Troubleshooting a B/W Controls 1500 Series Liquid Level Control System

Troubleshooting a B/W Controls 1500 Series Liquid Level Control System


Hi I’m Ryan with Nelson Northwest and in
this video we’re gonna take a look at troubleshooting Ametek B/W Controls 1500
series relays. At Nelson Northwest we’re frequently asked to help troubleshoot
liquid level control systems with B/W Controls Relays. In this video we’re
going to provide some tips for troubleshooting these systems. In general,
1500 relays are very reliable, but they’ve been around since the 1980s, so
there’s been plenty of time for systems with these relays to develop
problems. When level control systems with 1500s fail, by far the most common cause
is the electrode circuit, and operating with a faulty electrode circuit can
cause premature wear and ultimately failure of the relay. First let’s
troubleshoot the relay itself. To do this we’re going to need a slotted
screwdriver and a good multimeter. Remember, there are hundreds of volts on
the terminals, so this should be done by a qualified technician. We’ll start with
the basics: Does the relay have the correct line
voltage on terminals three and four? Are the connections on the relay secure
and corrosion free? Are the electrodes in the tank clean and
reasonably corrosion free? If you’re using an electrode holder with
connections Are the connections in good shape? Is there a good signal ground from the
relay to the liquid? This should be either a ground electrode or a solid
connection from the relay to a metal tank. If this is a new installation,
remember that the load contacts on this relay just provide a dry contact closure.
Hooking the two terminals of a contact to the two terminals of a starter coil
or single-phase pump won’t work. It’s a bit like a light switch: you have to put
power on one side and it will just switch it on and off. For new
installations, also make sure that the electrodes are within the acceptable
distance from the relay. Too far and the relay may not drop out correctly, or may
fail prematurely. Next, let’s rule out faults in the relay.
Turn off the power to the relay. We’ll have to disconnect the wiring, so make a
wiring diagram of the relay. Mark any unmarked wires and take a good photo
showing the connections. Disconnect all the wires from the relay
except the line voltage on terminals three and four. Measure continuity for each of the
contacts. Normally open contacts should read open,
and normally closed should read very low resistance. If the continuity is incorrect, the relay
is probably defective. Replacing bad contacts may be an option if the rest of
the relay is in good shape; otherwise, replace the relay. Now turn the power
back on to the relay. The relay should NOT pull in. Continuity of the contacts
should be the same. Measure the voltage across the secondary
terminals 7 and 8. It should be roughly equal to the rated secondary
voltage. A bit higher or lower is okay but if the voltage is significantly
lower than the rated voltage with no other connections on the secondary coil,
the relay is probably defective. Now turn the power off again. Put a jumper wire
across the secondary terminals 7 and 8. Turn the power back on. The relay should now pull in. If the
relay does not pull in with jumpered secondary coils, it’s defective.
Now measure continuity for each of the contacts. Normally open contacts should read very
low resistance, and normally-closed should now read open. If the continuity is incorrect, the relay
is probably defective. You’ll need to replace contacts or replace the entire
relay. Now turn the power off again. If no problems were found with the relay,
remove the jumper and reconnect the wires and all the terminals. The problem
is most likely in the electrode circuit. If the relay tests okay, make a
thorough inspection of the electrode circuit. Electrodes should be clean and
free of corrosion. Check all connections inside and outside
of the tank for low resistance. This includes wire connections on wire
suspension electrodes. Make sure that the signal ground from
the relay goes either to a dedicated ground electrode or has a good
connection to a metallic tank. One trick you can use to check electrode circuits
is to power off the relay and connect two electrodes together at the tank. Disconnect the electrodes at the relay
and test the resistance between the two. If the resistance is high, the wiring is
suspect. One final trick, if no problems have been identified so far, but the
system is still not working, is that you can simulate the electrode circuit in a
bucket. This will help to isolate problems with the relay from problems
with the electrode circuit. First fill a bucket with the same water that you’re
sensing. Cut lengths of insulated wire to simulate your electrodes. In this case we
have three. Strip the wires and wire the relay per your wiring diagram. For this demo we’ve wired a light to
simulate pump operation. Suspend the ends of the wires in your bucket, and remember
that when we energize the relay. these will have high-voltage. You can move the wires up and down to
simulate changing water level and see if the relay pulls in at the correct points. In addition to the tips we’ve provided
here, you can find troubleshooting information in the 1500 Relay
Installation Manual. The manual ships with new relays, and is also available on
our website. If you get stuck, we’re always happy to answer questions.

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