Bathroom Toilet Exhaust Fan Shaft Issue

[wyattlewis]

Hello,

I am working on a multi-story hotel and have come across an issue regarding the Bathroom Toilet Exhaust Fan Shaft.

Scenario: (I am an electrical engineer, so please pardon my lack of HVAC lingo.)
In each bathroom there is an exhaust fan that empties into a shaft spanning from the 1st floor up to the roof. At the top of this shaft there is a larger exhaust fan that discharges air to atmosphere.

Problem:
We have been told that the top exhaust fan must be on emergency power. This building being a hotel, does not have emergency power on site.

Potential Solution (I am certainly open to explore an options posed to me in comments.):

• If this is a legally required load, would it be possible to tap for power before the main service disconnect (in the same fashion as a fire pump)?

• If I can supply power to the roof exhuast fan before the main service disconnect with proper over-current protection, am I in violation of the main service disconnects uL listing?

Thank you, and I appreciate any help that can be offered!

 

[RICK NAPIER]

I can't see how tapping off prior to the main would meet the needs of emergency power. Is the requirement a local issue or they using a ICC or other code to require this.

 

[wyattlewis]

The comments we received stated the emergency power was required for fire protection (similar to a fire pump). The logic I am trying to follow is: If the fire department comes to a building and kills the power, will this satisfy the power requirement to this exhaust fan.

These were comments handed to me without any code citation. I am now trying to do the legwork of searching through the international building code.

I'm not 100% if the "emergency power" that is required necessarily has to be emergency generator backup or "provided power during emergency".

 

[raider1]

Why would a bathroom exhaust fan need to be provided with emergency power or legally required standby power?

IBC Chapter 27 has the requirements for emergency and legally required standby power for commercial buildings.

Chris

 

[RICK NAPIER]

Is this a High Rise? If so then IBC 403.4 may apply particularly 403.4.6 but I don't see this as requiring any special electrical requirements.

 

[ivsenroute]

More information is needed about the type building and height, area, etc.

Is this an existing building or new construction?

 

[augie47]

How we feel about the "ruling" that this fan needs to be on "emergency" power seems immaterial if a local authority has so dictated.
In answer to your question(s), Art 701.11 lists possible sources for such emergency power and 701.11(E) does recognize a tap ahead of the main service disconnecting means to be on possible answer.
If you go this route the disconnect means fed by that tap would need to meet the requirements of "service equipment" and would need to be so rated, and bonded, etc.

 

[RICK NAPIER]

The code section I cited from the IBC 403.4 describes ventilation requirements as an emergency system for smoke removal after a fire but does not require standby power. I am wondering if this is the confusion.

 

[wyattlewis]

ok, here is the codes that we are adhering to for this. Hopefully, this will clear up a lot of what if's.

Following the 2006 IBC 716.5.3 Shaft Enclosures:
There was a design decision that prevented us from having a smoke damper at every shaft penetration. There is an exception 2 (2.3) that states:

In Group B and R occupancies, equipped throughout with an automatic sprinkler system in accordance with 903.3.1.1, smoke dampers are not required at penetrations of shafts where: an exhaust fan is installed at the upper terminus of the shaft that is, powered continuously in accordance with the provisions of Section 909.11, so as to maintain a continuous upward airflow to the outside.

2006 IBC 909.11 Power Systems:

The smoke control system shall be supplied with two sources of power. Primary power shall be from the normal building power system. Secondary power shall be from an approved standby source complying with the ICC Electrical Code. The standby power source and its transfer switches shall be in a separate room from the normal power transformers and switchgear and shall be enclosed in a room constructed of not less than 1-hour fire barries ventilated directly to and from the exterior. Power distribution from the two sources shall be by independent routes. Transfer to full standby power shall be automatic and within 60 seconds of failure of the the primary power. The systems shall comply with this code or the ICC Electrical Code.

2006 IBC Commentary, Chapter 27: Electrical

...
Standby power systems are covered in Article 701 of NFPA 70 and are intended to provide electrical power for loads not as critical as those requiring emergency power. Standby power loads include smoke control systems; certain elevators; certain hazardous material operations; HVAC systems; refrigeration; and sewage pumps. Standby power systems must provide power within 60 seconds of failure of primary power.
Sources of power for emergency power systems (NFPA 70, Section 701-11) include storage batteries, generators, uninteruptable power supplies, and separate services. Sources of power for standby systems include those allowered for emergency systems plus a source taken from a point of connection ahead of the normal service disconnecting means.
...

NEC 2005, 701 Legally Required Standby Systems, III. Sources of Power, 701.11 (E)

(E) Connection Ahead of Service Disconnecting Means. Where acceptable to the authority having jurisdiction, connections located ahead of and not withing the same cabinet, enclosure, or vertical switchboard section as a service disconnecting means shall be permitted. The legally required standby service shall be sufficiently separated from the normal main service disconnecting means to prevent simultaneous interruption of supply through an occurrence in another service. FPN: See 230.82 for equipment permitted on the supply side of a service disconnecting means.

NEC 2005, 230.82(5)

Taps used only to supply load management devices, circuits for standby power systems, fire pump equipment, and fire and sprinkler alarms, if provided with service equipment and installed in accordance with requirements for service-entrance conductors

So i think that could help out some.

 

[augie47]

Hello,

• If this is a legally required load, would it be possible to tap for power before the main service disconnect (in the same fashion as a fire pump)?!

As mentioned, 701.11(E) allows this so it only matters if it is suitable by whomever is enforcing the change.

• If I can supply power to the roof exhuast fan before the main service disconnect with proper over-current protection, am I in violation of the main service disconnects uL listing?

I'm sorry, I don't understand that part of the question