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Parallax Power Supply L.L.C. Technical Note
ISSUES CONCERNING THE MOUNTING CLEARANCES FOR THE 7300 SERIES POWER CENTERS.
There seems to be some confusion about a statement in the Owner's Manual for the 7300 series power centers. The statement is in the Mounting clearances
portion of the document. The intention of this letter is to clarify the meaning and intent of the statements.
The statement is made that there must be provided a minimum of 22 inches clearance to the front of the converter. Also, that adequate room should be left for
wire routing and fan air intake located in the top and rear of the converter. Another marking on the nameplate label required by UL states that the converter
should not be mounted in zero clearance compartments because overheating and thermal shutdown will result.
As to the issue of the 22-inch clearance to the front of the converter:
This statement was made in reference to the NEC article 551-45(b) exception No 1 pertaining to the AC panelboard section of the converter. Also see the RVIA
handbook page E-66. It simply states that the power center panelboard must have 22 inches of clearance workspace after Installation.
The panelboard is considered exposed where the panelboard face is within 2 inches of the finished surface to which it is mounted . A non-locking decretive
door may be installed in front of the distribution panelboard however the panelboard must be within 2 inches of a finished surface, not including the door
thickness. This is so that the panelboard can be readily accessed when the door is opened, exposing the 22-inch minimum clearance workspace but not allowing
enough room between the panelboard and the door for storage.
As to the issue of the adequate room for wire routing and fan air intake:
Our intent here is to state that there must be enough clearance around the converter to provide adequate intake airflow for cooling the converter system
electronics. Also you must leave enough room for the AC and DC field wiring to be installed. In most cases leaving enough room for the field wiring will assure
adequate air intake clearance. The main concern seems to be about the clearance to the converter exhaust louvers located in the front of the converter when a
decorative door is added over the front of the converter. Because of physical design of the converter the exhaust louvers and the AC panelboard are in the same
plane, hence the added door will not be greater than 2 inches from the louvers because of compliance with NEC 551-45 (b) requirement for the panelboard. This
will restrict to some degree the exhaust airflow.
The only way to attack this problem is through trial and error. The converter must be placed under the clearance-limiting condition then its operation monitored
to verify correct operation. If the converter shuts down due to overheating then the clearance area must be increased to allow proper airflow. The converter has
been tested under completely blocked ventilation conditions and will not become a fire hazard but will not hold up to its full rated output load specifications.
Please keep in mind that operating the converter under restricted air flow conditions will elevate the operating temperatures inside the converter and may reduce
the life expectancy over time. The converter was designed to operate indefinitely at full load @25c (77f) ambient with the ventilation openings open to the
living quarters.
Parallax Power Supply L.L.C. cannot be held liable for poor performance or failures of the converter due to restricted air flow installations.
