Middleby Marshall PS555, PS570, PS360, PS200, PS220, PS224 PS310 manual Description, Com

SECTION 3 - SERVICING COMPONENTS

B. Description

The temperature controller consists of two main compo- nents: a sleeve or case (metal or plastic) with terminal con- nections on the back, and a plug-in chassis that includes the faceplate and circuitry. The sleeve is mounted to the panel or door of the oven, and the chassis is inserted into the front of the sleeve.

VERY IMPORTANT: When replacing a controller, you should ALWAYS replace the sleeve as well. Some control- ler models have sleeves of a similar size, but with DIFFER- ENT CONNECTIONS. Using an incorrect sleeve can dam- age the controller and cause the oven to function incor- rectly. Exception: The sleeve used on Controllers 36056 and 46837 is identical except for the information label.

D. Troubleshooting

1.Troubleshooting the Temperature Controller and Thermocouple(s) using the Altek Thermocouple Source (Middleby P/N 27170-0192)

•Turn the heat switch OFF.

•Disconnect the thermocouple leads from Terminals 7 and 8 on the temperature controller. Tape the ends to prevent shorting.

•Connect the white lead of the Thermocouple Source to Terminal 8 (+). Connect the red lead of the Ther- mocouple Source to Terminal 7 (-).

•Set the Thermocouple Source as close as pos- sible to the customer’s set point. Then, turn the BLOWER switch to the ON position.

C. High Limit/Cooldown Functions

Except where noted in Section A (Part Number Reference), the temperaturecontroller incorporates circuitry for the high limit and cooldown functions.

1.The High Limit function (terminals 11 and 12) will shut off the burner/heating elements if the oven temperature sensed by the thermocouple(s) exceeds 650°F/343°C. This function is used on most PS200-series and PS360- series gas ovens. All other oven models use a sepa- rate high limit control module.

If the high limit temperature is reached, an indicator on the controller will illuminate. The current controller (P/N 46837) has a lamp marked “OVERTEMP” to show this condition. Older controllers will have different indi- cators; you should refer to the operating instructions for the controller in question for assistance.

2.The Cooldown function allows the blowers to continue in operation after the operator switches off all operating switches on the control panel. The blowers will remain in operation until the cooldown switch opens (usually 180°F/82°C).

The temperature controller should read close to the customer’s set point. Failure indicates a problem with the temperature controller. If the temperature control- ler is functioning properly, check the thermocouples. Refer to Section IV, Thermocouples.

2.Troubleshooting the High Limit Switch

On ovens that use the high limit function of the tem- perature controller (most PS200-series and PS360-se- ries ovens), an intermittent high limit switch will cause intermittent operation of the burner. If you suspect that this is a problem, a good check is to place a 1A fuse in parallel around the switch contacts (terminals 11 and 12).

If the switch is functioning properly, the fuse will never carry a load. The only time the switch would open would be under a no-load condition.

If the switch is trying to open intermittently, however, the full current load of the blowers will be carried by the fuse. Regardless of the oven model, this load is far greater than 1A, and the fuse will blow.

E. Appendices

Appendix - Temperature controller terminal cross-reference, 4/02

Terminal for		Terminal for
28071-0012 and	Terminal for	36056 and	Description
28071-0018	34983	46837
1	TC+	8	+ TC
2	TC-	7	- TC
5	COM	5	Input to Temperature Control Relay
6	NO	4	Output to High Flame Solenoid or Heater Contactors
L2	L2	L2	Neutral
L1	L1	L1	Power
G	G		Ground
13	--	9	Input to Cooldown Relay
14	--	10	Output from Cooldown Relay
15	--	11	Input to High Limit Relay
16	--	12	Output from High Limit Relay
--	--	15	PID or Variable Pulse Output
--	--	16	PID or Variable Pulse Output

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