_Wiring, Circuits and Troubles_
=The Wire.= The size of the copper wire used in bell work is No. 16, or
No. 18, B and S gauge, and sometimes smaller, such as No. 20 to 22. But
smaller wire than No. 18 has too much resistance, and would necessitate
a larger battery power, even if its mechanical strength were not too
low. The insulating coverings are cotton saturated with paraffin wax or
compounds.
The covered wires are variously known as annunciator, office, or
weatherproof wire, these terms being mostly for distinction of the
coverings and not for the use to which the wire would be put.
Annunciator wire has two layers of cotton merely wrapped around the
copper and then saturated with paraffin.
Office wire has the two cotton layers braided, the inside one being
filled with a moisture-repelling compound.
Both office and annunciator wires have their outside coverings filled
with paraffin and highly polished.
From the ease with which annunciator wire is stripped of its cotton
covering, the braided office wire is to be preferred. These coverings
are made in a variety of colors.
Weatherproof covered wire is mostly used for electric light work, but
the sizes given above are good for bell work, although their larger
outside diameter makes them harder to conceal.
The approximate number of feet to the pound of office and annunciator
wire is given in the table.
=======================================
Office Wire. | Annunciator Wire.
----+--------------+-----+-------------
No. | Feet per lb. | No. | Feet per lb.
----+--------------+-----+-------------
12 | 35 | 18 | 180
14 | 55 | 20 | 225
16 | 95 | |
18 | 135 | |
=======================================
=Joints.= Upon the care with which a joint is made much depends, a
loose or poorly made joint will offer much resistance to the current.
The correct way to start a joint in annunciator, or office, wire is
shown in Fig. 22. About three inches of each wire to be joined is bared
of its insulation and scraped bright. The ends are then bent at right
angles to each other, hooked together and one end firmly twisted around
the other, as shown in Fig. 23. Any projecting pieces are cut off, and
the joints should then be _soldered_ to prevent corrosion.
[Illustration: FIG. 22
FIG. 23
FIG. 24]
Adhesive tape (“friction tape”) is wrapped around the joint, Fig. 24,
and pressed firmly together so that there is no chance of its
unravelling. The tape wrapping should extend across the joint and on to
about a half inch of the insulation around each wire.
=Running the Wires.= To detail all the operations of installing a
complex system of bell, alarm and annunciator wires would be impossible
from the reasons that conditions vary and space is limited. General
directions will then only be given to enable the inexperienced to run
such wires as may be needed in ordinary domestic work and to guard
against the most common causes of failure.
Wires may be run in tin tubes to prevent the depredations of rats and
mice, or they may be run with simply their own covering for protection;
it is presumed the latter is undertaken.
In a case where the building is of frame and in course of erection the
task is much simplified.
Having first decided upon the plan, number of bells, pushes, etc.
and their location, proceed to run the wires first in order that the
pushes, bells, etc. may not be injured.
But where the house is already occupied, as in the majority of cases
likely to be met with by the reader, the bell and battery may be set
first.
Take the case of an ordinary door bell with the push at the front door,
the bell in the kitchen and the battery in the cellar. If possible get
the wire on two spools; it will simplify matters if both wires are of
different colors. Starting at the push, have a foot of each wire for
connection and slack, and fasten each wire lightly to the woodwork
with staples, or double-pointed tacks, never putting two wires
under one staple nor driving in a staple so it cuts the insulation.
Some cases will require a staple about every foot, on straight runs
sometimes every three feet.
In many cases the wires can be partly concealed in the angle between a
moulding and the wall, or even in a groove of the moulding itself. When
running along a skirting, the wires may often be pushed out of sight
between it and the floor. Do not attempt to draw the wires too tight
or the changes of the weather may break the wires when the woodwork
shrinks or swells.
The wires will be, one from the push to the bell, one from the push to
the battery, and one from the bell to the battery. So it is probable
that the second wire can be run right through a small hole bored in
the flooring under the push, but inside the front door. In this case
it will be perhaps easier if the spool be left in the cellar and the
end of the wire be pushed up from below and stapled to the woodwork
near the push, leaving the cellar work to the last. Only one wire will
be run then direct to the bell upstairs and it can be better concealed
than two.
