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TEMPCO s.a. 4e ave. N°114, Z.I. des Hauts Sarts, B-4040 Herstal, Belgique. T:(32)04-2649458, F:(32)04-2649476, www.tempco.be, [email protected]
Les photos et caractéristiques présentés dans ce catalogue sont données à titre indicatif et ne sont pas contractuelles.
3.A.01.450-E-100910 page 6/7
13. Failure Mode
The Photohelic
®
circuit design provides certain protection in
the event of a loss of pressure or electrical power. In either
case, both relays will de-energize, returning to their normal
“zero pressure” state. The exceptions to this are models
with center zero ranges. Because the relays on all standard
models are always energized when the indicating (black)
pointer is to the right of their respective set points, the relay
action on loss of pressure will depend on set-point position,
since either of them could be located to the left of zero. As
an example; if the left pointer were set at -2 in. w.c. and
negative pressure was -3 in. w.c., a loss of that pressure
would allow the black pointer to return to the center and
thus cause the low set-point relay to energize.
If the LED should burn out, only the left-lower relay will de-
energize. The right-high relay will react as if pressure were
above its set-point and will remain energized even though
pressure might be below that setting. In this situation, only
termination of electrical power will allow the right-high relay
to de-energize.
MAINTENANCE
Dwyer Photohelic
®
Switch/Gages are precision instruments,
expertly assembled and calibrated at the factory. They
require no lubrication or periodic servicing. If the interior is
protected from dust, dirt corrosive gases and fluids, years of
trouble-free service may be expected. Zero adjustment
should be checked and reset occasionally to maintain accu-
racy. Any repairs necessary to either the Dwyer
Magnehelic® pressure gage or the electronic components
should be performed by a trained instrument mechanic. In
most cases, this is best accomplished by returning the
complete Photohelic
®
Switch/Gage to the Dwyer factory.
117 VOLT LINE
RESET JUMPERS
1/6 HP*
117 VOLT
LOAD
Fig. 9
High-Low Limit Control (Circuit HH)
*NOTE:
For larger motors, use the Photohelic®
in a maintained contact, 117 Volt Control or
Push Button Circuit of the motor starter.
