Roberts Gorden CRV-B-8, CRV-B-6, CRV-B-2, CRV-B-4 Selecting the Burners, Radiant Distribution

CRV-SERIES DESIGN MANUAL

EXAMPLE 2:

Given a building with a calculated heat loss of 500,000 Btu/h, what is the installed capac- ity required of a CRV-Series system mounted at 50' (15 m)?

CORAYVAC® Installed Capacity = Heat Loss x Radiant Adjustment x Height Adjustment.

For CORAYVAC® systems, a .80 radiant adjust- ment factor is used.

The height adjustment is 1% per foot over 20' (3% per meter over 6 meters), or 1.30.

∴CORAYVAC® Installed Capacity = 500,000 (Btu/h) x .80 x 1.30 = 520,000 (Btu/h).

Note in Example 2, if equipment had been convention- ally sized based on thermal output only, a nearly iden- tical input requirement would result. For mounting heights above 60' (18 m), no further correction is gen- erally necessary if the floor level radiant intensity is sufficient to establish a reserve capacity (hence, radi- ant comfort), and the heat loss

requirement is satisfied based on thermal output.

Due to the complexity of installations with mounting heights over 60' (18 m), it is advisable to contact Rob- erts-Gordon for further information regarding the spe- cific application.

4.3 Selecting the Burners

The number of burners and input for each must be specified in the design layout. The following factors should be considered when selecting burner input:

•Heat gain and distribution required.

•Mounting height.

•Flow loading restrictions.

•Length of radiant branches.

•Distance required between burners.

•Desired radiation intensity.

In general, lower burner inputs can be used for lower mounting heights and where lower heat gains are required. Higher burner inputs are used primarily with higher mounting heights and where high heat gain is required.

The number of burners required can be calculated by dividing the input rating of the selected sizes into the

calculated CRV-Series system required installed capacity.

4.4 Radiant Distribution

Radiant heat distribution at occupant level must be considered in the burner and design selection process.

Distribution of heat between radiant branches at floor level is more critical at the perimeter of buildings. This is where the heat loss is highest. Therefore, it may be possible to combine different applications of distribu- tion within the same building. The following figures show three different applications of rules to determine distribution.

4.4.1 Radiant Distribution (Average Coverage)

The aim of this distribution is to provide average or lighter than average radiant intensity and works well for general building heating. See Page 11, Figure 11. The distance between radiant branches can vary between 2.5 to 4 (or more) times the mounting height.

This distribution is commonly used in applications such as warehouses and lower heat loss areas of a building.

Lighter coverage can be used in areas where occu- pant traffic is low.

4.4.2 Radiant Distribution (Increased Coverage)

The aim of this distribution is to provide continuous radiant intensity. See Page 11, Figure 12. The distance between radiant branches is about 2 times the mounting height.

This distribution is commonly used in areas bordering high heat loss areas or areas requiring increased radi- ant intensity to achieve occupant comfort.

4.4.3 Radiant Distribution (Heavy Coverage)

The aim of this distribution is to provide increased radi- ant intensity in areas that range from sedentary work to spot heating for loading docks. See Page 11, Figure 13. The y dimensions in the diagram is the height above floor level where overlap of the radiant output will occur.

In practice, y = 6' (1.83 m) is commonly used in areas where occupant comfort doing sedentary work is an important factor. In loading bays, spot heating and areas of high heat loss, the horizontal distance (x) between branches can be as little as 0.5 times the mounting height.

10