If necessary it may be drawn under a carpet and not stapled, or it can
often be forced into the crack between two boards. But if not, run it
along the skirting, following the walls until it reaches below the
bell. It is often better to go entirely around a room than to cross
below a door.
If a door must be crossed the wire may either run up one side of the
frame and down the other or laid beneath the carpet on the sill. The
former is preferable, but takes more wire.
In many houses the bell wire as well as the battery wire may be run
across the cellar beams (Fig. 25), in which case bore a second hole for
it near the push; do not draw it through the same hole as the push to
battery wire. And, of course, here work upwards with the spool in the
cellar.
Having reached the bell location, run the third wire down into the
cellar to the battery. Now connect up the push, baring an inch or so
of each wire, push them through the holes provided in the push base,
screw down the push base and clamp the wires under the washers through
which the connection screws run. Do this neatly, be sure the ends of
the wires do not stick out, cut off what is left free of the bared
ends. Then connect the battery to the wire from the push and the wire
from the bell. The last thing is to scrape and fasten the bell wires to
the bell binding posts. Do this so that they cannot come loose and that
they make good contact.
[Illustration: FIG. 25]
The bell should now ring properly when the push is pressed.
To sum up, one wire leads from one spring of the push to the bell, one
wire from the other spring of the push to the battery, and another wire
from the remaining binding post on the bell to the remaining binding
post on the battery. It is immaterial whether the zinc terminal or the
carbon terminal go to the bell or push.
=Combinations of Bells and Pushes.= One of the wires in a bell circuit
may be replaced by the ground (Fig. 26). Connection may be made to a
gas or water pipe or to a metal plate buried deep in damp earth. Any
wire fastened to such a plate must be thoroughly soldered to it or a
voltaic action will be set up, which will eat it away at the point of
contact.
[Illustration: FIG. 26]
When one bell is to be rung from two or more points the pushes are to
be connected in multiple (Fig. 27) as if they were in series; all
would have to be closed to complete the circuit.
[Illustration: FIG. 27]
[Illustration: FIG. 28]
If two bells are to be operated from one push they may be in series
(Fig. 28), but in this case one of them must be arranged for single
stroke. If both were vibrating bells the armature of one would not
vibrate in unison with the other armature and the result would be
irregular contact breaking and intermittent ringing.
[Illustration: FIG. 29]
A preferable connection for two or more bells and one push is Fig. 29,
where the bells are in multiple. This requires more current than the
series method.
[Illustration: FIG. 30]
[Illustration: FIG. 31]
To ring two bells from either one of two points, the arrangement in
Fig. 30 will answer. It requires only two wires or one wire and ground
return, but two batteries. As both bells are in multiple both will
ring, the one nearest the push being depressed ringing the loudest.
This is a disadvantage. If the series arrangement in Fig. 31 be
selected, one bell must be arranged for single stroke. Both bells will
ring with equal power.
[Illustration: FIG. 32]
In Fig. 32 only the distant bell rings, the circuit having only one
battery but three wires, or two wires and ground return.
A plan where two batteries are needed but only two wires, or one wire
and ground is in Fig. 33. Double contact or three-point pushes are
necessary here, making one contact when depressed and a second one when
not being touched.
[Illustration: FIG. 33]
In this figure only the distant bell rings.
=Faults in Bells.= On examining many electric bells it will be noted
that only one binding post is insulated from the frame when the latter
is of iron (Fig. 34). As the armature spring _S_ is in electrical
connection with the frame _F_ by reason of its metal screws and
support, the circuit may run from the insulated post _U_ to the magnet
coils, thence through the insulated contact screw _C_ through the
armature spring (when it is making contact) and through the frame to
the uninsulated post _I_.
[Illustration: FIG. 34]
This saves labor, wire and complication, but if the insulation of the
post _U_, the wires _W V_, or the contact screw _C_ be injured, the
current may take a short path back to the frame.
If _C_ were thus grounded, the bell would act as a single-stroke bell.
