Servicing a rooftop package unit

dfru

We have a series of 460 volt 3 phase rooftop package units on the roof of a building. It is my understanding that in accordance with the National Electrical Code, 4 ft of clearance needs to be provided on the controls side of the unit, and in front of the disconnect switch. The engineer on the project insists that the 4 ft of clearance is not required since the unit is not energized during service and maintenance. I have never heard this argument used before, and know that at times the units need to be energized while the control panel is opened. I am reaching out to HVAC service technicians to provide me with a shopping list of service and maintenance procedures which do require that the equipment be energized. Any assistance would be much appreciated.

njtommy

Any time you are trouble shooting the equipment power may need to be energized depending on problems.
Also on PMs we would have power on to check amp draw on motors and compressors.
Along with checking operations of unit and ecomizer

dfru

Thanks
When checking refrigerant pressures and charge, the unit would need to be opened as well, correct? Where are the test ports typically located?

chief

I'm a master electrician in wisconsin. I also teach electrical code. Per nec 110.26(A) you need the working space for examination, adjustment, servicing or maintenance. Examination would include testing for the presence of voltage. OSHA and NFPA 70-E also spell out requirements for verifying that the power has been de-energized. Until it is verified de-energized you are to treat it as energized so the engineers theory is wrong.I don't know of an inspector who would accept the engineers argument either. hope this helps you. Good luck.

JUGHNE

The National Electrical Code book is often referred to "The Book of Exceptions" by many electricians.

Here we go: Article 110.26 (A) (1) Depth of working spaces for equipment likely to be energized while working on.....151-600 volts to ground (you may have 277 VAC to ground)....condition 2...(where your back is against another RTU)...space is 3.5'.....if you have another "hot" RTU open behind you then space is 4'. This is your "fall back/away space of safety".

The working space width is 30" or the width of the cabinet whichever is greater. The minimum height is 6.5'

Now imagine a dead short on a compressor and you pull in the contractor....even at 240 volts there may be an explosion of parts into your face, chest and of course the safety glasses you are wearing.....I literally have the T-shirt with holes burned in it for this event and the welded glasses I was wearing. Now with 480 VAC the energy is increased by 4 times. At one time I poo-pooed such rules as being for sissies. But after seeing, hearing and experiencing that shet happens, I think differently. The local AHJ has the book in hand and I would point the situation out to them. Once they are aware they most likely insist upon correcting the situation.........really a PITA to move a RTU on final inspection, huh. The engineer, (who may have never been on a roof) should be grateful to have this pointed out, but they often come out innocent.

njtommy

Test ports are generally located at the compressor. Some units do have a set of test posts located on the out side of the unit.
Other units like AAON and Lennox the compressors are located in the electrical control panels.

John Mills_5

http://hvac-talk.com/vbb/showthread.php?1852221-workers-comp-waiting-to-happen

You don't need clearance!