AC vs DC motors in industrial applications

I do a lot of electrical MCC and PLC designs for wood mills and mines, and we usually always use 600V AC premium efficiency motors. My boss came up to me today and he was apparently told that he should switch out his AC fan motor for his home furnace out to DC, because the current consumption would be 1/3 with the DC motor. So my boss then comes to ask me why won't we use DC motors in an industrial setting instead of all these AC motors?

I've never done motor designs for DC motors. Where is the rectifier located if you're used to having a 600V MCC? Can you get a DC motor MCC bucket? Most of all, I am trying to figure out how it's possible that the DC motor can only draw 1/3 of the HP when compared to the AC motor. Now, I was told that the DC motor and AC motors for the furnace fan in question was of the same HP. So, if that's the case, they are of the same wattage, meaning if the ac and dc voltages are the same, the current HAS to be the same. 

Also, why don't we use DC motors more in industrial settings (or am I just isolated and they are in fact super common)?

To add fuel to the fire, I was reading online about the correlation between ac and dc current, and the number "0.636" comes up a lot. I cant make any sense of this number whatsoever, so if someone can shed some light on that as well, that would be great!

In heavy power applications, with 3 phase power distribution, 3 phase motors are the obvious way to go. there are a number of motor configurations, squirrel cage induction motors are the ultimate in simplicity, and not having slip rings they require little maintenance, and in environments where there is the potential for an explosion due to fine particulate matter, or gas in the air, they win hands down.Like any other motors, they have a down side as well, see the article below.
In low power applications, universal motors are often used, they will run off AC or DC, and are typically found in single phase mains supplied applications.
A fan motor in the furnace application would be running a lot, so a small brush less motor would save a lot of maintenance problems, if a universal motor was the suggested replacement I think they got it wrong, it may be more efficient, but maintenance is also an issue. More details on the type of motor originally used, and what it was replaced with would be useful information.
There is a ton of stuff on the web,
https://en.wikipedia.org/wiki/Electric_motor
Motor selection is based on many factors, efficiency, starting torque, torque versus speed, complexity, maintenance, speed control etc., the article above lists typical characteristics.
Re the 0.636, this converts between AC and DC, and gives the average DC value, sort of thing you come across when converting AC to DC in power supply design in particular.
http://physics.tutorvista.com/electronics/ac-to-dc-conversion.html
cheers,
Richard

Air conditioning and DC electric engines are utilized to give imperative power supply to various modern applications. While the facts confirm that DC engines were created from air conditioning engines, there are critical contrasts between them. These distinctions can affect the execution of an application hardware. Consequently, mechanical clients need to comprehend the contrasts between these two engines, previously picking one for an application.
Understanding Air conditioning DC Electric Engines Contrasts
Here, we will take a gander at each engine independently to comprehend different angles like structure, base current, and capacity.
Air conditioning Engines: These use Rotating Flows (Air conditioning) to make mechanical vitality from electrical vitality. The plan of an air conditioner engine is the equivalent. They contain a stator, and a rotor. The stator delivers the attractive field, while the rotor pivots because of the attractive field's enlistment. While picking an air conditioner engine, you have to remember two essential highlights – the running rate (RPMS), and the beginning torque.
DC Engines: DC electric engines are mechanically commutated machines. They use Coordinate Flows (DC), and involve a pivoting armature winding, and a perpetual magnet, which goes about as a static field. These engines utilize static field and armature twisting associations with create distinctive speed and torque levels. Not at all like air conditioning engines, the speed of DC engines can be controlled by changing the voltage connected to the armature, or by modifying the static field current.
Air conditioning Engines v/s DC Engines
Since we have taken a gander at both electric engines independently, the distinctions that we have given in the focuses underneath will be simpler to get it.
Air conditioning engines depend on exchanging flows, while DC engines use coordinate flows.
DC engines get control from cells or batteries, which give steady voltage, empowering the stream of electrons in a solitary course. Air conditioning engines get control from air conditioning generators, making the electrons change their stream bearings.
The steady vitality stream of DC engines makes them perfect for applications requiring stable rates, torques, and activities. Air conditioning engines, with their consistent vitality changes, are perfect for mechanical and private applications.
Air conditioning engines are favored for blower control drives, cooling blowers, and water driven, and water system siphons. DC engines are favored for steel process moving hardware, and paper machines.
In the wake of taking a gander at the above focuses, you will understand that the power sources, and dimension of intensity control are the key factors that clients need to consider for air conditioning and DC engines. While picking an engine, it is constantly prudent to address a specialist designing association. They can take the points of interest of your application, and propose the correct kind of air conditioning and DC electric engine fixing answer for your necessities.