How do you calculate ventilation for gas appliances?

How do you calculate ventilation for gas appliances?

Calculation of air conditioning ducts

As you already know, section HS3 applies mainly to residential buildings. To the interior of the dwellings and to the waste storage rooms, storage rooms, parking lots and garages of the building itself. In buildings of other use to parking lots and garages. For buildings or premises for other uses, the RITE must be applied.

This section has been recently modified. Exactly last June 23 was published on the website of the technical code the updated healthiness document, which includes the modified section HS3. We already talked in a previous article about these modifications. You can consult these changes in this link:  This is the modification of DB HE and DB HS of the CTE.

2. The flow rate shall be the necessary to remove pollutants not directly related to human presence. The condition is satisfied with a minimum flow rate of 1.5 l/s per habitable room in periods of non-occupancy.

The required flow rate shall be 33 l/s for both intake and exhaust.  For the calculation of the hourly renewals we multiply by 3.6 for the change of units (3600s/1000l=m³/h) and divide by the volume of the dwelling in m³. For example, if the dwelling has a volume of 252.50 m³ (101 m²x2.5m): 33 l/s x 3.6 : 252.50 = 0.47 renewals/hour.

Calculation of gas ventilation grilles

As is well known, an HVAC system consists of heating, ventilation and air conditioning. Of these three branches, ventilation is usually overlooked or not given adequate importance because it is typically not as complex as the other two; however, there are times when a good ventilation system is the most economical and efficient option.

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The counterpart to CFM is the static pressure drop that exists upstream and downstream of the ventilation equipment. As with pumping equipment, ventilation equipment must be selected to move the fluid (in this case air) through the circuit (ductwork, for example, but not necessarily) and all the accessories that are installed throughout the ventilation air distribution system. This value is usually given in inches of water column.

There are many elements, in addition to ducts, grilles or dampers, that generate static pressure drop and must be considered when selecting a fan. Wall louvers, filters, bird screens, electric heaters and, of course, any other element that is installed within the air flow and represents an obstacle to circulation must be taken into account.

How to calculate the ventilation of a room

It is important that rooms with natural gas appliances have adequate ventilation. The ventilation grilles must be in perfect condition and it is important to ensure that they are not obstructed, always allowing air to escape.

Natural gas is lighter than air, so it tends to rise and disperse quickly in the atmosphere. For this reason, in the case of natural gas installations, the grille must be close to the ceiling.

If we glaze the terrace or clothesline, we will have to put new vents to ensure our safety. Remember that in the inspection of your natural gas installation, the authorized technician will check, among other things, the state of the vents so that the gas does not concentrate in the house if there is a bad combustion.

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Ventilation ducts

Ventilation grilles are the terminal elements of ventilation and air renewal systems. We find grilles in the supply circuit, designed to blow air into a room, and grilles in the return or extraction circuit, designed to collect the air inside the room to send it to the outside.

In exhaust systems (or return) grilles can be found: attached to ducts, in the false ceiling (if ventilation is done by plenum), or attached to walls if the ventilation is direct.

In the case of the CTE in its Basic Document HS 3 [Table 4.1] defines how to calculate the effective area of the ventilation openings of each room in cm2. This must be at least the largest of those obtained by the following formulas: