Appendix B
34
Chemical Hold Signal
The chemical hold interface on the FM7 is
accomplished by connecting an external relay
contact to the chemical hold input terminals in
the machine. The electrical arrangement is as
follows:
24VAC
Hold
24VAC Source
Chemical Terminal
Block in Washer
Chemical Hold
Relay in dispenser
system
FM7 Hold input
Limit of
Equipment
In operation, when the chemical hold relay is
closed by the dispenser, the washer pauses and
starts a hold timer. When the washer pauses
water is retained in the cylinder, all water fill
and chemical supply signals are turned off, and
the FM7 displays “HOLD” followed by the
minutes and seconds of the current hold time.
When the chemical hold relay is opened by the
dispenser, the washer will resume normal
operation. Any chemical signal programmed to
be on will turn back on, water fills and flushes
turned on will turn back on and the bath will
proceed as programmed. For example, if a
chemical signal is programmed for 10 seconds
and the hold input turns on after it has counted
down to 9 seconds, then after the hold signal is
turned off, the chemical signal will turn on and
resume the 9 second count down before the
program proceeds. For clarification, below is a
timing chart:
If the return of the chemical signal after the
hold period presents a problem for the
dispenser, then the signal can be programmed
for a short time. If the dispenser needs to see
the signal on during the hold period, then
latching relays need to be used for the chemical
interface, and an extra signal can be used as a
signal “reset” at the end of the chemical period.
The FM7 does not monitor the chemical hold
function when the machine is not running a
wash program. So hold input state changes will
have no effect if the machine is not running a
wash program.
No special programming is required for the
chemical hold function to operate as described.
Summary of Contents for FM7
Page 2: ......
