Pitco ME14S-C/MFD, Service Manual

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Chapter 1: HOW DOES IT WORK?
The McDonalds Electric fryer will have certain re-
actions to what is happening, knowing what these
reactions are and knowing what the machine is try-
ing to do will enable us to diagnose most of the prob-
lems likely to be encountered.
Heating System
Power to the machine is turned ON:
The computer is supplied with 24VAC and, if the
Drain Valve Handle is closed, the Proximity Switch
(S3) will supply 24 VAC to the DVI (Drain Valve
Interlock) Input at the computer.
The computer is turned ON:
The first computer in the "battery" of fryers (this in-
cludes either side of a split vat) to be turned ON will
energize a Relay (K15) that will turn the Hood sys-
tem ON. The Power On Relay (K2) will be ener-
gized, closing the circuit. If the Hi Limit (S1) is NOT
tripped the Safety Contactor (K10) will energize.
Computer calls for heat:
The Heat Demand Relay (K1) will energize supply-
ing the Heat Demand Contactors (K4, K5 & K6) with
24 VAC. This will also supply the computer with a
heat feedback signal.
Hi Limit System:
When the Hi Limit (S1) trips it causes the Relay (K3)
to energize opening the supply voltage circuit to the
Safety (K10) and Heat Demand (K4, K5 & K6)
Contactors. This Relay (K3) has a loop circuit that
will cause it to stay energized until the Hi Limit (S1)
resets and the power to the machine is turned OFF
and back ON again.