Disconnect doesn't kill equipment

[lile001]

We had a guy get a wollop from an HVAC unit that was disconnected.

He had turned off the local disconnect, and then started working inside the box. The power wiring came into the HVAC unit hot from the breaker, to some wire nuts, then out to the disconnect, and back in after the disconnecting means. So there are hot wires inside the unit even with the disconnect turned off. Our tech got a wake-up-call when he took these wire nuts loose.

Now, we told the guy for the umpteenth time that he should be using his non-contact voltage detector before he touches any wires. Even when he is staring at the disconnect 12" in front of his face. However, we are also convinced that it is "wrong" to wire a unit this way - there should be no hot wires inside an air handler if the disconnect is thrown.

We couldn't find anything in the code that says specifically one way or the other. Any opinions?

 

[RICK NAPIER]

Never trust a disconnect. I have had damaged disconnects that appear to open cleanly only to have left a phase still in contact.

 

[76nemo]

We had a guy get a wollop from an HVAC unit that was disconnected.

He had turned off the local disconnect, and then started working inside the box. The power wiring came into the HVAC unit hot from the breaker, to some wire nuts, then out to the disconnect, and back in after the disconnecting means. So there are hot wires inside the unit even with the disconnect turned off. Our tech got a wake-up-call when he took these wire nuts loose.

Now, we told the guy for the umpteenth time that he should be using his non-contact voltage detector before he touches any wires. Even when he is staring at the disconnect 12" in front of his face. However, we are also convinced that it is "wrong" to wire a unit this way - there should be no hot wires inside an air handler if the disconnect is thrown.

We couldn't find anything in the code that says specifically one way or the other. Any opinions?

What's the quote for thee exact opposite of "priceless"? What's a harsher term for ignorance? Can you see why exactly they would of done it that way to any benefit of theirs:-? What's the point of the second disconnect then???????

 

[daleuger]

What's the point of the second disconnect then???????

To keep guys like us on our toes and always thinking :grin:

 

[lile001]

Never trust a disconnect. I have had damaged disconnects that appear to open cleanly only to have left a phase still in contact.

Yes, the guy now knows he made a dumb mistake , and after we got done lecturing the poor fellow about safety rules, we are still left with the CODE question:

Is it legal to wire an HVAC unit with the hot wires inside the housing?

 

[BryanMD]

Is it legal to wire an HVAC unit with the hot wires inside the housing?

If it isn't... then there are about 10 billion RTU's that need to be changed.

 

[charlie b]

We couldn't find anything in the code that says specifically one way or the other. Any opinions?

Yea. 440.11 and the article 100 definition of "disconecting means."

 

[steve66]

Yea. 440.11 and the article 100 definition of "disconecting means."

Is there any requirement that the disconnect shuts off control wiring?

 

[rbalex]

Is there any requirement that the disconnect shuts off control wiring?

See 440.3(A) and 430.113.

 

[Jim W in Tampa]

Some units have the disconnect ( breaker) built in. Personally i would not have a splice inside your unit. But running up thru a RTU is normal. The real issue here is was the guy qualified to be working on it. A hot stick is a smart idea.

 

[iwire]

Some units have the disconnect ( breaker) built in.

I agree, the person working on the unit has to be aware.

Personally i would not have a splice inside your unit.

I did not like it but I have done it as directed by the boss.

The power wiring came into the HVAC unit hot from the breaker, to some wire nuts, then out to the disconnect, and back in after the disconnecting means. So there are hot wires inside the unit even with the disconnect turned off.

The company I worked for did hundreds of fan coil units exactly like that.

But running up thru a RTU is normal.

I agree, RTUs with factory installed disconnecting means often have you run the supply conductors through the unit itself and then into the disconnecting means.

The real issue here is was the guy qualified to be working on it. A hot stick is a smart idea.

I agree.