Gas Water Heater in Electrical Room 1

[wilsonv]

Hi there, I was asked to check an existing building. The building has a restaurant and a retail area and the intention is to renovate the retail area. I don't have any drawings yet on the existing conditions, the owner is working on that.
There are two gas operated water heaters inside the electrical room. Should this area be considered class 1, division 1? or is this installation in non compliance with the dedicated equipment space? The equipment inside the room is one Dry type transformer H.V. on primary (guess +/- 13kV), the main panelboard and 4 sub panels and of course all the things they don't have a place for store them. Any comments will be appreciated.

Thank you.

 

[davidbeach]

Does the electrical equipment have the required clearance? If so, I don't see any code issues; that isn't to say that mixing water heaters & panels is a good idea, but it isn't a code violation.

 

[wilsonv]

Thanks davidbeach, it seems that the clearance should be ok. I did not enter to the room because there are too many things around, once I get the drawings and they remove all the junk from the room I'm planning on take some measurements.
But don't you think that this location should be considered a Class 1, Division 1 as stated on the NEC section 500.5 (B)(1)(2). There is a chance of a gas leakage at this location. Also there is one exhaust fan right above the transformer (2 to 3ft above). By the way the water heaters are floor mounted.

 

[davidbeach]

I think the operative words of 500.5(B)(1)(2) would be "may exist frequently". I've not seen the area around gas water heaters treated as class I div 2, let alone class I div 1. Otherwise any place around gas piping would have to be classified for the theoretical possibility of a leak.

 

[stevenal]

One key word is frequently. The chance of a leak occurs anywhere the gas lines run. I would not expect such an occurrence to be frequent. Thermocouples close the gas valve if the pilot should go out, and generally fail closed. Some other key words are ignitable and concentration. Even if the gas valve should fail open, gas will discharge from the burner which is located directly beneath the vent pipe.

 

[wilsonv]

Thank you for your responses davidbench and stevenal, that makes sense.

 

[emfrey]

I think you have several code issues besides NEC -500.
1) The gas water heaters need ventilation and combustion air (NFPA 54)
2) You indicate that the TX is 13KV and therefore needs to be in an 3-hr fire rated room (NEC-110.31(A).
3) NEC-500.5(B)(1)(3) indicates that locations where breakdown or faulty operation of equipment may release ignitible concentrations of flammable gases or vapors------are class I Division 1 locations.
As "stevenal" indicates a "failure of equipment" would be if the gas valve would fail in the open position. The question is if the room ventilation and combustion air supply is sufficient to dilute to below ignition point.

 

[bigbillnky]

Goodevening wilsonv

The best advice I can give you is to talk to the AHJ, BEFORE starting any work (or quoting any price). He/she has the FINAL say as to the proper interpretation of the NEC as it applies to this area. That is the best way to avoid any potential problems or conflicts that may arise. Remember that codes vary greatly across the US in both interpretation and in enforcement, so an opinion from someone outside of your area may or may not be accurate. Also keep in mind that this work may involve other codes than just the NEC.

Bigbillnky,C.E.F.....(Chief Electrical Flunky)

 

[davidbeach]

emfrey, dry type transformers do not need to be in a vault until they reach 35kV (NEC-451.21(C)). Ventilation and combustion air is a separate issue from whether or not the electrical equipment can be in the room and has no bearing on the electrical equipment; it is its own issue independent from whether or not there is an electrical code issue with the room. In many years of doing building design, I have never encountered a classified area around a gas water heater, so if NEC-500.5(B) applies, there are vast number of location not in compliance, in many jurisdictions.

That said, it is lousy design for the electrical equipment and the gas water heaters to be in close proximity, but as far as I can tell it is not a code violation. Frankly, the pressurized water vessels and pipelines, particularly the pressure relief valves, give me more concern than the fact that they are gas water heaters.