Min. Distance from Transformer to Fire Hydrant?

7/19/2022

Is there an applicable code reference for minimum distance between a fire hydrant and a transformer?

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8 Comments

Pete H

7/19/2022 06:40:36 am

This write up by Mike Ruff at TES Engineering describes some clearance requirements, but doesn't source them to code. They do sound decent though.

https://www.tesengineering.com/electrical-engineering-clearances-for-pad-mounted-transformers-2/

"The sides of the transformer must be clear of all objects (including landscaping) for 3ft, and the transformer should be located 10ft horizontally from doors, windows or fire hydrants."

"Utility company transformers located on a site must also be located a minimum of 48” from fire hydrants."

7/19/2022 08:06:19 am

Depends if the transformer is a Autobot or Decepticon.

Ray Jackson

7/19/2022 08:41:16 am

In this day and age, it's really hard to tell which is which. All I can say for certain is, "Autobots, roll out!!!"

Jesse

7/19/2022 08:07:22 am

Can't think of a code of hand, but common sense should prevail.

I was once doing an underwriting survey for an insurer at an auto-shredder. A competing loss control engineer doing a flow test filled the MCC room with hydrant water resulting in an interruption of 2 months.

You'll only do that once.

Adam Jensen

7/19/2022 09:06:44 am

In Ontario, the local monopoly is Hydro One. They have their own set of Standards that apply to the installation of their equipment. As far as Code goes, I don't see any references.

They state 3m (~10') from the transformer's concrete pad to the hydrant on the access side, and 1m (~3') from the non-access sides.

So the Utility might be your best source of information.

Danial Bartle

7/19/2022 09:24:45 am

NFPA 1 (2021) 18.5.7 indicates clear space in general is 36in (914mm) in circumference and 60in (1524) in front of each connection greater than 2 1/2. I did not see a reference for the transformer, but it may be in NFPA 70 (NEC)

Franck

7/19/2022 09:44:42 am

If the purpose is to access the hydrant to use it in case of transformer fire, I would suggest to use the safe separation distances from NFPA 850 which depend on the oil quantity in the transformer (could be 5 ft, 25 ft or 50 ft minimum - 1.5, 7.5 or 15 m).

Ryan L Hinson

7/19/2022 10:09:40 am

NFPA 850 Section 7.4 provides some guidance regarding maximum hydrant spacing in general hydrant spacing for electric generating plants and high voltage direct current conversion stations...which includes discussion regarding transformers. Spatial separation of transformers and other equipment containing over 500 gal of oil is to be in accordance with Section 6.1.4 - Outdoor Oil-insulated Transformers, per Section 9.7.10. While hydrant location is not specifically addressed, consideration of access during firefighting operations in conjunction with spacing between transformers and other structures (including firewalls or fire barriers) and reachability by at least one hose stream per Section 12.3.7.3 should be included in any hazard evaluation.

Any monitor or handline nozzles used should be limited to narrow-fog or wider spray patterns.

If there is containment beneath your transformer, the hydrant's proximity from a pool fire should and drainage path should be considered.

IEEE Std 979 (referenced in NFPA 850 Section A.9.7.10 and elsewhere) recommends hydrants no more than 500 ft from mineral-oil-insulated transformers 500 gal or more. Hydrant systems also need suitable grounding clamps and cables available to ground firefighting vehicles.

Depending on the transformer oil-insulation volume, 10 ft spacing to a hydrant would appear to me to be too close for access during a fire at this transformer. Standard petrochemical firefighting best practice is to locate manually-activated appurtenances at least 50 ft away from the protected equipment. It seems to me this would be a good starting point per my understanding of your situation.

Good luck!

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Min. Distance from Transformer to Fire Hydrant?

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