If _U_ were grounded, the bell would not ring at all, as that would be
a short circuit on the battery between _I_ and _U_ and the latter would
also result if the bare wire were touching the frame at _V_.
If the bare wire touched the frame beyond _M M_, that is, along _W_, it
would be a single-stroke bell, as if _C_ were grounded.
As any one of these faults is likely to occur, they should be looked
for when the bell acts imperfectly, or not at all.
A very common fault in a bell is when its armature sticks to the cores
and thus does not make contact with the contact screw. This may be from
a weak spring or because of the loss of the pieces of brass inserted in
the ends of the cores to keep the armature away from actual contact. A
piece of a postage stamp stuck over the core end will often help out in
the latter case.
A high screeching noise from the armature vibrating too rapidly but
with too little play, may be from excessive battery power or the
contact screw being too far forward. The former will generally be
detected by the violent sparking as well as the rapid vibration.
In very cheap bells the platinum contacts may be replaced by German
silver or some other metal.
Platinum is necessary because the sparking would soon corrode other
metals, but it is very expensive. To test for platinum put a tiny drop
of nitric acid on the suspected metal. If bubbles or smoke appear it is
not platinum. After applying this test in any case however, carefully
wash off and remove all traces of the acid, as it will corrode the
metal into which the platinum is riveted.
Dirty contacts will decrease the current in the bell coils and it will
not work well, if at all.
Loose contact screws and wires also give trouble. The adjusting of
the contact screw is of the utmost importance, and should never be
attempted unless it is clearly necessary.
=Faults in Line.= In looking for a fault in a bell circuit make sure
the battery is working; if only one or two cells, put the ends of two
wires attached to the terminals on the tongue: a metallic taste will
indicate current.
Then see that the circuit wires are firmly clamped in the terminals and
no dirt or corrosion on the connections.
Next examine the push button and see that the wire connections at the
springs are perfect.
If there is no movement of the bell at all when the push is pressed
in, take a pocket knife or screw driver, and touch the blade across
the push springs. If there is current flowing sparks will be seen when
the blade breaks contact between the springs. If there are no sparks,
detach the wires from the bell and twist the bare ends together. Then
try again for sparks--they may now be very minute. The tongue test is
good here.
If current is detected, examine the bell for the defects first
mentioned.
But if no current is found at the push now the wires are broken
somewhere.
First short circuit the push springs by inserting a knife blade or
piece of wire so as to touch both of them. Then touch the two wires
at the bell, one to each side wire coming from the magnet coils. If
current is up to the bell and the coils are all right, a single stroke
should result.
Replace the wires in the binding posts, clean the platinum on both
contact screw and armature spring and try the adjustment. Troubles in
the bell will be mostly similar to those before mentioned.
If no current has been obtained at either bell or push, and the battery
is in good working order, the line must be tested for a cross or break.
If the wires are touching each other (Fig. 35) at some bare spot _S_
between the bell and the battery, it will be shown by the metallic
taste upon detaching one wire from the battery and laying it on the
tongue _T_, together with another wire _W_ from the disconnected
terminal of the battery. The current will travel from the battery to
the cross at _S_, then back along the second circuit wire to the tongue
and through the short wire to the battery.
[Illustration: FIG. 35]
If no current is obtained in this way it is probable that the wire is
broken.
[Illustration: FIG. 36]
The easiest way to find this is to take a bell to the battery and
connect it between the circuit wires and the battery (Fig. 36).
Then with a sharp knife carefully cut away a little piece of the
insulation from each wire beyond the bell and battery and short circuit
the bared spots with the knife blade _K_. Keep working towards the
push. The bell will ring each time at _K K_ until the break _D_ is
passed, at _C_ it will not. It becomes an easy matter then to locate it.
[Illustration: FIG. 37]
If the bell and push are far apart, as in Fig. 37, a break between the
push and the bell may be found as shown. With the knife blade _K_ at
different points the bell will ring, but after passing the break _D_ it
will not ring.
Such simple tests as are here given can be carried out by any one, but
far better results will be obtained if the reason for each is first
learned.
This can be readily done by a careful study of the diagrams and text.