Fisher 244EH, 244ER manual Mounting, Example

MOUNTING

Figure 2-2. Model 244EH Connection Head Temperature Rise vs. Extension Length

The Model 244EH installs in a connection head or universal head mounted directly on a sensor assembly, apart from a sensor assembly using a universal head, or to a DIN rail using an optional mounting clip. The Model 244ER mounts directly to a wall or to a DIN rail.

The Models 244EH and 244ER transmitters will operate within specifications for ambient temperatures between –40 and 185 °F (–40 and 85 °C).

In a direct mounting configuration using a Model 244EH transmitter, process heat is transferred from the thermowell to the transmitter via the connection head. If the expected connection head temperature is near or beyond specification limits, consider the use of additional thermowell lagging, an extension nipple, or a remote mounting configuration to isolate the transmitter from excessive temperatures. Figure 2-2provides an example of the relationship between transmitter housing temperature rise and extension length. Use Figure 2-2as a guide for determining adequate thermowell extension length.

(°C)	60
Ambient	50
Above	40
	30		4	8
				1
		5		5
					°
TemperatureRise			0		C		Pr
			°C
									oce		s
	20			Pr							s	Te						0123A-3044
	0			o		ce		s	s				m	per		at	ure
										Temp
												er
	10	250											atur		e
				° C	Pro
								cess			Temperature
		75		100			125				150		175				200	225
				Extension Length (mm)

Example

The transmitter specification limit is 85 °C. If the ambient temperature is 55 °C and the process temperature to be measured is 800 °C, the maximum permissible connection head temperature rise is the transmitter specification limit minus the ambient temperature

(85 –55 °C), or 30 °C. In this case, an extension of 100 mm meets this requirement, but 125 mm provides a margin of 8 °C, thereby reducing any temperature effects in the transmitter.

2-3