AHU disconnect switch or motor starter

[sergiyny]

Typically when I get mechanical drawings, I see some condensing unit on the roof which supplies a few air handler units in the office space. AHU's draw about 1 amp at 208V and I usually provide 2 pole manual motor starter for them. This time mechanical engineer showed on plan an AHU and a box right next to it with power requirements and a line with "Factory D.S: YES". Do they need a disconnect switches? Where do you install them? If AHU does not come with factory d.s., does it still need a d.s. or should it just be 2 pole motor starter?

 

[publicgood]

The mechanical engineer is placing the disconnect scope on the mech contractor. You likely still need to provide a starter. Reach out to the mechanical contractor to coordinate.

 

[kwired]

Since you said you normally provide a two pole MMS I am assuming these are single phase.

Such units usually have internal overload protection on the motors and do not require a controller that provides overload protection, a simple switch with proper current rating is all that is required for a disconnecting means, anything more then that is design specifications and not code required.

 

[Jraef]

And if your 2 pole manual motor starter is the style that is fully enclosed with a lockable exterior operating mechanism, that can serve as the disconnect mechanism. The push button styles usually cannot, but some offer qualifying accessories. The devil is in the details of what you select, starting with knowing what you need via coordination with the suppliers.