Chromalox PN401 specifications Optional Equipment, CHROMALOX TYPE TMC 7-DAY TIMER, Operation

OPTIONAL EQUIPMENT

Temperature Indicators (Suffix “D”)

(FXTH Heater Assembly and Control Center will have

suffix "D" e.g. FXTH-11206D, WCG15-213D)

MOUNTING

Temperature indicators are balanced for accurate reading in a normal vertical position unless specified otherwise. All pyrometers labeled "shielded meter" may be used in any type of panel with little or no effect on calibration. Those labeled "non-magnetic" must be used only on aluminum, plastic, wood or other non-magnetic panels. They will read low if mounted in a steel panel. Pyrometers which are labeled "magnetic" are intended for installation on steel panels. A steel compensating ring is normally supplied where panel material is not specified. Discard the ring when mounting on a steel panel. If the pyrometer is used on a non-magnetic panel, the steel ring must be used. Be sure the slit in the ring is at the top of the meter barrel and the ring is pushed as far forward as it will go.

THERMOCOUPLE SELECTION AND CALIBRATION

Each pyrometer is marked on the dial with the type of thermocouple and the total external resistance for which it is calibrated. Use of any other type of thermocouple or one with a higher resistance than marked will result in incorrect readings. (Type J thermocouples are normally used.) All standard pyrometers are calibrated for 10 ohms external thermocouple resistance and are provided with a 10 ohm cal- ibrating resistor bobbin. (Non-standard pyrometers are usually cali- brated for the specific external resistance ordered and no resistor bob- bin is supplied.) This resistor bobbin must be adjusted so the total resistance of the thermocouple and the bobbin add up to 10 ohms in order to maintain calibration accuracy. Therefore, for a 5 foot, 20 gauge, iron-constantan thermocouple, the resistance of the thermo- couple would be approximately 1.75 ohms and this resistance must be subtracted from the calibrating bobbin. Each turn of the wire on the resistor bobbin represents 0.5 ohms and for this example, 3-1/2 turns would be removed. The total resistance of the thermocouple plus the resistor bobbin would then add up to 10 ohms. For other values of thermocouple resistance, simply remove more or less turns to adjust for the total value of external resistance marked on the pyrometer dial.

It is very important the resistor wire be properly soldered after adjusting.

NOTE: When Thermocouples with external resistance higher than 10 ohms will be used, a special pyrometer will be required. The use of other than thermocouple wire for leads or extensions may result in improper ambient compensation.

ABBREVIATED TABLE OF THERMOCOUPLE RESISTANCE The table lists the resistance in ohms per pair-foot for various types of commonly used thermocouples for a number of different gauges of wire. By using this table, it is necessary only to measure the length of the thermocouple, knowing the type and gauge, to determine its approximate resistance. (Actual measurement of the thermocouple resistance is preferred to using the table.)

Ohms Per Pair - Foot

	Iron/Constantan	Copper/Constantan	Chromel/Alumel
Gauge B & S	(Type J)	(Type T)	(Type K)
8	.0215	.0184	.0365
10	.0341	.0293	.0580
12	.0542	.0466	.0922
14	.0863	.0741	.1470
16	.1370	.1180	.2330
18	.2180	.1870	.3710
20	.3570	.2980	.5900
22	.5510	.4690	.9370
24	.8770	.7530	1.490
26	1.390	1.200	2.370
28	2:220	1.910	3.770
30	3.520	3.030	5.980

CHROMALOX TYPE TMC 7-DAY TIMER

TMC 7-day Calendar, Electric Dial Timer is used to provide auto- matic start-up/off-on control of large tank heaters or could be set up for non-peak operation. Standard features: 7-day calendar dial per- mits different on/off schedules on different days of week. 2 to 14 replaceable trippers for up to 4 on/off operations per day, up to 28 on/off operations per week. 3 hour minimum on or off time; 21 hour maximum on or off time. Independent 4-pole design allows SPST, DPST, SPDT, switching. Manual on/off lever transfers switch opera- tion without disturbing daily or weekly preset schedule. Heavy duty synchronous motor suitable for operation between -40°F and +140°F. Switch slider bar assures positive switching. Heavy duty terminals accommodate up to AWG No.8 wire.

OPERATION

“Off” Setting - de-energizes the entire zone control circuit, thus de- energizing all heating-cooling equipment in the zone. This setting can be used for extended summer shutdowns, etc.

“Automatic” Setting - allows the Day-Night Clock Panel to cycle the control system according to the program clock dial tripper set- tings.

To Set Trippers - Refer to picture for typical setup of a Seven Day Program. Two trippers must be used for each day; an “A” tripper for switching from “Night Setback” to “Day Operation” and a “B” trip- per for switching from “Day Operation” to “Night Setback”.

CAUTION: To set the correct day and time at beginning of initial start-up, ROTATE THE PROGRAM CLOCK DIAL CLOCKWISE ONLY. DO NOT ATTEMPT TO TURN POINTER!

Adjusting and Maintenance of Time Switch:

1.Periodically check trippers to insure that they are tightly fastened to Program Clock dial. CAUTION: TIGHTEN TRIPPERS WITH FINGERS ONLY!

2.Rotate Program Clock dial CLOCKWISE one hour in Spring to adjust for daylight saving time (in areas where required). In Fall, carefully rotate clock dial CLOCKWISE approximately one full turn to reset at correct day and time for standard time. Check all trippers to insure they have not moved during rotation.

3.The Program Clock motor is permanently lubricated. Lubrication of other parts is not required.

4.The Program Clock switch contacts are factory set and need no field adjustment.

	Renewal		Volts
Model	Part No.	Operation	60 Hz	Switch	Amps
				4 Pole
TMC71	311-057070-001	Seven Day	120	2 N.O.	40
				2 N.C.

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