Elevator Shaft Cooling

[newmep]

To cool off a warm elevator hoist way (3 story tall),we are going to introduce conditioned air at 75 deg.
Is it better to extract air out from the top by an exhaust fan, or, force air in at the bottom with a fan?

Should the piston effect of elevator travel be considered?

Thanks,

 

[gepman]

I am not an elevator shaft expert so there may be others that can help you more.

If this is a new building then I would say that you should calculate the heat load on the elevator shaft and see if cooling is necessary. Here in California we haven't had much need to cool the elevator shafts. The shaft should have a top vent to relieve the pressure and vacuum caused by the elevator car going up and down and this usually provides enough air circulation.

If this is an existing building with a warm elevator shaft then I would draw the air out the top with a thermostatically controlled fan. It seems like a waste of outside air unless you will reduce your exhaust requirements somewhere else. Blowing the air in the bottom would tend to force the warm air out wherever there is a leak in the shaft contributing to your load elsewhere. You definitely need to take into account the piston effect.

Remember that there usually are strict fire code requirements on elevator shafts so any inlet opening will probably need to have a fire damper (except for the roof). It has been at least five years since I have done an elevator (I am in a somewhat different line of work now) so codes may have changed.

 

[IRstuff]

75ºF inlet air is already bordeline warm. When you add the heat load of the elevator, the car interior will be tropical.

TTFN

FAQ731-376

 

[gepman]

All of the elevators that I did had their own small A/C units to cool the elevator cars so car temperature was not an issue and I never did heat load calculations on the elevator car. The elevator shaft is an unoccupied space so I never performed heat load calculations on them.

Perhaps you should try to figure out why the shaft is so warm. Not much is allowed by code in an elevator shaft (except for the elevator, the powered equipment is usually required to be in a separate elevator equipment room) so there shouldn't be much heat load except for the heat rejection of the elevator car A/C, any air brought into the shaft vent, and some friction.

 

[newmep]

gepman,
this is an exisitng building and owner just installed A/C unit on the roof of car, so they created the problem of overheating shaft. I have done the heat load and know how much 70-75 deg air I need to keep the shaft at about 90 deg.

There is no top access to outside so we have to do a side exhaust very near the top. We are considering all fire codes. I was thinking about pushing air in from the bottom of the shaft and let it go out of the top (near top)louver with damper and any other cracks it can.

 

[AbbyNormal]

I would guess that if the piston effect did something significant you would not be worried about trying to cool the shaft

Take the "V" out of HVAC and you are left with a HAC(k) job.

 

[gepman]

It was unclear to me if the elevator shaft has an existing vent or not, so if it doesn't maybe just adding a vent would work.

A company that I once worked for always added vents at the top of the shaft but I have never really researched the subject of air flow in an elevator shaft due to elevator car movement. You would think that if the car had a piston effect on the way up it would also have the same effect on the way down and I have not seen any vents at the bottom of elevator shafts. Or perhaps if there is no place for the air to go on the way down it just passes around the car if there is sufficient space. Something for some interested person to call Otis, Thyssen Krup, or Schindler.

 

[IRstuff]

I don't think any elevators would be designed to be sufficiently syringe like to cause any actual pumping of air. The drag and compression forces would have to be quite substantial and reflected in the load capacity of the motors.

A home elevator appears to have 2 ft total clearance in one direction and 1 ft total clearance in the other:

http://www.easyelevators.com/planning.html

TTFN

FAQ731-376

 

[gepman]

I found this article on elevator shaft vents. Apparently the piston effect is small.

http://www.csemag.com/article/CA601661.html

 

[AbbyNormal]

Are the lobbies pressurized?

Take the "V" out of HVAC and you are left with a HAC(k) job.