Space Ray LTU Series Two Stage - Manual (Page 25)

Form #42710010
May 2013
-23-
B. B. B. B.
INDIRECT VENTING (UNVENTED HEATERS)
INDIRECT VENTING (UNVENTED HEATERS) INDIRECT VENTING (UNVENTED HEATERS) INDIRECT VENTING (UNVENTED HEATERS) — This heater requires ventilation in the building to dilute the
products of combustion and provide fresh air for efficient combustion. Where unvented heaters are used,
gravity or mechanical means shall be provided to supply and exhaust at least 4 CFM per 1,000 Btu/hr input
of installed heaters. Exhaust vents must be located at the highest point above and in the vicinity of the
heaters, and the inlet vents must be located below the level of the heaters. An exhaust hood (Part
#42924000) must be placed on the outlet collar of the draft inducer or on the existing 4” starting collar
when used unvented and must be mounted only in a
must be mounted only in a must be mounted only in a must be mounted only in an n n n upright upright upright upright position position position position and directed towards the reflector and directed towards the reflector and directed towards the reflector and directed towards the reflector
body body body body as shown. as shown. as shown. as shown.
Exhaust Hood
-Required for UNVENTED use-
Draft Inducer
(vertical position)
15.0) AIR FOR COMBUSTION
If indoor combustion air is to be supplied for a tightly enclosed area, one square inch of free area opening shall
be provided below the heater for each 1,000 Btu/hr of heater input. When outside air is used, the opening below
the heater shall be one square inch of free area for each 4,000 Btu/hr of heater input. In contaminated
atmospheres or high humidity areas, optional outside air for combustion is recommended. Adequate clearances
around the air inlet screen must be maintained at all times. In larger open areas of buildings, infiltration
normally is adequate to provide air for combustion.
15.1) DIRECT OUTSIDE AIR FOR COMBUSTION
Outside combustion air should be supplied directly to the heater when the building is subject to negative
pressure, or when contaminants or high humidity are present in the building air. These contaminants include
paints, solvents, corrosive vapors or any other foreign particles that may cause damage to the heater or result in
poor combustion.
Outside combustion air can be brought directly to the heater by a 4” diameter duct less than 50 ft. long or
equivalent (see table in Section C based on selected model and heat exchanger lengths). This is attached to the
4” diameter starting collar. The starting collar is fitted to the top of the control box cabinet after
after after after first removing first removing first removing first removing
and discarding the perforated cover and discarding the perforated cover and discarding the perforated cover and discarding the perforated cover. An approved vent cap must be placed directly on the end of the outside
combustion air inlet pipe. The combustion air inlet should be not less than 3 ft. (0.9m), either vertically or
horizontally, from the flue vent termination. The air intake terminal must be located not less than 1 ft. (30cm)
above grade. It is good installation practice to supply combustion air from the same pressure zone as the vent
outlet. Avoid bringing combustion air to the heater from an attic space. There is no guarantee that adequate
combustion air will be supplied.
In colder climates, where necessary, insulate the outside combustion air duct. Avoid locating the outside
combustion air duct directly above the control box. Provide a capped cleanout T as necessary. In high humidity
applications, the control box should be sealed with silicone sealer.