disburse from the glue and the tape falls off. Sealing ducts insures that air gets to its intended location rather than leaking out along the way.

Balancing dampers should be installed in all branch duct runs, ideally just after the main trunk. Balancing dampers allow for the adjustment of airflow to all areas of the house. Dampers are especially important in two story homes, which need to adjust airflow volumes between the main and second floor each winter and summer for the different requirements of heating and air conditioning.

Commissioning

Commissioning, or confirmation of the correct operation of the heating and ductwork distribution system in accordance with the design, is rarely done on new homes in Manitoba. As most homeowners do not realize the value of commissioning, they're not willing to pay their contractor for it.

A short system commissioning procedure will identify obvious problems for correction before they become a comfort complaint requiring a service call.

Once the entire system is installed and operational, a system of checks and adjustments needs to be done to bring the installed heating and distribution system into compliance with the original design. HRAI offers a training course for commissioning residential heating systems in which contractors learn all the detailed quality checking procedures from confirming gas pressures to balancing air flows.

Commissioning can be as simple as measuring air flows on a room by room basis and adjusting them to meet the design requirements. If the design calls for 25 cfm to be delivered by the bedroom floor grill and it measured to only be delivering 10 cfm, it will result in a cold bedroom in the winter months. One of the simplest methods of measuring relative air flow is with a garbage bag. By holding a garbage bag over an air supply grill and timing how long it takes to fill up with air, a rough approximation of air flow can be calculated. Experience has shown that major problems are quickly identified for correction when one supply grill fills the bag in three seconds and the next takes 12 seconds.