Replacement of Chamber Heater Elements - Sigma Systems ...

inTEST Thermal Solutions 

ISO 9001 Registered 

Tel: +1.781.688.2300 41 Hampden Road, Mansfield, MA 02048 USA www.inTESTthermal.com 

Replacement of Chamber Heater Elements 

_____________________________________________________________________________________________ 

Note: this Service Bulletin replaces SB2200.00 

Before You Start… 

Tools Needed: 

1/4” and 5/16” thin profile open end wrenches 

5/16” nut driver 

The Keys to proper heater replacement: 

a. Document the electrical connections to the heater 

before disassembly. The wiring diagram YOU 

CREATE will be needed to reconnect the heater. 

CAUTION: Nothing in this document will show or 

tell you how to reconnect the wires to the heater. 

b. Make sure that you have a heater element 

that matches the voltage and wattage for your 

chamber’s power source. 

c. When assembled, the heater elements must be 

electrically isolated from the mounting bracket. 

d. The proper tension must be achieved on the nuts 

that hold the elements to the mounting bracket. 

Too much tension will crack the porcelain isolators, 

too little tension allows the heater to move. Either 

condition can lead to the premature failure of the 

heater, and possible damage to the chamber. 

e. A Jam Nut must be used to secure the isolators and 

hardware. Refer to the image on the right for the order 

that the hardware must be installed. 

____________________________________________________________________________________________ 

ECO 120319 LMS197370_rev.A pg. 1




1. Place the male porcelain inserts onto the heater mounting screws. The small portion of the 

porcelain insert points away from the body of the heater element. 

Figure: 1 

Porcelain isolator(s) - Male 

2. Place the heater element on a flat surface with the mounting screws facing up. Put the Triangular 

mounting bracket on the heater and guide the screws and Porcelain Isolators (male) inserts through 

the holes in the mounting bracket. Repeat with additional elements, if any. 

Note: The bracket flange must point away from the heater element. 

Figure: 2 

Triangular Mounting Bracket 

ECO 120319 LMS197370_rev.A pg. 2




3. Place the female porcelain isolators over the screws and mate them to the male porcelain isolators 

protruding through from the opposite side. 

Figure: 3 

Porcelain Isolators - Female 

4. Place a Washer and a Standard Nut on each mounting screws. 

Figure: 4 

Washer and Standard Nut 

ECO 120319 LMS197370_rev.A pg. 3




5. Using a nut driver, tighten the standard nuts until they are just snug. 

NOTE This is a critical part of the assembly! 

Over tightening can crack the porcelain isolators and allow the heater to short and fail. 

Under tightening can leave too much play on the elements so they will rattle in the wind of the 

blower and can short on each other or the mounting bracket, and/or damage the porcelain isolators. 

Figure: 5 

Nut Driver to Tighten Standard Nut 

6. Once snug, use a felt pen to draw a line down the center of one of the nut flats and continue the 

line onto the female porcelain isolator. 

Figure: 6 

Mark Standard Nut and Porcelain Isolator (Female) 

ECO 120319 LMS197370_rev.A pg. 4




7. Back off (loosen) the standard nut 1/12 of a turn (1/2 flat), so that the nearest point of the nut lines 

up with the line on the porcelain isolator. 

This provides enough clearance to allow for the expansion and contraction that occurs as the parts 

undergo sever temperature changes in the chamber. 

Figure: 7 

Loosen Standard Nut – use Markings as a guide 

8. Attach the Wire Lug. 

Figure: 8 

Wire Lug 

ECO 120319 LMS197370_rev.A pg. 5




9. Use a Nut Driver to tighten a Standard Nut on top of the Wire Lug. 

Figure: 9 

Standard Nut on Wire Lug 

10. Install a Jam Nut on top of the Standard Nut. Use two wrenches: 

1 wrench to hold the Standard Nut 

1 wrench to tighten the Jam Nut 

Figure: 10 

Jam Nut 

ECO 120319 LMS197370_rev.A pg. 6




Appendix A:Heaters With Fiber Washers 

If you have a heater assembly that has fiber washers (shown in the images below), discard those washers. 

The Hardware and Procedure in this Service Bulletin negate the need for fiber washers. 

a. Diagram where all wires and bus bars are connected to the heater 

b. Disassemble your old unit and remove the fiber washers. (These washers were originally added to compensate 

for expansion and contraction). 

ECO 120319 LMS197370_rev.A pg. 7




c. To install a new heater, follow the Numbered Steps on the previous pages of this Service Bulletin. The number 

of heaters vary from system to system, but once you are finished, your installed heater(s) should look similar to 

this: 

ECO 120319 LMS197370_rev.A pg. 8




d. Reattach the bus bars and wiring to restore the heater wiring to its original condition. 

NOTE: You should use the wiring diagram you created before disassembling your heater. 

No Matter what your heater configuration is, document the bus and wiring before disassembly. 

Then follow the Numbered Steps in this Service Bulletin to install replacement elements. 

inTEST Thermal Solutions engineers highly customizable Thermal Chambers, as a result, there are many 

different configurations for Heaters. The image below shows one configuration with multiple heaters installed. 

This configuration does not use the Triangle Bracket, the Heaters are mounted on a Rectangular Bracket- - but the 

hardware used to mount the heaters is the same and a wiring diagram is needed to re-wire the heaters. 

ECO 120319 LMS197370_rev.A pg. 9

Replacement of Chamber Heater Elements - Sigma Systems ...

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