Parallel Condensing Units

[boater bill]

A mechanical contractor is wanting to change out a specified 6 ton condensing unit for 2-3 ton units in the field, (cost). This will affect 5 units for a total of 15 new breaker slots needed. The electrical loads for the panel won't be an issue but the number of spare breaker slots are. There is not enough room in the electrical room to have a sub-feed panel either.

Does anyone know of a Code or other problem with having the previously specified 60 amp breaker and #6 conductors run to a disconnect between the units and subfeeding the units from there. each unit would have their own 30 amp disconnect at the units. The run from the electrical panel to the disconnect will be about 50-60 feet. The buiding is under construction and to change the runs wouldn't be a significant problem in the field either.

Any thoughts?

 

[steve66]

Sounds like a feeder running to two branch circuits to me.

I don't see anything wrong with it.

STeve

 

[hillbilly]

A mechanical contractor is wanting to change out a specified 6 ton condensing unit for 2-3 ton units in the field, (cost). This will affect 5 units for a total of 15 new breaker slots needed. The electrical loads for the panel won't be an issue but the number of spare breaker slots are. There is not enough room in the electrical room to have a sub-feed panel either.

Does anyone know of a Code or other problem with having the previously specified 60 amp breaker and #6 conductors run to a disconnect between the units and subfeeding the units from there. each unit would have their own 30 amp disconnect at the units. The run from the electrical panel to the disconnect will be about 50-60 feet. The buiding is under construction and to change the runs wouldn't be a significant problem in the field either.

Any thoughts?

If you're talking about running one 60A feeder to a (min 60A) 4 space breaker panel mounted within sight of and less than 50' away from the A/C units and supplying each unit through a 30 amp breaker, I don't see a problem.

If you mean running a 60 amp feed to a termination point and then splitting off and running 2 (smaller) circuits to seperate 30A circuit breakers mounted at each A/C unit, the Tap Rules (240.21) will apply to the run between the JB and the circuit breaker at the unit.
steve

 

[Wes G]

Go for it!

Go for it!

Does anyone know of a Code or other problem with having the previously specified 60 amp breaker and #6 conductors run to a disconnect between the units and subfeeding the units from there. each unit would have their own 30 amp disconnect at the units. The run from the electrical panel to the disconnect will be about 50-60 feet. The buiding is under construction and to change the runs wouldn't be a significant problem in the field either.

Any thoughts?

Since the original intent was the 60A circuit go ahead and use it. Run it as Steve suggested to a spot near and in sight of your units and mount a small, 6 space sub panel and feed your units from there. Than you save the cost of disconnects at the units to boot!
___________________
Wes Gerrans
Instructor - Electrical Technology
Northwest Kansas Technical College
Goodland, KS

 

[boater bill]

I like the idea of the sub-panel. I am going to make sure that the mechanical contractor that is making me and the EC jump to save him money, will pay the EC for his T&M, not the owner.