Restroom Exhaust

[Scout2]

Can anyone advise me as to any codes that would prevent me from shutting off the exhaust fans in a restroom of a buildng during periods of non-occupancy? Note the AHU's are shoutdown at periods of non-occupancy.

 

[ChasBean1]

Scout2, no. Shut them down. An interlock with the AHU would be good. In fact, running the TX around the clock while the building AHU is down will in-filter that volume of unconditioned air through cracks, leading to mold in the summer, or unnecessary heat operation or pipe freezes in the winter. Good luck, -CB

 

[VEEKRISH]

Scout2,
What we do is to interlock the Rest Room Exhaust fan with the Rest Room Door. Every time the door opens the Fan comes on. Stays on for about ten minutes and then shuts off.
In some cases I've even hooked up the fan with the Rest Room Light. The fan switches on along with the light. Problem here is some guys forget to switch off the light!!!

 

[DouginMB]

Similar to what Veekish does, we operate the exhaust fans by ceiling-mounted motion detectors that have an integral timer.

 

[pmarty]

I was recently advised by my new boss ( structural engineer ) that restrooms should be under negative pressure per industry standards.

I understand that the new International Mechanical Code requires exhaust at 75 cfm per water closet or urinal, but I see nothing that requires this to be continuously exhausted or even that a restroom must be negatively pressurized.

Does that mean that one exhausts a total of 150 cfm if you have a toilet and a urinal or do you exhaust 75 cfm & choose one or the other as the basis for design?

If you did exhaust either 75 cfm or 150 cfm then would it not be possible to supply an equal amount of cfm without negative pressurization, generally with the supply air towards the entry & exhaust over the smelly areas?

A final question, can odors be prevented from passing through a door crack when the door is open thus causing depressurization to occur? Or is it possible for hydrogen sulfide ( rotton egg odor ) to travel from a point of high concentration to a point of low concentration irregardless of pressurization? I have driven by cattle farms in Nebraska that seem to emanate odors upwind for some reason.

Recent observations lead me to believe that industry generally has applied manual or automatic motion sensors at exhaust fan switches in rest rooms in the interest of energy conservation. Hopefully, this can continue to be the case. If one is concerned about odors, apply trap primers to floor drains, and install automatic flush valves at urinals & waterclosets.

However, I have come to the conclusion that I am an idiot since my boss tells me that I am. Don't tell anyone that I wrote these questions as I am sure that I could be fired for not being knowledgable.

 

[ChrisConley]

On a semi-related note to all this discussion a colleague and myself decided that taking exhaust air out of a washroom from the ceiling was a waste of air, as the problem is much lower. We decided that if one could remove the offending odour 'at the source' we could probably reduce airflow significantly, and improve air quality.

Our plan was to create a toilet seat, which could be connected to an exhaust fan that would act like an odor-trapping hood. We even started working out required velocities.

Our plan to take the washroom exhaust world by storm was then stopped by a quick search of the US patent office; sure enough someone had already patented the idea. Makes you wonder if there are any really original ideas.

 

[imok2]

Chris Conley: "Original Idea" To expand on your Idea, how about a vacuum system connected to a compressor that can compress the gas (farts) to be used to supply a boiler to heat the building , of corse supplemented with natural gas in case there are too many layoffs.(just kidding) Now back to business, 1990 & 1993 BOCA codes: 75 CFM/for water closet AND Urinal. For toilet rooms with ceiling hts.under 12' 2.0 CFM/sqft dictates. Womens rest rooms usually have less fixtures but if they are essentially the same size then use the amount of fixtures in the mens room.