How To Size A/C For Elevator Equipment Romm
How To Size A/C For Elevator Equipment Romm
(OP)
I'm working in Chicago and have been tasked with sizing the proper system for a three 10,943 lbs capacity elevators. The elevator equipment room is approx. 800 sq ft in size, with brick walls, and it is on the 18th floor.
How do I determine the size and type of unit to install?
The customer wants to have a 42,000 Btu split heat pump system installed (he wants supplemental heat in the frigid winters). I told my boss that I didn't think a heat pump in Chicago winters (weeks on end it can get well below 0 degrees) was a good choice. Also, the customer does not want the outdoor condenser to sit on the roof, it must be mounted on the side of the elevator room outside wall. This means that he has a residential split system in mind. Is this possible? Is this a good decision?
So, if someone could tell me how to take a proper load count on an elevator room (i.e. does one need to take the HP of the motors into consideration) and what the most prudent system configeration would be, I'd be verygrateful.
How do I determine the size and type of unit to install?
The customer wants to have a 42,000 Btu split heat pump system installed (he wants supplemental heat in the frigid winters). I told my boss that I didn't think a heat pump in Chicago winters (weeks on end it can get well below 0 degrees) was a good choice. Also, the customer does not want the outdoor condenser to sit on the roof, it must be mounted on the side of the elevator room outside wall. This means that he has a residential split system in mind. Is this possible? Is this a good decision?
So, if someone could tell me how to take a proper load count on an elevator room (i.e. does one need to take the HP of the motors into consideration) and what the most prudent system configeration would be, I'd be verygrateful.





RE: How To Size A/C For Elevator Equipment Romm
RE: How To Size A/C For Elevator Equipment Romm
RE: How To Size A/C For Elevator Equipment Romm
I have already cautioned my customer about using a heat pump in Chicago winters. Initially I had suggested a mini-split with 3 tons of cooling and to supplement the heat during the winter with electric heats; however, I was talking with a mechanical engineer colleague and he suggested that I install a Bard 3 ton 15 kw 230/3 phase wall mounted self contained packaged unit. He believes these sort of units work better in this application and and then there is the option of running a supply and return duct if we wanted to distribute the air more evenly. What are your thoughts on this?
RE: How To Size A/C For Elevator Equipment Romm
Best to you,
Goober Dave
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RE: How To Size A/C For Elevator Equipment Romm
Tim LaRocque
RE: How To Size A/C For Elevator Equipment Romm
Best to you,
Goober Dave
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RE: How To Size A/C For Elevator Equipment Romm
My first question is where is this mec room located?
If it is in a garage area then simplify your design by recirculating the garage air in the mec room with a wall mount evac fan and proportional air intake on the wall of the room, Use 10F as your delta T (where Q=CFM*1.085*delta T) solve for CFM(Flow).
If not possible to do this, then with the BTU (given heat dissapation) size your AC proportionlly. I recommend a standard residential type AC mini split, locate the evaporator in the mec room and if possible locate the condensor in the garage near by (reduce cost of refrigerent lines) in this arrangement the heat is returned in the garage in the winter thus helping heat the garage and in the summer the little heat given in the garage will be taken care of by the garage CO ventilation system (install a thermostat) again if a garage is available! OtherWise the condenser will have to be located outside (make sure you spec a low ambiant kit for the condensor for winter opperation). No need for a heat pump as said in previous post no good payback as you rarely or never need to heat unless your mec room is on the roof and all face of its envelope is exposed to the outside then add a baseboard for security factor. Check your réfrigèrent lines as the have a max. dist they can travel in terms of lift and equivalent lenght (when dist is an issue spec an inverter).
Hope this helps, that is the way it is done here with great success.
Genieconseil
RE: How To Size A/C For Elevator Equipment Romm
RE: How To Size A/C For Elevator Equipment Romm
a mechanic may have to work in that elevator room - they usually don't like CO etc. :)
RE: How To Size A/C For Elevator Equipment Romm
Motor duty factor has always been a number that I have struggled to be comfortable with. trashcanman states 50%.
When possible, I try and design a ducted FCU system located outside the elevator machine room for easier maintenance access. I just duct to the room boundary with a fire dmaper. I have never ducted into an elevator machine rooms for even distribution. Usually not enough space, and the room is so small, it is not typically needed, plus it has a wide temperature range requirement, usally 60 degF to 90.
My state code has a maximum but also a minimum room temp so heat will most likely be required. You should have a problem finding a heat pump with capacity down to 0 degF OA.
knowledge is power
RE: How To Size A/C For Elevator Equipment Romm
1. split system AC. Floor mounted FCU indoor if you have the space. no condensate piping over electric equipment.
2. Electric heat, you do need it in case your heat pump fails, you wet-pipe sprinkler pipe could freeze. Since you need some sort of stand-by heat, P does not make sense.
3. Use a wall mounted exhaust fan, maintain room temp with EF when OA temp is 80F or below. Use AC when above adj. of course) AND you get stand-by for your AC system along with an air side economizer.
As for the size, a 10,000 lbs elevator machine room is no more than 30HP motor, no more that 3-ton of heat. Keep in mind you only need to maintain 90F in the room. being on the 18th floor, even in the summer, it is cold up there, your EF by itself will do the job.