Ventilation for Indoor Truck Wash Bays 1

[cwigg66]

I am designing a facility in North Dakota that is to service large trucks all year round. The part of the facility in question is the indoor truck washing bays (two total), with roll up doors at each end. The bays are heated (ND winter design temp is -22F). Does anyone know what the ventilation/exhaust requirements would be for such a space. ASHRAE 62.1 lists Parking Garages at 0.75 CFM/SF and Auto Repair Rooms at 1.5 CFM/SF.

Questions are:

Which exhaust rate is more correct for this application? Maybe there is some other standard?
Can this be done with Make Up Air Units forcing in the required amount of OA and letting it leave via barometric or gravity dampers? Do I need exhaust fans?
What happens when there is no call for heating and the doors are shut and there's a truck idling inside? Seems like I need some sort of interlock to ensure air exchange when the space is occupied. CO sensors?

Thanks for all your input. I am sure I have left some details out so let me know what I need to add and I will do so. At this point, I am back and forth with the owner and architect trying to come to an agreement that I can be comfortable with.

Chris W.

Chris W., P.E.
Mechanical Engineer
Arco Engineering, Inc.

 

[chicopee]

I am sticking my neck on this one because large spray room use to spray vehicle and heavy duty equipment, 50 ft/min is recommended thru the cross section of the room by some of the insurance companies. In your case the bay doors are large to allow make up air when vehicles are in and out, so I would allow 25 ft/min of cross sectional ventilation up to a level of the tallest piece of equipment.
What you are not indicating is how much spray and steam would be generated, what are some of the hazards of cleaning solutions to which the persons washing the equipment would be exposed to. If the solutions are hazardous then you may have to increase air flow or provided repiratory protection with an air supply as well as protective gear.

 

[DrRTU]

Chris,
I have done a few of them in the Chicago area. Determine if the operator will purchase an automated system to wash the trucks. Some of the wash systems will be located at one end of the tunnel and are very tall. I am doing one now and the unit is 17’-0” tall. The washing unit travels over the stationary truck. Some vendors recommend walled off sections of the wash area with separate exhaust inlets. I use 1.5 cfm/ft2 over the complete floor area due to the need to remove air bourn water vapor when it’s very cold outside.

The key is not just the ventilation rate, it’s a capture and control of water vapor. I use NOx sensors (high 12” from deck) and CO (low 54”AFF) to ensure the makeup/heating and exhaust is on. I have used the following designs: #1. Unit heaters, relief hoods, and fans on cheap designs – the unit heaters have short life even with ss separated combustion. This design works on rooms w/o an automated system. #2. This design utilizes a 2 speed 100% oa direct fired MAU with 110 rise. This application works ok as long as the adj. profile plates in the MAU work good. Low spd at .75 cfm/ft2 and running when washing. SS low intensity IR heaters in the tunnel. I locate these on the long wall in the direction of truck travel, reflector at 45 degrees. Make sure all equipment and controls are sealed. MAU must have a DA motorized damper! Water vapor will travel up in the unocc time and freeze if you use an inlet damper. Exhaust at the washing end of tunnel and mau at opposite end. All duct must be SS or aluminum. SS tek screws and grilles. I once did a mau drop in G-90 and it rotted out in 2 years. Install a small fan for .05 cfm/ft to run 24hrs a day – it’s code and it drys out the room. Exhaust fans should be upblast. I like to use Greenheck kitchen exhaust fans. #3 Two (2) Cambridge S type units on the roof, usually 400s located at each end of the tunnel or room and exhaust fans in the center. Face the inlets hoods away from the exhaust fans. You will see this design in a lot of automated car wash lines. With Cambridge, the high DA temperature rise drives away the steam cloud. The operators do not have the “fog” as in system #1. Talk to your Cambridge rep., the company started in the car wash business.

Steve

 

[cry22]

why not connect the trucks' exhaust mufflers to an exhaust fan similar to those found in firehouses, magnets attach the exhaust duct to the tail pipe and then detaches away as the truck leaves the wash bay.
Agree with direct gas-fired MAU for such a space, I like hydronic wall radiators if you can instead of unit heaters. I also like the radiant heat approach if you have gas available.
Think of providing a slab heating system immediately after the wash bay. As the truck leaves, water drips off the truck and it builds ice on the exit and blocks the exit doors. Think of those guys shoveling ice at -22F weather (small 150 MBH boiler with circ pump should do).
Spec all pipes to be FRP and all hangers to be either SS or FRP, not just for the HVAC, for the plumbing, the electrcial tubings etc.
Of course, call for explsionproof stats and locate your controlsaway for chlorine environment if it is the case.