gas-fired emergency genset - issues?

[kwired]

I can see potential sewage backup into people's homes creating a legally required standby system on some level.

 

[electrofelon]

.... if all you legally need is an optional standby generator ...

I am not clear on that, it seems contradictory. Could you clarify?

 

[iwire]

I can see potential sewage backup into people's homes creating a legally required standby system on some level.

And it may well be, yet is still only required to have two hours of fuel on site.

Sorry if I seem nit picky here, I just think we keep going past what is code required and into design.

 

[GoldDigger]

I am not clear on that, it seems contradictory. Could you clarify?

Not well phrased.
Better would have been:
"If under the NEC your proposed generator would just be an optional standby supply...."

 

[electrofelon]

Not well phrased.
Better would have been:
"If under the NEC your proposed generator would just be an optional standby supply...."

Oh ok got it.

 

[kwired]

And it may well be, yet is still only required to have two hours of fuel on site.

Sorry if I seem nit picky here, I just think we keep going past what is code required and into design.

I will agree that it may only require two hours of fuel and if so anything beyond that is an optional design issue.

 

[topgone]

I will agree that it may only require two hours of fuel and if so anything beyond that is an optional design issue.

To add, we only refer to the code when some boney issues surface! Other than that, we design for contingencies that our clients wanted solved!

 

[iwire]

Provide whatever they are willing to pay for.

 

[lielec11]

You all went off on a tangent a bit here and I'm not trying to keep up.

If NEC 700 states a minimum of 2 hours of on-site storage, then common sense says NG isn't a viable source because you can't store NG at your site, correct?

Question 2... if I have egress lighting and fire alarm loads on my gen, does that automatically classify it as "emergency"? I think so, so how can that be up to the AHJ?

 

[don_resqcapt19]

You all went off on a tangent a bit here and I'm not trying to keep up.

If NEC 700 states a minimum of 2 hours of on-site storage, then common sense says NG isn't a viable source because you can't store NG at your site, correct?

First you can store NG as compressed natural gas at your site and there are compressors available to provide compressed storage. I am not aware of this actually being done. Second take a look at 700.12(B)(3) and its exception.

Question 2... if I have egress lighting and fire alarm loads on my gen, does that automatically classify it as "emergency"? I think so, so how can that be up to the AHJ?

Maybe, however if the egress lighting is of the "unit" type, the supply is not an emergency circuit. I think that the codes require the fire alarm to have battery back up and don't think the supply to the fire alarm panel is an emergency circuit, but not 100% sure.

 

[lielec11]

Maybe, however if the egress lighting is of the "unit" type, the supply is not an emergency circuit. I think that the codes require the fire alarm to have battery back up and don't think the supply to the fire alarm panel is an emergency circuit, but not 100% sure.

What do you mean when you says "unit" type? A lighting fixture with an integral battery backup that runs unswitched, almost like a night light?

 

[GoldDigger]

What do you mean when you says "unit" type? A lighting fixture with an integral battery backup that runs unswitched, almost like a night light?

Unit equipment, with internal energy storage, does not have to be always on.
It can have two line voltage inputs. One of them is switched to control the light normally and the other is unswitched so that the light can turn on unconditionally when normal power fails.

 

[hornetd]

I think that the codes should be changed to require more fuel for emergency generators, or at least dual fuel capability so they can run off NG instead of relying on a finite fuel source. My understanding is at least one of the hospitals in town only has a few hours of diesel for its gensets.

That may meet the requirements of the legally enforced codes for that locality but it will never pass inspection by the auditors from The Joint Commission. The Joint Commission is the organization that accredits health care facilities. Their standards for Emergency and required standby power are much more demanding then the requirements of local building codes.

 

[hornetd]

Emergency vs Legally Required Stanby vs Optional Standby

Emergency vs Legally Required Stanby vs Optional Standby

I think what paulengr is saying is that if all you legally need is an optional standby generator you will be wasting money if you specify an emergency generator instead.

Two issues that need to be separated. There is a difference in how the code treats Article 700 Emergency Systems verses Article 701 Legally Required Standby Systems verses Article 702 Optional Standby Systems.

Believe it or not the alternate power supplies required by the The Joint Commission; formerly the Joint Commission on Accreditation of Healthcare Organizations (JCAHO); are Optional Standby Systems as described in Article 702 of the NEC. Only a system required by law can be a Article 701 Legally Required Standby System.

The only thing that the NEC demands of an optional standby generator is that it be adequately isolated from utility power.