User`s guide

Appendix A - Logic Application Examples
Furnace Relay Ladder Logic Conversion Example
234 UMC800 Control Builder User’s Guide Release E
1/01
Furnace Relay Ladder Logic Conversion Example
Furnace Relay Ladder Logic Diagram - Part A
L2L1
Load Front Chamber
Furnace ON Lamp
Front Chamber Door
Solenoid (Open)
Front Chamber Door
Solenoid (Close)
Purge Timer (10 Min.)
Inner Furnace Door
Solenoid (Open)
Relay Logic
requiring
UMC800
conversion
This is a portion of a batch furnace relay
logic diagram. Contacts 6-LSCR, 3-LSCR,
and 5-LSCR are from external control relays
which are turned on by limit switches 6-LS,
3-LS, and 5-LS for powering the solenoids.
1-CR
2-LT
R
1-PB
2-PB
1-CR
6-LSCR
3-LSCR
SOL-A
SOL-B
5-LSCR
1-LS
1-CR
1-TR
2-CR
SOL-C
ON
OFF
115 VAC
G
Power ON Lamp
2-CR
3-LS
3-CR
5-LS
6-LS
5-CR
6-CR
A Latch block is used for the
Start/Stop circuit replacing the
external control relay for latch-in.
This latch output connects
directly to the 2-LT lamp output
block plus the 4-In AND block
which has two permissive limit
switch inputs (6-LS and 3-LS)
rather than the control relay
contacts which are no longer
required. The output of the AND
block allows the SOL-A solenoid
to be driven ON directly via the
UMC 800 discrete output card,
provided power requirements are
met. The Latch output is also
ANDed with the 1-LS limit switch
input to activate an ON delay
timer whose output directly drives
the SOL-C solenoid. SOL-B is
driven directly based on the 5-LS
limit switch status.
14 Function Blocks