System Sensor DH500 - Manual (Page 5)

D500-08-00 5 I56-512-07R
Use a 0.193-inch diameter (#11) drill and add the appropri-
ate number of holes so that the total number of holes
exposed to the air flow in the duct is 10 to 12. Space the
additional holes as evenly as possible over the length of the
tube.
Note: This procedure should only be used in an emer-
gency, and it is not intended as a permanent sub-
stitute for ordering the correct length tubes.
Step 5. Field Wiring
Wiring Installation Guidelines
All wiring must be installed in compliance with the
Canadian Electrical Code and the local codes having juris-
diction. Proper wire gauges should be used. The conduc-
tors used to connect smoke detectors to control panels and
accessory devices should be color-coded to prevent wiring
mistakes. Improper connections can prevent a system from
responding properly in the event of a fire.
For signal wiring, (the wiring between interconnected
detectors or from detectors to auxiliary devices), it is rec-
ommended that single-conductor wire be no smaller than
16 gauge (1.5 square mm), and that two- or three-conduc-
tor wire be no smaller than 18 gauge (1.0 square mm). The
last foot or so of conduit should be flexible steel conduit
(available in electrical supply houses) which facilitates eas-
ier installation and puts less strain on the conduit holes in
the housing. Solid conduit connections may be used if
desired.
Smoke detectors and alarm system control panels have
specifications for allowable loop resistance. Consult the
control panel manufacturer’s specifications for the total
loop resistance allowed for the particular model control
panel being used before wiring the detector loop.
Wiring Instructions
The DH500 is designed for easy wiring. The housing pro-
vides a terminal strip with clamping plates. Wiring con-
nections are made by stripping approximately 1/2-inch of
insulation from the end of the wire, sliding this bare end
under the plate, and tightening the clamping plate screw.
Step 6. Install the Filters
Most duct installations are subject to dust accumulation.
System filters remove a large percentage of this contamina-
tion, but cannot remove all of it. Dust inside the duct detec-
tor causes problems. First, very fine particles of dust can
enter the detector sensing chamber and cause the unit to
go into alarm. Second, the accumulation of dust and dirt
necessitates a more frequent periodic cleaning schedule,
which can result in substantial cost and/or down time.
Disposable sampling tube filters can greatly reduce the nui-
sance alarms caused by dust, and can also significantly
extend the maintenance interval. To install the sampling
tube filters, simply push the filter adapter into the exhaust
tube, and then push the filter onto the adapter tube on the
left, as shown in Figure 6. Then install the other filter over
the end of the inlet sampling tube.
Filters require periodic cleaning or replacement, depending
on the amount of dust and dirt accumulated. Visually
inspect the filters at least quarterly; inspect them more
often if the dust accumulation warrants it. Replacement fil-
ters can be ordered from System Sensor (exhaust
tube/intake tube filter P/N F36-05-00).
The filters do not substantially affect smoke performance
under normal conditions. There is very little restriction of
smoke entry even when up to 90% of the filter is clogged.
Visual inspection is usually adequate to determine whether
the filters should be replaced because such a high percent-
age of contamination is required to affect performance.
However, if further testing is desired, a Dwyer Model 460
(or equivalent) Differential Pressure Gauge may be used.
Simply compare the differential pressure readings with and
without the filters attached. There should be little or no dif-
ference. If the difference exceeds 10%, replace the filters. In
CAUTION
SAMPLING TUBE
FILTERS
SAMPLING TUBE
MOUNTING
SCREWS
DETECTOR HEAD
EXHAUST
FILTER ADAPTER
DETECTOR BASE
INLET SAMPLING TUBE
FOAM GASKET
Figure 6. Sampling tube filter installation:
A78-2106-00