Diesel Pumps in Class 1 Div 2

[wastewateguy]

We are replacing a diesel driven pump in a sewage bypass pump station. The pump is manually activated in case of high flows reaching the wastewater treatment plant. The station is old and has not been designed to meed the NFPA 820 requirements. The station is a wet well/dry well confirguration and the pump and engine are located in the dry well, with the pump below grade and the diesel engine above grade. There is no separation between the basement (where the pump is) and the ground floor where the diesel engine sits. We are intending to classify the entire space as Class 1 Div 2 since continuous ventilation would need to be hooked up to stand by power - which does not exist and will not fit on the site. It is also a waste of money bearing in mind that this station is only operated very intermittently. All electrical and control equipment will be replaced with components suitable for use in a Class 1 Div 2 location. My first question is: Is it possible to locate a diesel engine in a Class 1 Div 2 location or will it need to be modified to suit? Second question: Bearing in mind that the pump is only initiated manually in a severe storm event, a combustible gas detector would indicate if the conditions were safe to operate the pump - would this be a compliant approach? Final Question: Would we be better off trying to obtain a variance from the jurisdiction having authority. NOTE: This facility is in Ontario Canada and while we have our own electrical code, it generally defers to NFPA 820 for wastewater plants. Thanks in advance.

 

[rbalex]

I’ve been mulling over how to address this post.

It’s been over 15 years since I used the CEC. At that time, Zones had become the preferred method of electrical area classification although Divisions were still permitted. Canadian Zones were much better aligned with IEC than US Article 505.

This creates some subtle but serious issues; the most significant is US electrical area classifications are used solely for selecting electrical equipment. IEC Zones definitely do and other Canadian Building Codes may use area classification to address mechanical and structural issues as well.

That said, an NEC compliant design would not affect the diesel engine except for selecting controls, metering, etc. You would need to consult NFPA 820 for any mechanical constraints.

I personally have a low opinion of combustible gas detection. Effectively you have acknowledged you have a Division 2 location whether the system is operating or not.