Dual Contactors for Hydrocarbon Heater Circuits

[rinezry]

I was reading a project spec and came across a requirement for dual contactors for hydrocarbon heater circuits. Can anyone tell me why this is required and whether it is covered in any standards, ie ANSI, IEE, BS?

 

[jbartos]

Suggestion: It appears that in some instances the dual contactors are obsoleted and replaced by contactors with arc suppressors.
Visit

http://www.amdry.com/documents/TechBulletin146.pdf

etc. for:
115 VOLT DUAL CONTACTOR (P/N 880771) OBSOLETED
EFFECTIVE IMMEDIATELY, ADC Part No. 880771 (115 Volt Contactor Arc Suppressor [A.S.] Board Conversion Kit), is no
longer available and has been OBSOLETED from the ADC inventory. The replacement for this particular conversion kit is ADC Part No.
882256, 115 Volt SPST Contactor Arc Suppressor (A.S.) Board DSI (Direct Spark Ignition) Conversion Kit (which includes instructions, as well as the necessary wiring and hardware).