Despatch RFD Series - Manual (Page 17)

RFD Oven Series Owner’s Manual T HEORY OF O PERATION
Version 1 17
Copyright © 2012 by Despatch Industries.
All rights reserved. No part of the contents of this manual may be reproduced, copied or transmitted in any form or by any
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retrieval systems without the written permission of Despatch Industries, unless for purchaser's personal use.
Fresh Air Damper
Control
Exhaust Damper
Control
3.2. Damper Control
The RFD Series oven includes a manually adjustable fresh air
damper mechanism which controls the flow of fresh air into the
chamber. The fresh air damper control is located on the left side of
the oven (Figure 5
and Figure 6). The oven also includes a
manually adjustable exhaust damper located on the exhaust stack
on top of the oven (Figure 6).
Fresh air and exhaust dampers (Figure 5) control the amount of air
exchanged as well as the oven chamber pressure. The RFD exhaust
damper and fresh air damper are designed to remain slightly open
to allow gases released from processed solvents to escape. In
“closed” position, the dampers are actually slightly open. When the
fresh air damper is closed and the exhaust damper is open, oven
chamber pressure tends toward negative. When the fresh air
damper is open and the exhaust damper is closed, the oven chamber
pressure tends toward positive (Table 1).
A negative oven pressure may draw ambient air into any opening,
causing cool spots to occur. The slightly pressurized chamber
produces the effect of pushing air to the corners of the chamber.
However, too much positive pressure may force hot air or process
vapors out of any openings in the oven into the work area. Ideally,
the fresh air and exhaust dampers should be closed as much as
possible and the oven should be maintained at a neutral or slightly
positive pressure.
Table 1. Damper Positions for Chamber Pressure.
Warning!
Maintain slight positive pressure
to regulate heat.
Too much positive pressure in an
oven can create a high outer skin
temperature as hot air is forced
out through panel joints and
around door seal. High outer skin
temperature could warp the front
of the oven.
Damper Position
Fresh Air Open Closed
Exhaust Closed Open
Chamber Pressure Positive Negative
Figure 5. RFD Fresh Air Damper
Control.
Figure 6. RFD Exhaust Damper
Control.