Mechanical interlock - load calculation

[Rock86]

Mechanical engineer asked me today...

A building with very limited room for increased load is looking to add electrical heating coils to their air handling units. The theory is to add an interlock to transfer the connection from the condensing units to the heating coils. In theory, because of the interlock, could the load calculation be counted as one load instead of two?

 

[Rock86]

220.51 Exception.... maybe???

 

[drktmplr12]

if they cannot run coincidentally due to being physically interlocked, you take the greater of the two.

 

[Rock86]

if they cannot run coincidentally due to being physically interlocked, you take the greater of the two.

Thanks. That was my thought.

 

[don_resqcapt19]

if they cannot run coincidentally due to being physically interlocked, you take the greater of the two.

I see nothing in 220.60 that even suggests a physical interlock is required. It really doesn't even require an electrical interlock. Just requires that it be "unlikely" that the two loads will be energized at the same time.

 

[Rock86]

I see nothing in 220.60 that even suggests a physical interlock is required. It really doesn't even require an electrical interlock. Just requires that it be "unlikely" that the two loads will be energized at the same time.

Thanks.